78
THE POTENTIAL
OF CHINESE SWINE BREEDS TO IMPROVE
PRODUCTION
EFFICIENCY
PORK
IN THE U.S.
David G. McLaren
Animal Sciences Department
University of Illinois
Urbana, IL 61801
Summary
The importation
of "exotic" germplasm
represents
a powerful
technique
for genetic
improvement of indigenous livestock populations, and is part of the heritage of our modem breeds
of swine. Certain Chinese breeds offer great promise for improvement of litter size in U.S. swine,
although presenting
problems in the areas of composition
and economy of growth.
Mating
American x Chinese gilts around five months of age and weaning gilt and sow litters of 11 to 13
pigs (vs eight months and eight pigs weaned a litter for occidental crosses) appears realistic. Their
25% Chinese offspring will probably be unacceptably fat, however, and the increase in sow
productivity is unlikely to compensate for the poorer carcass merit of the progeny.
Fortunately, selection for feed efficiency and lean content are effective in swine, and it should
be possible to move Chinese (or some composite American - Chinese) populations to satisfactory
levels for these traits. We are also living in an age of rapidly changing technology, and the shortterm impact of compounds such as porcine somatotropin and the 13-adrenergic agonists on partChinese hogs might be such that the disadvantages of the prolific breeds become less critical. The
long-term possibility
of transgenics
makes the hyperprolific
Chinese pig a valuable genetic
resource.
One-hundred and forty-four boars and gilts of the Taihu and Min breeds are presently in
quarantine in Florida. These animals will be used in both basic and applied research projects, with
the objective to increase prolificacy
in U.S. commercial
sow population
by the year 2000.
Scientists at the University of 121inois,Iowa State University and the ARS-Meat Animal Research
Center, Nebraska, plan to apply classical breeding methodologies,
in conjunction
with new
molecular genetic techniques, to utilize these Chinese pigs to improve the efficiency of pork
production. It is anticipated that about 10 years of research and development will be required in
order to establish a 50% Chinese dam line that has utility as the dam or grand-dam of U.S. market
hogs.
Presented at the 38th Annual National Breeders' Roundtable, May 4-5, 1989, St. Louis, MO.
"]9
Introduction
One-hundred and forty-four Chinese pigs arrived at the Harry S. Truman Animal Importation
Center (HSTAIC), Fleming Key, Florida, on March 26, 1989; the fhst such importation to North
America. The 66 Meishan gilts and 33 Meishan, 24 Fengjing and 21 Min boars had spent 60 days
in quarantine under the scrutiny of USDA-APHIS
(Animal and Plant Health Inspection Service)
veterinarians in the Peoples' Republic of China, and will spend a further 120 days at the HSTAIC
prior to release. The University
of I11inois, Iowa State University
and the USDA-ARS
(Agricultural Research Service) will share the pigs and costs (approximately $1.5 million) equally.
Chinese pigs have been imported to the U.S. because they have large litters. Gilt litters of 13
pigs born, and third and subsequent parity litters of 15 to 18 pigs, are typical for Taihu sows
(I._gault, 1985); four or five pigs more than the average U.S. commercial sow. Sow productivity
(pigs / sow / year) has a large impact on pork production costs. Increasing pigs weaned per litter
from 8 to 11 has been estimated to reduce the costs per 18 kg pig produced by $9 (Stevermer eta/.,
1980). The relevance to the U.S. industry, which produced 88 million market hogs in 1987, is
clear.
Despite its economic importance, litter size in occidental (western) breeds has shown little
improvement over the past thirty years (Noguera and Legault, 1984; Sellier and Legault, 1986).
Litter size in minois increased from 6.4 to a little over 7.0 pigs in the 1950s, and remained at this
level until the late 1960s, then falling to around 6.8 in the 1970s (Figure 1). Litter size did,
however, increase from 6.8 pigs in 1979 to 7.6 pigs in 1987, which might be whoUy
environmental or partly genetic.
Given the commitment
of resources to the importation of Chinese pigs (in addition to
importation costs, the State of Illinois has constructed a $1.8 million facility for research with
imported pigs, for example), it seems timely to review what is known regarding hyperprolific
Chinese pigs, and to consider how they might be used to address both basic and applied research
hypotheses.
Historical
Perspective
Domestication of swine in China dates back to at least 3,000 B.C and, over time, Chinese
pigs have had a profound effect on the development of world swine breeds. A large number of
pigs from South China were imported into the Roman Empire in the 3rd century B.C. and used to
improve indigenous European breeds (Yu, 1987).
From probably the 16th through the 18th
century A.D., pigs from South China were imported to England and used in the development of
80
modem breeds, particularly the Yorkshire and Berkshire (Phillips and Hsu, 1944; Epstein and
Bichard, 1984; Wang, 1988). By the end of the 18th century, breeds with Chinese ancestry had
replaced almost all indigenous English breeds (Yu, 1987).
7_
•m
7.0
oi
6_
6.0
1945
I
I
I
I
!
I
!
I
1950
1955
1960
1965
1970
1975
1980
1985
Figure 1. Pigs per litter, Illinois, 1945 to 1987.
(Source: IllinoisAgriculturalStatisticsService)
The Berkshire and Yorkshire breeds in the United States originated with importations from
England in 1823 and 1893, respectively.
Chinese pigs, introduced into 19th Century America,
also played a role in the formation of the Poland-China and Chester White breeds (Briggs and
Briggs, 1980).
production,
Importation
of promising
foreign breeds has a long tradition
with the Landrace the most recently introduced
in livestock
breed of swine to contribute
substantially to U.S. pork production (the first importation of Landrace pigs from Denmark was in
1934).
The prolific Chinese swine breeds have developed over thousands of years of isolated
evolution. Their extreme prolificacy might be the result founder effects, favorable mutation(s),
and(or) selection. Almost certainly, these breeds have been selected in some way for prolificacy.
Peasant
farmers would traditionally
keep one or two sows to provide feeder pigs to other
households (Haley, 1988). Prolificacy would clearly be a major selection objective under such a
81
system. Some Chinese pig populations may ean'y genes affecting Utter size not present, or present
at much lower frequencies, in occidental populations. It is possible that a gene or genes with large
favorable effects on litter size exists, however there is little evidence to support this hypothesis.
That Chinese pigs arc very fat may be explained in part by the traditional grade-and-yield
system in China, which has been a higher retail price the thicker the backfat (Chen, 1986). Major
Chinese cities are, however, reported to have begun changing their pig carcass grading systems in
1982 to reflect a shift in consumer demand toward lean pork (Chen, 1986). The Peoples' Republic
of China also imported large numbers of Danish Landrace, Duroc and Hampshire pigs in the 1980s
to use in crossbreeding systems geared to lean meat production (Jiang et al., 1988).
The Case for Importation
of Prolific
Breeds
of Chinese
Swine
Gianola et al. (1982) and Legault (1983) characterized certain Chinese breeds of swine as
follows:
1.
Exceptionallyprolific(on average, 9 to 17 pigs born alive per litter).
2.
Early maturing (reaching puberty between two and four months of age).
3.
Hardy, long-lived and docile.
4.
Adapted to production systems where forages are routinely fed.
5.
Low growth rate (.25 to .80 kg/day).
6.
Small mature size and poor feed efficiency.
7.
8.
Fat carcasses (20 to 50 mm baekfat), but an excellent meat quality.
Poor conformation.
The fact that litter size has failed to show consistent improvement in the U.S. over the past
thirty years (Figure 1) is not difficult to explain. Heritability of litter size in swine is only about
.10 (Strang and Smith, 1979; Haley et al., 1988). Selection based only upon performance of the
dam reduces accuracy even further. Emphasis on improving growth and carcass performance has
dominated most selection programs, and low selection intensities and the importance of random
genetic changes in small populations have probably contributed to the apparent failure of litter size
to respond to intra-herd selection over the years.
That litter size can be improved by selection, and achieve response in general agreement with
that predicted from theory, has been demonstrated by "hyperprolifie" selection schemes.
Such
schemes involve selecting the top 1 to 2% of a large recorded sow population, based upon four
litter records, forming a hyperprolifie
nucleus herd and backcrossing
to sons of other prolific
sows. With or without hyperprolific schemes, a rate of genetic change in litter size born of 2% of
82
the population mean a year should be achievable with selection, comparable to rates expected and
achieved for growth and carcass traits (Smith, 1984). Although lowly heritable, litter size has a
relatively large variance, and AG as a proportion of _ - h2.i.CV per generation.
Assuming an
annual rate of 2% of the mean, increasing average Utter size from 10 to 14 pigs born alive would
take 20 generations of effective selection.
Research in France, based upon a founder population of one Meishan boar and two sows
imported in 1979, found a difference between Large White and Meishan lines of approximately
four standard deviations for yield of lean tissue (16 kg) and one standard deviation (2.9 pigs) for
litter size weaned (Bidanel, 1988; OUivier, 1988). An F1 Large White x Meishan sow, however,
has similar Utter size to the Meishan, plus the disadvantage in lean yield is only 25% in the market
hog. In addition, it should be possible to increase carcass lean by selection in a half-Chinese
composite line to an acceptable level within 10 generations, without a correlated decline in
prolificacy (Brien, 1986).
Selection for lean growth in a Large White-Meishan composite might prove to be 50% more
efficient than in an occidental line due to early sexual maturity (Biclanel, 1988). OUivier (1988)
estimated that such a composite could outperform conventional dam lines with two or three years
of intense selection for production traits. Adding two or tkree years lag for random mating to
disrupt linkage groups prior to selection, and considering returns to the entire crossbreeding
system rather than just the terminal sector, a 10 year period might be reasonable in order to
establish a 50% Chinese clam line that has utility as the clam or grand-dam of market hogs.
The U.S. Importation
The 66 Meishan gilts and 33 Meishan, 24 Fengjing and 21 Min boars comprising the joint
ARS / University of Illinois / Iowa State University importation are from 10 Meishan, 8 Fengjing
and 7 Min families. Fengjing and Min gilts were not available for export. Animals are said to be
from different families if they are unrelated back to their grandparents (not absolutely true, but
close). Each cooperating institution will receive a sample of pigs from all families.
The Meishan and Fengjing are two breeds from the lake Taihu region near Shanghai. Taihu
pigs appear to be the most prolific in China. The region is characterized as temperate, with the
temperature averaging 15.7° C and ranging from an annual low of -9.1 ° C to an annual high of
38.2 ° C (Cheng, 1984). In order to maintain genetic diversity among imported lines and to include
previous adaptation to cold climates as a potentially valuable attribute, boars of the prolific Min
(aka Damin, Minzu, Ming) breed of Heilongjong Province, North China, were included in the
83
importation. The temperature averages 4.9 ° C, ranging from an annual low of -36.5o C to a high
of 36.4o C (Cheng, 1984). The Min has perhaps one pig less a fitter than Taihu females, but might
prove to somewhat faster growing and leaner than the Taihu, in addition to being cold tolerant.
History
of the Importation
Effort
The existence of highly prolific breeds of swine in China was noted as long ago as 1944 by
Phillips and Hsu, and later confirmed by Epstein (1969). The 1989 importation of 66 Meishan
gilts and 33 Meishan, 24 Fengjing and 21 Min boars from the Peoples' Republic of China
represents the culmination of a consistent effort over the past 10 years by a number of scientists,
administrators and producers in the U.S. to import hyperprolifie Chinese germplasm.
In 1978 the Illinois Pork Producers Association funded a literature review and study to look
at the feasibility of importing prolific Chinese pigs. The University of Illinois subsequently sent a
team to China in 1980 to investigate sources of potentially useful germplasm in the field. A request
to import semen at this time was denied by APHIS (the Animal and Plant Health Inspection Service
of the USDA).
In 1981 the Office of International Cooperation and Development (OICD-USDA)
rated a
proposal to import Chinese germplasm as "highest priority" (Gianola, personal communication).
Negotiations with APHIS continued, but it was not until 1986 that a protocol for the isolation and
testing of Chinese pigs to be imported to the U.S. was signed by APHIS and PRC veterinarians.
Regulations for importation of semen from the PRC have also been established.
The State of Illinois appropriated $1.75 million in 1985 for a facility at the University of
Illinois, Urbana, to be used for research with imported breeds of swine. Negotiations to purchase
and quarantine Chinese pigs were also initiated around this time. Construction of the University of
minois research facility was completed in late 1988.
Given economies of scale for quarantine and transportation costs, and the eagerness of other
research groups to become involved in the importation, the University of Illinois, Iowa State
University and the ARS (USDA Agricultural Research Service) became equal partners in a joint
importation of Chinese pigs. A purchase agreement was signed by representatives of the ARS and
CABS (the China National Animal Breeding Stock Import and Export Corporation) on September
28, 1988, and 144 Chinese pigs arrived at the USDA quarantine station on Fleming key, Florida,
on March 26, 1989.
84
Swine Breeding
in China
The Peoples' Republic of China is home to 41% of the world's pigs and 22% of the world's
human population (FAO, 1987). Pork is the primary meat consumed in China, and pig manure the
most important source of organic fertilizer (Chen, 1986; Yu, 1987).
Gianola et al. (1982) reported only 7% of China's grain production
as used in animal
production. Forages, aquatic plants (e.g., water hyacinth), domestic and industrial wastes and byproducts contribute
heavily to swine nutritional programs.
However,
the increase in pigs
slaughtered in recent years (up 17% between 1984 and 1986; FAO, 1987) has been attributed to
increased availability of feed grains, as well as the elimination of fixed pork prices in 1985 (Yu,
1987).
Epstein (1969) and Cheng (1984, 1985), reporting over 100 "breeds" of swine in China,
noted that many breeds were the same type of pig distinguished according to the locality in which
they were found. Given the variability of topography and climate, and the diversity in management
and market systems in China, the development of a large number of breeds is understandable.
Additionally, the teaching of Mendelian genetics and statistics was forbidden in the Peoples'
Republic between 1949 and 1956, and animal breeders followed the ideas of the Russian geneticist
Mitchourin, resulting in a proliferation of new breeds (Gianola eta/., 1982).
The number of "officially" recognized breeds in China in 1983 was 66 (Cheng, 1983; Wang,
1988). These consisted of 48 native, 12 developed and 6 imported breeds. Many foreign breeds
have been imported
into China to use as terminal sire breeds and, more recently,
development of composites.
in the
Most influential have been the Middle Yorkshire, Berkshire and
Kmirov imported in the 1950s, the English Large Yorkshire, Soviet Large White and Landmce in
the 1960s, and the Danish Landrace, Duroc, Hampshire in the 1980s (Jiang et aL, 1988).
Reviews of research conducted in China have provided comparative data on indigenous
swine breeds (Wu and Zhang, 1982; Zhang et al., 1983; Cheng, 1983, 1984; Xu, 1985a,b; Wang,
1988). In general, North and Central China breeds are considered fairly prolific, with litter sizes
of 12 to 13 pigs and 14 to 16 teats. Pigs of the Lower Chan_iang
(Yangtze) River Basin type,
particularly the Taihu breed, have earned a reputation for high prolificacy (Zhang et al., 1983;
Cheng, 1983, 1984; Wang, 1988). Zhang et al. (1986) grouped 25 native, 12 dev_0Ped and 5
imported breeds into six different types based upon cluster analysis.
China breeds, the Min and the Bamei, classified as "prolific type".
The Taihu and two North
85
There are seven types of Taihu pig, with the Meishan, Fengjing, Jiaxing-Black and Erhualian
the best known (Wang, 1988). They have the characteristic Chinese "pot belly" appearance (an
adaptation to roughage feeding), with large heads and large, lop ears, black or black-grey hair and
deep, fleshy skin wrinkles, particularly on the face. The Meishan is distinguished by having white
feel
Young Taihu boars can mate and fertilize females at 90 days of age with a fertility rate of
40%, rising to 100% at 120 days of age (Cheng, 1983). Boars are not typically used on breeding
farms until six to eight months of age and 80 to 90 kg live weight, however. Taihu gilts reach first
estrus at approximately three months of age, with body weights of 15 to 25 kg.
Taihu sows typically have 16 to 18 teats and weigh 120 to 175 kg. First and second litters of
13 live pigs (11.5 weaned), and 15 live pigs (12.5 weaned) for parity three and greater appear
average. Pig birth weight averages .9 kg. Growth rates between .30 and .46 kg/d, and carcasses
with 32 mm backfat and 15 to 19 cm 2 loin eyes yielding 40 to 45% percent lean, have been
reported for Taihu pigs (Wu and Zhang, 1982; Zhang et al., 1983; Cheng, 1983, 1984; Wang,
1988).
Mix, sows average 150 kg live weight and have course, black hair with a dense undercoat in
the winter that allows sows to farrow in an open shed at 4° C (Cheng, 1984). Min pigs average 16
teats and reach puberty around 140 days of age. Sows average first and second litters of 12 live
pigs (10 weaned), and 14 live pigs (11 weaned) thereafter (Wu and Zhang, 1982; Zhang et al.,
1983; Xu, 1985a; Chert, 1987; Wang, 1988). Pig birth weight averages 1.0 kg. Growth rates
between .40 and .50 kg/d, and carcasses with 45% percent lean and 23 cm 2 loin eyes, have been
reported for Min pigs.
Thus although early maturing and prolific, Taihu and Min pigs are reported to have low
birth weights, grow slowly and to have fat carcasses with a small amount of lean meal
Results of
Chinesegrowthandcomposition
experiments
were,however,
obtained
usingdiets
andproduction
systemsdiffcring
markedlyfromthoseemployedinthemid-western
UnitedStates.
Nevertheless,
results obtained with a small sample of Taihu pigs in France confirm that these pigs will likely
prove highly unfavorable for lean growth under U.S. production and management conditions.
Research
in France
Comparative data on Chinese pigs under western conditions has come from work conducted
in France. A gift of nine Chinese pigs, one boar and two sows of each of the three breeds, arrived
at the Domaine Experimental du Magneraud, a research farm in Western France, on November 24,
86
1979. Six were Taihu pigs (three Meishan and three Jiaxing-Black), and the remainder were of a
CentralChina breed, the Jinhua, noted for the qualityof its hambut not for prolificacy.
The extremely narrowgenetic base in the Frenchlines does, of course,precludeoverzealous
extrapolationto otherpopulations. Nevertheless,the workin Francehasprovided data concerning
performance of these pigs under modem husbandry conditions, and provides the first reports
concerningphysiological mechanismsunderlyingprolificacyin the Taihupig.
Initial matings were purebred Chinese, and Chinese boars mated to Large White and French
Landrace sows to produce six types of FI cross (Legault, 1983). The European females were then
progressively replaced by 50% Chinese F1 females. Meishan and Jiaxing gilts born in France
were also inseminated by Large White boars, and various F1 types used to produce 25%Chinese
pigs.
Sows were kept in an open-front building in close proximity to boars for about four weeks
after mating in order to confirm pregnancy. Females were than moved to pasture lots until the last
week of gestation and fed 1.6 to 2.2 kg of concentrates (15.5% crude protein and 3100 Kcal
DE/kg), plus 3 to 4 kg of forage, per day. Suckling pigs had free access to a commercial ration
after five days of age, and pigs were weaned at 29 to 30 days of age.
Despite the narrow genetic base, French results have been in general agreement with
expectations based upon reports from China. Purebred Meishan and Jiaxing females averaged 16
and 20 teats, and 81 and 91 days of age at puberty, respectively. F1 Meishan (x Large White or
French Landrace) and F1 Jiaxing females averaged 15 and 17 teats, and reached puberty at 87 and
93 days of age, respectively (Legault et al., 1984).
There are also a number of areas in which Clfinesepigs are reported to differ behaviorally
from domestic pigs (Mormede et al., 1984). For example, it appears that Chinese pigs axe very
docile (Rombauts et al., 1982), possibly reflecting differences in social behavior associated with
the large litter sizes pigs are reared in.
The Meishan, F1 Meishan (x Large White or French Landrace) and F1 Jiaxing breed groups
in France proved to be highly prolific (Table 1). Purebred Jiaxings were not, probably because
foundation animals were related. Excluding Jinhua crosses, F1 Chinese dams weaned an average
of 13 pigs per litter, 41% more pigs than purebred European dams. Litter weight at 21 days was
larger for F1 Meishan and Ft Jiaxing females than for other breed groups, while Large White and
French Landrace sows consumed 40 to 60 kg more concentrates during lactation than 1/4-Chinese
and Meishan femalesproducing equivalent 21 day litter weights.
87
Table I.
Litter size and weight and lactation feed intake for purebred Chinese, I/2-Chinese, 1/4Chinese, and purebred European sows a
Genetic
No. of
Litter size
Liner weight (kg_
Lactation
type of
litters
Total
Born
At
At 21
feed intake
the damb
(sows)
born
alive
birth
days
(kg)C
MS
115 (35)
14.9d
14.0d
13.1d
16.2d
57.3 d
101.1 d
JX
86 (29)
11.6e
10.8e
10.0e
9.5 e
38.5 e
85.4 e
LW, FL
42 (22)
10.7e
10.2e
9.2 e
14.7 d
56.8 d
161.8f
1/2-MS
107 (42)
15.3d
14.5d
12.8d
19.3 f
67.8 f
130.0g
1/2-JX
68 (29)
15.2 d
14.7d
13.2d
15.8 d
64.5 f
130.7g
1/4-Chinese 63 (24)
11.5e
a From Legault et al. (1984).
10.8e
9.9 e
15.6 d
57.6 d
118.7h
Weanedc
b MS = Meishan, JX = Jiaxing, LW = Large White, FL = French Landrace, 1/2-MS =
MS x (LW and FL), 1/2-JX = JX x (LW and FL), 1/4-Chinese = LW x (1/2 MS or 1/2 JR).
e 3Oday lactation, concentrate feeding.
d,e,f,g,h Means within the same column with different letters differ significantly (P<.05).
Crossing the Meishan and Jiaxing breeds with Large White and French Landrace pigs thus
produced females that reached puberty around three months of age, consumed less feed during
lactation and weaned heavier litters than European purebreds, and weaned 5 to 8 extra pigs per sow
per year. Unfortunately F1 European crosses, which would have provided a more meaningful
control, were not included in the study.
While the reproductive advantage of certain Chinese breeds of swine is clear, these breeds are
highly unfavorable for lean tissue growth and carcass composition.
Growth rate and feed
efficiency were poor in 1/4-Chinese pigs relative to European controls (Table 2). Ham, loin and
estimated lean were significantly lower, and fat measures higher, in 1/4-Chinese pigs (Legault et
aL, 1985). Estimated differences in carcass lean content are even likely to be biased downwards as
prediction
equations
used were based upon European
pigs (Sellier
and Legault,
1986).
Reflectance, water retention capacity and pH were better, in general, in 1/4-Chinese carcasses, as
reflected by the slightly higher meat qualityindex scores.
88
Table 2.
Growth and carcass traits in 1/4-Chinese and control European slaughter pigs a
Trait
1/4-MS
No. animals (dams)
317 (31)
Average daily gain, 26-100 kg, kg/d
Feed-to-gain ratio
.790e
3.63 e
Genetic tTpeb
1/4-JX
306 (20)
.754d
3.74 c
Control
85 (22)
.818 e
3.40 d
Dressing percent
77.9 e
78.4d
78.3 cd
Carcass length, cm
95.8 c
97.9 d
97.0 d
31.1 c
27.3 c
29.9 d
25.6 d
27.8 e
25.1 d
Back:fat thickness,
mm
rump
back
Ham weight, kg
8.39 c
8.28 d
8.86 e
Loin weight, kg
10.47 c
10 54c
11.20 d
Shoulder weight, kg
5.59 c
5.60 c
5.51 e
Belly weight, kg
4.32 e
4.39 d
4.23 c
Estimated percent lean
45.6 e
45.1 e
49.1 d
Meat quality hadex
86.3 c
86.1 e
85.8 e
a From Legault et al. (1985).
b All sired by Belgian Landrace boars, sows MS = Meishan, JX = Jiaxing, Control = French
Land_race-LargeWhite.
e,d,e Means within the same row with different letters differ significantly (P<.05).
While 1/4-Chinese pigs grew at an acceptable rate in the French study, their feed efficiency,
dressing percentage, carcass, composition and carcass grade were not competitive with the 100%
European three-breed cross pigs. In fact, the cost savings associated with producing the 1/4Chinese pig were cancelled out by poorer feed conversion and the penalty imposed under the EEC
carcass grading system (Legault eta/., 1985).
Evaluation of 1/2- and 1/4-Chinese sows was subsequently carried out under field conditions
in France (Bruel et al., 1986; Gueblez et al., 1986, 1987). Gueblez et a1.(1987) summarized
reproductive data from Meishan x Large White and 1/4-Meishan 3/4 Large-White sows used in 65
commercial herds, with contemporary Large White x French l.andrace sows as controls (Table 3).
The 1/2-Meishan sows weaned 26.4 pigs / sow / year, vs control sows with 21.0 pigs / sow /
year, a 26% advantage.
than controls.
The 1/4-Meishan sows averaged 22.6 pigs / sow / year, only 8% more
89
Within-sire comparisons for production traits of 1/4--Chinese, 1/8-Chinese, and crossbred
European control pigs were conducted at central test stations (Table 3). Growth rote and feed-togain ratio were poorer for the 1/4-Chinese pigs than for controls, but differences were not
significant.
Differences in carcass merit were highly significant, however, with 4.2% less lean
tissue for 1/4.-Chinese pigs, and 2.5% less for 1/8-Chinese pigs. Gueblez et al. (1987) concluded
that the increase in sow productivity was insufficient to compensate for the poorer carcass merit of
the offspring.
Table3. Results
ofa field
evaluation
of crossbred
LargeWhite - Meishansows and central
performance
testing
ofprogeny
a
Trait
1/2MS
Control
1/4MS
Control
No. sows
234
-
219
3,183
No. litters
662
-
477
7,098
Litter size born
13.9
-
11.8
11.0
Litter
sizebornalive
13.2
-
11.2
10.3
Litter size weaned
10.8
-
9.4
9.0
7.9
-
9.0
14.1
Pigs weaned / sow / year
26.4
-
22.6
21.0
No. pigs b
No. sires c
76
36
77
36
101
54
100
54
836
858
825*
852
Weading to rebreeding interval, d
Average daily gain, g/d
Feed-to-gain ratio
3.07
3.00
2.98
2.94
Dressing percent
71.1"*
71.8
72.3**
72.9
Carcass lean, %
49.4**
53.6
51.7"*
54.2
Meat ualitv index
10.7"
9.9
10.3
10.6
a after Gueblez et al. (1987); 1/2 MS = Large Whim x Meishan; Control = Large White x French
Landrace; single control for prolificacy means.
b Pigs produced by part Chinese sows are 1/4 or 1/8 Meishan.
c Part Chinese and control pigs sired by the same European boars.
* Part Meishan and control means differ (P<.05).
** Part Meishan and control means differ (P<.01).
90
Recent studies have found maternal heterosis for Meishan x Large White crosses to be 20%
for number born alive and number weaned, very high when compared to the 6 to 10% typical for
occidental
breed crosses
(Bidanel,
1988, Bidanel et al. 1989b).
Individual
heterosis (not
significant for Utter size born) was 17%, and maternal heterosis 34%, for 21-day litter weight in
this study.
Individual heterosis for post'weaning average daily gain was 23%, and maternal
heterosis 5% (Bidanel, 1988, Bidanel et al. 1989a).
Large White - Meishan breed differences for prolificacy were largely maternal.
Twenty-
seven Meishan dams with Large White sired fetuses had 14.9 pigs a Utter, whereas 11 Large White
dams with Meishan x Large White fetuses averaged 11.4 pigs a litter, for instance (Bidanel et al.
1989b).
Breed differences (Large White - Meishan) for growth traits of approximately
200 g
average daily gain, -.9 feed-to-gain ratio, 4% for dressing percentage, and 15% for carcass lean
content were largely direct in origin (Bidanel, 1988).
Reproductive
Physiology
The basis for large litters in certain Chinese breeds is not completely understood. Research at
the University of Rlinois with domestic breeds has found that, for number of ovulations from 3 to
18, and number of fetuses from 2 to 13, ovulation rate and number of fetuses are highly correlated.
When the number of fetuses exceeds 13, fetal number is not at all correlated with number of
ovulations, but is highly correlated with length of the uterus (Wu et al., 1987). This corroborates
earlier work that found that each uterine horn could successfully support about seven fetuses to
term (Dziuk, 1968; 1985; Webel and Dziuk, 1974).
Research on the growth of the uterus (Wu and Dziuk, 1988a, b; Wu et al., 1988) has found
variation in length between female swine. Length before puberty is highly correlated with length
after puberty and during pregnancy.
Uterine length is positively correlated with number of live
fetuses (Wu et a/., 1987), and negatively correlated with number of mummified fetuses (Wu et al.,
1988).
Rombauts
et al. (1982) reported estrous cycle length as ranging from 19 to 21 days in
Chinese and F1 Large White x French Land_race gilts, similar to that usually found in European
breeds (not included as experimental controls). Ovulation rates of 15 and 16 for five Meishan and
six Jiaxing females (Rombauts et al., 1982) were similar to rates of 14 to 15 reported for Large
.White and Landrace females (Legault and Gruand, 1981).
Bolet et al. (1986) reported that larger litters in Meishan vs Large White sows were
associated with lower embryonic mortality, while ovulation rates were similar for the two breeds.
91
This, however,
was not the case for highly
selected
'hyperprolific'
Large White
sows.
Hyperprolifics had a higher ovulation rate and embryonic mortality (Table 4), suggesting genetic
differences between Chinese and Large White sows might be due to genes not present in the Large
White.
Table 4.
Comparison of Meishan, Large White and "nyperprolific' Large White sows for Utter
size born (LSB), ovulation rate (OR) and embryonic mortality rate (EMR) a
No. ofsows
Genetic
typcb
LSB
OR
EMR
MS
16
17
LW
20
'hyperprolific' LW
25
Mean ± standard
error
LSB
OR
EMR (%)
16
15.7 ± 1.5
17.2 ± 1.2
16 + 9
15
13
12.1 ± 1.1
17.6 ± 0.8
26 ± 7
18
17
13.1 + 1.3
22.9 + 1.0
41 ± 7
a From Bolet et aL (1986).
b MS = Meishan, LW = Large White.
Wu et al. (1987) proposed that uterine length is the key factor determining prenatal mortality
in swine, and that differences in uterine capacity account for differences in prolificacy between
Taihu and occidental sows. Bazer et al. (1987, 1988), however, reported a lower ovulation rate
(14.9 vs 16.29)and shorter uteri (199 vs 281 cm) for Meishan vs Large White gilts. Nevertheless,
conceptus survival was greater in the Meishan gilts, and associated with more rapid and uniform
development between days 8 and 20 of gestation, suggesting that factors regulating conceptus
development may determine prolificacy in swine.
Contrary to the French results, preliminary findings from the U.K. suggest higher ovulation
rates for Meishan (18.7) than for Large White (15.2) gilts (Haley, 1988). Clearly additional
research is necessary before the physiological mechanism of prolificacy in the Taihu sow can be
said to be understood.
numbers
The narrow genetic base in the French lines, and the generally small
of animals used in experiments,
experimental results so obtained.
suggest the need for cautious
interpretation
of
92
Molecular
Genetics
Preliminary studies conducted in France on different breeds of domestic and Chinese pigs
suggest that some genes associated with growth, development, ovulation rate and litter size are
closely linked to the swine major histocompatibility (the SLA, for swine leukocyte antigen)
complex (Rothschild et aL, 1987; Vaiman et aL, 1988). Researchers at Illinois and Iowa plan to
investigate SLA polymorphism and its association with with disease and production waits in the
Chinese pigs (L. B. Schook, M. F. Rothschild, personal communication).
Marker assisted selection to improve rate of genetic improvement is not a new concept, but
our present rudimentary knowledge concerning the swine genome (see Fries and Ruddle, 1986)
precludes application at this time. Use of DNA restriction fragment length polymorphism (RFLP)
and variable number tandem repeat (VNTR) markers to map the genome of livestock species
appears promising, and will help characterize genetic differences between Chinese and occidental
breeds at the molecular level.
The possibility exists that a major gene or genes may be largely responsible for the high
prolificacy of the Taihu breeds (Sellier and Legault, 1986). If found to be the case, this would
present exciting possibilities for the development of hyperprolifie transgenic strains in the furore.
In addition, there are suggestions that Chinese pigs may be resistant to certain strains of E. Coli
(Chappuis et aL, 1985). Such resistance is probably the result of a single gene that might be
incorporated into transgenies. Chinese or part-Chinese lines transgenie for a gene or genes of the
somatotropin releasing factor / somatotropin / insulin-like growth factor system might also be
possible in the future.
Other Research Groups
Albania, Great Britain, Hungary, Japan, Korea and Thailand have all imported Taihu pi_
from China (Wong, 1986). Jiaxing semen from the INRA (French) population was introduced
into Spain and F1 litters from Iberian sows produced in 1985 (Dobao et al., 1986, 1988). Ten
Taihu pigs were exported from the Peoples' Republic of China to Japan in 1986. Twenty-nine
Chinese pigs from France went to Wageningen, the Netherlands, in 1987 (Van der Steen, 1988).
Great-Britain imported 21 Meishan gilts and 11 Meishan boars from China in 1987. This,
and the U.S. importation, represent the only two western samples of this Chinese germplasm to
date with sufficient unrelated founders to provide acceptable genetic diversity in closed "nucleus"
lines. At least one additional U.S. population appears likely to become established in the furore. A
93
notice concerning
importation
of Chinese semen to the U.S. by a swine breeding company
(Dekalb) appeared in the Federal Register recently (Glosser, 1989).
The U.K. research program is funded in part by five breeding companies (Haley, 1988),
who will presumably have certain fights regarding commercial use of the germplasm. Although
the Illinois / Iowa / ARS project does not have corporate support at present, that might become a
logical component as the project develops, particularly ff results indicate applicability
to the
industry. Breeding companies, unlike experiment stations, have the infra-structure required to
multiply and disseminate genetic improvement to the commercial producer.
Implications
for U.S. Pork Production
While performance data obtained overseas has been helpful in assessing which Chinese
breeds are of interest, the possibility of genotype x environment interactions, and the extremely
narrow genetic base in the French lines, prohibit generalization of findings. Thorough evaluation
of pure and crossbred Chinese pigs under U.S. production conditions
assess their potential contribution
is essential in order to
to the U.S. pork industry and to develop optimal utilization
strategies. Scientists at the three institutions importing live animals expect to spend at least five
years evaluating the Chinese pigs before any germplasm is released to the industry.
Litter size is of major economic importance to commercial
pork producers.
Improving
numerical productivity (pigs weaned / sow / year) would reduce the number of breeding females
required to produce a given output. While variable costs may increase somewhat as numerical
productivity increases, fixed costs would be spread over a larger number of animals. In addition,
earlier maturity would reduce generation interval and increase the number of pigs produced per
female per year of presence in the breeding herd.
It has been estimated that increasing the number of pigs weaned per litter from 8 to 11 would
decrease the cost of producing a 40 lb pig from $34 to $25 (Stevermer et al., 1980). The potential
impact of increased litter size on cost of pork production is clear.
The need to increase efficiency of production of lean pork is one of the greatest challenges
facing the U.S. swine industry today. Although per capita meat consumption has increased rapidly
since the 1950s, pork consumption has remained relatively static. Poultry consumption, about half
that of pork in the late 1950s, increased to equal that of pork in the early 1980s. Expressing pork
price and consumption relative to that of poultry (Figure 2), the trend to consume less pork as the
price increased is clear. Increasing efficiency of production will result in greater short-term profits,
stimulating over-production and ultimately lower prices. If, however, pork prices can be reduced
94
while maintaining quality and profitability, we can expect increased demand for U.S. pork both at
home and on world markets.
_0
50
1955
1960
1965
1970
1975
1980
1985
1990
Year
Figure 2.
Pork price and consumption, relative to fryers and all poultry, respectively.
(Sources: USDAAgriculturalOutlook,LivestockandPoultrySituationand OutlookReport,
WorldAgric.SupplyandDemandEstimate.s;1988estimated,1989projected).
For the pork industry to remain competitive with poultry will require the production and
marketing of both new and traditional lean products, with acceptable muscling and palatability, at
competitive
prices.
In the present climate of uncertain consumer demand and low prices for
livestock products, increased efficiency of pork production is vital to the continued welfare of the
industry, for it is only by becoming more efficient that pork prices can be held down.
Whereas the Taihu and Min breeds offer great promise for increasing sow productivity, they
grow more slowly, convert feed less efficiently, and have carcasses with less lean and more fat
than domestic U.S. breeds. Fortunately, selection for lean growth has been shown to be effective
in swine (Hetzer and Miller, 1973; MitcheU eta/., 1982; Ollivier, 1986), and it should be possible
to select for improved lean content and feed efficiency while maintaining prolificacy in "composite"
American-Chinese
populations.
Expected rates of annual selection response for traits such as
backfat and carcass lean in pigs are approximately 2% of the population mean (Fletzer and Miller,
1973; Smith, 1984). It should, therefore, be possible to increase carcass lean in a half-Chinese
95
line from an initial mean of perhaps 46% to 55% within 10 years. Early sexual maturity might also
allow a generation interval of less then a year, accelerating genetic progress.
We are also living in an age of rapidly changing technology, and the impact of so-called
repartitioning agents (porcine somatotropin (PST); 13-adrenergic agonists) on pan-Chinese hogs
may make the excessive famess of the prolific breeds less critical. Whether there are genotype x
treatment interactions for lean and obese genotypes is unknown.
Experiments treating different
lines of rats and mice with the [3-agonist elenbuterol (Berne et al., 1985; Eisen et al., 1988) have
suggested such interactions might be importang and Kanis er al. (1988) reported that PST had the
greatest effect on the fattest genotype ('Duroc, vs Pietrain and Dutch Yorkshire x Landrace pigs).
There is one reported experiment where Chinese pigs were treated with PST (McLaughlin et
al., 1988). The pigs were all of the Beijing Black breed, a composite involving the Berkshire,
Yorkshire and some Chinese breeds (FAO, 1984). While not a hyperprolific breed, it does appear
to be fatter and less efficient at converting feed than breeds used in the U.S. The authors argued
that responses in feed efficiency, growth rate and carcass lean in the Beijing Black were greater
than those published
for U.S. hogs, but as no U.S. pigs were included
in the study any
conclusions regarding genotype x treatment interaction are speculative.
In the absence of grade and yield marketing there is little incentive to produce a leaner, more
muscular, pig than is ctn'rently marketed by most U.S. producers. If the prolificacy of the Chinese
sow Could be incorporated
with no loss in growth or carcass quality over currently produced
market hogs, the improvement
in efficiency
of pork production
(defined as cost per unit of
product)
wouldbe substantial.
Simulated Effectson ProductionEconomics
Bidancl(1988,1989)estimatedgeneticp.arameters
from a crossbreeding
experiment
conducted
atINRA withMeishanandLargeWhitepigs,and simulated
economicefficiency
for
alternative
crossbreeding
systemsinvolving
theMeishanbasedupontheseestimates.
Costsand
returns
fornucleus,
multiplier
and commercialsub-systems
were considered,
aswereselection
effects
ovcrtime,fora systemwith100,000
commercialsowsfarrowing.
Bidanel(1988,1989)concluded,
ashad Lcgaultetal.(1985)and Gueblezetal.(1987)
previously,
thatdirect
useoftheFrenchMeishanwouldnotincrease
efficiency
ofcommercial
pork
production
underEuropeanmarketing
conditions.
The bestmid-termsolution
appeared
tobe the
creation
of,and selection
within,
a 50% Meishancomposite.
Use ofsucha composite
toproduce
96
the dam of commercial sows was expected to become competitive with conventional Large White x
Landrace sows within about five years, and superior after that.
When pork is priced by lean weight (as in France), fatness will dominate the selection index;
yet when pork is priced by live weight (as is the case to a much greater extent in the U.S.),
reproductive
traits dominate
the index (Tess, 1986).
This suggests that relatively
rapid
incorporation of Meishan genes into U.S. commercial herds might improve cost-return ratios.
The swine crossbreeding system simulation model PigCross 1.3© (McLaren et al., 1987)
was used to conduct a preliminary evaluation of alternative crossbreeding
Meishan, Yorkshire, a Meishan-Yorkshire
systems involving
composite, Duroc, Landrace and Hampshire lines.
PigCross 1.3© calculates costs and returns for purebred nucleus, multiplier and commercial subsystems in a 20,000 sow system operating
under mid-western
U.S. economic
conditions.
Minimum individual herd size is 100 sows, and results are presented as system efficiency (lifetime
costs per sow divided by lifetime product per sow, $ / kg pork).
Calculations were based upon input genetic, economic and management parameters. Value
of live weight market hogs was determined using NPPC "pork value" guidelines (NPPC, 1984).
Genetic parameters assumed axe given in Table 5. Breed differences for conception rates were
assumed to be zero. Mean fin'stservice conception rate was assumed to be 69.5%, with maternal
and paternal heterosis of 3.1 and 6.2%, respectively. The same parameters for breeding season
conception rate were assumed to be 88.6, 3.1 and 2.3%, respectively. Paternal heterosis was
assumed zero for all other traits. Recombination effects were assumed zero for all traits.
Results (Table 6) suggest that, for the assumptions made, an unimproved Meishan or a
Meishan-Yorkshire
composite might be competitive with American breeds. Meishan and 50%
Meishan in three-breed rotations faired well, with an increased advantage in three-breed terminal
systems, as would be expected.
These results are not, however, to be considered at all reliable. The genetic parameter values
are at best educated (and possibly poor) guesses. The U.S. research program seeks to estimate
parameters
that will allow evaluation
of the Chinese germplasm.
More detailed
models
incorporating effects of selection will be developed and used to plan breeding strategies in the
l]linois project. Prediction of net effects on production efficiency and comparison of alternative
strategies for incorporating desirable characteristics of the Meishan, Fengjing and Min into the
commercial sow population are required.
,
97
Table 5. Genetic parameter values assumed in the PigCross 1.3© simulation a
Traitb
ParameterC
LSB
SURV, %
Ix
10.53
70.81
gID
gIL
gly
glMs
glMs.v
gltI
- .09 d
.22 d
1.00 d
4.00 d
4.00 d
- 1.00 d
gM D
gML
gMy
gMMs
gMMs.Y
gMa
WWT, g
ADG, g/d
F/G
BF, mm
10,888
650
3.39
32.21
-
.88
5.05
- 4.48
4.71
4.71
0
633
024
-416
-600
-530
633
15
21
11
- 220
110
0
-.25
.10
.03
.60
.30
- .10
- 1.00
.29
1.73
7.00
4.40
- 4.50
- 2.13
1.12
- 2.12
5.00
5.00
-340
478
-332
-450
-400
-3
6
- 1
- 70
- 35
0
0
0
0
0
0
0
0
0
0
o
o
o
o
-34o
hlD,y
hiD,t,
hIv,L
hiD,Ms
hlL,Ms
hIy,Ms
hlD,Ms_Y
hID,H
hIH,L
hlL,Ms.Y
hlH,Ms.Y
hIl-i,p
.10
.20
1.00
.50
.50
1.20
.30
.10
.10
.75
1.00
.20
4.31
5.73
9.88
5.00
5.00
5.00
4.50
4.00
4.00
12.0
4.00
4.00
300
300
300
300
300
300
300
300
300
300
300
300
80
74
55
I00
100
135
90
60
60
60
60
60
hM
I.I
e
5.66
300
0
- .20
- .20
- .20
- .20
- .20
- .20
- .20
- .20
- .20
- .20
- .20
- .20
0
.8
.8
.8
.8
.8
.8
.8
.8
.8
.8
.8
.8
0
a Johnson(1981),
Gianolaetal.(1982),
McLarenetal.(1987),
Bidanel(1989),
andguess-work.
b LSB = litter
sizeborn;SURV = preweaningsurvival;
WWT = weaningweight;ADG =
postweaning
averagedaily
gain;FIG = feed-to-gain
ratio;
BF = average(first
rib,
last
rib,
last
lumbar vertebra) carcass baclcfat thickness.
e _t =fixed constant; gI = direct genetic effects; gM = breed mammal effects.
D, L, Y, Ms, Ms-Y and H suffixes represent the Duroc, Landrace, Yorkshire,
Meishan-Yorkshire composite and Hampshire breeds, respectively.
d gI+gM
e except for hMD2/_s,hMLY_s= 1.7 and hMy_is = 2.3.
Meishan,
98
Table 6. Crossbreeding system efficienciesa
i
System
Pureline
Duroc (19)
Landrace (L)
Ms-Y composite
Hampshire (H)
Yorkshire (Y)
Meishan (Ms)
,
i
$ / k_ porka
.8450
.8489
.8656
.8681
.8832
.9998
3-breed rotation
D, Y-Ms, L
D, Y-Ms, H
D, Y, L
D, L, H
D, L, Ms
Ms-Y, L, H
D, Y, Ms
.7622
.7643
.7676
.7676
.7780
.7728
.7812
3-breed terminal
H x (L x Ms-Y)
H x (D x Ms-Y)
H x (D x L)
D x (L x Ms-Y)
D x (L x Ms)
D x (Y x Ms)
D x (Y x L)
4-breedterminal
.6626
.6673
.7070
.7201
.7499
.7500
.7568
(H x D) x (L x Ms-Y)
(13x L) x (Y x Ms)
(DxY) x (L x Ms)
.6878
.7499
.7510
_brced rotation
D, Ms-Y, L, H
D, Y, L, Ms
.7602
.7706
4-17reedrotaterminal
.
D x H, L, Ms-Y
.7389
D x Y, L, Ms
.7421
H x D, L, Ms-Y
.7434
Calculated assuming genetic parameters given in
Table 5 using the model PigCross 1.3© (McLaren et
al., 1987).
99
Experimentation
It will be necessary to characterize the Chinese pigs as far as possible during the fwst few
years of research in the U.S. Work at the University of Illinois, Iowa State University and the
ARS Meat Animal Research Center, Nebraska (MARC) will be coordinated to an extent, with
common pedigree recording, pooling of data and germplasm exchange, but will take the form of
independent projects at each station.
All three stations will maintain a pure Meishan line, but only Iowa and MARC plan to gradeup to the Fengjing and M.in (M. F. Rothschild
and L. D. Young, personal communication).
Illinois will evaluate Chinese x Yorkshire females, form a composite line and select for lean
growth.
MARC will estimate crossbreeding
parameters
in crosses with Duroc and a white
synthetic line, while Iowa will collaborate with Illinois in molecular genetic research and conduct
its own breed evaluation program, probably with Landrace pigs. Projects across stations will
therefore be comprehensive and complementary, rather than replications of the same experiment.
The Illinois
Chinese
Pig Project
Overall objectives of the planned inter-disciplinary
research involving Chinese pigs at the
University of lllinois are: 1) to study mechanisms of reproduction, growth and disease resistance
in the Meishan breed; 2) to evaluate alternative F1 Chinese x Yorkshire females; 3) to develop a
hyperprolific 50% Chinese - 50% American composite line; and 4) to evaluate direct response to
selection for lean tissue growth rate and feed efficiency, and correlated response in litter size, in
this line.
Most of the scientific evidence indicates litter size to be genetically and phenotypically
tmcorrelated with growth and carcass characteristics
(Brien, 1986). It is still possible, however,
that prolificacy genes in Chinese pigs have unfavorable pleiotropic effects on lean growth traits,
and change in litter size will therefore need to be closely monitored during the selection experiment.
All 22 Illinois Meishan gilts will be bred pure in September, 1989, to establish the population
at the University of Illinois Imported Swine Research Facility. The Meishan herd will be expanded
to 30 sows and maintained
thereafter as a genetic resource.
A frozen semen bank will be
established from foundation
boars of the three Chinese breeds, replicated across experiment
stations.
Determining the extent to which number of ovulations and uterine length contribute to the
prolificacy of these pigs is clearly a research priority. Number of ovulations and uterine length will
i00
be determined surgically on the Meishan females post-mating, and number of fetuses counted by
laparotomy at approximately 45 days of gestation. The first litters will be farrowed in January,
1990, and age at puberty will be determined in male and female offspring using non-invasive
techniques.
Growth and reproduction of purebred Meishan pigs will be compared for conventional cornsoybean diets vs high-fiber diets traditionally fed in China. Growing-finishing pigs will be treated
with repartitioning agents as availability of compounds and pigs allows. Feeding trials will be
conducted with purebred Meishan and Yorkshire control pigs to estimate potential rates of fat and
protein deposition, to identify the effect of genotype on gut capacity and feed intake, and to identify
the effect of genotype on the relationship between protein deposition and energy intake.
Metabolic characteristics (lipid and glucose metabolism in vivo) will be assessed in purebred
Meishan barrows and Yorkshire control pigs. Approximately 50 Meishan barrows and 50 gilts,
and an equal number of control pigs, will be slaughtered at 105 kg live weight to obtain carcass
data. Sensory (taste panel) evaluation of the meat will also be conducted.
Early puberty and high reproductive
development
rates suggest differences
and behavior of Chinese pigs.
behavior, including teat order development
are likely in the sexual
Behavioral studies will investigate
farrowing
and maintenance, docility of Chinese pigs in man-
animal interactions and investigation of the development of such behavior and evaluate sexual and
social development and behavior of Chinese pigs and crosses.
The second generation of pigs will be produced by mating Meishan, Fengjing, Min and
Yorkshire boars to Meishan and Yorkshire females (Table 7). Pigs will be bred in February,
1990, and will fan'ow in June, 1990. Semen from 10 'unrelated' Yorkshire / Large White sires,
selected for lean growth, will be used. Sample barrows will be slaughtered for carcass evaluation.
Table7. Generation
2: Producing
F1 Chinesegilts
(numberoflitters)
Breed of sire
Breed of dam
Meishan
Yorkshire
Meishan
10
I0
Yorkshire
10
Fen_in[_
-
Nfin
-
I0
I0
I0
I
i01
Matings to produce the third generation will take place in December, 1990, and litters will
farrow in April 1991 (Table 8).
Table 8. Generation 3: Evaluation of sow productivity of F1 Chinese sows (number of litters)
Breed of sire
Breed of dam
Meishan
York x Meishan
30
....
York x Meishan
-
10
10
10
York x Fengiing
York x Min
---
10
10
10
10
10
10
Meishan
York x Fen_ing
York x Min
Selection of 1/2-Chinese lines to incorporate into a composite line, based upon reproductive,
growth and carcass performance, will then take place. Two generations of random mating will be
conducted prior to commencing selection for lean tissue growth rate and feed efficiency.
from the basepopulation
Semen
will be frozen and:stored. Selection based upon individual and family
_information, and upon informative genetic markers as they become available, will be practiced,
with avoidance ofclose inbreeding.
The Yorkshire breed has been selected for inclusion in the composite for a number of
reasons. The Yorkshire is the numericaUy dominant 'maternal' breed in the U.S., and as such is
probably the most relevant purebred control against which to compare the Meishan. The relatively
large number of Yorkshire breeders should also facilitate identification
genetic and health requirements.
of farms that meet our
In addition, we feel it is critical that the breed used in developing
the composite line be free of the stress syndrome gene, otherwise selection for lean growth will
inevitably result in a line of stress susceptible pigs. This precludes use of the Landrace breed
(Webb et al., 1982). Lastly, research in French suggests excellent combining ability between the
Meishan and Large White {Bidanel, 1988; Bidanel et al., 1989b). While the same may be true for
crosses between the Meishan and other occidental breeds, this has yet to be demonstrated.
Evaluation of composite performance to produce 1/4-Chinese market hogs will be carried out
by top-crossing litter mate gilts to, e.g., Hampshire, Duroc, and possibly "exotic" (French or
German Pietrain, Belgian Landrace) breeds of terminal sire.
Evaluation of 1/4-Chinese dams
producing 1/8-Chinese market hogs will be conducted as deemed necessary.
102
Conservation
Chinese breeds of swine represent a reservoir of diverse genetic material, some of which has
promise for utilization in U.S. pork production systems. The University of Illinois, Iowa State
University and the ARS-USDA will cooperate in managing the U.S. Chinese swine genetic
resource by maintaining replicated semen banks and cooperating in recording of pedigrees. Given
uncertainty
regarding
future conditions
of production
and marketing,
and the increasing
dependence internationally on fewer and fewer breeds as pork production becomes more intensive,
it seems reasonable that efforts should be made to conserve existing breeds that may be of some
value in the future.
Many occidental pig breeds have already been lost, but with the formation of new breeds,
and national varieties of breeds evolving into distinct types, there is little danger of a disastrous
loss of genetic variability in pig populations (Irdng, 1986). Rendel (1984) estimated that livestock
industries would be secure (from a genetic point of view) if no industry relied on less than five
staple breeds, each with an effective population size equivalent to a rate of inbreeding of no more
than 0.3% a generation.
Land (1986) agreed that large scale conservation of livestock breeds should not be necessary
to maintain genetic variability, and would probably be ineffective as an aid to genetic improvement
as it is unlikely that adequate resources would be provided for the evaluation of populations even if
they were conserved.
There is, however, an emotive case for conservation,
and Land (1986)
suggested that this provides breeders with the opportunity to conserve breeds with potentially
useful characteristics and to use them to develop populations for specific purposes and possible
future requirements.
Smith (1986) has argued the need for developing a variety of breeding stocks for different
sets of objectives to provide for flexibility in the future. Importation of exotic Chinese germplasm
to the U.S. will fulfill both basic and applied research objectives aimed at increasing prolificacy in
commercial sows in the U.S. in the year 2000, and the long-term possibility of transgenics makes
these hyperprolific pigs a valuable genetic resource.
Conclusions
The need to increase efficiency of production of lean pork is one of the greatest challenges
facing the swine industry today. Chinese breeds of swine offer a valuable resource with which to
both increase prolificacy in the national swine breeding population, and conduct basic research
concerning biology of the pig. Using the Chinese pig as a research model will help us better
103
understand porcine reproduction and growth, knowledge that might then bc applied to improving
thepcrformancc ofAmericanbreeds.
Scientists
attheUniversity
ofIllinois,
Iowa StateUniversity,
and theARS-Mcat Animal
ResearchCenter,Nebraska,anticipate
theirresearchwith prolific
Chinesepigswillyield
knowledgeand genesthatwillimprovelitter
sizeand thusefficiency
ofU.S.porkproduction.
If
theprolificacy
oftheChinesesow couldbcincorporated
withno lossingrowthorcarcass
quality
overcurrently
producedmarkethogs,theimprovementinefficiency
ofporkproduction
wouldbc
substantial.
104
Literature
Cited
Bazer, F. W., W. W. Thatcher, F. M. Botte and M. Terqui. 1987. Conceptus and uterine
development in Large White (LVO and prolific Chinese Meishan (MS) gilts. J. Anita. Sci.
65 (Suppl. 1): 381 (abstr.).
Bazer, F. W., W. W. Thatcher, F. M. Botte and M. Terqui. 1988. Sexual maturation and
morphological development in Large White and prolific Chinese Meishan pigs. J. Reprod.
Fert. 83: 723-728.
Berne, R. S., J. Novakofski and P. J. Bechtel. 1985. Effects of the 13-agonist clenbuterol on
body and tissue weights in four strains of rats. J. Anita. Sci. 61(Suppl.1): 256 (Abstr.).
Bidanel, J.P. 1988. Bases zootechniques et ggngtiques de l'utilisation en 61evage intensif des
races prolifiques Chinoises - cas du pore Meishan. Th_se pr6sent6e _ rInstitut National
Agronomique Paris-Grignon.
Bidanel, J. P. 1989. Etude de strat6gies de valorisation en croisement de la race porcine Meishan.
3. Evaluation compar6e de diff6rents syst_mes de croisement. Journ_es Rech. Porcine en
France 21: 361-366.
Bidanel, L P., J. C. Caritez, J. Heury, J. Gruand and C. Legault. 1989a. Etude de strat6gies de
valorisation en croisement de la race porcine Meishan. 2. Estimation des param&res du
eroisement pour les earact_res de production. Journ6es Rech. Porcine en France 21: 353360.
Bidanel, L P., J. C. Caritez and C. Legault. 1989b. Etude de stratdgies de valorisation en
croisement de la race porcine Meishan. 1. Estimation des param&res du croisement pour les
caract&res de productivit6 des truies. Journ6es Rech. Porcine en France 21: 345-352.
Bolet, G., F. Martinat-Botte, A. LocateUi, J. Gruand, M. Terqui and F. Berthelot.
1986.
Components of prolificacy in hyperprolific Large White sows compared with the Meishan
and Large White breeds. G6n&. $61. Evol. 18: 333-342.
Brien, F.D. 1986. A review of the genetic and physiological relationships between growth and
reproduction in mammals. Anita. Breed. Abstr. 54: 975-997.
Briggs, H. M. and D. M Briggs.
Co., Inc., New York, NY
1980. Modem Breeds of Livestock.
4th Ed. MacmiUian Pub.
Bruel, L., J. Boulard, D. Brault, J. C. Caritez, Y. Houix, B. Jacquet, G. Le Henaff, C.
Perrocheau, J. P. Hunavot, J. L. Vrillon and C. Legault. 1986. Evaluation des croisements
Sino-Europ6ens dam les 61evages Franqals. Premier r_sultats obtenus darts la r6gion PoitouCharentes. Journ6es Rech. Porcine en France 18: 277-284.
Chappuis, J. P., Y. Duval-Iflah, 1L Ducluzeau and P. Raibaud. 1985. Resistance of gnotobiotic
Large White and Chinese piglets to in-vivo attachment of a K88ab enterotoxigenic
Escherichia coli strain. Reprod. Nutr. D6velop. 25(1A): 49-60.
Chen Runsheng.
45-48.
1986. Pig production in People's Republic of China. Pig News and Info. 7(1):
105
Chen Runsheng. 1987. Development of the Sanjiang White breed of pigs. Pig News and Info.
8(3): 309-313.
Cheng Peilieu. 1983. The animal genetic resources of China and the possibility of establishing
data banks. In: Animal genetic resources: Conservation by management, data banks and
training. FAO A/tim. Prod. Health Paper 44/1: 137-141.
Cheng Peilieu. 1983. A highly prolific pig breed of China - The Taihu pig. Parts I and II. Pig
News and Into. 4(4): 407-425.
Cheng Peilieu. 1984a. A highly prolific pig breed of China - The Taihu pig. Parts 11/and IV.
Pig News and Info. 5(1): 13-18.
Cheng Peilieu. 1984b. Livestock breeds of China. FAO Anita. Prod. Health Paper 46: 159-169.
Cheng Peilieu. 1985. China pig breeds. World Anita. Rev. 56: 33-39.
Dobao, M. T., J. Rodrig/tfiez, L. Sill6, M. A. Toro and C. Legault. 1986. Preliminary results of
crosses between Jiaxing and Iberian breeds of pigs. 37th Ann. Meet. Europ. Assoc. Anita.
Prod., Budapest, Hungary, Sept. 1-4.
Dobao, M. T., J. Rodrigftfiez, L. Sili6 and M. A. Tom. 1988. Mejora de la prolificidad de cerdos
Ibericos mediante cruzamiento con la raza Jiaxing.
Proc. I Congreso Monografico
International "Mejora Genetica del Ganado Porcino", Lorca, Spain. 1: C1-C3.
'
:
Dziuk, P. L 1968. Effect of number of embryos and uterine space on embryo survival in the pig.
J. Anita. Sci. 27: 673-676.
Dziuk, P.J. 1985. Effect of migration, distribution and spacing of pig embryos on pregnancy
and fetal survival. J. Repro. Fert., Suppl. 33: 57-63.
Eisen, E. J., W. J. Croom, Jr. and S. W. Helton. 1988. Differential response to the 13-adrenergic
agonist cimaterol in mice selected for rapid gain and unselected controls. J. Anita. Sci. 66:
361-371.
Epstein, H. 1969. Domestic Animals of China.
Royal, England.
Commonwealth
Agric. Bureaux, Farnham
Epstein, H. and M. Bichard. 1984. Pig. In: Mason, I. L. (Ed.). Evolution of Domesticated
Animals. Longman, N.Y.
FAO. 1987. FAO Production Yearbook.
the United Nations, Rome, Italy.
1986. Vol. 40. Food and Agriculture Organization of
Fries, R. and F. H. Ruddle. 1986. Gene mapping in domestic animals. In: St. John, J. (Ed.).
10th BeltsviUe Syrup. Agric. Research: Biotechnology for solving agricultural problems,
Vol. 10.
Gianola, D., C. Legault and L C. Caritez. 1982. Evaluation of Chinese swine germplasm in
France: Preliminary results. Proc. Univ. 111.Pork Industry Conf., Dee. 2-3, UrbanaChampaign. pp. 39-55.
Glodek, P. 1982. Selection responses in pigs: Results and implications.
Congr. on Genet. Appl. to Livest. Prod., Madrid, Spain. V: 568-577.
Proe. 2nd World
106
Glosser, J. W. 1989. Importation of porcine semen from China.
12639-12642.
Federal Register 54(58):
Gueblez, R., L. Bruel and C. Legault. 1987. Evaluation des croisements Sino-Europtens en
conditions de terrain en France: Bilan gtntral. Journtes Rech. Porcine en France 19: 25-32.
Gueblez, R., C. Legault, L. Bruel and G. Le Henaff. 1986. Reproduction and production results
of crossbred Chinese pigs under field conditions in France. 37th Ann. Meet. Europ. Assoc.
Anita. Prod., Budapest, Hungary, Sept. 1-4.
Haley, C. 1988. Chinese pigs: Research starting to give results. Pig Farming Suppl. Dec: 2728.
Haley, C. S., E. Avalos and C. Smith. 1988. Selection for litter size in the pig. Anita. Breed.
Abstr. 56(5): 317-332.
Hetzer, H. O. and L. R. Miller. 1973. Selection for high and low fatness in swine: Correlated
responses of various carcass gaits. J. Anita. Sci. 37: 1289-1301.
Jiang Zhihua, Ge Yunshan and Zhang Jian. 1988. Crossbreeding of pigs - its development and
experimantal results in China. Pig News and Into. 9(3): 257-263.
Johnson, R. K. 1981. Crossbreeding in swine: Experimental results.
923.
J. Anita. Sci. 52: 906-
Kanis, E., IC H. de Greef, W. van der Hel, J. Huisman, R.D. Politick, M.W.A. Verstegen, P.
van der Wal and E.J. van Weerden. 1988. Interactions of recombinant porcine somatotropin
(rPST) treatment with genotype and slaughter weight for production traits of growing pigs.
J. Anita. Sci. 66 (Suppl. 1): 296 (Abstr.).
King, J. W.B.
1986. Introduction and commentary to plenary session IId: Evaluation and
utilization of breed resources: Swine. 3rd World Congr. Genet. Appl. Livest. Prod.,
Lincoln, NE. X: 23-25.
Land, R.B.
1986. Genetic resource requirements under favorable production marketing
systems: Priorities and organisation.
3rd World Congr. Genet. Appl. Livest. Prod.,
Lincoln, NE. XII: 486-491.
Legault, C. 1978. Analyse des composantes
Zootech. 27: 457.
de la productivite numerique des truiles.
Ann.
Legault, C. 1983. Reproductive performance of Chinese pigs in pure and crossbreeding.
Natnl. Swine Improvement Fedn. Meet., Dec. 4-6, St. Louis. pp. 45-50.
Proc.
Legault, C. 1985. Selection of breeds, strains and individual pigs for prolificacy.
Fert. Suppl. 33: 151-166.
J. Reprod.
Legault, C. et J. C. Caritez. 1983. L'exptrimentation sure le pore chinois en France. 1.
Performances de reproduction en race pure et en croisement. Gtn&. S6l. Evol. 15: 225-240.
Legault, C., J. C. Caritez, J. Gruand et L P. Bidanel. 1984. Le point de l'exptrimentation sure
les races chinoises en France: Reproduction et production. Joumtes Rech. Porcine en
France. 16: 481-494.
107
Legault, C., J. C. Caritez, I. Gruand et P. Sellier. 1982. Premier bilan de l'exptrimentation sure
le pore chinois en France. 3. Croissanee et composition corporelle en croisement _tdeux ou
trois voies, lourntes Reeh. Porcine en France. 14: 143-150.
Legault, C. et J. Gruand. 1981. Effects additifs et non additifs des genes sur la preeocite
sexuelle, le taux d'ovulation et la mortalite embryonnaire ehez la jeune truie, lourntes de la
Recherche Porcine en France 13: 247-253.
Legault, C., P. Sellier, J. C. Caritez, P. Dando et J. Gruand. 1985. L'experimentation sure le
pore ehinois en France. 1I. Performances de production en croisement avee les races
europeennes. Gtn6t. S6I. Evol. 17: 133-152.
Mason, I. L. 1969. A World Dictionary of Livestock Breeds, Types and Varieties.
Commonwealth Agricultural Bureaux, England.
2nd Edn.
McLaren, D. G., D. S. Buchanan and J. E. Williams. 1987. Economic evaluation of alternative
crossbreeding systems involving four breeds of swine. 1. The simulation model. J. Anita.
Sci. 65: 910-918.
McLaughlin, C. L., C. A. Bate, Qi Shun-Zhang, Wang Lian-Chun and Xie Jin-Pu.
1989.
Responses of Beijing Black hogs to porcine somatotropin. L Anita. SCI. 67:116-127.
Morm&ie, P., R. Dantzer, R. M. Bluthe et J. C. Caritez. 1984. Differences in adaptive abilities
of three breeds of Chinese Pigs. Behavioral and neuroendocrine studies. Gtn&. $61. Evol.
16: 85-102.
Noguera, L L. and C. Legault. 1984. Trends in productivity of sows during the last 10 years in
France. Pig News and Info. 5(3): 205-212.
NPPC. 1984. The Pork Value Approach - Paying for Value. National Pork Producers Council,
Des Moines, IA.
Ollivier, L. 1986. Results of a long-term selection experiment for lean tissue growth in the pig.
3rd World Congr. Genet. Appl. Livest. Prod., Lincoln, NE. XII: 168-180.
Ollivier, L. 1988. Future breeding programmes in pigs. In: Advances in animal breeding. Proc.
Syrup. honour 1L D. Politick, 11-14 Sept., Pudoc, Wageningen. pp. 90-106.
Phillips, R. W. and T. Y. Hsu. 1944. Chinese swine and their performance compared with
modem and crosses between Chinese and modem breeds. J. Heredity 35: 365-379.
Rendel, J.M. 1984. Decline in the number of breeds, its consequences and remedies. Genetics:
New frontiers. Proc. XV Intl. Congr. of Genet. 4: 23-33.
Rombauts,
P., G. Mazzari and F. du Mesnil du Buisson.
1982.
Premier bilan de
l'exp6rimentation sur le pore Chinois en France. 2. Estimation de eomposantes de la
prolifieitt: taux d'ovulation et survie foetale. Journ6es Rech. Porcine en France 14: 137142.
Rothschild, M. F., Ch. Renard, C. Legault and M. Vaiman. 1987. Effect of SLA haplotypes on
birth and weaning weight and on deficit of homozygotes in Meishan pigs. Anita. Genet. 18:
33-34 (Abstr.).
108
Sellier, P. and C. Legault. 1986. The Chinese prolific breeds of pigs: Examples of extreme
genetic stocks. In: Smith, C., J. W. B. King and J. C. McKay (Eds). Exploiting New
Technologies in Animal Breeding. Oxford Univ. Press, England.
Smith, C. 1984. Rates of genetic change in farm livestock. J. Agric. Res. Dev. 1: 79-85.
Smith, C. 1986. Variety of breeding stocks for the production-marketing range, and for flexibility
and uncertainty. Proc. 3rd World Cong. on Genet. AppL to Livest. Prod., Lincoln, NE. X:
14-20.
Stevermer, S., A. MueUer and W. Singleton. 1980. Economics of reproductive performance and
breeding herd management.
Pork Industry Handbook factsheet PIH-45.
Illinois
Cooperative Extension Service. 4pp.
Strang, G. S. and C. Smith. 1979. A note on the heritability of litter traits in pigs. Anita. Prod.
28: 403-406.
Tess, M.W. 1986. The impact of production / marketing system on Needing objectives in swine.
Proc. 3rd World Cong. on Genet. Appl. to Livest. Prod., Lincoln, NE. X: 3-13.
Vaiman, M., Ch. Renard and N. Bourgeaux. 1988. SLA, the Major Histocompatibility Complex
in Swine: Its influence on physiological and pathological traits. In: Warner, C. M., M. F.
Rothschild and S. J. Lamont. (Eds). The Molecular Biology of the Major Histocompatibility
Complex of Domestic Animal Species. Iowa State University Press, Ames, IA. pp. 23-38.
Van der Steen, H. A. M. and P. N. de Groot. 1988. Use of Meishan to improve maternal
performance traits in pigs. In: Advances in animal breeding. Proc. Syrup. honour R. D.
Politiek, 11-14 Sept., Pudoc, Wageningen. pp. 182-183.
Wang Lin Yun. 1988. Pig Needs in China. Pig News and Info. 9(4): 408-413.
Webb, A. J., A. E. Carden, C. Smith and P. Imlah. 1982. Porcine stress syndrome in pig
breeding. Proc. 2nd World Congr. on Genet. Appl. to Livest. Prod., Madrid, Spain. V:
588-608.
Webel, S. K. and P. J. Dziuk. 1974. Effect of stage of gestation and uterine space on prenatal
survival in the pig. J. Anita. Sci. 38: 960-963.
Wong, S. 1986. Meishan pigs of China.Mime.o, internal USDA-APHIS / OICD report.
Wu, i S. and Wen-chart Zhang. 1982. Genetic analysis of some Chinese breeds as a resource
world hog improvement.
Proc. 2nd World Congr. on Genet. Appl. to Livest. Prod.,
Madrid, Spain. VIII: 593-600.
Wu, M.C. 1987. The influence of uterine growth on the potential litter size in Chinese and
occidental pigs. Ph.D. dissertation, Urbana, IL.
Wu, M. C. and P. J. Dziuk. 1988a. Procedures for measuring length of the pig uterus. J. Anita.
Sci. 66: 1712-1720.
Wu, M. C. and P. J. Dziuk. 1988b. Ovarian influence on uterine growth in prepubertal gilts. J.
Anita. Sci. 66: 2893-2898.
109
Wu, M. C., M. D. Hentzel and P. I. Dziuk. 1987. Relationships between uterine length and
number of fetuses and prenatal mortality in pigs. J. Anim. Sci. 65: 762-770.
Wu, M. C., M. D. Hentzel and P. J. Dziuk. 1988. Effect of stage of gestation, liner size and
uterine space on incidence of mummified fetuses in pigs. J. Anita. Sci. 66: 3202-3207.
Xu Zhen-ying. 1985a. On the biological and economical traits of ten Chinese indigenous breeds
of pigs. Part 1. Pig News and Info. 6(3): 301-309.
Xu Zhen-ying. 1985b. On the biological and economical traits of ten Chinese indigenous breeds
of pigs. Part 2. Pig News and Info. 6(4): 425-431.
Yu Youtai. 1987. Three hundred million pigs. In: Sylvan Wittwer, Yu Youtai, Sun Han, and
Wang Lianzheng (Eds). Feeding a Billion: Frontiers of Chinese Agriculture. Michigan
State Univ. Press. pp. 309-323.
Zhang, Wenean, W. E. Rempel and Zhongge Zhang. 1986. A cluster analysis of performance
data of Chinese breeds of swine. Proc. 3rd World Congr. on Genet. Appl. to Livest. Prod.,
Lincoln, NE. X: 75-81.
Zhang, Wen-chen, J. S. Wu and W. E. Rempel. 1983. Some performance
prolific breeds of pigs in China. Livest. Prod. Sci. 10: 59-68.
characteristics of
Question:
D. Pollock
ii0
i) Are the Chinese
applying
any
and programs
to retain
fertility
growth
and fat in these various
2) How
Response:
many
teats
do
these
breed improvement
techniques
and fecundity
but improve
strains
described?
females
have?
D. McLaren
It is difficult
to assess
the extent to which
the Chinese
are attempting
to exploit
the prolificacy
of breeds
such as
the Taihu and Min in production
systems
designed
to produce
lean pork.
Many foreign
breeds have been imported
into
China over the past 30 years to be used as terminal
sire
breeds
in crossbreeding
programs,
and the Chinese
government
has required
the use of indigenous
dam breeds
and exotic
lean-meat
type sire breeds
in commercial
pork production
systems
(Jiang et al.; 1988).
Development
of new composite
breeds
such as the Sanjiang
White, derived
from the Landrace
and the Min, is also an apparently
prevalent
swine breeding
strategy
(Chen, 1987).
Biotechnological
research
projects
aimed at producing
highly prolific
lean meat strains
of pig
in China have also been reported
(Chern, 1988, ASM news,
54:555-558).
Taihu sows typically
average
14 teats.
Question:
J.P.
have
16 to 18 teats,
and
Min
pigs
Gibson
I) Avalos and Smith showed that index selection
could lead
to rapid genetic
improvement
of litter size.
If breeders
are not using this index does it mean that litter size is
not worth much to them?
2) How would a change
in sale practices
in the U.S. from
liveweight
to a grading
system affect the economic
value
Taihu pigs.
Response:
D.
of
McLaren
Tess (1986) showed that when pigs are priced
by lean yield,
fatness dominates
the selection
index.
When pigs are priced
on liveweight,
however,
sow productivity
will dominate
the
index.
Litter size therefore
has a relatively
high economic
value for most U.S. pork producers,
who market
on a live
weight basis.
The failure of many breeders
to use, e.g., a family index or
BLUP to improve
rate of response
of litter size in general
purpose
and maternal
lines stems from the complexity
of such
systems
compared
to indexing
based upon individual
performance
(contemporary
comparisons),
and the lack of economic
incentives
to improve
the accuracy
of existing
selection
programs.
A i/2-Taihu
sow producing
i/4-Chinese
market
hogs might well
improve
efficiency
of liveweight
production,
but not of lean
pork production.
The system for marketing
hogs will be a
major determinant
of the economics
value of unimproved
Taihu
pigs in commercial
pork production
systems.
i