The Effects of Amount of Whole Barley, Barley Bulk Density, and
Form of Roughage on Feedlot Lamb Performance,
Carcass Characteristics, and Digesta Kinetics1
Patrick G. Hatfield*,2, Julie A. Hopkins†, Geoff T. Pritchard‡, and Carl W. Hunt‡
*Montana State University Bozeman, 59717; †USDA-ARS, U.S. Sheep Experiment Station, Dubois,
ID 83423; and ‡Department of Animal and Veterinary Sciences, University of Idaho, Moscow 83843
ABSTRACT:
We conducted two feedlot trials and
one metabolism trial to evaluate the effect of barley
level, barley bulk density, and physical form of
roughage on lamb growth performance and digesta
kinetics. Level of whole barley (50, 70, 90%) and type
of roughage (chopped or pelleted alfalfa) were evaluated in Trial 1 (50 d period). Trial 2 (50 d ) evaluated
barley bulk density (heavy = 671 and light = 607 kg/
m3) , form of roughage (pelleted or chopped alfalfa),
and level of barley (80 or 40%). The influence of
treatments used in Trial 2 on digesta kinetics was
evaluated in Trial 3. Gain:feed increased and DMI
decreased ( P < .10) linearly with increasing level of
barley, and ADG and DMI were greater ( P < .10) for
lambs fed pelleted vs chopped alfalfa in Trial 1. The
70% barley diet produced the highest yield grade and
kidney-pelvic fat and the lowest leg score among
barley levels ( P < .10). Lambs fed pelleted alfalfa had
heavier carcasses and a thicker body wall than lambs
fed chopped alfalfa ( P < .02). In Trial 2, DMI was less
and gain:feed greater ( P < .01) for lambs fed the
heavy barley than for lambs fed the light barley and
for the 80% barley diet compared to the 40% barley
diet. Lambs fed pelleted alfalfa had greater dressing
percentages than lambs fed chopped alfalfa. Backfat
and body wall thickness were greater ( P < .10) for
lambs fed the 80% barley diet than for those fed the
40% barley diet. In Trial 3, retention time of barley
was greater ( P < .10) for lambs fed light rather than
heavy barley, and retention time of alfalfa was greater
( P < .10) for lambs fed chopped compared with
pelleted alfalfa. Acetate:propionate ratio was greater
( P < .10) for lambs fed light vs heavy barley and
lambs fed the 40 vs 80% barley diets. Ruminal pH was
lower ( P = .05) and in situ barley digestion greater ( P
= .03) over time in lambs fed the 80% barley diet than
in lambs fed the 40% barley diet. Feedlot lamb ADG
was not always greatest with high levels of barley;
however, gain:feed improved at the higher barley
levels. The higher barley levels seemed to result in
fatter lambs.
Key Words: Sheep, Grain, Alfalfa, Feeds
J. Anim. Sci. 1997. 75:3353–3366
Introduction
Management practices to improve growth performance of weaned ruminants include manipulating
feed so that digestion is neither too rapid, which can
result in digestive problems, nor too slow, which can
result in poor feed efficiency (Cheng et al., 1991).
Ruminal fermentability differs among grains. Small
cereal grains, such as barley, are more rapidly
fermentable than corn and grain sorghum (Waldo,
1Research was supported in part by a grant from the Idaho
Barley Commission. Appreciation is expressed to Ed Vadnais for
technical assistance.
2To whom correspondence should be directed: Phone (406)
994−7952; fax (406) 994−5589; E-mail [email protected].
Received November 22, 1996.
Accepted August 12, 1997.
1973). Increased ruminal fermentation of barley can
result in greater microbial protein and total
metabolizable protein flowing to the small intestine
(Feng et al., 1995). However, barley is noted for being
variable in bulk density and starch content (Reynolds
et al., 1992), which would likely affect its fermentable
energy content. Excessive fermentable carbohydrate
from barley can disrupt ruminal fermentation and
create negative associative effects (Mould et al.,
1983). Therefore, fermentable carbohydrates in barley
should be closely managed to optimize ruminal
function. Dietary forage characteristics such as level,
type, and physical form of roughage are factors that
affect mastication characteristics and might thereby
affect the ruminal environment when highly fermentable carbohydrates from barley are fed. Our objective
was to evaluate the effect of barley level, barley bulk
density, and physical form of roughage on digesta
kinetics and lamb growth performance.
3353
3354
HATFIELD ET AL.
Table 2. Ingredient composition (% as-fed basis) of
supplement used in all three trialsa
Materials and Methods
The experimental protocol was reviewed and approved by the Animal Care and Use Committee at the
USDA-ARS Sheep Experiment Station near Dubois,
ID as outlined in the publication Guide for the Care
and Use of Agricultural Animals in Agricultural
Research and Teaching (Consortium, 1988).
Trial 1
April-born whiteface wethers ( n = 96, average
initial BW = 36.3 kg) were used in a 3 × 2 factorial
experiment to evaluate the effects of level of barley in
the diet (50, 70, or 90% whole barley, as-fed basis;
Table 1 ) and type of roughage (chopped vs pelleted
alfalfa hay) on feedlot performance and carcass
characteristics. Wethers and their dams had been
previously grazed on sagebrush-bunchgrass spring
range followed by alpine meadow grazing. Wethers
were weaned in early September, then grazed on
sagebrush-bunchgrass range until the start of the
experiment on October 6.
Wethers were fed in outdoor pens (25 m2) with four
pens/treatment and four lambs/pen. Feed was
provided twice daily at 0730 and 1600 in quantities
sufficient to allow ad libitum consumption. Feed
offered was recorded daily and feed refusals were
collected and recorded when more than 500 g of
refused feed accumulated in the feed bunk. When the
wethers entered the feedlot, they received a diet
composed of 30% whole barley and 70% pelleted or
chopped alfalfa plus 115 g·wether−1·d−1 of a commercially prepared pelleted supplement (Tables 1 and 2).
The amount of barley in the diet was increased by 10
percentage units every 3rd d until the appropriate
barley level in the finishing diet (plus supplement)
was reached. Lambs fed the 50, 70, and 90% barley
diets reached these barley levels on d 7, 13, and 19,
respectively.
Wethers were weighed at the beginning of the
study, after 21 d, and at the end of the
50-d study. Weights were recorded after an overnight
shrink without feed or water. Data collected included
Ingredients
Wheat mill feed
Soybean meal
Alfalfa
Calcium carbonate
Bentonite
Salt
Potassium chloride
Sodium bicarbonate
Lasalocid (68 g ) b
Zinc methioninec
Vitamins A (8,000 IU) and D (800 IU)
Vitamin E (40,000 IU)
Monocalcium (21%)
aSupplement was fed daily at the rate of
bBovatec, Hoffman LaRoche, Inc., Nutley,
cZinpro 100, Zinpro Corp, Edina, MN.
%
32.23
30.67
15.00
11.81
5.00
2.33
1.40
.68
.41
.35
.08
.02
.02
115 g/wether.
NJ.
BW gain and DMI. Gain:feed ratios and net energy for
gain (based on actual intake and NRC, 1985 feed
values) also were calculated. Fecal starch was determined by collecting fresh fecal samples (off the
ground) from the pens on d 29, 36, 43, and 50, and
composited by pen over time.
At the end of the study, all lambs were slaughtered
at a commercial abattoir and carcass measurements
were obtained. Carcass weight, dressing percentage,
backfat, bodywall thickness, and kidney and pelvic fat
were measured. Yield and quality grade, and leg
conformation score were determined subjectively by a
USDA grader.
Pen ( n = 24, with four wethers/pen) was the
experimental unit for all feedlot performance data
(ADG, DMI, and gain:feed), and individual lamb ( n =
93) was the experimental unit for carcass data. Data
were analyzed using the GLM procedure of SAS
(1988). Models for performance data included linear
and quadratic effects for level of barley, the fixed effect
of form of roughage, and the two-way interaction. In
addition, models for carcass measurements included
carcass weight as a covariable.
Trial 2
Table 1. Chemical composition (% of DM) of alfalfa
(chopped or pelleted), barley, and supplement
used in Trial 1
Alfalfa
Item
OM
CP
ADF
ADL
NDF
IVDMD
Starch
Pelleted
Chopped
Barley
Supplement
85.0
16.9
42.7
8.7
48.1
63.6
—
92.5
16.8
46.9
10.2
51.5
64.7
—
98.6
12.5
8.3
1.6
20.3
84.2
53.4
75.4
22.3
17.5
3.6
31.2
78.6
15.0
April-born whiteface wether lambs ( n = 192,
average initial BW = 34.9 kg) were used in a
50-d feedlot experiment to evaluate the effects of
heavy and light whole barley (Table 3 ) on performance. Heavy and light barley (both 15% Klages:85%
Morex) had a bulk density of 671 kg/m3 (i.e., 52.1
pounds/bushel) and 607 kg/m3 (i.e., 47.2 pounds/
bushel), respectively. The influence of form of roughage (pelleted or chopped alfalfa hay) and level of
barley in the diet (80 or 40% as-fed basis) also were
evaluated. Wethers and their dams had previously
grazed on sagebrush-bunchgrass spring range followed
by alpine meadow grazing. Wethers were weaned in
BARLEY DENSITY AND ROUGHAGE FORM IN LAMB DIETS
Table 3. Variety and physical characteristics of barley
and chemical composition (DM basis) of
feeds used in Trials 2 and 3
Barley
Alfalfa
Item
Heavy
Light
OM
NDF
CP
IVDMD
Starch
Klages variety, %
Morex variety, %
Plump, %a
Bulk density, kg/m3b
98.9
23.9
13.3
82.4
60.8
15.0
85.0
83.0
671
98.8
38.2
12.8
79.8
57.9
15.0
85.0
19.0
607
aOver 2.38 × 19.1-mm sieve.
bHeavy = 52.1 and Light = 47.2
Pelleted Chopped
86.7
53.6
14.2
68.6
92.5
53.1
15.7
69.6
pounds/bushel.
early September, then grazed on sagebrush-bunchgrass range until the start of the trial on September
17.
Wethers were fed, weighed, and slaughtered in the
same manner described in Trial 1. Pen ( n = 32, with
six wethers/pen) was the experimental unit for all
feedlot performance data and individual lamb ( n =
48) was the experimental unit for carcass data. Data
were analyzed as a 2 × 2 × 2 factorial using the GLM
procedure of SAS (1988). Models for feedlot data
included fixed effects for type of barley, level of barley,
form of roughage, and all interactions. Models for
carcass data also included carcass weight as a
covariable.
Trial 3
Eight ruminally cannulated whiteface wethers (12
mo old, average BW = 45 kg) were used in a blocked 4
× 4 Latin square design to examine the influence of
the treatments used in Trial 2 on digesta kinetics. The
two Latin squares (blocks) were either 40 or 80%
whole barley treatments with barley type and form of
alfalfa represented within each square. Lambs within
either the 40 or 80% whole barley diet block remained
on that level of barley for the entire trial.
Before the trial began, wethers were adapted to
either a 40 or 80% whole barley diet as described for
Trial 2. Wethers were then adapted to metabolism
crates (75 × 125 cm). Feed was offered twice daily at
0730 and 1630 in a quantity that allowed ad libitum
consumption. Ad libitum intake of a mix of the two
types of barley was determined for each wether during
a 10-d adaptation period before Period 1. During the
study, each wether received 85% of this predetermined
ad libitum intake.
Days 1 to 10. Each period began with an adjustment
period, which consisted of 5 d of group-feeding wethers
the appropriate amount of whole barley, pelleted or
chopped alfalfa, and supplement followed by 5 d on
3355
treatment diets in metabolism crates. Wethers were
adapted to wearing fecal bags and harnesses at the
same time they were adapted to the metabolism
crates.
Days 11 to 15. At 0700 on d 11, wethers received a
single dose via the ruminal cannula of 30 g of
ytterbium (Yb)-labeled alfalfa (pelleted = 15,001 mg/
kg of Yb; chopped = 22,616 mg/kg of Yb) and 25 g of
chromium (Cr)-mordanted whole barley (heavy =
41,929 mg/kg of Cr; light = 57,187 mg/kg of Cr) to
estimate ruminal retention time. Chopped and
pelleted alfalfa were labeled with YbCl3 using a
procedure described by Prigge et al. (1981). In brief,
forage was soaked in a solution of 2.5 g YbCl3/L of
deionized water for 48 h and stirred three times daily,
after which the forage was strained and washed with
water once every hour for 6 h. After washing, forage
was dried at 50°C.
Barley was mordanted using the procedure of Uden
et al. (1980) by first drying for 48 h at 95°C. After
drying, barley was soaked in water and Na2Cr2O7
containing Cr equal to 6 to 8% of the fiber weight. The
material was then covered with foil and baked at 95°C
for 24 h, after which it was suspended in water and
rinsed repeatedly until the rinse water was clear.
When rinsing was complete, the mordanted fiber was
allowed to stand for 1 h in water that contained
approximately 100 g of ascorbic acid/kg of fiber.
Rinsing was repeated until the rinse water was clear,
and the fiber was dried at 50°C for 48 h.
Rectal grab samples were taken at 0, 4, 8, 12, 16,
20, 24, 28, 32, 36, 42, 48, 54, 60, 72, 84, 96, and 108 h
after dosing. Samples were dried at 100°C to determine the DM content of each sample. Dried samples
were ground to pass a 1-mm screen, and an aliquot
was packed into polyethylene vials for analysis of Yb
and Cr content by neutron activation (Hartnell and
Satter, 1979).
Total fecal output was determined during this
5-d period using fecal collection bags. Fecal collection
bags were emptied twice daily at 0730 and 1630. Feces
were weighed, and a 5% aliquot (by weight) was
retained from each sample and refrigerated. Fecal
aliquots were composited by wethers within period,
and a subsample was frozen for later analysis of
starch, OM, and DM. Rectal grab sample weights were
included in the calculation of total fecal output.
Days 16 and 17. Approximately 100 mL of digesta
was collected via the ruminal cannulas at 0800, 1100,
1400, and 1700 on d 16 and 0900, 1200, 1500, and
1800 on d 17 to account for daily variation in ruminal
conditions. Sample pH was determined using a
Corning pH/°C 107 meter, then samples were strained
through 40-mesh cambric bags, acidified with 1 mL of
7.2 N H2SO4/100 mL, composited by wethers within
period, and frozen for later VFA analysis.
Days 18 to 20. In situ rate of barley and alfalfa
disappearance in the rumen was determined using
nylon bags (52 mm × 130 mm, pore size = 53 mm )
3356
HATFIELD ET AL.
containing the appropriate barley or alfalfa. All feeds
were ground to pass a 2-mm screen, and a
2-g sample was placed in the nylon bag, which was
then heat-sealed. Type of barley and form of alfalfa
were incubated in lambs fed the corresponding treatment diet. Bags were placed in the rumen of each
wether on d 18 at 0700. Duplicate bags were removed
from the rumen of each animal following incubation
periods of 0 (cold water rinse only), 1, 2, 4, 8, 12, 24,
and 48 h. Blank bags also were removed at each
collection time. Not all wethers were represented with
blank bags at all collections; however, all treatments
were represented at each collection time. When bags
were removed from the rumen, they were rinsed in
cold water, dried at 100°C for 24 h, desiccated, and
weighed.
Laboratory Procedures. Dry matter, ash, and Kjeldahl-N (feed samples only) of feed and fecal samples
were determined with AOAC (1984) procedures.
Neutral detergent fiber, ADF, and ADL of diets and
supplements were determined by the nonsequential
procedures of Goering and Van Soest (1970). In vitro
DM disappearance of diet and supplement samples
was evaluated using the Tilley and Terry (1963)
procedure. Ruminal inoculum was obtained from two
ruminally cannulated yearling wethers that were fed
alfalfa hay.
Feed and fecal samples for starch analysis (modification of the technique described by Aman and
Hesselman, 1984) were weighed into 50-mL screw-top
centrifuge tubes. Twenty-five milliliters of a 1 M
acetate buffer and 250 mL of Takatherm II (Solvay
Enzymes, Valley Research, South Bend, IN) was
added. Tubes were placed in a water bath (90 to
95°C), removed after 30 min, cooled, and 50 mL of
suspended amyloglucosidase was added. Tubes were
incubated at 55°C for 12 h then centrifuged at 2,500 ×
g for 10 min. A 100-mL aliquot of supernatant fluid
was transferred to a 12-mm × 75-mm glass culture
tube, 4.9 mL of deionized water was added using an
adjustable pipette, and the contents were then gently
vortexed. One milliliter of this solution was transferred to another glass culture tube, and 2 mL of
combined glucose color reagents (Sigma glucose kit,
Sigma Chemical, St. Louis, MO ) was then added.
Samples were incubated at 37°C for 30 min before
reading optical density at 460 nm in a spectrometer.
Volatile fatty acid analysis was performed using the
method described by Erwin et al. (1961). Five
milliliters of preserved ruminal fluid was placed in a
15-mL centrifuge tube, and 1 mL of 25% ometaphosphoric acid was added. Tubes were allowed
to stand for 30 min then centrifuged for 10 min at
3,000 × g. The supernatant fluid was used for analysis
of VFA with gas chromatography. Columns were 183
cm long and 2 mm i.d. acid-washed glass. The
following temperatures were used: injector = 170°C;
column = 125°C; and detector = 175°C (FID). The
following flow rates were used: N = 20 mL/min; air =
300 to 400 mL/min at 234,422 Pa; and H = 30 mL/min
at 82,937 Pa.
Neutron activation (Hartnell and Satter, 1979)
was used to determine Yb and Cr concentrations in
fecal samples. A .05-g aliquot of each fecal sample was
packed into a polyethylene vial and subjected to
neutron activation. Barley and alfalfa retention time
were calculated algebraically using the equation
defined by Galyean (1993). Retention time was
calculated as Sci·ti·∅/Sci·∅, where ci = the current
marker concentration at time collection ti· and ∅ = the
time interval between the current and the previous
collection time. Total tract dry matter digestibility
( DMD) was calculated as: 100 × [(DMI − FO) /
DMI)].
Ytterbium concentration in labeled alfalfa (chopped
and pelleted) was determined with atomic absorption
spectrophotometry using the procedure described by
Ellis et al. (1982). A 2-g aliquot of ground alfalfa
sample was ashed at 500°C overnight, covered with 3
M HCl:3 M HNO3, and allowed to stand for 12 h. The
sample was then filtered into an acid-rinsed
50-mL volumetric flask through Whatman #4 filter
paper and brought to volume with deionized water.
Chromium concentration in mordanted barley
(heavy and light) was determined using the procedure described by Williams et al. (1962). A .5-g
aliquot of ground, mordanted barley sample was ashed
at 600°C for 90 min in a silica basin. After the sample
cooled, 3 mL of phosphoric acid-manganese sulfate
solution and 4 mL of potassium bromate solution were
added. The sample was then boiled on a preheated
hotplate until all effervescence ceased or a slight
purple color was noticed. The digest was then cooled
and washed with deionized water completely into a
100-mL volumetric flask that contained 10 mL of a
5,000 ppm CaCl2 solution. The digest was brought to
volume with deionized water, allowed to settle overnight or filtered before determination of Cr content by
atomic absorption spectrophotometry.
Statistical Procedures. Wether was the experimental
unit in the blocked 4 × 4 Latin square. The two blocks
were level of whole barley (40 or 80%). The model for
DMI, DMD, alfalfa and barley retention, and VFA
concentrations included type of barley, form of alfalfa,
level of barley, type of barley × form of alfalfa, period,
and animal nested within level of barley. Level of
barley (block) was tested using animal nested within
level of barley as the error term. Other dependent
variables were tested using the residual error term.
Ruminal pH, in situ alfalfa DMD, and in situ barley
DMD were analyzed using the SAS (1988) repeated
measures analysis. The model included time, type of
barley, form of alfalfa, level of barley, type of barley ×
form of alfalfa, period, and animal nested within level
of barley. Level of barley was tested using animal
nested within level of barley as the error term. Other
dependent variables were tested using the residual
error term.
3357
BARLEY DENSITY AND ROUGHAGE FORM IN LAMB DIETS
Table 4. Performance by lambs fed 50, 70, or 90% whole barley in Trial 1
Item
No. of lambs (pens)
BW, kg
Initial
Day 21
Day 50
Average daily gain, kg
Days 0 to 21
Days 22 to 50a
Days 0 to 50
Daily DMI, kg/lamb
Days 0 to 21
Days 22 to 50
Days 0 to 50
Gain:feed g/kg
Days 0 to 21
Days 22 to 50a
Days 0 to 50
Lambs treated for digestive and respiratory
problems (lambs/pen)
Days 0 to 21
Days 22 to 50
Days 0 to 50
Net energy for gain,
Mcal/kg
Days 0 to 50
Fecal starch, %b
aInteraction
bAverage of
50%
70%
90%
SEM
Linear
Quadratic
32 ( 8 )
32 ( 8 )
32 ( 8 )
—
—
—
.51
.81
.75
.77
.79
.45
.66
.23
.98
36.5
43.1
47.9
36.1
44.2
47.5
36.3
42.8
47.1
.32
.17
.23
.38
.11
.23
.31
.15
.22
.025
.012
.010
.81
.35
.43
.04
.01
.72
1.43
1.49
1.47
1.49
1.39
1.43
1.31
1.22
1.26
.034
.052
.039
.02
.01
.01
.01
.60
.16
.35
.76
.08
.10
.01
.61
204
114
153
254
79
157
225
123
171
16.7
16.4
7.4
.25
1.50
1.75
.50
1.38
1.88
.12
2.13
2.25
.232
.600
.597
.71
.47
.56
.29
.56
.87
.873
1.30
1.055
1.01
1.038
1.48
.0459
.220
.02
.58
.09
.17
of level of barley and form of alfalfa, P < .05.
samples collected from each pen on d 29, 36, 43, and 50.
Results
Trial 1
Level of whole barley and form of alfalfa did not
affect ( P > .20) lamb BW (Tables 4 and 5). Lamb
ADG was greatest (quadratic P = .04) for the 70%
whole barley diet during the first 21 d of the trial but
least (quadratic P = .01) for this diet from d 22 to 50.
Lamb ADG from d 0 to 21 and d 0 to 50 was greater
( P < .03) for lambs fed pelleted alfalfa than for those
fed chopped alfalfa (Table 5). Level of barley interacted with form of alfalfa ( P = .01) for ADG from d 22
to 50. During this period, ADG was greatest for
chopped alfalfa combined with 50% whole barley ( P =
.03; .21 kg); ADG for chopped alfalfa combined with
90% whole barley was .17 kg; ADG for pelleted alfalfa
combined with 50% whole barley was .13 kg or with
90% whole barley was .14 kg. However, ADG was less
( P = .03) for the 70% whole barley and chopped alfalfa
diet (.07 kg) than for the 70% whole barley and
pelleted alfalfa diets (.16 kg).
From d 0 to 21, daily DMI (Table 4 ) was greatest
for the 70% whole barley, intermediate for the 50%
whole barley, and least for the 90% whole barley
(quadratic, P = .01). From d 22 to 50 and 0 to 50,
however, DMI decreased linearly ( P = .01) with
increasing barley level in the diet. Daily DMI from d 0
to 21 and d 0 to 50 was greater ( P = .01) by lambs fed
pelleted alfalfa than by lambs fed chopped alfalfa
(Table 5). Net energy for gain responded quadratically ( P = .09) to increasing level of whole barley in
the diet, and the 70 and 90% diet were similar and
higher than the 50% whole barley diet (Table 4).
Lambs fed pelleted alfalfa had more ( P = .02) energy
available for gain than those fed chopped alfalfa
(Table 5).
Gain:feed responded quadratically to increasing
level of barley during d 0 to 21 ( P = .10) and 22 to 50
( P = .01). The 70% whole barley diet was most
efficient from d 0 to 21 and least efficient from d 22 to
50 (Table 4). For the entire trial ( d 0 to 50), gain:
feed increased with increasing level of whole barley in
the diet (linear P = .08). Feed efficiency was not
affected by form of alfalfa for any of the feeding
periods (Table 5). A level of barley × form of alfalfa
interaction was detected ( P = .01) for gain:feed from d
22 to 50. During this period, feed efficiency did not
differ for the chopped alfalfa (133 and 135) and the
pelleted alfalfa (84 and 95) diets combined with the
50 and 90% whole barley, respectively. However, feed
efficiency was lower ( P = .01) for the chopped alfalfa:
70% whole barley diet ( 5 0 ) than for the pelleted
alfalfa:70% whole barley diet (100).
Level of whole barley did not affect lamb digestive
or respiratory problems (Table 4). Lambs fed pelleted
alfalfa tended ( P = .14) to have more digestive and
respiratory problems from d 0 to 21 than lambs fed
3358
HATFIELD ET AL.
Table 5. Performance by lambs fed chopped or pelleted alfalfa in Trial 1
Item
No. of lambs (pens)
BW, kg
Initial
Day 21
Day 50
Average daily gain, kg
Days 0 to 21
Days 22 to 50a
Days 0 to 50
Daily DMI, kg/lamb
Days 0 to 21
Days 22 to 50
Days 0 to 50
Gain:feed g/kg
Days 0 to 21
Days 22 to 50a
Days 0 to 50
Lambs treated for digestive and
respiratory problems (lambs/pen)
Days 0 to 21
Days 22 to 50
Days 0 to 50
Net energy for gain, Mcal/kg
Days 0 to 50
Fecal starchb
aInteraction
bAverage of
Chopped
Pelleted
SEM
P
48 ( 1 2 )
48 ( 1 2 )
—
—
.413
.662
.613
.41
.20
.30
36.5
42.8
47.1
36.1
44.0
48.0
.30
.15
.21
.38
.14
.24
.020
.010
.008
.01
.48
.03
1.29
1.35
1.32
1.52
1.39
1.45
.028
.042
.032
.01
.44
.01
211
111
157
242
101
164
14.7
14.9
8.2
.16
.61
.37
.08
.92
1.00
.50
2.40
2.92
.189
.491
.487
.14
.04
.01
.91
1.47
1.06
1.05
.037
.180
.02
.12
of level of barley and form of alfalfa, P < .05.
samples collected from each pen on d 29, 36, 43, and 50.
chopped alfalfa (Table 5). From d 22 to 50 and d 0 to
50, lambs fed pelleted alfalfa had more ( P < .04)
digestive and respiratory problems than lambs fed
chopped alfalfa.
Fecal starch was not affected by level of whole
barley (Table 4). Fecal starch tended ( P = .12) to be
greater for lambs fed chopped alfalfa than for those fed
pelleted alfalfa (Table 5).
Backfat, bodywall thickness, and quality grade
were not influenced by level of whole barley in the diet
(Table 6). There was a tendency ( P < .12) for a
quadratic response among levels of whole barley, and
the lambs receiving the 70% whole barley tended to
have greater dressing percentage, kidney and pelvic
fat, yield grade, and lower leg score than lambs fed the
50 and 90% whole barley diets. Carcass weight and
bodywall thickness were greater ( P < .02), and
dressing percentage tended to be greater ( P = .15), for
lambs fed pelleted alfalfa than for those fed chopped
alfalfa (Table 7). Interactions for level of whole barley
and form of alfalfa were detected ( P <. 05) for carcass
weight and leg score. Lambs fed the pelleted alfalfa
and the 70 (26.3 kg) or 90% (25.4 kg) whole barley
diets had greater ( P < .10) carcass weights than
Table 6. Carcass characteristics of lambs fed 50, 70,
or 90% whole barley in Trial 1
Item
50%
70%
90%
SEM
Linear
Quadratic
No. of lambs
Carcass wt, kga
Dressing %
Backfat, cm
Bodywall, cm
Leg scoreab
Kidney and pelvic fat, %
Qualityb
Yieldc
30
24.7
51.7
.61
2.11
11.3
2.35
11.1
2.1
31
25.3
53.2
.58
2.16
10.9
2.84
11.2
2.4
32
24.9
52.6
.56
2.08
11.1
2.61
11.1
2.1
—
.31
.55
.030
.084
.15
.148
.089
.098
—
.75
.23
.34
.75
.41
.21
.57
.95
—
.16
.12
.94
.58
.08
.05
.57
.07
aInteraction of level of barley and form of
b10 = Choice−; 11 = Choice; 12 = Choice+.
cGrade 1 through 5.
alfalfa, P < .05.
3359
BARLEY DENSITY AND ROUGHAGE FORM IN LAMB DIETS
Table 7. Carcass characteristics of lambs fed
chopped or pelleted alfalfa in Trial 1
Item
No. of lambs
Carcass wt, kga
Dressing, %
Backfat, cm
Bodywall, cm
Leg scoreab
Kidney and pelvic
fat, %
Qualityb
Yieldc
Chopped
Pelleted
SEM
P
46
24.5
52.1
.58
1.98
11.0
47
25.4
53.0
.58
2.24
11.2
—
.20
.43
.025
.061
.12
—
.02
.15
.85
.01
.47
2.57
11.1
2.1
2.63
11.1
2.3
.121
.07
.08
.69
.83
.20
aInteraction of level of barley and form of
b10 = Choice−; 11 = Choice; 12 = Choice+.
cGrade 1 through 5.
differ between types of barley. From d 0 to 21, ADG
was greater ( P < .01) for lambs fed chopped than for
those fed pelleted alfalfa and greater for those fed 80%
than for those fed 40% whole barley. The opposite
response was noted from d 22 to 50. A type of barley ×
form of alfalfa interaction was detected ( P = .03) for
ADG during d 22 to 50. When chopped alfalfa was fed,
ADG was .19 and .17 kg for lambs fed heavy and light
barley, respectively. Lambs fed light barley and
pelleted alfalfa had a greater ( P = .07) ADG than
lambs fed pelleted alfalfa and heavy barley (.23 and
.21 kg; respectively).
During the entire trial, DMI by lambs fed light
barley was greater ( P < .01) than DMI by lambs fed
heavy barley (Table 8). Daily DMI was greater ( P =
.01) by lambs fed chopped compared with pelleted
alfalfa from d 0 to 21 but did not differ between forms
of alfalfa from d 22 to 50 or d 0 to 50. Daily DMI by
lambs fed the 40% whole barley diet was greater ( P <
.01) than DMI by lambs fed the 80% barley diet from
d 22 to 50 and d 0 to 50. Daily DMI did not differ
between barley levels from d 0 to 21. Type of barley ×
form of alfalfa interactions were detected ( P < .05) for
daily DMI for d 22 to 50 and d 0 to 50. Dry matter
intake was greater ( P < .05) for the pelleted alfalfa:
light barley diets (1.62 and 1.56 kg for d 22 to 50 and
d 0 to 50; respectively) than for the chopped alfalfa:
light barley diets (1.48 and 1.49 kg for 22 to 50 and d
0 to 50; respectively). Net energy for gain did not
differ between any of the treatments.
From d 0 to 50, gain:feed was greater ( P = .01) for
heavy than for light barley diets (Table 8). Gain:feed
alfalfa, P < .05.
lambs fed chopped alfalfa and 70 (24.4 kg) or 90%
(24.3 kg) whole barley diets. Lambs fed chopped
alfalfa:50% whole barley tended ( P = .13) to have a
higher leg score than those fed the pelleted alfalfa:50%
whole barley diet (11.5 and 11.1; respectively). The
opposite was noted for lambs fed the 70% whole
barley:pelleted alfalfa treatment, resulting in a
greater ( P = .02) leg score than lambs fed 70% whole
barley:chopped alfalfa (11.3 and 10.5; respectively).
Leg score for lambs fed either chopped or pelleted
alfalfa and the 90% whole barley diet was 11.1.
Trial 2
Type and level of whole barley and form of alfalfa
did not affect lamb BW (Table 8). Lamb ADG did not
Table 8. Performance by lambs fed heavy or light barley at 40 or
80% of the diet with chopped or pelleted alfalfa in Trial 2
Barley
Item
No. of lambs (pens)
BW, kg
Initial
Day 21
Day 50
Average daily gain, kg
Days 0 to 21
Days 22 to 50a
Days 0 to 50
Daily DMI, kg/lamb
Days 0 to 21
Days 22 to 50a
Days 0 to 50a
Gain:feed, g/kg
Days 0 to 21
Days 22 to 50a
Days 0 to 50
Net energy for gain, Mcal/kg
Days 0 to 50
Form
Heavy
Light
Chopped
Pelleted
40%
80%
SEM
96 ( 1 6 )
96 ( 1 6 )
96 ( 1 6 )
96 ( 1 6 )
96 ( 1 6 )
96 ( 1 6 )
—
35.1
39.8
46.1
34.8
39.7
45.8
35.1
40.7
46.1
.62
.62
.66
34.6
39.9
45.6
35.3
40.5
46.3
34.9
40.6
45.8
.26
.20
.22
.26
.20
.22
.29**
.18**
.22
.24
.22
.23
.25**
.21**
.22
.28
.19
.22
.008
.006
.004
1.39**
1.46**
1.44**
1.48
1.55
1.53
1.48**
1.48
1.48
1.39
1.53
1.48
1.45
1.69**
1.62**
1.42
1.32
1.35
.023
.022
.021
181
131
155**
1.03
167
123
146
1.07
191**
116**
149
1.03
of barley × form of alfalfa interaction, P < .05.
**,*Means within paired comparison differ, **P < .01, *P < .05.
aType
Level
158
140
152
1.07
162**
118**
138**
1.06
187
138
164
1.04
6.8
3.8
2.4
.021
3360
HATFIELD ET AL.
Table 9. Carcass characteristics of lambs fed heavy or light barley at 40
or 80% of the diet with chopped or pelleted alfalfa in Trial 2
Barley
Item
No. of lambs
Carcass wt, kg
Dressing %
Backfat, cm
Body wall thickness, cm
Kidney and pelvic fat, %
Leg scorea
Qualitya
Form
Level
Heavy
Light
Chopped
Pelleted
40%
80%
SEM
24
24.1
49.8
.61
.38
2.65
1.1
11.0
24
24.5
50.2
.61
2.35
2.51
11.2
11.1
24
24.0
48.9†
.61
2.29
2.62
11.2
11.1
24
24.6
51.1
.58
2.44
2.53
11.1
11.0
24
24.0
49.6
.56*
2.31†
2.44
11.1
10.9†
24
24.6
50.4
.66
2.56
2.71
11.2
11.1
—
.38
.59
.033
.081
.115
.06
.05
a10 = Choice−; 11 = Choice; 12 = Choice+.
**, *, †Means within paired comparison differ, **P < .01, *P < .05, †P < .10.
also tended to be greater ( P < .14) for heavy than for
light barley diets from d 0 to 21 and d 22 to 50 (Table
8). Chopped alfalfa diets resulted in a greater ( P =
.01) gain:feed from d 0 to 21 and a lower ( P = .01)
gain:feed from d 22 to 50 than pelleted alfalfa,
resulting in no difference in gain:feed between forms
of alfalfa from d 0 to 50. The 80% whole barley diet
resulted in greater ( P < .01) gain:feed during the
entire 50-d trial than the 40% whole barley diet. A
barley type × form of alfalfa interaction was detected
( P = .05) for gain:feed from d 22 to 50. Gain:feed
tended ( P= .10) to be lower for chopped than for
pelleted alfalfa when fed with heavy barley (124 and
139: respectively). The same relationship, but of
greater magnitude ( P = .01), was noted for chopped
and pelleted alfalfa when fed with the light barley
(109 and 142; respectively).
Carcass characteristics did not differ between types
of barley (Table 9). Lambs fed pelleted alfalfa had a
greater ( P = .06) dressing percentage than lambs fed
chopped alfalfa. Other carcass characteristics did not
differ between forms of alfalfa. Lambs fed 80% whole
barley had greater ( P < .10) backfat, bodywall
thickness, and quality grade than lambs fed 40%
whole barley.
Trial 3
Dry matter intake and total tract DMD for cannulated wethers did not differ between type or level of
barley, or form of alfalfa (Table 10). However, DMD
tended ( P < .16) to be greater for chopped than for
pelleted alfalfa and greater for 80% than for 40%
whole barley diets. Barley retention time was greater
( P = .08) for light than for heavy barley. Barley
retention time did not differ between forms of alfalfa
and levels of barley. Alfalfa retention time was greater
( P = .04) for chopped than for pelleted alfalfa and
tended ( P = .12) to be greater for light than for heavy
barley. Alfalfa retention times did not differ between
levels of whole barley.
Ruminal propionate and valerate concentrations
were lower ( P < .10) and the acetate:propionate ratio
greater ( P = .09) for light than for heavy barley
(Table 11). Acetate, isobutyrate, butyrate, isovalerate, and total VFA concentration did not differ
between types of barley. Total VFA, acetate:propionate ratio, and individual VFA did not differ between
forms of alfalfa. The acetate:propionate ratio was
greater ( P = .02) for the 40% whole barley than for
the 80% whole barley. Although no other VFA
measurements differed between levels of whole barley,
acetate tended to be less ( P = .12) for 80% than for
40% whole barley.
The repeated measures mean comparison for ruminal pH was lower ( P = .05) for lambs fed the 80%
whole barley diet than for lambs fed the 40% barley
diet (Figure 1). Mean ruminal pH did not differ
between types of barley or forms of alfalfa. Ruminal
pH was greater ( P = .01) 1 h after feeding for lambs
fed chopped than for lambs fed pelleted alfalfa.
Repeated measures mean ruminal in situ barley
digestion was greater ( P = .03) for lambs fed 80%
than for those fed 40% whole barley diets (Figure 2).
Ruminal in situ barley digestion tended ( P = .14) to
be greater for lambs fed chopped alfalfa than for lambs
fed pelleted alfalfa and was higher at two time points
(24 h, P = .01; 48 h, P = .02). Ruminal barley
digestion was greater at 24 h ( P = .01) and 48 h ( P =
.07) for lambs fed heavy than for lambs fed light
barley, but the overall P-value was .25.
Repeated measures mean in situ alfalfa digestion
did not differ between treatments (Figure 3).
However, at 4 h, alfalfa DMD disappearance was
greater ( P < .02) for lambs fed light barley and
pelleted alfalfa than for lambs fed heavy barley and
chopped alfalfa.
Discussion
Amount of Grain
Roughage in feedlot diets is one of the most
expensive ingredients on an energy basis (Bartle and
Preston, 1991). However, Grovum (1988) stated that
3361
BARLEY DENSITY AND ROUGHAGE FORM IN LAMB DIETS
Table 10. Dry matter intake, total tract digestion, and alfalfa and barley retention time for lambs fed heavy or
light barley at 40 or 80% of the diet with chopped or pelleted alfalfa in Trial 3
Barley
Form
Level
Item
Heavy
Light
Chopped
Pelleted
40%
80%
SEM
No. of lambs
DMI, kg
Total tract DMD, %
Barley retention, h
Alfalfa retention, h
4
1.39
79.25
50.61†
44.70
4
1.40
79.18
55.27
48.81
4
1.38
80.12
51.48
49.35*
4
1.41
78.31
54.40
44.16
4
1.48
76.99
53.61
45.39
4
1.30
81.44
52.27
48.12
—
.15
2.14
1.76
1.75
**, *, †Means within paired comparison differ, **P < .01, *P < .05, and †P < .10.
sheep consume more energy when fed diets containing
relatively large amounts of alfalfa compared with
concentrates. Tucker (1975) reported that in lambs
fed diets containing 25, 50, and 75% barley and dried
grass, the 50% barley diet resulted in the greatest
Figure 1. Ruminal pH of cannulated wethers fed
heavy or light barley at 40 or 80% of the diet with
chopped or pelleted alfalfa in Trial 3. The SEM
associated with ruminal pH at 1, 3, 6, and 9 h after
feeding was .06, .05, .07, and .12, respectively. aP-value
associated with repeated measures mean comparison.
bP-value associated with within time mean comparison.
Time effect, P = .01. Time × form P = .01.
Figure 2. Rate of barley digestion in wethers fed
heavy or light barley at 40 or 80% of the diet with
chopped or pelleted alfalfa in Trial 3. The SEM
associated with rate of barley digestion at 4, 8, 12, 24,
and 48 h of incubation was 1.07, 1.40, 1.41, .80, and .90,
respectively. aP-value associated with repeated measures mean comparison. bP-value associated with within
time mean comparison. Time effect, P = .01. Time × type
of barley, P = .02.
3362
HATFIELD ET AL.
Table 11. Ruminal VFA concentrations (millimole/liter) for lambs fed heavy or light
barley at 40 or 80% of the diet with chopped or pelleted alfalfa in Trial 3
Barley
Form
Level
Item
Heavy
Light
Chopped
Pelleted
40%
80%
SEM
No. of lambs
Acetate
Propionate
Isobutyrate
Butyrate
Isovalerate
Valerate
Total
Acetate:propionate
4
67.0
20.1
.9
17.9
1.1
2.2
109.2
3.4
4
65.7
17.9†
.8
16.8
1.1
1.9*
104.3
3.8†
4
64.8
19.3
.9
16.4
1.1
2.1
104.6
3.5
4
67.9
18.6
.9
18.3
1.1
2.1
108.8
3.7
4
69.8
17.9
.9
15.6
1.2
2.0
107.3
4.0
4
63.0
20.0
.8
19.1
1.0
2.2
106.1
3.2*
—
1.97
.80
.05
.90
.05
.08
2.58
.15
**, *, †Means within paired comparison differ, **P < .01, *P < .05, and †P < .10.
Figure 3. Rate of alfalfa digestion in wethers fed
heavy or light barley at 40 or 80% of the diet with
chopped or pelleted alfalfa in Trial 3. The SEM
associated with rate of alfalfa digestion at 4, 8, 12, 24,
and 48 h of incubation was .41, 2.41, .79, .71, and .60,
respectively. aP-value associated with repeated measures mean comparison. bP-value associated with within
time mean comparison. Time effect, P = .01.
energy intake and lamb performance. McClure et al.
(1994), working with grazing and confined lambs,
found that performance by lambs grazing alfalfa
pastures approached performance of those fed diets
containing 90% whole corn (220 and 257 g/d, respectively). In contrast to these findings, Thomas and
Dahmen (1986) reported that with increasing barley
levels (from 20% to 80% barley) in the diet, DMI
decreased, daily gains increased, and feed required
and feed cost per unit of gain decreased.
From d 0 to 50 in Trials 1 and 2, gain:feed was
positively influenced by increasing barley level;
however, ADG was not affected by barley level. In
both trials, DMI decreased with increasing level of
barley. Net energy for gain, in contrast to the findings
of Grovum (1988), did not increase with decreasing
level of barley in the diet. Donefer et al. (1963), using
a 5 × 5 Latin square with Cheviot ewes fed either 100:
0, 85:15, 70:30, 55:45, or 40:60 alfalfa:barley in
complete pelleted diets, also found that total DE
intake remained essentially constant with increasing
increments of barley. Ross et al. (1985) found that
lambs fed diets containing 80, 60, and 40% milo with
chopped alfalfa hay did not differ in ADG or daily
DMI, but lambs fed the 40% concentrate diet required
more feed per unit of gain than lambs fed either the
60% or 80% concentrate diets.
At the ruminal microbial level, DE of highconcentrate diets is used more efficiently than DE
from a 50% hay:50% grain diet (Kozub and Hironaka,
1992). The inefficiency caused by combined feeding of
cereals and forage at equal or approximately equal
proportions is probably a result of a combination of
catabolite repression of cellulolysis due to the presence
of free sugars and the inhibitory effect of low pH on
cellulose digestion (Cheng, 1991). Hence, efficient use
of the nutrients in either grain or forage at the
ruminal level is diminished when these two are fed in
combination, particularly in diets that are two times
maintenance or less (Joanning et al., 1981). Results
of our study, as well as those of Tucker (1975), Ross
et al. (1985), and Grovum (1988), conflict with the
BARLEY DENSITY AND ROUGHAGE FORM IN LAMB DIETS
basic understanding of ruminal function outlined by
Cheng (1991) and Kozub and Hironaka (1992).
Possible explanations for this conflict are that 1 )
lambs are more susceptible to acute acidosis than
cattle (Huntington, 1988) and 2 ) high-concentrate
diets may result in the best feedlot performance under
low stress environments. In Trials 1 and 2, the higher
dietary barley levels were associated with greater
ADG during the 0 to 21 d period and lower ADG
during the 22 to 50 d period. In both trials,
temperatures were lower and precipitation increased
during the 22 to 50 d period. Apparently, the roughage
helped to maintain intake levels during inclement
weather, when lamb intake of high-grain diets
dropped, demonstrating the importance of total DMI.
In Trial 3, cannulated lambs fed the 80% whole
barley diet tended to consume less feed and had a
higher rate of in situ barley digestion. Donefer et al.
(1963) and Ross et al. (1985) reported that DMD
increased with increasing barley level in the diet.
Poore et al. (1990), using six ruminally cannulated
steers fed diets containing 30, 60, and 90% concentrate plus a 50:50 mixture of wheat-straw and alfalfa
hay, found that intake was greater for the 60 and 90%
concentrate diets than for the 30% concentrate diet,
and that total DM digestibility increased with increasing percentage of concentrate.
In Trial 3, ruminal pH and acetate:propionate were
lower for lambs fed the 80% barley diet than for those
fed the 40% barley diet. There was no difference in
total VFA concentration, and only a tendency for
acetate to be lower and butyrate and valerate to be
higher in the 80% barley diet. Although Leventini et
al. (1990) reported that ruminal pH showed no
response to increasing barley-based supplements
when level of concentrates were less than 50% in a
mixed-grass hay diet, Poore et al. (1990) reported
that ruminal pH decreased with increasing level of
concentrate when concentrate levels increased to 90%
of the diet.
Kaufmann et al. (1980) also reported that ruminal
pH decreased with higher starch intake, and that
propionic acid increased and acetic acid decreased
until the ratio was approximately 1:1 at a pH of 5.2. In
Trial 3, no difference in total VFA concentration was
noted. Donefer et al. (1963) also reported that
acetate:propionate decreased from 2.4 for a 100%
alfalfa diet to 1.6 for a diet containing 40% alfalfa:60%
barley. Proportions of acetic and propionic acids were
greater and proportions of butyric acid were less in the
100% alfalfa diet than in the 40% alfalfa diet.
Although Leventini et al. (1990) reported an
increase in fluid passage rate associated with increasing level of a barley-based supplement, mean particulate retention time seemed to decrease with a ruminal
buffer and was least with a 30% barley-based supplement and greater with either a 10 or 50% barley-based
supplement when fed without a buffer. Poore et al.
3363
(1990) reported that ruminal DM fill did not differ
among treatments but tended to decrease with increasing level of concentrate. In Trial 3, we detected
no difference in retention time between the two levels
of barley tested.
In Trial 1, backfat, bodywall thickness, and quality
grade were not influenced by level of whole barley in
the diet, and there was only a tendency for lambs
receiving the 70% whole barley to have greater
dressing percentage, kidney and pelvic fat, yield
grade, and lower quality grade than lambs receiving
either the 50 or 90% whole barley diets. In Trial 2,
backfat, bodywall thickness, and quality grade were
greater for lambs fed the 80% than for those fed the
40% whole barley diet. Fortin et al. (1985), using
Hereford × Shorthorn bulls and steers, found that
increased barley intake from 0 to 1.35 kg DM/100 kg
of live BW had no effect on carcass weight, dressing
percentage, fat thickness, loin eye area, or quality
grade when the cattle were slaughtered at similar
weights. McClure et al. (1994) reported that lambs
finished on alfalfa had similar muscle mass and less
fat compared to those finished on 90% corn diets.
However, having lower carcass fat may not be totally a
function of diet. In confinement studies that investigate levels of dietary energy on body composition,
diet and lack of aerobic exertion are completely
confounded. Lambuth et al. (1970) reported that ADG
did not influence total retail yield or edible portion,
but the lambs on the high ADG diet had a lower
percentage of total fat trim and higher percentage of
bone than the slower-gaining lambs. In addition, these
researchers also reported that lambs with heavier
slaughter weights had a higher percentage of total fat
trim than lambs with lighter slaughter weights. Ross
et al. (1985) found that level of concentrate did not
affect any of the carcass traits measured except
percentage of rib; the 80% concentrate diet resulted in
a greater percentage of rib than either the 40% or 60%
concentrate diets. The reason for the differences noted
in these studies is not clear. However, age of the
animal, time on feed, and environmental conditions
may all play a role in differences in carcass characteristics with different levels of concentrate.
Form of Roughage
Thomas and Dahmen (1986) reported that BW
gain by feedlot lambs was greater and feed was used
more efficiently when lambs were fed 20% roughage in
the form of coarsely ground alfalfa than when pelleted
alfalfa was used as the roughage source. In Trial 1,
lambs fed pelleted alfalfa had greater ADG, DMI, and
NEg than lambs fed the chopped alfalfa from d 0 to 50.
It is unclear in the work by Thomas and Dahmen
(1986) whether differences in chemical composition
existed between chopped and pelleted alfalfa. One
possible explanation for the differences noted between
our results and those of Thomas and Dahmen (1986)
3364
HATFIELD ET AL.
is that in our Trial 1 the chopped alfalfa was higher in
ADF, ADL, and NDF but similar in CP to the pelleted
alfalfa (Table 1). However, in Trial 2, NDF was
similar for the chopped and pelleted alfalfa (Table 3).
In Trial 2, lambs fed chopped alfalfa had greater
ADG and gain:feed during d 0 to 21 than lambs fed
pelleted alfalfa. The opposite relationship was noted
from d 22 to 50, in which lambs fed the pelleted alfalfa
had greater ADG and gain:feed than lambs fed the
chopped alfalfa diets. The reason for this difference is
unclear. Perhaps lambs adapt more quickly to grain
when fed in combination with chopped rather than
pelleted alfalfa.
In Trial 1, from d 0 to 50, lambs fed pelleted alfalfa
were treated for digestive and respiratory problems
more frequently than lambs fed chopped alfalfa. In
addition, fecal starch was greater for lambs fed
chopped than for those fed pelleted alfalfa. The lower
fecal starch in lambs fed pelleted alfalfa could account
for the superior performance by these lambs compared
with lambs fed chopped alfalfa. The greater incidence
of health problems in the lambs fed the pelleted alfalfa
is an important consideration in selecting a form of
roughage but may simply be indicative of a higher
energy diet because of greater DMI.
Dressing percentage tended to be greater in Trial 1
and was greater in Trial 2 for lambs fed pelleted
alfalfa than for those fed chopped alfalfa. In addition,
carcass weight and backfat thickness also were
greater for lambs fed pelleted alfalfa in Trial 1 than
for lambs fed chopped alfalfa. Hatfield (1994)
reported that although ADG did not differ between
mixed whole and pelleted barley-alfalfa diets, DMI
was greater and dressing percentage was less for the
mixed whole diet compared with complete pelleted
diets. Clanton and Woods (1966) found no difference
in carcass characteristics between steers fed chopped
and those fed pelleted alfalfa. Findings of Thomas and
Dahmen (1986) were opposite those of the present
study and previous work by Hatfield (1994). Weir et
al. (1959) also reported that dressing percentage was
greater for lambs fed pelleted alfalfa than for lambs
fed chopped alfalfa; however, chopped alfalfa was
18.4% CP and pelleted alfalfa was 21% CP. It would
seem from the results of these studies that the control
factor is not so much form of roughage, but which diet
resulted in the greatest BW gain, which positively
influences dressing percentage.
Owens and Goetsch (1988) reported that grinding
long forage decreased digestibility and increased feed
intake by decreasing ruminal stratification, rumination, and ruminal retention time. Merchen (1988) fed
ground and pelleted grass at one to three times
maintenance and noted that pelleting decreased
roughage retention time at all levels of intake
compared with chopped grass hay. In Trial 3, lambs
fed the pelleted alfalfa had lower ruminal retention of
alfalfa than lambs fed chopped alfalfa. Total tract
DMD tended to be greater in lambs fed chopped alfalfa
diets than in lambs fed pelleted alfalfa. In situ alfalfa
DM disappearance did not differ between forms of
alfalfa (Figure 3). In situ alfalfa DM disappearance
was determined with ground samples, which would
presumably mask the form of alfalfa treatments
because differences in true rate of ruminal roughage
digestion would be greater with unground samples.
Level and form of fiber in the diet will influence
rumination time and the degree to which a fiber mat
is developed in the rumen. The level and form of fiber
for which starch from different types of barley is used
most efficiently without adversely affecting lamb
performance and the amount of time required to finish
lambs is unknown. Goetsch et al. (1987) reported that
coarsely chopped hay tended to decrease ruminal
starch digestion of ground corn diets but increased
ruminal starch digestion of whole corn diets in beef
steers. In Trial 3, barley ruminal retention tended to
increase in lambs fed pelleted compared with chopped
alfalfa. In situ ruminal barley disappearance tended to
be greater in lambs fed chopped compared with
pelleted alfalfa.
Grain Bulk Density
The relationship between grain bulk density and
animal performance is unclear. Bulk density seems to
be closely related to animal performance at the lower
end of the bulk density scale. In Trial 2, lamb ADG
was not affected by barley bulk density. Lambs that
were fed low bulk density barley consumed 6% more
feed than those fed high density barley. They were,
however, 6% less efficient at converting feed to gain
than lambs fed high bulk density barley. Thomas et al.
(1962), Grimson et al. (1987), and Mathison et al.
(1991) also reported a similar response to changing
bulk densities of barley in beef cattle research.
Engstrom et al. (1992) reported that feed efficiency
was improved as the starch content of the barley
varieties increased. However, Hanke and Jordan
(1963) found that lambs fed whole heavy barley ate
more barley and gained faster than lambs fed whole
light barley (669 kg/m3 and 363 kg/m3) , but, when
barley was pelleted, bushel weight had no effect on
lamb performance. Crenshaw et al. (1987) reported
no effect of bulk density on performance of pigs fed
mixed pelleted barley diets that were 630, 570, 530,
and 500 kg/m3.
Thomas et al. (1962) found no difference in daily
feed consumption between 580 and 640 kg/m3 steamrolled barley fed to Hereford steers at 80% of the diet
and only a minor advantage for the heavy barley in
terms of weight gain and feed efficiency. Mathison et
al. (1991) evaluated barley of 430, 590, 640, and 660
kg/m3 in high-concentrate diets fed to beef steers. The
light barley had 9% less starch than the two heavier
barleys. This difference, however, resulted in only a
2% decrease in OM digestibility for the light barley.
BARLEY DENSITY AND ROUGHAGE FORM IN LAMB DIETS
When growth performance was measured, steers fed
the light barley diet had similar DMI and daily gain
but required 6% more feed DM per unit gain than
steers fed the heavier barley diet. Again, the higher
bulk density barley (640 kg/m3) produced no improvement in growth performance compared with the
intermediate (590 kg/m3) barley. Similarly, Grimson
et al. (1987) evaluated barleys with a density of 478,
556, and 666 kg/m3 in high-concentrate diets (85%
barley) for feedlot steers. No differences were found as
a result of bulk density for DMI and daily gain.
However, a 1.2% increase in feed efficiency was
observed for each unit increase in bulk density from
the low to medium bulk density barleys. Similar to
Mathison et al. (1991), they found no further benefit
from the heavy bulk density barleys. It is unclear why
this plateau effect occurs as barley reaches higher
bulk densities.
Mathison et al. (1991) reported that OM digestibility in all-concentrate diets containing light barley
(430 kg/m3) was 2% less than OM digestibility in
diets containing heavier barley (590, 640, and 660 kg/
m3) . Steers fed the light barley had a 6% increase in
gain:feed (nonsignificant) compared with steers fed
the two heavier barleys. Carcass characteristics were
not influenced by grain density.
The results of Trial 3 do not seem to support
performance data in Trial 2. Lambs fed light barley
had greater DMI than lambs fed heavy barley, even
though alfalfa and barley ruminal retention times
were greater in lambs fed light compared with heavy
barley, indicating that ruminal fill was not limiting
intake in this trial. Heavy barley, however, had
greater in situ DM disappearance at 24 and 48 h than
light barley. Possibly, because of the lower NDF and
higher starch in the heavy barley, DMI by lambs fed
the heavy barley may be regulated more by
chemostatic controls than by physical characteristics
of the diet.
Implications
Although average daily gain of feedlot lambs was
not always greatest with higher levels of barley, gain:
feed was improved with higher levels of barley in the
diet; however, the higher levels of dietary barley
seemed to result in fatter lambs. Weather conditions
are an important factor affecting differences in dry
matter intake and average daily gain among the
different levels of barley in the diet. Although heavy
bulk density barley may result in better gain:feed,
true differences in barley are best determined by
starch and fiber content. In addition, regulation of
intake (chemostatic vs kinetic) may be different with
different bulk densities or levels of starch. Form of
roughage resulted in mixed results on lamb performance; however, cost of processing roughages and
3365
method of feeding (i.e., bunk or self-feeders) may be
more important factors in determining the form of
roughage. The tendency in both feedlot trials for
pelleted alfalfa to result in higher dressing percentage
and a thicker body wall is of interest but unexplainable.
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