Faculty of Agricultural and
Nutritional Science
Inbreeding and genetic variability
in Holstein Horse breed
ascertained by pedigree data
1L.
Roos, 1D. Hinrichs, 2T. Nissen, 1J. Krieter
1Institute
of Animal Breeding and Husbandry, Christian- AlbrechtsUniversity Kiel
2Verband der Züchter des Holsteiner Pferdes, Abteilung Zucht, Kiel
World Breeding Federation for Sport Horses
General Assembly and Seminar October 18th - 20th 2015,
Vienna, Austria
Christian-Albrechts-University
Kiel
Institute of Animal Breeding and Husbandry
Outline
1.
2.
3.
4.
5.
6.
Introduction
Aims of the study
Material and Methods
Results
Discussion
Conclusions and Perspectives
Introduction
• Holstein Horses are expressive sport horses with preferential
aptitude for show jumping, originated in Schleswig-Holstein,
Germany
• Breeding organisation founded in 1935
• In 19th century formation of the breed influenced by Yorkshire
Coach and Thoroughbred horses
• Agricultural mechanisation: breeding goal shifted from medium
weight draft horse to large framed riding horse
• Refinement driven by Anglo Normans and Thoroughbreds
• Studbook for mares closed, use of foreign stallions minimized
Aims of the Study
• Point out updated levels of inbreeding (incl. “age” of
inbreeding) and effective population size
• Determine proportion of foreign blood in population
• Specify genetic contributions of outstanding ancestors to
current structure of breeding stock
Material and Methods
Pedigree data :
• Breeding stock: 7,693 mares, 225 licensed stallions (2012)
• Total pedigree: 131,272 animals (until 2010)
• After revision: 129,923 animals analysed
• First recorded ancestor born in 1869
• Reference population: horses born 1990 until 2010
(n = 78,677)
• Essential metrics of population structure calculated for
reference population
→ software: PEDIG (Boichard, 2002)
Material and Methods
Inbreeding:
• Calculated by methods of Meuwissen and Lou (1992) and van
Raden (1992).
• Method of Kalinowski et al. (2000) used to determine “age of
inbreeding”:
→ Classical inbreeding (Wright, 1922) divided into two parts:
ancestral inbreeding (homozygous alleles, met in the past)
new inbreeding (alleles which are homozygous first time)
3. Material and Methods
Effective population size (Ne) :
Defined as the number of (breeding) individuals in an idealised
population under random genetic drift to generate the same
amount of genetic diversity as the population under study
→ computed with classical approach:
•
Based on increase in inbreeding coefficient (ΔF)
between last generation of reference population and their
parents
Ne = 1/(2ΔF)
Material and Methods
Additional analysis:
• Genetic contributions of foreign breeds:
English Thoroughbred, Anglo Normans (Selle Francais),
Hanoverian warmblood and Anglo Arabians
• Determination of genetic contribution of outstanding male and
female ancestors and its development over time
• 20 numerically largest Holstein mare lines analysed for
average inbreeding and genetic contributions
Results
Population structure:
Metrics of pedigree analysis for reference population
Parameter
Unit
Value
Pedigree Completeness
%
88
average Generation equivalent
generations
5.62
Generation Interval
years
10.3
F reference population (all horses)
%
2.27
Fanc (Kalinowski, 2000)
%
0.08
Fnew (Kalinowski, 2000)
%
1.38
Effective population size
n
55.3
Founders
n
3,194
Effective founders
n
50.2
Ancestors to explain 50% of gene pool
n
11
Results
Inbreeding coefficients for some other breeds:
• Some of these populations are smaller and completeness
of pedigree information is better, compared with Holstein
breed
Results
Inbreeding in Holstein Horse breed:
• 94,544 animals of total population are inbred (72.8%)
• Coefficient of inbreeding for reference population (all horses)
estimated as 2.27%
• For the total population, value of 1.57 % was computed
• Most of the inbreeding occurred in recent five generations
Results
Development of inbreeding in Holstein Horse breed by time:
Average inbreeding per time (inbred and non-inbred horses)
Results
Effective population size:
Development of effective population size (Ne) per generation
Results
Genetic contribution of foreign breeds (%):
Results
Most formative male ancestors:
stallion
year of
birth
genet.
contribution (%)
Cor de la bryere A.N.
1968
11.55
Ladykiller xx
1961
8.61
Capitol I
1975
6.81
Cottage son xx
1944
4.55
Ramzes A.A.
1937
3.07
Loretto
1932
3.05
Marlon xx
1958
2.04
Alme A.N.
1966
2.03
Farnese
1960
1.74
Ramiro
1965
1.47
• Founders of todays “most
wanted” sire lines determined
as most formative ancestors
• Origin of formative males
reflect results for
contributions of foreign breeds
• 50% Thoroughbred and
Anglo Norman (French)
stallions
Results
Genetic contribution of outstanding male ancestors over time
genetic contribution %
year of birth
Results
Most formative female ancestors:
mare (famous progeny) year of
birth
genet.
contribution (%)
Warthburg (Landgraf)
1962
3.70
Tabelle (Calypso I , II, …)
1959
2.43
Deka (Caletto I and II)
1967
2.13
Dorette
1956
1.41
Ricarda
1957
1.01
• Mares with strongly used male progeny out of mating
with prev. described line founding stallions
Results
Analysis of dam lines:
• Only two of Holsteins nummerically biggest mare lines
contributed more than 1%:
Line 628 B (2.05%), Line 18A2 (1.40%)
• Line 474 A is most inbred with average inbreeding
coefficient of 2.37%
• Most inbred animal of whole population was a male with
31.4 % out of mare line 569
Discussion
Inbreeding:
• reason for increase in average inbreeding per time could be
concentration on only few stallions out of certain sire lines
enforced by artificial insemination
• Hamann and Distl (2008) calculated average inbreeding
coefficient for Hanoverian warmblood reference population of
1.33%
• with closed Studbook for mares, access of different breeds into
Holstein breeding program is limited
• therefore, greater inbreeding coefficient was expected
compared with the other warmblood breeds
Discussion
Effective population size:
• With 55 animals, effective population size was determined on
a low level
• Hamann and Distl (2008) computed value of 372.34 effective
animals for Hanoverian breed
Teegen et al. (2008) defined 158 effective animals for
Trakehner horse
Discussion
Important ancestors' contribution:
• Contribution of important ancestors to Holstein horse gene pool is
not as balanced as described for other breeds
• 50% of genetic variability of the gene pool can be explained by 11
animals
• Unbalanced arrangement of ancestors` contribution is a further
characteristic of strong use of particular sires and could be
deemed as a reason for loss of genetic variability
Conclusions and Perspectives
Conclusions
• Results illustrate loss of genetic diversity related to
unequal contribution caused by intensive use of particular
sires
• Inbreeding mostly occurred in newer generations
• Low Ne endangers preservation of genetic variability
• In recent past: stagnation in rate of inbreeding and slight
increase in number of effective animals
• Rising trend in Ne
Conclusions and Perspectives
Perspectives:
• Rising trend in Ne might be caused by changes in breeding
policies → more open access for foreign stallions
• Follow this way with caution could be possibility to
preserve needed volume of genetic variability
• Further investigations must be done on consequences of
inbreeding and allelic loss in Holstein horses, especially for
functional traits
Thank you for
your attention !!
thankfully supported by: