Effects of inbreeding and other genetic components on equine fertility.
Abstract: The Finnish mating records of Standardbred trotters (SB; n = 33 679) and Finnhorses (FH; n = 32 731) were analysed to study the effect of the level of inbreeding on foaling rates and to estimate the heritability of foaling rate. A linear mixed model was assumed, with the outcome of the foaling (foal or no foal) as the trait of the study. A restricted maximum likelihood-based method was used to calculate the estimates of the variance components. Predictions of breeding values and estimates of fixed effects were also calculated. The average level of inbreeding was 9.9% in the SB and 3.6% in the FH. The average foaling rates were better in the SB (72.6%) than in the FH (66.3%), but within each breed intense inbreeding had a statistically significant negative effect on foaling rate (P < 0.05). Also, the mating type, the age and breeding type of the mare, and the age of the stallion had statistically significant effects on foaling rate (P < 0.001). The heritability of foaling rate was between 3.4% and 3.7% in SBs and between 5.5% and 9.8% in FHs, when the outcome of the foaling was considered to be a trait of the expected foal. With the same model, the estimates of maternal genetic effect were 4.7% for SBs and 3.2% for FHs, and the estimates of the permanent environmental effects of the stallion were between 1.3% and 1.7%. Avoiding matings with very high inbreeding coefficients would improve foaling rates. It would also be possible to devise a breeding program for better equine fertility, but because the heritability is low, improvement of environmental factors deserves special attention.
Publication Date: 2009-12-01 PubMed ID: 22443550DOI: 10.1017/S1751731109990553Google Scholar: Lookup
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- Journal Article
Summary
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This research examines how inbreeding among Standardbred trotters and Finnhorses impacts their fertility and ability to have foals. The study suggests that avoiding high levels of inbreeding can help to increase foaling rates, even though genetic factors have a relatively small influence on these rates.
Research method and subjects
- For this study, the researchers analyzed Finnish mating records of two horse breeds: Standardbred trotters (SB) and Finnhorses (FH) – around 66,000 records in total.
- A linear mixed model was used, treating the result of the mating (foal or no foal) as the trait to be studied.
- A restricted maximum likelihood-based method was employed for the variance components’ calculation.
- Also, estimates were made of breeding values and fixed effects among the horses studied.
Key Findings
- The average level of inbreeding among the Standardbred trotters was found to be 9.9% and 3.6% in the Finnhorses.
- Foaling rates were higher in the Standardbred trotters at 72.6%, compared to the Finnhorses at 66.3%.
- Significantly, the study found that even within each breed, intense inbreeding had a statistically significant negative effect on foaling rates.
- The type of mating, age and breeding type of the mare, and the age of the stallion all had statistically meaningful effects on foaling rates.
- The heritability of the foaling rate was between 3.4% and 3.7% for Standardbred trotters and between 5.5% and 9.8% for Finnhorses, when the foaling outcome was deemed a trait of the expected foal.
- In the Standardbred trotters, estimates of maternal genetic effect were 4.7% and 3.2% for Finnhorses. Also, the estimates of the permanent environmental effects of the stallion were between 1.3% and 1.7%.
Implications and Conclusions
- The study concluded that avoiding high levels of inbreeding could increase the foaling rates in these species.
- While it may be feasible to create a breeding program to improve equine fertility, the research suggests that because heritability of the foaling rate is relatively small, more focus should be placed on improving environmental factors instead.
Cite This Article
APA
Sairanen J, Nivola K, Katila T, Virtala AM, Ojala M.
(2009).
Effects of inbreeding and other genetic components on equine fertility.
Animal, 3(12), 1662-1672.
https://doi.org/10.1017/S1751731109990553 Publication
Researcher Affiliations
- 1Department of Animal Science, University of Helsinki, Koetilantie 5 (PO Box 28), 00014 Helsinki, Finland.
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