Author
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Cole, John |
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Submitted to: Genetic Selection Evolution
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 11/16/2015 Publication Date: 11/30/2015 Citation: Cole, J.B. 2015. A simple strategy for managing many recessive disorders in a dairy cattle breeding program. Genetic Selection Evolution. 47:94. Interpretive Summary: There are a number of harmful alleles circulating in livestock populations that have negative effects on health and fertility if an animal inherits two copies of the defective gene. It is fairly easy to avoid matings among carriers when there are only a few such genes to keep track of. However, the number of known recessives continues to increase, which presents a challenge to breeders when mating their animals. This research describes a method that can be used to plan matings while accounting for undesirable recessive defects. Technical Abstract: Background: High-density single nucleotide polymorphism genotypes have recently been used to identify a number of novel recessives that adversely affect fertility in dairy cattle. Current methods for mate allocation do not use that information, and it will be increasingly difficult to manage matings when a large number of recessives must be managed. Results: A simple, sequential mate allocation method that constrains inbreeding and accounts for the economic effects of Mendelian disorders was developed and compared with random mating, truncation selection, and Pryce's method of constraining genomic inbreeding for several different scenarios, including 6 hypothetical alleles and 12 recessives currently segregating in the US Holstein population. Pryce's method and the modified Pryce's method showed similar ability to reduce allele frequency, particularly for loci with frequencies greater than 0.30. The modified Pryce's method may outperform Pryce's method for low-frequency alleles with small economic values. Cumulative genetic gain for the selection objective was slightly higher using Pryce's method, but rates of inbreeding were similar across methods. Conclusions: The proposed method appears to reduce minor allele frequencies for recessives with low frequencies faster than other methods, and can be used to maintain or increase the frequency of desirable recessives. It can easily be implemented in software for mate allocation, and the code used in this study is freely available as a reference implementation. |
