A simple strategy for managing many recessive disorders in a dairy cattle breeding program

Area of Science:

• Animal Genetics
• Quantitative Genetics
• Dairy Cattle Breeding

Background:

• High-density SNP genotypes identify novel recessive mutations affecting dairy cattle fertility and other traits.
• Current mate allocation strategies often overlook genomic information, complicating management as mutation numbers increase.

Purpose of the Study:

• To develop and evaluate a modified genomic mating strategy accounting for economic impacts of Mendelian disorders.
• To compare this modified strategy against random mating, truncation selection, and the original Pryce method.

Main Methods:

• A modified Pryce method was developed, incorporating economic values of Mendelian disorders.
• The modified Pryce method was compared to existing strategies using scenarios with 6 and 12 recessive alleles in US Holstein populations.

Main Results:

• Both Pryce methods effectively reduced recessive allele frequencies, especially for common alleles (>0.30).
• The modified Pryce method showed superior performance for low-frequency alleles with minor economic impact.
• Genetic gain was marginally higher with the Pryce method, while inbreeding rates were comparable across methods.

Conclusions:

• The proposed method accelerates the reduction of undesirable recessive allele frequencies.
• This strategy can be adapted to manage desirable recessive alleles and is software-implementable.
• Freely available code supports the implementation of this advanced mate allocation tool.