Summary The provided pedigree of a herd of 250 Angus cattle was used to simulate the impacts of different numbers and frequencies of loss of function (LOF) alleles at essential loci using the simultaneous mate selection and allocation software program, MateSel. Three simulations were run modeling: 76 essential loci with LOF alleles at low frequencies (Low 76), 7 essential loci with LOF alleles at high frequencies (High 7), and 50 essential loci with LOF alleles at random variations of high and low frequencies (Random 50). Within each simulation, different breeding strategies were explored: (1) selection against carrier animals as a class, and (2) selection against the occurrence of homozygous affected calves (i.e. carrier matings). The data indicate that while strong selection against carriers did result in fewer homozygous affected calves, it came at considerable expense to genetic progress. However, selection against homozygous affected calves largely by mate allocation to avoid only the mating of LOF carriers at the same essential gene locus also avoided homozygous affected calves, but allowed for rates of genetic progress comparable to those obtained without consideration of LOF alleles. Furthermore, a small number of essential loci can be relatively easily managed to minimize the loss of genetic gain irrespective of the LOF allele frequencies. However, if LOF alleles are present at a high number of essential loci, especially with a random distribution of LOF allele frequencies, the power of a software program like MateSel is crucial to evaluate all mate pair combinations and optimally assign mate allocations to maximize genetic progress while minimizing the occurrence of homozygous affected calves. Keywords: loss of function alleles, mate selection, lethal, recessive

Lindsay Upperman, Brian Kinghorn, Michael MacNeil, Alison Van Eenennaam

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume Electronic Poster Session - Theory to Application 3, , 701, 2018
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