Genotyping Strategies of Selection Candidates in Sheep Breeding Programs

Genotyping strategies for both ram and ewe selection candidates were investigated to maximise the benefit of genomic selection while minimising genotyping costs. Through stochastic simulation we investigated both early and late-stage genomic selection of rams using a selection index that contained an early in life measurement (post-weaning weight) and a hard to measure trait (intra-muscular fat) that was not measured on selection candidates. We also simulated genotyping strategies for female selection candidates in breeding programs using natural mating, multiple ovulation and embryo transfer (MOET) or juvenile in vitro fertilisation and embryo transfer (JIVET). Our results showed that genomic selection of rams lifted genetic gain by 40%. Genomic testing the top 20% of ram selection candidates achieved 80% of the maximum benefit using late-stage genomic selection, while testing 47% of the top ranked rams implementing early-stage genomic selection was required to achieve 80% of the benefit. Genetic gain lifted by a maximum of 15-65% for genomic testing in (only) ewe selection candidates. To achieve 80% of the maximum benefit of genomic selection, 65%, 35% and 45% of ewe selection candidates required genomic testing each year for natural, MOET and JIVET breeding programs, respectively. Genotyping ram selection candidates provided the best value for money.