IMPROVING GENETIC PREDICTIONS FOR DAIRY ANIMALS USING PHENOTYPIC AND GENOMIC INFORMATION
Title: Use of Haplotypes to Estimate Mendelian Sampling Effects and Selection Limits
Submitted to: World Congress of Genetics Applied in Livestock Production
Publication Type: Proceedings
Publication Acceptance Date: June 1, 2010
Publication Date: August 1, 2010
Citation: Cole, J.B., Van Raden, P.M. 2010. Use of Haplotypes to Estimate Mendelian Sampling Effects and Selection Limits. World Congress of Genetics Applied in Livestock Production. Proc. 9th World Congr. Genet. Appl. Livest. Prod., Leipzig, Germany, Aug. 1–6, 4 pp.
Interpretive Summary: Every individual receives two copies of each chromosome during fertilization, one from its sire and one from its dam. In the past, only the average of the gene effects on the two chromosomes could be calculated. Using new computing procedures and large numbers of DNA markers for thousands of cows and bulls the gene effects now can be identified for individual chromosomes. An analysis of 3,689 animals from the Jersey breed found that there is more variation among individual chromosomes than previously calculated, and that the population can be changed more than reported in earlier studies. It is not currently possible to predict which chromosomes will be inherited by individual animals, but improvements in technology may permit the screening of large numbers of embryos to identify those inheriting desirable combinations of chromosomes, which could then be bred to other animals with favorable sets of chromosomes.
Haplotypes of 3,689 Jersey cattle were used to derive upper and lower bounds for Mendelian sampling (MS) effects and selection limits. Matings of the 25 best and poorest bulls to all genotyped cows were simulated to determine the impact of genomic selection on MS. Lower and upper bounds of MS were 2,175 and 49,290, respectively. MS variance was slightly larger in the top group (58,149) than the bottom group (51,556). Upper and lower bounds for
the selection limit were 5,243 and 13,254, respectively. For comparison, top U.S. Jersey bull in January, 2010, had a breeding value of +1,180. The MS variance from the top and bottom simulated matings was 31,022 and 47,820, respectively. Selecting animals rather than chromosomes may result in slower progress, but limits may be the same because chromosomes will become homozygous with either strategy.