The introduction of genomic selection (GS) in dairy cattle has opened new possibilities to increase the rates of genetic gain. The objective of this study was to measure the impact of GS on Net Merit (NM) genetic gain of US Holstein (HO), Jersey (JE) and Brown Swiss (BS) cattle, using a four-path model of genetic improvement, and to compare these with those predicted by theory. Predicted Transmitted Abilities of NM calculated by the US Council on Dairy Cattle Breeding were used in this study. A total of 36,541,779 HO, 3,283,745 JE and 612,767 BS cows and 366,496 HO, 40,369 JE and 16,290 BS bulls, born since 1975 were included in the analysis where generation intervals (GI) and annual genetic gain (GG) were calculated for four paths of selection (Sire of Bulls [SB], Dams of Bulls, Sires of Cows and Dams of Cows). Results showed that the effect of GS on GI was important, especially for the SB path for HO and JE where GI decreased by half compared with previous periods. After introduction of GS, BS maintained the rate of change of GG ($2.8/year) while HO increased it to $21 and JE to $12, more than ten and twenty times higher than the previous years for each breed and much higher than the gains predicted in previous studies. Keywords: genomic selection, genetic gain, dairy cattle.

Felipe de Jesus Ruiz-Lopez, Adriana García-Ruiz, John B Cole, George R Wiggans, Curt P Van Tassell

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume Electronic Poster Session - Biology & Species - Bovine (dairy) 2, , 710, 2018
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