A.R. Guarini*, M. Sargolzaei*,‡, L.F. Brito*, V. Kroezen*, D.A.L. Lourenco†, C.F. Baes*, F. Miglior*,§, J.B. Cole#, and F.S. Schenkel*,1
*Centre for Genetic Improvement of Livestock, Department of Animal Biosciences, University of Guelph, Guelph, Ontario, Canada
†Department of Animal and Dairy Science, University of Georgia, Athens, Georgia, USA
‡The Semex Alliance, Guelph, Ontario, Canada
§Canadian Dairy Network, Guelph, Ontario, Canada
#Animal Genomics and Improvement Laboratory, ARS, USDA, Beltsville, Maryland, USA
1Corresponding author
2018 J. Dairy Sci. (?)
© American Dairy Science Association,
2018. All rights reserved.
Individuals may download, store, or print single
copies solely for personal use.
Do not share personal accounts or passwords
for the purposes of disseminating this article.
The effects of two deleterious recessive haplotypes on reproduction performance of Ayrshire cattle, Ayrshire Haplotype 1 (AH1) and Ayrshire Haplotype 2 (AH2), were investigated in Canadian Ayrshire cattle. Their phenotypic effects on stillbirth (SB) rate and 56-day non return rate (NRR) were calculated by estimating the interaction of service sire carrier-status with maternal grandsire (MGS) carrier-status using the official Canadian evaluation models for those two traits. The interaction term included 9 subclasses for the 3 possible conditions of each bull: haplotype carrier, non-carrier, or not genotyped. A total of 394 carriers and 1,433 non-carriers were available for AH1, whereas numbers of carriers and non-carriers for the AH2 haplotype were 313 and 1,543 respectively. The number of matings considered for SB was 34,312 for heifers (first parity) and 115,935 for cows (later parities). For NRR, 49,479 matings for heifers and 160,528 for cows were used to estimate haplotype effects. A negative effect of AH1 on SB rates was observed, which were 2.0% higher for matings of AH1-carrier sires to dams that had an AH1-carrier sire; this effect was observed for both heifers and cows. However, no significant effect was observed for the impact of AH1 on NRR. The AH2 haplotype had a negative impact on NRR, with 5.1% more heifers and 4.0% more cows returning to service, while no significant effect was found on SB rates. The harmful effects of AH1 and AH2 on reproduction traits were validated in the Canadian Ayrshire population. This information is of great interest for the dairy industry, allowing producers to make mating decisions that would reduce reproductive losses.
Keywords: 56-day non-return rate, geneic evaluation, recessive disorders, stillbirth