Estimating the impact of the deleterious recessive haplotypes AH1 and AH2 on reproduction performance of Ayrshire cattle

Authors: GUARINI, ALINE - University Of Guelph; SARGOLZAEI, MEHDI - University Of Guelph; BRITO, LIUZ - University Of Guelph; KROEZEN, VICTORIA - University Of Guelph; LOURENCO, DANIELA - University Of Guelph; BAES, CHRISTINE - University Of Guelph; MIGLIOR, FILIPPO - Canadian Dairy Network; Cole, John; SCHENKEL, FLAVIO - University Of Guelph

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/18/2019
Publication Date: 6/1/2019
Citation: Guarini, A., Sargolzaei, M., Brito, L., Kroezen, V., Lourenco, D., Baes, C., Miglior, F., Cole, J.B., Schenkel, F. 2019. Estimating the impact of the deleterious recessive haplotypes AH1 and AH2 on reproduction performance of Ayrshire cattle. Journal of Dairy Science. 102(6):5315-5322. https://doi.org/10.3168/jds.2018-15366.
DOI: https://doi.org/10.3168/jds.2018-15366

Interpretive Summary: The reproduction performance of a population is a key indicator of its sustainability in the medium and long term. Therefore, identifying genetic factors associated with reduced reproduction performance is of crucial interest for the dairy cattle industry worldwide. We investigated the impact of two recessive lethal haplotypes in the Canadian Ayrshire cattle population and estimated their effects on key reproductive traits. This information is imperative when defining what actions should be taken to properly address the issue of increasing incidences of deleterious recessive haplotypes in a population under intense genetic selection.

Technical Abstract: 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.