Location: Dale Bumpers Small Farms Research CenterTitle: Relationship of Anti-Mullerian hormone to reproductive traits in Katahdin ewes bred in late spring or fall
|ACHARYA, MOHAN - University Of Arkansas|
|RORIE, RICK - University Of Arkansas|
Submitted to: Small Ruminant Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/13/2020
Publication Date: 1/16/2020
Citation: Acharya, M., Burke, J.M., Ashworth, A.J., Rorie, R.W. 2020. Relationship of Anti-Mullerian hormone to reproductive traits in Katahdin ewes bred in late spring or fall. Small Ruminant Research. 8:48-56. https://doi.org/10.4236/arsci.2020.81005.
Interpretive Summary: Selection for fertility and ability to breed out-of-season in sheep allows farmers to maximize reproductive performance. Concentrations of anti-Mullerian hormone (AMH), a relatively stable hormone over time, has been shown to predict fertility in beef cattle; breeding values generated by data collection over generations is valued as well. Scientists from the Agricultural Research Service - Booneville, AR and University of Arkansas determined that AMH was not useful in predicting fertility or out-of-season breeding ability in sheep, but estimated breeding values generated by the National Sheep Improvement Program were useful in predicting performance of first time lambing. This information is important to sheep producers, scientists, veterinarians, and extension specialists aiming to improve reproductive performance in sheep.
Technical Abstract: Circulating anti-Mullerian hormone (AMH) concentration is an endocrine marker for fertility in many species. Objective of the study was to determine the relationship between serum concentrations of AMH and reproductive traits in ewes bred in spring or fall. Blood was collected at breeding from Katahdin ewes between 0.7 and 9-yr age of in 2015 (n = 162) and 2017 (n = 244) for the analysis of serum concentrations of AMH using different immunoassays (Equine and Ovine AMH in 2015 and Ovine AMH in 2017; AnshLab). Data on ewes were collected between 2008 and 2018. Serum AMH concentrations were either expressed quantitatively or divided into quartiles (AMH Q1 through Q4, with Q1 lowest and Q4 highest). Relationships between AMH and first exposure pregnancy rate as lambs or yearlings to spring or fall breeding, number of lambs born to first lambing, age at first lambing (using lifetime records), and estimated breeding values (EBVs) for number of lambs born (NLB), number of lambs weaned (NLW), maternal weaning weight (MWT), weaning weight (WWT), and maternal index were determined. Correlations were determined using PROC CORR (SAS), and PROC GLM was used with AMH concentrations as a dependent variable or AMH quartile as a dependent or independent variable, and included season in the models. There were no significant correlations detected between serum concentrations of AMH or quartiles and reproductive traits (P > 0.05). Serum concentrations of AMH tended to be lower (P = 0.07) and quartiles were lower (P = 0.08) in ewes that became pregnant in spring (only 8 of 162 ewes total) compared with fall bred or ewes that failed to become pregnant in 2015, but no differences detected in 2017. Age at first lambing was negatively correlated with EBVs for WWT (R = 0.17; P = 0.006), NLW (R = 0.13; P = 0.03) and maternal index (R = 0.15; P = 0.01), and more prolific ewes at first lambing had a higher EBVs for NLB (R = 0.38; P < 0.001), NLW (R = 0.33; P < 0.001), and maternal index (R = 0.26; P < 0.001), regardless of season of first breeding. The least square means pregnancy rate was -5.1 ± 5.5% and 69.0 ± 4.0%, respectively, for spring and fall breeding (P < 0.001), resulting in older spring compared with fall bred ewes at first lambing (2.0 ± 0.05 vs. 1.4 ± 0.05 yr, P < 0.001). While AMH did not predict fertility in ewes in this study, higher EBVs for reproductive performance (NLB, NLW, maternal index) were associated with younger ewes and greater prolificacy at first lambing.