Tanner JC, Barrell GK. Reproductive performance of a cohort of Standardbred mares under a commercial breeding system.
Equine Vet J 2024;
56:776-785. [PMID:
37559421 DOI:
10.1111/evj.13989]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Accepted: 07/27/2023] [Indexed: 08/11/2023]
Abstract
BACKGROUND
Despite being a large commercial breeding industry, there is little published data on the reproductive success of Standardbred mares.
OBJECTIVES
To quantify the reproductive performance of Standardbred mares under artificial breeding systems in a commercial setting and determine the incidence of early embryonic and other pre-partum losses.
STUDY DESIGN
Retrospective cohort study.
METHODS
Data from four commercial farms were collected across four breeding years, and all mares were bred via artificial insemination. A total of 3995 mares contributed 7229 mare years. First-cycle pregnancy rate (FCPR) and end of season pregnancy rate (SPR) were analysed in mixed-effects logistic regression models. Time-to-conception interval was analysed in a Cox regression model.
RESULTS
The mean FCPR was 61.4% (confidence interval [CI] 60.3%-62.6%), the mean end of SPR was 84.7% (CI 83.8-85.5%), the mean live foal rate (FR) was 73.1% (CI 72.1%-74.2%). Mares located on-farm were more probable to be pregnant in terms of both FCPR (odds ratio [OR] 1.168, CI 1.018-1.340, p = 0.026) and SPR (OR 2.026, CI 1.673-2.454, p < 0.001), mares inseminated with thawed-frozen semen were less probable to be pregnant in terms of FCPR (OR 0.598, CI 0.457-0.783, p < 0.001) and SPR (OR 0.479, CI 0.354-0.647, p < 0.001) compared with insemination with fresh-extended semen. Older mares (14 years and older) were less probable to be pregnant in terms of FCPR (OR 0.795, CI 0.688-0.919, p = 0.002) and SPR (0.435, CI 0.352-0.538, p < 0.001) compared with young mares (3- to 8-year old).
MAIN LIMITATIONS
Retrospective data relied on accurate record keeping of stud farms and no mare-treatment or ovulation induction records were available. Live FRs relied mostly on annual foaling returns so fetal/foal deaths may be underrepresented.
CONCLUSION
This study provides substantial baseline data on reproductive performance for Standardbred mares managed under a commercial artificial breeding system.
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