Subfertility in Stallions

I was not aware that a stallion’s fertility regularly went through periods of subfertility. Here they examine the chemistry of the seminal fluids and try to match it up with these periods and found that the amount of caseins (a family of phosphoproteins) present was highly correlated with fertility status and hypothesize that casein has a protective effect on the sperm.
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Proteomic analysis of spermatozoa reveals caseins play a pivotal role in preventing short-term periods of subfertility in stallions
Biol Reprod. 2022 Jan 12;ioab225.
Authors
Róisín Ann Griffin 1 , Aleona Swegen 1 2 , Mark A Baker 1 , Rachel Ann Ogle 1 , Nathan Smith 3 , Robert John Aitken 1 , David Anthony Skerrett-Byrne 1 4 , Sean Fair 5 , Zamira Gibb 1
Affiliations

1 Priority Research Centre for Reproductive Science, University of Newcastle, New South Wales, Australia.
2 Nuffield Department of Women’s and Reproductive Health, University of Oxford, Oxford, United Kingdom.
3 Analytical and Biomedical Research Facility, Research Division, University of Newcastle, Callaghan, New South Wales, Australia.
4 Pregnancy and Reproduction Program, Hunter Medical Research Institute, New South Wales, Australia.
5 Laboratory of Animal Reproduction, Department of Biological Sciences, Biomaterials Research Cluster, Bernal Institute, University of Limerick, Limerick, Ireland.

Abstract

Stallions experience transient fluctuations in fertility throughout the breeding season. Considering pregnancy diagnoses cannot be ascertained until ~14 days post-breeding, the timely detection of decreases in stallion fertility would enhance industry economic and welfare outcomes. Therefore, this study aimed to identify the proteomic signatures reflective of short-term fertility fluctuations, and to determine the biological mechanisms governing such differences. Using LC-MS/MS, we compared the proteomic profile of semen samples collected from commercially “fertile” stallions, during high- and low-fertility periods. A total of 1702 proteins were identified, of which, 38 showed a significant change in abundance (p ≤ 0.05). Assessment of intra- and inter-stallion variability revealed that caseins (namely κ-, α-S1-, and α-S2-casein), were significantly more abundant during “high-fertility” periods, while several epididymal, and seminal plasma proteins (chiefly, epididymal sperm binding protein 1 [ELSPbP1], horse seminal plasma protein 1 [HSP-1] and clusterin), were significantly more abundant during “low-fertility” periods. We hypothesised that an increased abundance of caseins offers greater protection from potentially harmful seminal plasma proteins, thereby preserving cell functionality and fertility. In vitro exposure of spermatozoa to casein resulted in decreased levels of lipid scrambling (Merocyanine 540), higher abundance of sperm-bound caseins (α-S1-, α-S2-, and κ-casein), and lower abundance of sperm-bound HSP-1 (p ≤ 0.05). This study demonstrates key pathways governing short-term fertility fluctuations in the stallion, thereby providing a platform to develop robust, fertility assessment strategies into the future.

Keywords: biomarker; capacitation; fertilisation; infertility; membrane stability; subfertility.