Season does not have a deleterious effect on proportions of stallion seminal plasma proteins

Abstract

The mechanism by which the content of the major groups of seminal plasma proteins in stallion semen changes between the breeding and non-breeding seasons remains unknown. Here, we investigated the proportions of non-heparin-binding, phosphorylcholine-binding, and heparin-binding proteins in seminal plasma with the aim of relating them to sperm quality and testosterone levels in good and bad freezer stallions. Only minor variations in the major protein groups were found between the breeding and non-breeding seasons. In the non-breeding season, a higher content of a subset of non-heparin binding proteins as well as of heparin-binding proteins was found. Analysis of semen characteristics revealed a somewhat contrasting picture. While only minor variations in sperm kinematics and sperm morphology were found between seasons, the flow-cytometric measurements of mitochondrial membrane potential and also, to some extent, reactive oxygen species production indicated lower sperm quality in the breeding season. Chromatin integrity and testosterone levels were unchanged between seasons. The results suggest that stallion ejaculates could be used year-round for freezing, since only minor differences in protein composition exist between the breeding and non-breeding seasons, as well as between good and bad freezers. In addition, sperm quality is not impaired during the non-breeding season.

Semen quality and freezability analysis during breeding and non‐breeding seasons in heavy draft stallions in southern Chile

“…Other studies revealed lower DNA fragmentation and low intracellular calcium level, and higher total motility, viability (Wach‐Gygax et al., 2017) and progressive motility in the non‐breeding season (Greiser et al., 2020). Other studies found no differences between seasons in sperm quality (kinetic, morphological and functional parameters), testosterone concentrations or concentration of seminal plasma proteins in stallion semen (Blottner, Warnke, Tuchscherer, Heinen, & Torner, 2001; Johannisson et al., 2020; Warnke et al., 2003).…”

Kallikrein proteoforms and reproductive parameters in stallion are conditioned by climate

“…Morte et al 8 reported differences in spermatic concentration, vitality and morphology, but the progressive motility did not differ among seasons. Recently, Ebel et al 9 evaluated seasonal changes in the quality of sperm from fertile stallions, and only viability showed higher values during the breeding season; Johannisson et al 10 found minor variations in kinematics and morphology of sperm among seasons.…”

“…Seminal plasma proteins and factors surrounding them have been studied in different mammals, especially bulls 13 – 15 and stallions 16 – 18 . Such proteins are involved in important stages of fertilisation, such as the establishment of sperm reserves in the oviduct, capacity modulation and interaction between gametes 10 , 16 . Identifying, characterising and quantifying seminal plasma proteins therefore allow inferences about the animal reproductive status.…”

“…Groups of proteins have been reported as associated with mammalian 19 and stallion reproductive capacity, such as fibronectin type II modules, cysteine-rich secretory proteins (CRISPs) and spermadhesins 16 , albumins and kallikreins 9 . In horses, different semen proteins have been reported for the breeding and non-breeding seasons 9 , 10 . Few two-dimensional electrophoresis (2-DE) proteomics studies have added information about the mapping of seminal plasma proteoforms of mammals, including equines 18 , 20 .…”