Seasonal variations in quantitative and qualitative sperm characteristics in fertile and subfertile stallions

Abstract

Abstract. Horses are seasonal breeders with a natural breeding season beginning in spring and extending through midsummer. In this study, quantitative and qualitative parameters of chilled stallion semen were compared between fertile and subfertile stallions and between the breeding and the non-breeding season. Semen quality parameters compared included ejaculate volume, sperm concentration, total sperm number, sperm morphology, and computer-assisted semen analysis (CASA)-derived sperm movement characteristics obtained from two groups of warmblood stallions (n=8; four fertile stallions and four subfertile stallions), which differ in the seasonal pregnancy rate 80 %–90 % (fertile) vs. 40 %–60 % (subfertile). A total of 64 ejaculates were collected from the stallions (n=8; four in the breeding season and four in the non-breeding season of each stallion). No significant differences in the semen quality parameters between the fertile and the subfertile stallions in the non-breeding season were observed. However, in the breeding season the proportion of morphologically normal sperm, total motility, progressive motility, average path velocity (VAP), and curvilinear velocity (VCL) were significantly higher in the fertile group (P<0.05) when compared with the subfertile group. In addition, a significant seasonal variation in the proportion of morphological normal sperm was found in the fertile group between the breeding and the non-breeding season (P<0.05). Moreover, significant seasonal variations (P<0.05) in CASA parameters of mean VAP, straight line velocity (VSL), and beat-cross frequency (BCF) were observed in the fertile and the subfertile stallions, which tended to be lower in the non-breeding season. In conclusion, differences between the fertile and the subfertile stallions were observed only in the breeding season, and a few of CASA-derived parameters seemed to be significantly lower during the non-breeding season in both the fertile and the subfertile stallions.

Monthly Evaluation of Testicular Biometry and Sexual Behavior With Respect to Seminal Aspects of Arabian Stallions Under Subtropical Conditions in Kuwait

“…The sexual beheviour is the highest in summer and spring, however it is usually reduced in winter (Waheed et al, 2015). Additionally, sexual behavior, ejaculate volume, total sperm output and motility were found to be higher during summer and spring compared to winter (Suliman et al, 2020). These findings are matching with our finding reported that the number of mounts per ejaculation, reaction time, time to erection, ejaculation times and time to ejaculation were significantly lower in summer season compared with other seasons.…”

Some Parameters of Stallion Semen Ejaculates During Different Seasons

“…The ejaculate gel volume was not significantly different in the breeding season and the non-breeding season. This result is in agreement with Suliman et al (2020). While, Morel (2008) reported that the ejaculate gel volume was higher in the breeding season than non-breeding season.…”

“…While, Warnke et al (2001) reported that the motility of stallion sperm is higher in winter (non-breeding season) than in summer and spring (breeding season) Evaluation of sperm cell concentration showed that no significant difference between stallions in breeding season and non-breeding season. These data was in a harmony with the results reported by Suliman et al (2020). These data is not in agreement with results obtained by (Janett et al, 2003 andWach-Gygax et al, 2017) who reported that the sperm cell concentration of stallion ejaculate was lower in the summer (breeding season) than in winter (nonbreeding season).…”

Predicting the Outcome of Equine Artificial Inseminations Using Chilled Semen

“…There is also an absence of any knowledge on the time of insemination or any veterinary care that the mare is provided before or after insemination. Therefore, given that previous studies suggest sperm movement is significantly associated with fertility [ 18 , 19 , 20 ], we primarily focused this study on this attribute of semen quality.…”