Comparison of different mathematical models to assess seasonal variations in the longevity of DNA integrity of cooled‐stored stallion sperm

Abstract

Dynamic assessment of sperm DNA fragmentation (SDF) has shown to give fuller understanding of stallion semen quality; however, there have been limited attempts to use this parameter to investigate seasonal changes in productive functions. The aims of this study were to: (a) establish a reliable mathematical model to describe the longevity of cooled‐stored sperm DNA integrity; (b) to examine the effect of seasonal variations on SDF. Ejaculates were cooled to 5°C, and SDF was analysed after 0, 6 and 24 hr of storage. The coefficient of determination (R2) was calculated after fine‐tuning linear (LIN), exponential (EXP) and second order polynomial (POL) models. R2 was significantly higher (p < .001) for POL than for LIN and EXP. The rate of DNA degradation was calculated using the slopes of POL equations. After assessing the rate of change of the POL functions, significant differences between the acceleration of DNA fragmentation were found (p < .01) among seasons, being higher for winter and summer than spring and autumn. In conclusion, DNA analysis of stallion sperm fits better to a second order polynomial mathematical model, being spring the best season to collect and process cooled stallion semen in order to maintain the DNA integrity of the stallion sperm.

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

“…The effect of season on stallion reproduction has not been clearly established. Some authors reported that the non‐breeding season impairs endocrine profiles (Dhakal et al., 2011), number of Sertoli cells (Johnson, Varner, Tatum, & Scrutchfield, 1991), sexual behaviour characteristics, such as number of mounts per ejaculation and reaction time in the presence of an oestrous mare (Clay & Clay, 1992; Johnson, 1991; Picket, Faulkner, & Voss, 1975; Picket & Voss, 1972), and semen quality including semen volume, sperm concentration, total sperm number (Clay & Clay, 1992; Johnson, 1991; Picket et al, 1975; Picket & Voss, 1972), sperm kinetics (Jasko et al, 1991), total sperm number with progressive motility (Greiser, Sieme, Martinsson, & Distl, 2020), DNA fragmentation (Ortiz et al., 2020) and production of reactive oxygen species (Mislei, Bucci, Malama, Bollwein, & Mari, 2020). 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).…”