Guinea Pig Sperm Morphology and Fertility under Different Photoperiod

SIMPLE SUMMARY: Sperm morphology can predict the reproductive potential of males, since the high rate of abnormalities could determine their infertility. In this study, the morphological characteristics of spermatozoa from guinea pigs subjected to different photoperiodic stimuli were determined. The sperm morphology of guinea pigs subjected to a photoperiod by LED light, a photoperiod by sunlight, and a room without a direct light source were compared. In the LED light photoperiod, the spermatozoa had the largest perimeter and nuclear area; in addition, the age of mating and first calving of the females was earlier than in the room without a direct light source. In the photoperiod by sunlight, no pregnancies were achieved. LED light photoperiod can improve the morphological quality of guinea pig sperm and therefore, their reproductive capacity. ABSTRACT: Sperm morphology can predict the reproductive male fertilizing potential. This study aimed to determine the morphological and morphometric spermatozoa characteristics from guinea pigs subjected to different photoperiodic stimulation. Thirty F1 guinea pigs were randomly assigned to three photoperiodic treatments: FT1 (photoperiod with 10 Light/14 Dark LED light), FT2 (photoperiod with 10L/14D sunlight), and FT0 (room without direct light source). At 107 ± 9.8 days of age, sperm concentration and motility were higher in the FT0 and FT1 groups (p < 0.05); furthermore, there were no differences in nucleus length and ellipticity between the FT0 and FT1 groups, but the sperm of the FT1 group was higher in perimeter and nuclear area, while that of the FT0 group was higher in roughness, regularity, midpiece length, and tail (p < 0.01). Expanding acrosome (Type 2) was more frequent in the FT2 group, but there was variation in head measurements between all morphological categories. Pregnancy rate, calving age, and mating age were higher in the FT0 group; meanwhile, the FT1 group initiated successful matings earlier (p < 0.01). The FT0 group had a higher fertility rate, and the age of mating and first calving were earlier in the FT1 group than the FT0 group, but no pregnancies were reported for the FT2 group. Photoperiodic stimulation can increase the morphometric dimensions of guinea pig spermatozoa, favoring the reproductive characteristics, but sunlight could reduce their size due to heat stress.