Effects of heat exposure during summer on spermatogenesis in boar

抄録

Seasonal poor semen quality has been a well-known problem in boars across the world. Normal spermatogenesis is temperature dependant. Therefore, it is necessary to interpret the mechanism that high ambient temperature lead to poor semen quality in boar and elucidate whether the elevated temperature damaged spermatogenesis in boars’ testis when boars are being exposed to the elevated ambient temperature. Five boars were selected and exposed to elevated ambient temperature. After boars received 3-day heat exposure, semen collection was standardized to 18 continual times with a 3-day interval to determine the variables: semen characteristics, sperm viability, motility parameters, abnormal spermatozoa, composition of seminal plasma and testosterone level in seminal plasma and serum. The total sperm count was lowest by the end of second week. The higher abnormal spermatozoa percentage and lower motile spermatozoa percentage were observed by the end of second week and during week 3, 4 and 5 after heat exposure. Additionally, there was no significant change in semen volume, testosterone levels and concentrations of ions and total protein in seminal plasma before and after heat exposure. The spermatocytes and spermatids present in the testes at the time of heat exposure resulted in a higher percentage of spermatozoa with low motility. These results suggest that poor semen quality was attributed to the damaged spermatocytes and spermatids during a single 3-day heat exposure in hot summer months.