Elevated body temperature directly contributes to heat stress infertility of broiler breeder males.

Alterations in the male reproductive tract, sperm, or both may be responsible for heat stress infertility of broiler breeder males. The present study was conducted to determine the direct effects of hyperthermia during heat stress on sperm viability, the spermquality index (SQI), and seminal plasma ion concentrations by incubation of semen in vitro at and above normal body temperature. Thirty-seven Cobb males were divided into the upper (best group = B) and lower (poor group = P) 50% of the population according to their SQI. Semen characteristics and seminal plasma ion concentrations (Ca++, Na+, K+, and Cl-) for B and P males were evaluated at two temperature treatments (41.5 and 42.5 C) and four incubation times (0, 30, 60, and 90 min). The results revealed that sperm viability and the SQI were decreased by increasing incubation temperature and duration of exposure. Seminal plasma ion concentrations were not affected by semen incubation temperature; however, plasma Ca++ concentration in the P-SQI group was higher than that of the B-SQI group. Seminal plasma K+ concentration increased in both SQI groups over time. In conclusion, it is apparent that changes in semen characteristics due to elevated body temperature alone contribute to heat stress infertility of broiler breeders.