The effects of heat stress and sperm quality classification on broiler breeder male fertility and semen ion concentrations.

1. The present study was undertaken to determine the effects of heat exposure on fertility, semen quality, and semen ion concentrations of broiler breeders classified on sperm quality index (SQI) before heat stress. 2. Cobb males (108) were individually caged in 6 temperature-controlled rooms. Each room contained an equal number of males from each of the 4 SQI population quartiles as follows: best (B), good (G), fair (F), and poor (P). Three rooms were heated to 35 degrees C, and the other three rooms were maintained at a constant 23 degrees C as controls. For each SQI group in each room, 15 Leghorn hens were artificially inseminated (5 x 10(7) sperm/hen) once a week for 8 weeks for fertility observations. 3. Body weight, sperm concentration, SQI, and fertility of P males were lower than in the other three SQI groups. Body temperature of the top three SQI groups was increased by heat exposure, but body temperature was not altered by heat stress in the P group. Fertility, sperm viability, and SQI of the top three SQI groups, but not the P group, was decreased by heat stress. Seminal plasma K+ of P males was lower than that of B males. However, seminal plasma Ca2+ concentration of P males was higher than that of B males. 4. In conclusion, high ambient temperatures had more impact on semen quality and fertility of males in the top 75% of the SQI population than in males in the bottom 25% of the population. In addition, calcium ions (Ca2+) appear to play a major role in heat stress infertility.