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.

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.

If semen quality was known prior to insemination, sperm doses could possibly be decreased, maximizing the number of hens inseminated. The sperm quality index (SQI), an indicator of overall semen quality, is determined by the number of deflections in a light path due to sperm movement inside a capillary tube. The objectives of this study were 1) to determine the age at which the SQI becomes a static predictor of semen quality and 2) to determine if fertility of males with a higher SQI responds more favorably to insemination dose reduction than that of males with a lower SQI. Weekly from 23 to 32 wk of age, 144 Cobb males were tested for SQI. At 32 wk of age, males were placed into four groups that represented the SQI population quartiles as follows: poor, fair, good, and best. A fifth SQI group, uncategorized, was created to determine fertility of the original population by mixing equal amounts of semen from each of the four groups. Semen was collected weekly from 33 to 40 wk of age from 18 males in each of the four groups, pooled by group, and used to inseminate 30 hens per group with 50 or 100 million sperm. Eggs were collected daily, incubated, and broken out to determine fertility. Correlation coefficients between weekly SQI results and overall averages for individual males indicated that the SQI stabilized after the birds were 28 wk of age. The main effect for SQI selection revealed that the best SQI group had the highest fertility (88%), which did not differ from the good (83%) or fair group (82%) but was greater than the uncategorized group (80%). Fertilities of the top three groups and the uncategorized group were higher than the poor group (63%) (P< 0.0001, SEM 2.18). In addition, there was an interaction between SQI classification and insemination dose. Fertilities of the top three SQI groups were similar at the 50 and 100 million sperm doses. However, the poor and uncategorized SQI groups had lower fertility at the 50 million dose as compared to the 100 million dose. By categorizing males into SQI groups after 28 wk of age, insemination dose can be reduced, maximizing a male's fertilizing potential.

The present research was undertaken to determine the role of seminal plasma in heat stress (HS) infertility. Males were exposed to HS at 32 C or maintained at 21 C as controls. Centrifugation and reconstitution of semen samples created four final treatments: control sperm + control plasma (CsCp), control sperm + HS plasma (CsHp), HS sperm + HS plasma (HsHp), and HS sperm + control plasma (HsCp). Semen samples with HS males' seminal plasma had lower sperm quality index values than those containing plasma from control males. Seminal plasma from HS males diminished fertility of control sperm, and control seminal plasma did not improve fertility of HS sperm. Therefore, regardless of seminal plasma source, HS sperm had a lower fertilization rate than control sperm. Also, seminal plasma from semen samples with HS sperm (HsHp and HsCp) contained lower Ca, Na+ and Cl- concentrations than seminal plasma from semen samples with control sperm (CSCp and CsHp). When HS seminal plasma was mixed with control sperm, plasma ion concentrations increased, indicating an efflux of ions from the control sperm to the HS seminal plasma. On the other hand, when control seminal plasma was mixed with HS sperm, plasma ion concentrations decreased, indicating an influx of ions from the control seminal plasma to the HS sperm. Therefore, control sperm appear to have higher intracellular ion concentrations than the sperm from HS males. In conclusion, high temperatures might decrease male fertility by decreasing seminal plasma and intracellular ion concentrations.