author(s)
Mridula Sharma, Yaqoob Bhat, Nishant Sharma and Anoop Singh

abstract
Heat stress is a well-known problem causing huge economic losses to the buffalo breeders as well as dairy industry. Heat stress has a direct effect on breeding efficiency of both male and female buffalo and reduces the performance of buffalo bulls. Identification of the factors which affect the spermatic production and the quality of the semen has a major importance in improvement of bull fertility. A total of 42 ejaculates from 2 buffalo bulls were collected twice a week through AV (artificial vagina) method for 6 months at Semen Production Centre, department of Veterinary Gynaecology and Obstetrics, Pantnagar India, and analyzed using least squares analysis to quantify the effect of temperature humidity index (THI) on various semen quality parameters. The THI was divided into 3 groups, i.e. Group I (64 to 72, n=10), Group II (72 to 78, n=13) and group III (78 to 84, n=18). THI variations had no significant effect on Hypo-osmotic swelling test (76.33±3.38, 73.33±3.44 and 72.00±4.76) and Methylene Blue reduction test (7.60±0.79, 6.93±1.01 and 7.47±0.95) but had a significant (P<0.05) effect on percent live sperm (83.00±1.07^b, 80.67±2.18ab and 77.67±1.98a) and Concentration of sperm (973.33±1.00b, 935.00±0.90aband 900.00±1.50^a) The results of this study indicated that the live sperms and concentration of sperms decreases significantly (P<0.05) with the increase in THI. The value of percent live sperm, concentration and HOST reactive sperms was found highest at mean THI value of 68.42 (Group 1). Thus, it may be concluded that the hot-humid season with Higher THI adversely affect the various seminal attributes of buffalo bull.