Reaction time, seminal fructose, fructolytic index and blood testosterone profile in Holstein-Friesian and crossbred bulls

This study was carried out at a central sperm station over a period of 10 m onths on 11 sexually mature (4-6 year-old) healthy bleeding bulls of 3 gene tic groups (4 HF; 4 K HF and 3 K J) under weekly twice semen collection sch edule. The overall means of reaction time, seminal fructose and fructolytic index recorded at monthly intervals were 88.25 +/- 14.19 sec, 546.38 +/- 2 9.02 mg% and 1.08 +/- 0.06 respectively. The serum testosterone profile stu died once on each bull at 10 min, 6 hr and 24 hr post-semen collection aver aged 7.11 +/- 1.05, 3.66 +/- 0.44 and 5.44 +/- 0.62 ng/ml, respectively. Th e influence of breed was significant only for testosterone levels, which al so varied significantly between breeds and between sampling intervals. The values were higher in K J. bulls and also at 10 min and 24 hr post semen co llection in all the 3 breeds. The results suggest that semen collection tim e or actual collection evokes stimulatory response through hypothalamus on Leydig cells to secrete greater amount of testosterone, although the correl ations of above traits with seminal attributes and fertility rates of bulls were very low and nonsignificant.