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

Abstract

This study was carried out at a central sperm station Over a period of 10 months on 11 sexually mature (4-6 year-old) healthy breeding bulls of 3 genetic groups (4 HE; 4 K HF and 3 K J) under weekly twice semen collection schedule. The overall means of reaction time, seminal fructose and fructolytic index recorded at monthly intervals were 88.25 ± 14.19 sec, 546.38 ± 29.02 mg% and 1.08 ± 0.06 respectively. The serum testosterone profile studied once on each bull at 10 min, 6 hr and 24 hr post-semen collection averaged 7.11 ± 1.05, 3.66 ± 0.44 and 5.44 ± 0.62 ng/ml, respectively. The influence of breed was significant only for testosterone levels, which also varietl 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 collection in all the 3 breeds. The results suggest that semen collection time or actual collection evokes stimulatory response through hypothalamus on Leydig cells to secrete greater amount of testosterone, although the correlations of above traits with seminal attributes and fertility rates of bulls were very low and nonsignificant.