Effect of genotypes on reaction time, refractory period, semen index and liquid stored semen quality of breeding bulls in Bangladesh

The present study was conducted with the aim to reveal the effect of genotypes on reaction time, refractory period, semen index and liquid stored (at 4oC) semen quality of breeding bulls in Bangladesh. Semen was collected twice a week from Holstein Friesian, Sahiwal and Brahman breeding bulls. Reaction time and refractory period were examined for the breeding bulls. Semen volume, sperm concentration and total spermatozoa/ejaculate were measured immediately after collection. It was revealed that genotype had a significant (P<0.01) effect on semen volume, sperm concentration, total sperm output and refractory period but not in reaction time. From the point of view of semen index, semen quality of Holstein Friesian breeding bulls was superior to Sahiwal and Brahnman breeding bulls. Progressive motility, live and normal spermatozoa of fresh semen did not differ significantly but after dilution progressive motility differed significantly (P<0.05) in different genotypes of breeding bulls. During preservation time (0 to 120 hours), progressive motility, normal and live spermatozoa changed significantly (P<0.05) in each genotype with the progress of time. During 0 hour, 72 hours and 120 hours of preservation, progressive motility was found in Holstein Friesian (73.11±1.12%, 53.11±5.14%, 13.40±2.53%), Sahiwal (78.21±1.68%, 64.96±4.60%, 13.22±1.42%), and Brahman (75.21±1.68%, 54.86±4.40%, 16.96±4.42%), respectively. On the other hand, non-return rate was found insignificant (P>0.05), where higher fertility was observed in Holstein Friesian bull (67.2%) followed by Sahiwal (63.7%) and Brahman bull (57.38%). In a nutshell, Holstein Friesian bull has better fresh, diluted and preserved semen quality than the other two genotypes and after the 3 days of preservation, semen quality in respect of progressive motility, normal and live spermatozoa drastically deteriorated. Therefore, it is recommended that preserved semen of different genotypes should be used for AI within 3 days of liquid semen preservation at 4oC.