Age Effects on Semen Quality and Sperm Kinematics of Red Chittagong Cattle (RCC) Bull in Bangladesh

Semen quality may be affected by several genetic and environmental factors. This study was designed to evaluate the effects of age on semen quality, kinematic properties, and frozen semen production potentialities of Red Chittagong Cattle (RCC) bulls. Eighty-eight (88) ejaculates from 12 breeding bulls (4 bull/group) of RCC breed were used in this experiment. The bulls were categorized into three groups based on their age (Group 1: 2.5-4.0 years, Group 2: 4.0-6.0 years, Group 3: 6.0- 8.0 years). Semen was collected once/week regularly in the early morning (6-6.30 AM) with an AV set. Different motility, morphology, and kinematic properties of sperm were evaluated by Computer Assisted Sperm Analyzer (CASA). One-way ANOVA followed by Duncan's multiple range post-test was used to assess differences among the mean using SPSS (25.0) software. Bull age has no significant effects on semen volume and concentration. Although a higher volume was found for group 3 (4.36±1.00) followed by group 2 (4.13±1.28) and group 1 (4.02±1.00). Sperm concentration increases with the increase of bull age. There were no significant differences found (p>0.05) for none of the motility parameters in fresh and frozen RCC bull semen irrespective of age. Significantly higher distal droplet (%) was observed for older bulls followed by group 2 and group 1 bulls. All breeding bulls irrespective of their age have more than two folds higher proximal droplet % than the normal value. Bull age has no significant difference in sperm kinematics and dose/ejaculates (p>0.05). With the increasing age of the bull, the number of dose/ejaculates (418.91±166.11 in group-3 vs. 384.75±137.33 in group-1) increases. In this experimental condition, RCC breeding bulls can be used for breeding purposes for up to 8 years with similar efficiency as a younger bull if the bulls have proper physical fitness for mounting and semen collection.