Studies on scrotal biometry, ejaculate characteristics and fertility in Ongole bulls

Abstract

The biometry of scrotum and testes, age, body weight, semen characteristics and fertility rates were studied in two groups of pure Ongole breed bulls. Group-I (n=25) constitutes retrospective analysis of data previously generated in respect of above characters on mature bulls aged between 3 and 9 years. Group-II (n=9) bulls aged between 3 and 6 years were subjected to semen collection once a week and their body weight and scrotal biometry was recorded in different age group. 90 ejaculates equally distributed between bulls were used to study various physical characters and the fertility rate of each bull was evaluated by inseminating 20 estrus cows per bull. The average body weight of Group-I and Group-II bulls was 715.76 and 481.11 Kg and their mean age was 84.56 and 50.33 months respectively. A significant positive correlation (P<0.01) was observed between age and body weight in the both groups of bulls. The average scrotal circumference was measured to be 36.68 and 36.22 cm in Group-I and Group-II bulls respectively. The mean length and width testes was found to be 13.77 and 9.83 in Group-I bulls and 15.22 and 9.78 cm in Group-II bulls respectively. The scrotal circumference, testicular length and width were found to be uniformly increasing up to 5 to 6 years of age in both groups of bulls. In both groups the age, body weight and scrotal circumference were positively correlated. The overall mean ejaculate volume was measured to be 5.78 and 4.88 ml in Group-I and Group-II respectively. The mean mass activity was 2.95 and 2.50 in Group-I and Group-II respectively. The overall mean percentage of initial motility was recorded as 75.00 and 71.00 in Group-I and Group-II respectively. Significant difference was noticed between bulls of both groups in respect of mass activity and initial motility which may be attributed to individual variation. The mean ejaculate volume was significantly (P<0.05) different between bulls and between collections of Group-I. The mean sperm concentration (millions per ml) was 1337.80 and 1176.00 in Group-I and Group-II bulls respectively. Significant difference (P<0.05) was observed between bulls and between collections in Group-I, where as in Group-II bulls no significant difference was noticed both between bulls and between collections. 80.03 and 70.88 per cent of live sperms were recorded in both Group-I and Group-II bulls respectively and there was significant (P<0.05) difference was observed between bulls of both groups. The overall mean percentage of head, mid piece, tail and total sperm abnormalities in Group-I and Group-II bulls respectively was 2.3, 1.04, 3.34 and 6.83 and 2.43, 0.96, 4.72 and 8.08. The total sperm abnormalities differed significantly (P<0.01) between bulls of both groups. Pre thaw and post the motility studies, which were conducted in Group-II bulls, revealed mean values as 69.55 per cent and 57.85 per cent. The post the motility was significantly (P<0.05) lower than pre freeze motility. The overall fertility rate of Group-I and Group-II bulls was 71.63 per cent and 63.55 per cent respectively. In both the groups the bulls with maximum scrotal circumference (40 cm) showed highest (>85 per cent) fertility rates. The fertility rate was observed to be positively and significantly and correlated with scrotal circumference, sperm concentration, mass activity and percentage of live spermatozoa. From the results of the present study it may be concluded that the age, body weight and scrotal circumference were positively correlated. The pre freeze motility was significantly higher than post motility. The fertility rate was found to be consistently higher in Ongole in comparison to other Indian breeds.