Study on reproductive activity and evaluation of breeding soundness of jacks (Equus asinus) in and around Debre Zeit, Ethiopia
Livestock Research for Rural Development
Addis Ababa University, Faculty of Veterinary Medicine, Department of Clinical Studies, P. O. Box 34, Debre Zeit, Ethiopia
An evaluation of the reproductive performance and breeding soundness of jacks was carried out through a study on phenotypic traits (n=107), castrated jacks (n=22) and semen evaluation (n=3). Measurements including age, body condition score (BCS), body weight and testicular parameters were taken. Semen was collected using artificial vagina and was subjected to both gross and microscopic evaluation. The overall mean (±SD) BCS, age, and body weight for the jacks in the phenotypic study were 3.32±0.8, 11.1±4.7years, and 126 ±14.6kg, respectively. There was a significant difference (p<0.05) in the mean scrotal circumference between the different BCS categories. A highly significant (p<0.001) difference was observed in scrotal circumference among the different age groups with adult animals having the largest scrotal circumference. The mean (±SD) testis weight of the castrates was 276±33g while the ratio of testis weight to body weight was 1:2.1. A significant correlation was found between testis weight and scrotal circumference (r=0.43, p<0.05), testis weight and BCS (r=0.47, p< 0.05), and testis weight and body weight (r=0.81, p<0.001). The mean (±SD) semen volume was 39.9±14.5ml. The mean (±SD) jell-free volume, motility and sperm concentration were 28.8±10.7ml, 85.4±8.6%, and 533 ± 33.1 x 106/ml, respectively. BCS, scrotal circumference and testis weight were significantly correlated to sperm concentration (p<0.05; r=0.69; r=0.85 and 0.80, respectively). The mean time to erection was 3.3 minutes while length to semen collection was 5.4 minutes. The present study shows critical evaluation of the phenotypic traits to be important for stud selection and breeding soundness evaluation of jacks such as in artificial insemination.
Animalia; Carangidae; Equus asinus