PHYSICOCHEMICAL CHARACTERISTICS OF SEMEN FROM BUFFALO BULLS (BUBALUS BUBALIS) AS AFFECTED BY TREATMENT OF TWO DIFFERENT DOSES OF RECOMBINANT BOVINE SOMATOTROPIN (rbST)

A total of 15 buffalo bulls were divided into three comparable experimental groups to study the effect of two different doses of recombinant bovine somatotropin (rbST) on physical and chemical characteristics of semen during the hot months of the year (April to September). The first group (G1) was left untreated and served as control, while the 2 nd (G2) and 3 rd (G3) groups were injected subcutaneously either with 250 or 500 mg Somatech ® /14 days/animal for eight successive injections, respectively. Bulls had an initial body weight around 350.9 kg and aged 16 to 18 months. Blood samples were collected fortnightly to determine testosterone and insulin like growth factor-I (IGF-I) in peripheral blood plasma, while semen was collected twice weekly to determine semen traits. Treated groups with rbST had higher (P<0.05) ejaculate volume than G1 by 5 and 12.5% for G2 and G3, respectively. Sperm concentration (x 10 6 /ml) was also higher (P<0.05) than G1 by ~10 and 14% for G2 and G3, respectively, which reflected an increasing (P<0.05) of sperm output by ~16 and 28% and live sperm output (P<0.05) by ~21 and 38% for G2 and G3, respectively. Sperm mass motility, advanced motility and live sperm were insignificantly higher in G2 and G3 (P>0.05), and sperm abnormalities were lower (P>0.05) in (G2) compared to (G1). IGF-I was higher (P<0.05) in rbST treated bulls (776 and 876 ng/ml, for G2 and G3, resp.) than that in G1 (594.7 ng/ml). Similar trend was observed for testosterone concentration being lower (P<0.05) in G1 (5.62 ng/ml) compared to G2 and G3 (8.08 and 9.78 ng/ ml, resp.). In conclusion, treated buffalo bulls with rbST either 500 mg or 250 mg /14 days/animal/ eight injections improved semen physical characteristics favorably to the 250 mg dose.