Authors: I.J. JAMES, O.A OSINOWO, O.F. SMITH , M.N. BEMJI, P.I. REKWOT
Journal of Agricultural Science and Environment 2010
Abstract
Twenty-four West African Dwarf (WAD) goats were used to study the pattern of milk yield response to recombinant bovine somatotropin (rbST) administered in a sustained-delivery vehicle. The goats were divided equally
into four treatment groups, each comprising of six does. The first group (control, T0) received no rbST while the other groups received rbST (T , 20 mg; T 40 mg; T , 60 mg) injected at 2week intervals commencing from the 7th week postpartum for 6 weeks. Pattern of milk yield response to rbST was significantly (p<0.05) influenced by rbST dose, day from rbST treatment, order of rbST treatment and parity. Milk yield of treated goats increased from day 1 of treatment, peaked between day 5 and day 8 after treatment and progressively decreased until day 14 of treatment but that of the control decreased progressively from day 1 till day 14 of treatment. The mean relative response of DMY to rbST treatment for T , T and T exceeded T by 50.36, 68.00 and 71.16 % respectively and significantly affected the shape of the lactation curve, thus, improving persistency of lactation. The patterns of DMY for T ,T and T were well-fitted by the Wood’s equations: Y = 16.628n1.728e-0.439n (R2 1 2 3 = 63.1), Y = 25.198n0.836e-0.239n (R2 = 75.6) and Y = 0.008n9.081e-1.352n (R2 = 42.3) respectively.The administration of 40 mg dose of rbST appears to elicit DMY response that favoured milk yield persis- tency. But since highest DMY was observed with 60 mg dose of rbST, estimation of optimal dose that would elicit maximum DMY response may be required in order to validate the statement. Our findings suggest that rbST administration to WAD goats after peak of lactation can enhance milk yield, galactopoiesis and persistency of lactation indicating higher milk yield in extended lactation.