Journal of Animal Science, Vol 77, Issue 1 17-24, Copyright © 1999 by American Society of Animal Science

JOURNAL ARTICLE

The effect of bovine somatotropin treatment on production of lactating angora does with kids

J. J. Davis, T. Sahlu, R. Puchala, M. J. Herselman, J. M. Fernandez, J. P. McCann and S. W. Coleman
E. (Kika) de la Garza Institute for Goat Research, Langston University, OK 73050, USA.

Fourteen Angora does (35+/-2 kg), each with a single kid and in the first month of lactation, were used to determine ongoing (Period 1) and residual (Period 2) effects of chronic bovine somatotropin (bST) treatment. Specifically, we sought to determine whether chronic bST treatment was capable of improving milk yield, and thus kid growth, and mohair production of nursing does. The experiment consisted of a 2-wk pretreatment period, 5 wk of weekly subcutaneous treatment of slow-release bST (n = 7; Period 1), and a 4-wk posttreatment period (Period 2). The weekly dose of bST was calculated to release 100 microg/(kg BW.d(-1)). To estimate milk production, kids were separated from the does daily for 5 h, and their BW was recorded before and after suckling. The difference in BW was taken as milk production for 5 h. Fiber growth was measured by shearing does at the start of the experiment and at the end of Periods 1 and 2. Dry matter intake and BW of does were not affected by bST (P>.05). Average daily gain of kids that were suckling bST-treated does was higher (P<.05) than for kids of untreated does during Period 1 (184 vs. 139 g/d) but not during Period 2 (140 vs. 136 g/d; P>.10). Treatment with bST did not affect (P>.10) milk composition or clean fleece production in either period. Injection of bST did not affect (P>.10) plasma concentrations of glucose (mean = 49.5 mg/dL), urea N (mean = 19 mg/dL), total protein (mean = 72.5 g/d), or NEFA (mean = 122 microEq/L). During the period of bST treatment, plasma concentrations of somatotropin and IGF-I were increased (P<.05), concentrations of thyroxine and cortisol were decreased (P<.10), and plasma insulin levels were unchanged (P>.10) by bST. In conclusion, treatment of Angora dams with bST did not change DMI or mohair growth, but it improved growth of their kids.