- The effect of bovine somatotropin (bST) and undegradable protein
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The effect of bovine somatotropin (bST) and undegradable protein on fiber production, ADG and blood metabolites of Angora wethers.
J.J. Davis., T. Sahlu, R. Puchala and M.J. Herselman.
E (Kika) de la Garza Institute for Goat Research, Langston University,
Twenty-four Angora wethers (Age = 12 mo and BW = 27 kg) were used in a 2 x 2 factorial experiment to study the effect of undegradable protein and exogenous bST on fiber production, ADG and blood metabolites. The treatments were two levels of bST (0 and 100 μg kg-1 d-1) and either casein (C) or formaldehyde-treated casein (FC). The C and FC were included in a TMR (12.9%CP and 61.4% TDN) for the entire experimental period and made up 50% of the protein content of the diet. The study consisted of a 2 week pretreatment period, 8 weekly subcutaneous administrations of a slow release bST (n=12; Animal Sciences Division, Monsanto Co.) (period 1) and 8 weeks post-injection (period 2). Dry matter intake (mean = 1.02 kg/d; P > .50) was not affected by either FC or bST. FC increased ADG over the whole experimental period (47 vs 30 g/d; P < .04) while bST had no effect (mean = 38.5 g/d; P > .66). Clean fiber production was increased by FC (17.6 vs 13.9 g/d, P < .001 and 18.1 vs 15.1 g/d, P < .02 for Periods 1 and 2, respectively) but was not affected by bST (mean = 15.8 and 16.6 g/d, P > .30 for Period 1 and 2, respectively). Fiber diameter (mean = 35.4 μm) was not affected by either bST or FC. Fiber length growth (μm/d) in each period was not affected by FC (mean = 874 and 786; P > .47) but was increased by bST in Period 2 (833 vs 738; P < .048). Plasma concentrations of glucose (61.9 mg/dL) , total protein (68 g/L) or nonesterified fatty acids (118 μEq/L) were not affected by either bST or FC (p > .05) during Period 1. Plasma urea levels were lower for FC goats during Period 1 (6.4 vs 8.7 mg/dL; P < .02). This study indicated that bST had no effect on ADG or fiber growth. Supplementation of the diet with formaldehyde treated casein significantly increased fiber growth and ADG but did not change fiber diameter or length.
J. Anim. Sci. 72 (Suppl 1), 183