Submitted to: Journal of Animal Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/21/2001
Publication Date: N/A
Citation: Interpretive Summary: Somatotropin has been shown to increase milk yield and muscle growth in livestock. These increases have been reported to be due to a combination of a direct action of the somatotropin on the metabolism of absorbed nutrients and to stimulation of cell proliferation. In dairy cows, higher incidence of mastitis was reported with injection of bovine somatotropin. The approval of rbST by the Food and Drug Administration (FDA) in early 1994, has led to an increase in its use in a large number of commercial dairies in the USA. Although there is a growing interest in commercial goat production, the use of bovine somatotropin (rbST) in goat dairies is sporadic due to the paucity of information on potential benefits and herd health. In addition, the inconsistent reports on the effect of exogenous rbST on reproduction necessitates further investigation in the goat. The objective of this study was to evaluate the level of peripheral hormones and general hematological profile of dairy goats receiving a daily dose of rbST. When administered daily at 40 microgram/Kg of body weight, rbST did not adversely affect the hematological profile, the reproductive efficiency and incidence of mastitis of dairy goats.
Technical Abstract: The effect of daily injection of recombinant bovine somatotropin (rbST) on the level of peripheral hormones and general hematological profile of dairy goats was evaluated in two experiments lasting six and ten weeks, respectively. In experiment 1, fifteen multiparous mature lactating dairy goats (51 kg) in late lactation were screened for subclinical mastitis, and blocked according to milk yield. In experiment 2, eighteen multiparous lactating goats (60 kg) in mid-lactation were similarly selected. In each experiment, the goats were randomly assigned to either a control (.9% saline daily) or a treatment group. The treated group received daily injection of 40 microgram of rbST/kg of BW. Total red blood cells and white blood cells were not affected by daily rbST injection in both experiments. In both experiments, the level of circulating growth hormone increased with daily injection of rbST. The concentrations of LH, T3 and T4 were not affected by exogenous hormone injection. Progesterone concentrations increased with rbST injection in experiment 1 but were not affected in the second experiment. There was a significant increase in level of progesterone with time in both experiments regardless of treatment. At the dose of 40 microgram/kg of BW, rbST does not influence reproductive status or disrupt the health status of mature lactating dairy goats.