Concentrations of bovine somatotropin and insulin-like growth factor-I in serum and milk samples of crossbred dairy cows treated with prolonged-release bovine somatotropin

A. R. Azizan, R. H. Phipps, W. E. Wan Hassan, D. L. Hard, I. A. Forsyth and J. A. Taylor

Abstract

Secretion of bovine somatotropin (BST) and insulin-like growth factor-I (IGF-I) was measured in lactating crossbred Sahiwal-Friesian dairy cows injected with prolonged-release bovine somatotropin (sometribove). The study showed an increase of two to threefold in both BST and IGF-I secretion in the blood serum. Serum BST and IGF-I increased significantly (p <0.05) on day 2 and remained high on day 9 as compared with the non-injected control. Both values decreased on day 14 after the injection. The mean values for serum BST concentration at day 2 and day 9 of cycle 8, and 14 days post-injection period were 6.3, 6.6 and 4.3 ng/mL respectively while the corresponding mean serum IGF-I values were 185.8, 215.1 and 104.9 ng/mL. On the other hand, the skimmed milk analysis of those cows showed no significant difference (p >0.05) in BST and IGF-I levels.

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