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Journal of Dairy Science Vol. 73 No. 9 2444-2452
© 1990 by American Dairy Science Association ®
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Sixty-Day Infusions of Somatotropin-Releasing Factor Stimulate Milk Production in Dairy Cows

G. E. Dahl 1, L. T. Chapin 1, S. A. Zinn 1, W. M. Moseley 1, T. R. Schwartz 1, and H. A. Tucker 1

1 Department of Animal Science, Animal Reproduction Laboratory, Michigan State University, East Lansing 48824 and The Upjohn Company 7921-25-4, Reproduction and Growth Physiology Research, Kalamazoo, MI 49001

Twenty-four Holstein cows were infused intravenously with sterile water (placebo) or 1, 3, or 12 mg of recombinant bovine somatotropin-releasing factor 1-45-homoserine lactone/d for 60 d. Relative to placebo (22.8 kg/d), 3 and 12 mg of somatotropin-releasing factor increased yield of milk to 28.8 and 33.3 kg/d during infusion. At 1 mg of somatotropin-releasing factor, milk averaged 27.5 kg/d during infusion but was increased above placebo only through 39 d. After infusion of 12 mg somatotropin-releasing factor ended, milk (26.4 kg/d) remained above placebo amounts (20.6 kg/d) for 15 d. Three and 12 mg of somatotropin-releasing factor increased serum somatotropin from .7 (placebo) to 8.2 and 10.3 mg/ml when averaged across 1, 30, and 59 d, whereas 1 mg increased somatotropin to 5.8 ng/ml after 1 d but had no effect at 30 or 59 d. Within 17 h of cessation of somatotropin-releasing factor infusion, serum concentrations of somatotropin were similar across all groups. On d 59, 3 and 12 mg infusions increased insulin-like growth factor I from 115.8 (placebo) to 204.7 and 261.4 ng/ml of serum. We conclude that somatotropin-releasing factor increased serum concentrations of somatotropin and milk yield in a dose-dependent manner for at least 60 d. Also, galactopoietic effects of somatotropin-releasing factor persisted for 15 d independent of increased concentrations of somatotropin in serum following withdrawal of somatotropin-releasing factor.

Key Words: somatotropin-releasing factor • milk yield • somatotropin

Submitted on February 14, 1990
Accepted on April 26, 1990




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H. Shingu, K. Hodate, S. Kushibiki, Y. Ueda, E. Touno, M. Shinoda, and S. Ohashi
Hormonal and Lactational Responses to Growth Hormone-Releasing Hormone Treatment in Lactating Japanese Black Cows
J Dairy Sci, June 1, 2004; 87(6): 1684 - 1693.
[Abstract] [Full Text] [PDF]


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