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Sixty-day infusions of somatotropin-releasing factor stimulate milk production in dairy cows
G E Dahl1, L T Chapin, S A Zinn
1Department of Animal Science, Michigan State University, East Lansing 48824.
Insights
Recombinant bovine somatotropin-releasing factor significantly increased milk yield and serum somatotropin in Holstein cows. These galactopoietic effects persisted even after treatment cessation, indicating sustained benefits for dairy production.
Area of Science:
- Animal Science
- Endocrinology
- Dairy Science
Background:
- Bovine somatotropin (BST) plays a crucial role in regulating milk production.
- Understanding the efficacy of BST-releasing factors is vital for enhancing dairy yields.
- Previous research has explored hormonal interventions to optimize milk production in cattle.
Purpose of the Study:
- To evaluate the dose-dependent effects of recombinant bovine somatotropin-releasing factor (rbSRF) on milk yield and hormonal profiles in Holstein cows.
- To determine the duration of galactopoietic effects following rbSRF administration.
- To investigate the impact of rbSRF on serum concentrations of somatotropin and insulin-like growth factor I (IGF-I).
Main Methods:
- Twenty-four Holstein cows were intravenously infused with sterile water (placebo) or 1, 3, or 12 mg/d of rbSRF for 60 days.
- Milk yield was recorded daily.
- Serum concentrations of somatotropin and IGF-I were measured at various time points.
Main Results:
- rbSRF administration increased milk yield in a dose-dependent manner, with 3 and 12 mg/d yielding 28.8 and 33.3 kg/d, respectively, compared to placebo (22.8 kg/d).
- Elevated milk production persisted for 15 days after cessation of the 12 mg/d rbSRF infusion.
- Serum somatotropin and IGF-I levels were significantly increased by rbSRF, with effects on IGF-I observed on day 59.
Conclusions:
- Recombinant bovine somatotropin-releasing factor effectively increases milk yield and serum somatotropin concentrations in a dose-dependent manner over 60 days.
- The galactopoietic effects of rbSRF demonstrate a sustained benefit for milk production, even after treatment withdrawal.
- rbSRF represents a promising therapeutic agent for enhancing dairy cow productivity.
Abstract:
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 ng/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.
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