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Related Experiment Videos

Somatotropin treatment for a second consecutive lactation.

R J Annexstad1, D E Otterby, J G Linn

  • 1Department of Animal Science, University of Minnesota, St. Paul 55108.

Journal of Dairy Science
|September 1, 1990
PubMed
Summary

Recombinant bovine somatotropin (bST) administration during a second lactation increased milk yield and feed efficiency in Holstein cows. However, bST did not negatively impact cow health or overall physiology.

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Area of Science:

  • Animal Science
  • Dairy Science
  • Endocrinology

Background:

  • Recombinant bovine somatotropin (bST) is used to enhance milk production in dairy cows.
  • Investigating the effects of bST during a second lactation is crucial for understanding long-term impacts.

Purpose of the Study:

  • To evaluate the effects of daily recombinant bST administration during a second successive lactation on milk yield, composition, body weight, body condition, and health in Holstein cows.
  • To determine the dose-dependent effects of bST on these parameters.

Main Methods:

  • Twenty-five Holstein cows received daily subcutaneous injections of physiological saline (control) or 10.3, 20.6, or 33 mg bST/d for 38 weeks, starting 4-5 weeks postpartum.
  • Milk yield, composition (including calcium and phosphorus), body weight change, body condition score, feed efficiency, and incidence of health issues were monitored.

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  • Blood samples were analyzed for hormone, chemistry, and hematology parameters.

    • Main Results:

    • bST administration resulted in a linear increase in 3.5% fat-corrected milk (FCM) yield, ranging from 8% to 36% over controls.
    • Feed efficiency improved by 9% to 30% in bST-treated cows compared to controls.
    • No significant adverse effects on overall health (mastitis, ketosis, milk fever) or body weight gain were observed, although body condition score temporarily declined in bST-treated groups.
    • Milk calcium and phosphorus were slightly higher only in the 10.3 mg/d bST group.

    Conclusions:

    • Recombinant bST can be safely administered during a second lactation to enhance milk production and feed efficiency without compromising cow health.
    • The study suggests that bST does not alter normal physiology or productive capacity in lactating cows under the experimental conditions.
    • Further research may explore optimal dosages and long-term effects across multiple lactations.