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Selected hormonal changes with summer fescue toxicosis.
F N Thompson1, J A Stuedemann, J L Sartin
1Dept. of Physiol. and Pharmacol., College of Vet. Med., Univ. of Georgia, Athens 30602.
Journal of Animal Science
|September 1, 1987
Summary
High fescue endophyte content consistently suppressed serum prolactin (PRL) in Angus steers. Nitrogen fertilization did not affect PRL, but high endophyte increased basal growth hormone (GH) levels.
Area of Science:
- Animal Science
- Endocrinology
- Forage Quality
Background:
- Fescue endophyte infections can impact livestock health and productivity.
- Understanding the hormonal effects of endophyte-infected fescue is crucial for cattle management.
Purpose of the Study:
- To investigate the effects of fescue endophyte content and nitrogen fertilization on serum prolactin (PRL) and growth hormone (GH) in Angus steers.
- To determine the relationship between PRL levels and average daily gains.
Main Methods:
- Angus steers were assigned to low or high fescue endophyte content treatments.
- Nitrogen fertilization rates were varied (low and high).
- Jugular blood samples were collected for serum PRL and GH analysis before and after thyrotropin-releasing hormone (TRH) administration.
Main Results:
- High endophyte content significantly suppressed serum PRL in steers during 1984 and in October 1983.
- Nitrogen fertilization did not affect PRL levels.
- Mean basal GH concentrations were elevated in steers consuming high endophyte fescue.
- No significant relationship was found between basal PRL areas and average daily gains.
Conclusions:
- High fescue endophyte content negatively impacts prolactin levels in Angus steers.
- Endophyte infection, not nitrogen fertilization, is the primary driver of observed hormonal changes.
- Elevated basal GH in high-endophyte groups warrants further investigation into growth implications.