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Influence of Adrenocorticotropin upon Milk Production, Milk Constituents, and Endocrine Measures of Dairy Cows¹

Reproductive Physiology Research Laboratory, Department of Animal Science, North Carolina State University, Raleigh 27650

³ Reprint requests.

ABSTRACT

Ten lactating Holstein cows were injected intramuscularly with either 200 IU of adrenocorticotropin or saline every 6 h for 42 h. Blood concentrations of corticosteroids, glucose, sodium, and potassium, and milk yield and constituents were measured before, during, and after the injection period. Mean corticosteroid increased eightfold for adrenocorticotropin 1 h after first injection, remained significantly higher than controls during the injection period, and then decreased to preinjection concentrations 13 h after last injection. Mean milk yields were similar at 8 h after first injection, then decreased for adrenocorticotropin during the injection period. Increases in glucose concentrations accompanied suppression of milk yield for adrenocorticotropin. After injections glucose concentrations returned to preinjection concentrations at 13 h after last injection whereas milk yield for adrenocorticotropin remained suppressed for several milkings. Milk protein yields decreased for adrenocorticotropin during and after the injection period. Fat percentage for adrenocorticotropin increased though fat yield was unaffected. Concentrations of somatic cells in milk were unchanged by adrenocorticotropin treatment, but sodium was increased and potassium decreased during injection. Mammary gland function in lactating dairy cows may be affected adversely by exaggerated increases of concentrations of corticosteroids in blood.

¹ Paper No. 8169 of the journal Series of the North Carolina Agricultural Research Service, Raleigh. Use of trade names in this publication does not imply endorsement of the products mentioned.

² Department of Dairy Science, University of Maryland, College Park 20742.