Adrenocortical response in cows after intramuscular injection of long-acting adrenocorticotropic hormone (tetracosactide acetate zinc suspension).
The objectives of this study were first to show adrenocortical response to a long-acting adrenocorticotropic hormone preparation (tetracosactide acetate zinc suspension) (ACTH-Z) and its effect on adrenocortical function in beef cows (Experiment 1) and second to apply the ACTH-Z challenge in dairy cows based on cortisol concentrations in milk collected at routine milking (Experiment 2). In Experiment 1, four beef cows in luteal phase were challenged with ACTH-Z, and plasma cortisol concentrations were determined for 48 h after the injection at 30-min to 2-h intervals. A rapid ACTH test was conducted 3 days before and 2 h after the completion of ACTH-Z injection for 48 h to investigate the effect on adrenocortical function. Plasma cortisol concentrations increased significantly 30 min after ACTH-Z injection (p < 0.001), and the high cortisol levels were maintained for approximately 10 h after the injection. In Experiment 2, eight dairy cows were subjected to ACTH-Z challenge 1-2 weeks and 4-5 weeks post-partum. Blood and milk samples were taken at morning and afternoon milking. All the cows showed a significant increase in cortisol concentrations in plasma as well as in skim milk 8 h after ACTH-Z injection 1-2 weeks and 4-5 weeks post-partum (p < 0.001). There was a significant correlation between plasma and skim milk cortisol concentrations 8 h after ACTH-Z challenge (r = 0.74, p < 0.001). The results obtained in this study suggest that elevated levels of plasma cortisol are maintained for approximately 10 h after ACTH-Z treatment without adverse effect on adrenocortical function and a long-acting ACTH-Z challenge based on cortisol concentrations in milk, which were collected at the morning and the afternoon milking, can be a useful tool to monitor adrenocortical function in cows.
Thinh
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NC
Laboratory of Theriogenology, Department of Veterinary Medicine, Faculty of Agriculture, Yamaguchi University, Yoshida, Yamaguchi, Japan. tnakao@yamaguchi-u.ac.jp
Yoshida
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Long
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Yusuf
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M
Nakao
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T
D000818:Animals; D002417:Cattle / Q000502:physiology*; D003366:Cosyntropin / Q000008:administration & dosage / Q000494:pharmacology*; D003692:Delayed-Action Preparations; D005260:Female; D006854:Hydrocortisone / Q000032:analysis / Q000097:blood*; D007273:Injections, Intramuscular; D008892:Milk / Q000737:chemistry; D013997:Time Factors
D003692:Delayed-Action Preparations; D003366:Cosyntropin; C006418:adrenocorticotropin zinc; D006854:Hydrocortisone