Publications > Animal Science > 2002 > Volume 75 Part 2 > View abstract

Animal Science Abstract

Plasma concentrations of cortisol and progesterone during the period of reproductive development in beef and dairy heifers

N. C. Rawlings^1,A, J. P. Kastelic², A. C. O. Evans^1,B, P. M. Bartlewski¹, A. P. Beard^1,C, R. K. Chandolia^1,D and S. J. Cook¹

^AE-mail: norman.rawlings@usask.ca
^BPresent address: Department of Animal Science and Production, University College of Dublin, Faculty of Agriculture, Bellfield, Dublin 4, Ireland.
^CPresent address: Department of Agriculture, University of Newcastle upon Tyne, NEI 7RU, UK.
^DPresent address: Department of Gynaecology and Obstetrics, College of Veterinary Sciences, CSS Haryana Agricultural University, Hisar, 125004, India.

¹Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon, Saskatchewan S7N 5B4 Canada
²Agriculture and Agri -Food Canada, Lethbridge Research Centre, Lethbridge, Alberta, T1J 4B1, Canada

Abstract

The plasma concentrations of cortisol and progesterone during reproductive maturation in the heifer calf were examined. Six beef heifer calves were handled and bled every 2 weeks (control), 30 were left unhandled (naive). At 13, 21, 30, 39 and 47 weeks of age, a different group of naive heifers and the control heifers were bled every day for 5 days (puberty seen at 57•4 (s.e. 1•3) weeks). Thirty-nine dairy heifer calves were allocated to seven groups to receive adrenocorticotropic hormone (ACTH) at either 4, 7, 9, 16, 26, 36 or 46 weeks of age (puberty expected around 43 weeks of age). Plasma concentrations of cortisol increased at 21, 30 and 39 weeks of age in frequently handled and naive beef heifers; the increase was greater at these ages in the naive beef heifers (age and treatment P < 0•01). No age trend was apparent for plasma concentrations of cortisol and progesterone prior to ACTH injections (t = 0) in frequently handled dairy heifers. Adrenal progesterone secretion did not change with age in beef heifers, but naive beef heifers had greater plasma concentrations than frequently handled beef heifers. ACTH induced cortisol release in dairy heifers as early as 4 weeks of age (P < 0•05), but the response was greater in dairy heifers 16 weeks old and older (P < 0•05). A progesterone response to ACTH in dairy heifers was not seen until animals were 9 weeks old. It is concluded that as heifers mature reproductively, there is a parallel increase in the sensitivity of the adrenal gland to ACTH and handling stress.

Keywords: corticotropin, heifers, hydrocortisone, progesterone, puberty

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