Effect of Shearing During Winter Period on Milk Yield and Adrenal Function in Ewes with Different Level of Milk Production


Research Institute of Animal Science, BG-2232 Kostinbrod, Bulgaria


GUDEV, D., I. ALEXIEV and S. ALEXANDROV, 2000. Effect of shearing during winter period on milk yield and adrenal function in ewes with different level of milk production. Bulg. J. Agric. Sci., 6: 469-472

Twelve ewes of the Danube merino breed were allocated into two groups according to their daily milk production as follows: first group – 402 ml and second group – 181 ml. The ewes were shorn immediately after weaning which was carried out during the second half of February.
This study was designed to investigate the effect of the low ambient temperature on plasma cortisol level, adrenal response to ACTH, haemolytic activity of complement and the average daily milk production for 11 days following the shearing. The shearing caused a decline of milk yield in first group ewes and the lower level of milk production was maintained up to the end of the experiment. There was no change of milk yield in second group ewes.
Plasma cortisol level increased on day 7th after shearing in both groups of ewes and remained higher. Adrenal response in ewes of both groups to ACTH was similar. Haemolytic activity of complement in experimental group was almost twice those of control group.

Key words: cortisol, complement, milk yield, ACTH, stress
Abbreviations: ACTH– adrenocorticotropin