Last update: April 19, 2011 11:25:18 AM E-mail Print





MJ Herselman & A.A. van Loggerenberg

Grootfontein Agricultural Development Institute, Middelburg 5900


High abortion rates in high fibre producing Angora goats have been linked to hypo-adrenocorticism. Subsequent investigations to relate different characteristic problems of high fibre producing breeds of small stock to hypo-adrenocorticism revealed contradictory results. The objective of this study was to investigate adrenal activity in breeds of small ruminants with varying potentials for fibre production. Angora goats, Merino, Afrino, Dorper and Namaqua Afrikaner sheep (6 animals per breed) were kept in pens between the age of two and fourteen months. Twelve blood samples per animal were collected monthly for cortisol assays. Mean concentration of plasma cortisol was higher (P < 0.01) in Namaqua Afrikaner sheep than in the other breeds and plasma cortisol concentration in Angora goats was lower (P < 0.05) than that of Afrino, Dorper and Namaqua Afrikaner sheep. Intravenous injection of 0.1 IU insulin / kg body weight caused a prompt fall in blood glucose concentration in all breeds. Plasma cortisol increased as response to the drop in blood glucose but peak plasma cortisol concentration in Angora goats was three to five times smaller as compared to other breeds. Likewise, the response in plasma cortisol to intravenous injection of 1 mg corticotropin releasing factor (CRF) per kilogram body weight was three to four times smaller in Angora goats than other breeds. It is concluded that a form of hypo-adrenocorticism may contribute to some disorders of the carbohydrate metabolism commonly observed in Angora goats.



Proc. S.A. Soc. Anim. Prod. 34, 134