Effect of high ambient temperature on serum cortisol, triiodothyronine, prolactin and growth hormone in swamp buffaloes
1987
Prapa Loypetjra | Narongsak Chaiyabutr | Somchai Chanpongsang (Chulalongkorn Univ.,Bangkok(Thailand). Faculty of Veterinary Science.)
The present study was undertaken to determine the diurnal pattern of hormone levels in buffaloes, and the effects of heat stress on plasma hormone concentrations. Eight buffalo heifers aged 2-3 years were selected for the experiments. They were divided into shade and non-shade groups for 20 days. The blood samples were collected from indwelling catheterized jugular vein and sera were separated. The physiological changes for heart rate, respiratory rate and body temperature were recorded. Serum Cortisol, Triiodothyronine (T3), Prolactin (PRL) and Growth Hormone (GH) concentrations were determined by using RIA procedures at the Environmental Physiology Laboratary, UMC, USA.Serum Cortisol levels significantly increased from 3.9 +- 0.54 ng/ml. for shade AM (25 degree celsius) to 6.4 +- 0.59 ng/ml.for non-shade PM (35 degree celsius) (P .05). Serum PRL increased linearly from 36.8 +- 3.92 ng/ml. in shade to 117.3 +- 8.83 ng/ml. of non-shade period. Indications of correlation between thermal humidity index (THI) and serum concentrations of PRL and cortisol were obtained. The average T3 level (0.38 +- 0.02 ng/ml) in the morning shade groups was not significantly different when compared with that in the afternoon non-shade group (0.34 +- 0.021 ng/ml). The GH levels nonsignificantly decreased from 4.4 + 0.14 ng/ml. of shade period to 4.2 +- 0.14 ng/ml. of non-shade period
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