Effect of temperature on reproductive hormones and egg quality in the native Thai chicken

Environmental influence on the avian reproductive system is well recognised. This study investigates the effects of ambient temperature on egg quality in the native Thai Chicken (Gallus domesticus). Effects on prolactin (PRL) and ovarian steroids in chickens housed under different temperatures were also elucidated. Sixty female chickens were divided into four groups. Groups 1, 2, and 3 were reared under controlled temperatures of 33 +/- 2 degrees C, 31 +/- 2 degrees C, and 27 +/- 2 degrees C, respectively. Group 4 was reared under an uncontrolled natural temperature (approximately 27 degrees C). Blood samples were collected from each chicken once a week for 11 weeks, and plasma PRL, oestradiol (E), progesterone (P), and testosterone (T) levels were determined utilising enzyme-linked immunosorbent assays. The results revealed that E levels were significantly higher in chickens reared under low ambient temperature (27 degrees C) when compared with those exposed to 31 degrees C and 35 degrees C. No significant differences in PRL, P, and T levels were observed. Egg quality was affected by high ambient temperature. Eggshell thickness of chickens housed at 35 degrees C was thinner than those of other groups. These results indicate that changes in ambient temperature affect circulating levels of E but not PRL, P, and T. Thermally-stressed environments with high temperatures therefore impact egg quality in the native Thai chicken by reducing eggshell thickness.