Effects of peripheral ghrelin on growth performance, selected blood biochemical parameters and thyroid hormone in Japanese quail (Coturnix coturnix japonica)

The aim of present study was to investigate the effects of peripheral administration of ghrelin on performance and some serum parameters of Japanese quail. One hundred twenty 21 day-old male Japanese quails were divided into three groups for a 35 days experimental rearing period. The control group (G0) included no injection as an intact, the second group (treatment 1/G50) received 50 ng ghrelin/kg body weight (BW), and the third group (treatment 2/G100) was given 100 ng ghrelin/kg BW. Ghrelin was administrated (I. P. administration) at the onset of the experimental rearing period on 21-day old birds. Blood samples were taken at two different times: 1) 12 hrs after the injection, and; 2) at the end of the rearing period (on day 35). The effects of ghrelin were evaluated during experimental rearing periods. There were no changes in feed intake and body weight gain (BWG) following ghrelin administration at different dosages (50 or 100 ng/kg BW), whereas a minor decrease in feed intake was observed in G100 group. Feed conversion ratio (FCR) is significantly decreased in G50 and G100, compared to control (P<0.05). Thyroxin (T4) was increased in ghrelin-administered groups in both samples (short/long-term). In conclusion, ghrelin administration in Japanese quails may improve FCR, and stimulate secretion of thyroid hormones, without severe effects on feed intake. However, it did not have considerable effects on carcass characteristics and serum biochemical measures in short and long-terms in Japanese quails.