Effects of peripheral administration of ghrelin antagonist [D-Lys<sup>3</sup>]-GHRP-6 on growth performance and blood biochemical indices in broiler chickens

Abstract

Abstract. In the present study, possible effects of peripheral administration of ghrelin antagonist [D-Lys 3 ]-GHRP-6 on chicken performance, thyroid hormones level and serum biochemical parameters were investigated. Broiler chicks divided into five experimental groups were reared up to day 42. On day 21, a treatment was assigned to the five groups: group 1 (control), chickens without any administration of peptide or solution; group 2 (G50), chickens with intraperitoneal (IP) injection of 50 ng per 100 g body weight (BW) of D-Lys 3 peptide on day 21; group 3 (G100), chickens with IP injection of 100 ng per 100 g BW of D-Lys 3 peptide on day 21; group 4 (G150), chickens with IP injection of 150 ng per 100 g BW of D-Lys 3 peptide on day 21; and group 5 (G200), chickens with IP injection of 200 ng per 100 g BW of D-Lys 3 peptide on day 21. On days 21 (post-injection) and 42 (post-rearing), blood samples were obtained from the animals for laboratory analyses. Experimental groups administered the GHS-R antagonist showed less feed intake -i.e., administration of greater doses led to less feed intake (P < 0.01). Daily weight gains within groups G150 and G200 decreased (P < 0.01) in comparison with the control. The feed conversion ratio (FCR) did not differ among the groups. There was a significant difference between control and experimental groups for glucose, total cholesterol and phosphorus levels (P < 0.01) in postinjection samples. In post-injection and post-rearing blood samples, the thyroid hormone (T 3 and T 4 ) in 6 h increased in treated groups in comparison with the control (P < 0.01). The infusion of ghrelin antagonist [DLys 3 ]-GHRP-6 reduces feed intake and body weight. With regard to increase in T 4 level, it can be inferred that [D-Lys 3 ]-GHRP-6 may increase metabolic rate, lipolysis and weight loss, which is similar to results obtained in mammalian species.