Effect of pulsatile or continuous administration of pituitary-derived chicken growth hormone (p-cGH) on lipid metabolism in broiler pullets

Abstract

1. The effects of pulsatile and continuous intravenous administration of exogenous, pituitary-derived chicken growth hormone (p-cGH) on lipid metabolism and endocrine/metabolite levels of broiler-strain pullets were studied. 2. Eight-week-old pullets were administered p-cGH or vehicle over a 10 min period every 90 min for 7 days. 3. Pullets were also administered the same daily amount (123 μg/kg of body weight/day) continuously for 7 days. 4. Feed intake, body weight gain, in vitro lipogenesis and hepatic enzyme activities were determined with certain hormones identified with the control of growth. 5. Pulsatile p-cGH administration for 7 days lacked effect on weight gain, feed efficiency, muscle or bone development. 6. Abdominal fat pad size was decreased ( P < 0.05) by pulsatile but not continuous administration of p-cGH. Pulsatile p-cGH administration also decreased ( P < 0.05) in vitro lipogenesis. Liver malic enzyme and isocitrate dehydrogenase activities were increased ( P < 0.05) by pulsatile but not continuous administration of p-cGH. In contrast, glutamic oxaloacetic transaminase activity was increased by a continuous infusion of p-cGH. 7. Plasma concentrations of T 4 corticosterone and triglycerides were decreased ( P < 0.05) by a pulsatile but not a constant infusion of p-cGH. 8. Plasma T 3 and GH were increased ( P < 0.05) by pulsatile p-cGH compared to both a continuous infusion of p-cGH and the saline controls. 9. This study is the first to prove that in the broiler chicken, the pattern of exogenous p-cGH administration is a factor influencing in vitro responses to the hormone.