Response of young broiler chickens to chronic injection of recombinant-derived human insulin-like growth factor-I.
The purpose of this study was to determine if exogenous insulin-like growth factor-I (IGF-I) would improve growth rate or body composition of young broiler chickens. Broiler cockerels were given a daily intramuscular (im) injection of sodium acetate buffer (buffer control), 100 or 200 micrograms recombinant-derived human IGF-I (rhIGF-I) per kg body weight from 11 to 24 days of age. Exogenous IGF-I did not affect the average daily gain, average daily feed consumption, or the gain-to-feed ratio of broiler chickens. Although daily injection of 200 micrograms/kg of rhIGF-I reduced (P less than 0.05) body ash content, there was no significant effect of IGF-I treatment on either body fat or protein content. Plasma GH levels were depressed (P less than 0.05) by chronic treatment with rhIGF-I. In contrast, plasma levels of T3 and T4 were not affected by rhIGF-I treatment. The half-life of rhIGF-I in plasma was determined at 25 days of age in naive control or chronically-injected chickens after a single intravenous dose of 50 micrograms rhIGF-I/kg. We found a single compartment, first-order disappearance pattern of rhIGF-I from chicken plasma. The half-life (t1/2) of rhIGF-I in plasma was similar (t1/2 = 32.5 min) for naive controls (injected once) or chronically-treated chickens which had received a daily injection of rhIGF-I (100 or 200 micrograms/kg) for 14 d. These data indicate that daily injection of IGF-I cannot be used to enhance growth performance or body composition of broiler chickens when given during the early growth period. The depression of plasma GH levels in rhIGF-I-injected chickens supports a negative-feedback role of IGF-I on pituitary GH secretion.
McGuinness
M C
MC
Department of Animal Science and Agricultural Biochemistry, College of Agricultural Sciences, University of Delaware, Newark 19717-1303.
Cogburn
L A
LA
D000818:Animals; D001823:Body Composition / Q000187:drug effects; D002645:Chickens / Q000033:anatomy & histology / Q000254:growth & development*; D004305:Dose-Response Relationship, Drug; D004435:Eating / Q000187:drug effects; D006207:Half-Life; D006801:Humans; D007273:Injections, Intramuscular / Q000662:veterinary; D007275:Injections, Intravenous / Q000662:veterinary; D007334:Insulin-Like Growth Factor I / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology*; D008297:Male; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology; D015430:Weight Gain / Q000187:drug effects
D011994:Recombinant Proteins; D007334:Insulin-Like Growth Factor I