Effect of subcutaneous infusion of pituitary-derived chicken growth hormone on growth performance of broiler pullets.

The effect of subcutaneous infusion of pituitary-derived chicken growth hormone (p-cGH) on plasma hormone/metabolite status and growth performance of young broiler pullets was investigated. Two-week-old pullets were surgically prepared and maintained via a fluid swivel/spring tether/harness system. Birds were subcutaneously infused 24 h a day for 21 days with 1.0 mL/day of either a p-cGH or vehicle (control) solution (20 micrograms/kg BW/day). Subcutaneous infusion of p-cGH had no significant effect on growth performance parameters in comparison with controls. Differences between levels of overall feed intake, net BW gain, feed efficiency, and carcass composition were not significant for treatments. However, dressing percentage was lower in p-cGH treated birds than in vehicle infused birds (P less than .04). Growth hormone treatment resulted in a modest degree of enlargement of the liver (P less than .06). However treatment had no effect upon wet weights of other measured organs or upon parameters of longitudinal bone growth, including length and mass of the tibiotarsus and width of the epiphyseal growth plate. Differences between treatment groups in preinfusion plasma concentration of GH, insulin, and glucose were not significant. Postinfusion plasma concentrations of GH were elevated over three-fold by p-cGH treatment (P less than .0001), with no treatment differences in plasma insulin or glucose concentrations. This study indicated that a sustained, 24-h elevation in plasma GH concentration in response to a physiological dosage of exogenous p-cGH is ineffective in altering growth performance of young, rapidly growing meat type chickens.