RESPONSES TO EXOGENOUS PULSATILE TURKEY GROWTH-HORMONE BY GROWING 8-WEEK-OLD FEMALE TURKEYS

A study was conducted in turkeys to determine the effects of pulsatile infusion of turkey growth hormone (tGH) on growth, feed conversion, c arcass component parts, carcass composition, plasma metabolite concent rations, and other hormones associated with growth. Female turkeys, 8 weeks of age, were dually cannulated via the right jugular for intermi ttent (10 min every 2 hr) infusion of tGH at a low dosage (4.5 mu g tG H/infusion or 54 mu g/day), a high dosage (18 mu g tGH/infusion or 216 mu g/day) or vehicle infused controls (vehicle, 0.025 M NaHCO3, 0.025 M Na2CO3 + 5 mg/ml NaCitrate, pH 9.4). Treatment was for 18 days. The second cannula was used to serially bleed the turkeys (5 or 10 min be tween samples) at 4 and 16 days of treatment to determine concentratio ns of GH, glucose, triacylglycerides (TG) non-esterified fatty acids; (NEFA), and uric acid (UA). Overall GH was increased 74% above the con trol group in the low and 195% in the high treatment group. Baseline G H was increased 52% in the high group above: the control group. The am plitude of GH peaks increased 292% in the low, and 574% in the high gr oup above the amplitude of naturally occurring peaks in the control gr oup. Infusion of tGH for 18 days did not affect overall daily gain, fe ed conversion, final body weight, tibiotarsus length, weights of pecto ralis major, pectoralis minor, gastrocnemius or biceps femoris muscles , or weights of liver and offal. Abdominal fat pad weight (70% decreas e), and percentages of carcass fat (4.9% decline) and carcass dry matt er (2.3% decline) were lower in the high treatment group. Plasma TG an d glucose were unaffected by treatment. Overall plasma NEFA concentrat ion was increased in the high treatment group, and this increase was a ssociated with an increase in the baseline concentration and incidence of pulses of NEFA, but not with the amplitude concentration of NEFA p ulses. The dynamic nature of plasma NEFA concentration observed in thi s study suggests single time point measurements of this metabolite may not appropriately detect treatment effects. Plasma overall uric acid (UA) was decreased in the high treatment group in comparison to the co ntrol group, and this decrease was associated with a decrease in the b aseline concentration of UA but not in the amplitude concentration nor incidence of UA pulses. Plasma insulin-like growth factor-I (IGF-I) c oncentrations were increased in the low treatment group at 4 but not a t 16 days of treatment. Plasma triiodothyronine (T-3) was increased in both the high and low treatment groups at 16 days of treatment, while tetraiodothyronine (T-4) was depressed in the high treatment group in comparison to the control group. It was concluded that tGH infused in a pulsatile pattern in growing female turkeys does not affect body we ight gain, feed conversion, or weight of muscles,but does affect carca ss fat content and plasma concentrations of NEFA and UA, and concentra tions of the growth hormone associated hormones, IGF-I, T-3 and T-4.