EFFECT OF VARYING AMBIENT-TEMPERATURE AND PORCINE SOMATOTROPIN TREATMENT IN PIGS ON FEED-INTAKE AND ENERGY-BALANCE TRAITS

Effects of feeding levels (64 g kg(-0.75) d(-1)= low; 87 g kg(-0.75) = high) and recombinant porcine somatotropin (rpST) on energy balance t raits of castrate pigs (approximately 53 kg live weight) in 8 groups o f 12 each were studied in a 2x2 factorial arrangement. In two consecut ive balance periods of 12 d each, ambient temperatures were changed 3 degrees C each day at 0900 in a stepwise fashion from 23 to 8 degrees C and then upward from 8 to 23 degrees C. Four groups received 4 mg of rpST per day per animal and four groups received a placebo. Control h igh feeding level pigs were pair-fed with ad libitum fed rpST-treated pigs. Pigs treated with rpST showed an increased heat production of 65 kT kg(-0.75) d(-1) and maintenance requirement (MEm) of 75 kT kg(-0.7 5) d(-1) compared to control. Protein deposition was 130 and 176 g d(- 1), and fat deposition 210 and 134 g d(-1) in control and rpST-treated pigs, respectively. Feed:gain ratio improved from 2.92 to 2.26 and ra te of gain from 665 to 840 g d(-1) with rpST. High feeding level pigs had increased heat production (+ 97 kT kg(-0.75)) and retained more en ergy (+ 220 kT kg(-0.75) d(-1)). They also showed increased protein an d fat depositions, and rate of gain. Pigs at optimal and suboptimal te mperatures showed similar metabolic responses to rpST. (C) 1997 Elsevi er Science B.V.