The selection of protein intake by pigs treated with porcine somatotropin

The hypothesis that pigs can select a protein intake to meet their lean growth requirement when given a choice of two diets, differing in protein content, was tested in this study. Seventy-two gilts (PIC Camborough x Canabrid), of an average initial body weight of 20 kg, were allotted to one of four pens with half-slatted concrete floors and two electronic feeders. Two pens of pigs were assigned to a choice-feeding system (choice) and two pens to a single-feeding system (single). Half of the pigs in each pen received a daily injection of 100 micrograms/kg BW of porcine somatotropin (ST) and the other half received a daily injection of saline. Feed intake of individual pigs was recorded on a daily basis with the Feed Intake Recording Equipment (FIRE) system. Pigs assigned to the choice-feeding system were given two feeds of different protein content, 10 or 24%, but with similar digestible energy content (13.7 MJ of DE/kg). The single diet contained 16% CP during the grower period and 14% throughout the finisher period. Overall weight gain of pigs was not affected by feeding system or ST injection; however, feed intake was decreased by injection of ST (P = .006) and by choice feeding (P = .005). Choice-fed pigs showed decreased dietary protein intake compared with single-fed pigs. The increased deposition rate of lean and protein with injection of ST did not stimulate an increase in protein consumption. Choice feeding and ST injection lowered the amount of feed or protein required per unit gain, or per unit of lean or protein deposited.(ABSTRACT TRUNCATED AT 250 WORDS)