Administration of porcine somatotropin by sustained-release implant: growth, carcass, and sensory responses in crossbred white and genetically lean and obese boars and gilts.

Abstract

Previous studies have documented the efficacy of porcine somatotropin administered by sustained-release implant (pST-SR) in promoting rate and efficiency of lean growth in genetically lean and obese barrows and gilts. Herein, those studies have been extended to include contemporary crossbred boars and gilts. The study consisted of 18 treatment groups in an arrangement of three lines, two sexes, and three doses of pST; 10 crossbred and obese boars and gilts assigned per dose, 10 lean gilts assigned per dose, and 6 lean boars assigned per dose. Pigs were implanted s.c. behind the ear at 55.2 +/- .3 kg BW. Pigs received no implant, or one or two implants designed to deliver 2 mg of recombinantly derived pST/d (i.e., doses of 0, 2, or 4 mg of pST/d). At 14-d intervals feed consumption, BW and backfat were recorded. At the end of the 42-d trial the pigs were slaughtered and offal components weighed, and carcasses were dissected into untrimmed and trimmed wholesale cuts. Loin chops were collected for evaluation of sensory attributes, including boar taint. During each 14-d period of the trial feed consumption was reduced, gains were unchanged or greater, and efficiency of live weight gain was increased (P < .05). At slaughter, weights of the organs were increased and the weight of the trimmed primal cuts was increased in all line x sex groups with increasing dose of pST-SR. Treatment with pST-SR had no effect on the sensory attributes of juiciness, tenderness, pork flavor, and off-flavors. The panel detected a reduction (P < .01) in boar taint in meat from pST-SR-treated boars. Administration of pST-SR improved efficiency and quantity of pork produced by both boars and gilts of genotypes representing a diverse range of lean growth potential. In addition, pST-SR improved the acceptability of meat from boars.