EVALUATION OF LONG-TERM SOMATOTROPIN IMPLANTS IN FINISHING PIGS

Ninety pigs were used to investigate the efficacy of long-term implants of porcine somatotropin (pST) in improving growth, feed:gain ratio, and carcass characteristics in pigs at three dose levels (0-, 100-, and 200-mg pST implant) from 71 to 99 kg live weight. The use of long-term implants did not alter (P > .05) growth rate. Administration of the 200-mg pST implant resulted in a 15% reduction in feed consumption, and this reduction was significant (P <.05). The feed:gain ratio was improved (P < .05) in pigs that received the 200- compared with 0-mg pST implant (3.2 vs 2.62 of kg feed/kg of gain). In pigs that received the 200- or 100-mg pST implant, there was a reduction (P < .05) in carcass weight; however, carcass length was similar (P > .05) regardless of pST treatment. Administration of the 200-mg pST implant resulted in 25 and 38% reductions (P < .05) in last rib fat and leaf fat compared with the 0-mg pST implant. The weights of kidneys and head were increased by the pST administration. The weights of wholesale cuts were not affected by the administration of the pST implant. However, separable skin and fat from the ham, loin, and picnic were lower (P < .05) in pigs that received the 200-mg pST than in pigs that received the 0-mg pST implant. Meat color and structure were similar across pST treatments, indicating that the use of long-term pST implants was not detrimental to meat quality. The results represent a significant step in the efficacious use of a long-term delivery system for pST as opposed to the laborious daily infection schedule.