Recombinant porcine somatotropin alters performance and carcass characteristics of heavyweight swine and swine fed alternative feedstuffs
1991
McNamara, J.P. | Brekke, C.J. | Jones, R.W. | Dalrymple, R.H.
The efficacy of recombinantly derived porcine somatotropin (rpST) in improving the performance and carcass characteristics of heavyweight finishing pigs was determined. In Study 1, 36 pigs were killed for determination of initial carcass composition at 102 kg, and 36 pigs each were given 0, 1.5, 3, 6, or 9 mg of rpST/d from 102 to 136 kg live weight. Corn-soybean meal diets fed contained 19.8% CP and > 1% lysine. Study 2 tested the effects of 3 mg/d on pigs for 4 wk from 84 kg BW fed a corn-soybean meal or a triticale-barley-peas diet. Performance variables (ADG, average daily feed intake [ADFI], and feed efficiency [FE]) were measured weekly. Treatment with rpST increased (P < .01) ADG and FE and decreased (P < .01) ADFI in both studies. In Study 1, leaf fat, backfat thickness, belly thickness, and carcass fat were all decreased (P < .01) linearly by rpST. Loin eye area (LEA), total trimmed lean, and total protein content were increased quadratically (P < .01). At the 3-mg dose, ADFI, ADG, and FE were 87, 130, and 137% of control, and LEA, backfat, total protein gain, and total fat gain were 107, 80, 136, and 52% of control. Loin eye area was not increased (P > .05) in the pigs in Study 2; however, backfat thickness was reduced 16% by rpST (P < .01). The effects of rpST were the same on both dietary regimens (P > .05). These studies demonstrate the effectiveness of rpST in increasing ADG and carcass leanness and improving FE in heavyweight pigs and in pigs fed alternative feedstuffs.
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