Influence of daily recombinant porcine somatotropin injections on the lysine requirement and reproductive performance of finishing pigs
Abstract
24 pigs were assigned randomly to one of six treatments with 2 levels of rpST and 3 levels of dietary lysine in a 14% CP diet. Somatotropin treatment decreased feed intake and daily gain during the metabolism period. Additional lysine resulted in a linear increase in feed intake and ADG within rpST-treated animals. 48 pigs were assigned to one of four treatments with 2 levels of rpST and 2 levels of dietary lysine in 20% CP diet. Barrows gained faster than gilts across all treatment combinations. Somatotropin-treated pigs had reduced daily gains when fed the 0.60% lysine diet; however, when dietary lysine was increased to 1.00%, ADG, and feed efficiency increased. Both control and rpST-treated gilts responded to increased dietary lysine levels with improved 21 d ADG. Barrows injected with rpST and fed 1.00% lysine diets had lower excretion rates than barrows on the basal diet. 72 pigs were assigned to one of four dietary lysine levels contained in an 18% CP diet. Increasing the lysine density had no effect on the ADG in barrows or gilts. Feed intake and feed to gain were decreased in barrows, whereas only F/G was decreased in gilts fed increased levels of lysine. Nitrogen excretion was decreased linearly by increasing dietary lysine to 1.32% of the diet in barrows. No effect was observed in gilts. 40 gilts assigned to one of four treatments with rpST and duration of treatment as the factors. Somatotropin treatment decreased FI and F/G after 28 d of treatment. Dose or duration had no effect on age at puberty, proportion of gilts attaining puberty or conception rate. Treatment with rpST increased the weight of gilts at puberty. Fetal lengths and weights were lower in gilts that received 4 mg/d rpST to puberty. Serum concentrations of LH and number of LH secretory peaks were similar after 60 d of administration. Somatotropin treatment decreased gain in pigs fed low lysine diets. Feed conversion was consistently improved with rpST treatment. These data indicate that rpST injections are detrimental if essential amino acid levels are inadequate and higher than normal levels of lysine are required for rpST enhancement of performance. (Abstract shortened with permission of author.)
Degree
Ph.D.
Advisors
Cline, Purdue University.
Subject Area
Livestock
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