| Abstrakt: |
An experiment was conducted to evaluate the interactive effects among porcine somatotropin (pST), salbutamol, and dietary lysine on growth performance, nitrogen balance, and carcass characteristics of finishing barrows (n = 32; 62.8 kg initially). Two replicate 32-d studies were set up in a split-plot design to evaluate singular and combined use of pST (0 or 4 mg/d) and salbutamol (0 or 2.75 ppm of the diet) as whole-plot treatments and diets containing .8, 1.2, 1.6, or 2.0% lysine as subplot treatments. Dietary lysine levels were administered within subplots in a 4 × 4 Latin square with pigs allowed 4 d of adjustment to diets followed by 4 d of urine and feces collection for determination of N retention and apparent digestibility of DM and N. Interactions between lysine and salbutamol were not found (P> .16). A pST × lysine interaction (P< .05) resulted in ADG being maximized at 1.2% lysine for pST-treated pigs (lysine quadratic, P< .02) but decreased linearly (P< .02) with increasing lysine for pigs receiving buffer. Pigs injected with 4 mg/d of pST had improved gain:feed (G:F) up to 1.2% lysine (lysine quadratic, P< .05), but no further increase to 2% lysine, whereas pigs injected with buffer showed no benefit from increased lysine (pST × lysine, P< .06). Pigs receiving buffer had greater increases in plasma urea N (PUN) as lysine increased than those receiving pST (pST × lysine, P< .002), but PUN was reduced by pST (P< .001) regardless of lysine level.(ABSTRACT TRUNCATED AT 250 WORDS) |
