Abstract
One experiment was conducted to investigate the impact of feed allowance and ractopamine supplementation on growth, carcass and meat quality traits in barrows and immunocastrated male pigs. Eighty finishing male pigs (95.79 ± 1.71 kg) were allocated in a 2 × 2 × 2 factorial treatment design with two castration methods (CM) (physically (BA) x immunologically (IM) castrated pigs), two ractopamine supplementation programs (RAC) (0 vs 10 ppm in the feed) and two feeding allowance schemes (FA) (restricted (RT) vs ad libitum (AL)) from 131 to 160 days of age. RAC-fed pigs were heavier (P < 0.01) and RT pigs were lighter (P < 0.001) at the end of the evaluation period. Average daily weight gain was higher in IM (P < 0.05) and pigs fed diets without RAC and RT showed lower daily weight gain (P < 0.05). RAC improved feed efficiency regardless of CM and FA (P < 0.001). BA were fatter at 131 days of age (P < 0.001). RAC deaccelerated backfat deposition (P < 0.001) and improved lean muscle deposition (P < 0.01) after the 29-day duration of the trial. RAC increased slaughter weight (P < 0.01), hot carcass weight (P < 0.05) and lean muscle weight (P < 0.05). RT pigs showed decreased slaughter weight (P < 0.001) and backfat thickness was increased in BA fed diets without RAC (P < 0.01). BA pigs fed diets with 0 ppm RAC showed the highest backfat thickness and IM pigs fed diets with 0 ppm showed the lowest backfat depth (P < 0.01). IM AL pigs fed diets with 0 ppm showed the highest percentage of muscle and BA RT and BA AL pigs fed diets with 0 ppm showed the lowest lean muscle percentages (P < 0.01). Loin muscle area was reduced in RT pigs (P < 0.001) and increased by RAC (P < 0.05). Feeding RAC increased meat shear force (P < 0.01). In conclusion, our results confirm that rearing immunologically castrated males is a profitable alternative for pork producers and that feed restriction after the second vaccination negatively influences growth and carcass parameters, which can be partially compensated by ractopamine supplementation.
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