Research was conducted in Australia into the effects of ractopamine on the performance and carcass characteristics of entire boars and immunocastrated male pigs. K.L. Moore of the Department of Agriculture and Food for Western Australia and co-authors have recently published their paper in Animal Production Science (CSIRO).

Sixty entire male pigs (Large White × Landrace × Duroc crossbred) were individually reared from 45 to 114 kg liveweight in a 2 × 3 factorial experiment to determine the interactive effects of sex (entire male pigs vs. male pigs immunologically castrated using Improvac with vaccinations administered at 13 weeks of age and five weeks before slaughter). Also, a ractopamine feeding program (constantly fed 0 or 5 ppm ractopamine for 26 days before slaughter versus a step-up programme where 5 ppm of ractopamine was fed for 14 days followed by 10 ppm ractopamine for the final 12 days before slaughter) on growth performance, carcass composition and pork quality was launched.

Following the second vaccination, immunocastrated pigs ate more (P<0.001) and grew faster (P<0.05) than entire male pigs without affecting feed conversion efficiency. Dietary ractopamine supplementation for the last 26 days before slaughter improved feed conversion ratio (P=0.024) and daily gain (P=0.046). Dietary ractopamine supplementation also increased carcass total tissue (P=0.023) and total lean (P=0.027) content without affecting the objective meat quality (P>0.05) in both entire and immunocastrated male pigs.

The effects of dietary ractopamine and immunocastration were additive, such that pigs that were immunocastrated and received ractopamine grew 18 per cent faster than control entire males. However, a step-up programme of ractopamine supplementation did not provide further improvements in growth performance and carcass composition when compared with constant 5 ppm ractopamine supplementation.

These findings indicate that ractopamine supplementation improved growth performance in entire and immunocastrated male pigs, thereby offering a means of improving growth performance of entire males without detrimental effects on pork quality.

Reference

Moore K.L., F.R. Dunshea, B.P. Mullan, D.P. Hennessy and D.N. D'Souza. 2009. Ractopamine supplementation increases lean deposition in entire and immunocastrated male pigs. Animal Production Science 49(12): 1113–1119. doi:10.1071/AN09076

Further Reading

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