Submitted to: Animal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/20/2008
Publication Date: 1/1/2009
Citation: Mitchell, A. 2009. Effect of ractopamine on growth and body composition of pigs during compensatory growth. Animal. 3(1):173-180.
Interpretive Summary: Following a period of restricted dietary intake, young pigs exhibit compensatory growth that is characterized by an accelerated growth rate that usually includes more fat and less muscle than in pigs continuously fed ad libitum. Fat and lean deposition in growing pigs can also be influenced by feeding the beta-adrenergic agonist, ractopamine. The purpose of this study was to examine the effect of ractopamine supplementation on growth, body composition, and the efficiency of energy and protein deposition in pigs during uninterrupted or compensatory growth from 60 to 100 kg. Under conditions of ad libitum intake, compensatory growth resulted in greater lean tissue deposition and improved efficiency of protein deposition, but had no significant effect of fat deposition or efficiency of energy deposition. Addition of ractopamine to the diet resulted in enhanced growth, reduced fat deposition, increased lean deposition, with an improvement in efficiency of protein deposition and a reduction in energy efficiency. The results of this study demonstrate that during compensatory growth, pigs will respond positively to ractopamine treatment resulting in an additional increase in growth rate consisting of increased lean tissue growth and reduced fat deposition. The additive effects of compensatory growth and ractopamine are consistent with different mechanisms of action.
Technical Abstract: The purpose of this study was to measure the growth and body composition of pigs during normal or compensatory growth from 60 to 100 kg, without (cont) or with ractopamine (rac) supplementation (20 mg/kg of diet). Thirty-four pigs were scanned by dual X-ray absorptiometry (DXA) for body composition analysis at a starting weight of 61.4 kg and at a final weight of 100.4 kg. Half the pigs were fed ad libitum throughout (8 cont and 9 rac). The other half were fed at maintenance for eight weeks and then scanned again by DXA. Following maintenance feeding the pigs were fed ad libitum (9 cont and 8 rac) to the final weight. Compensatory growth resulted in a 30% increase in the rate of weight gain, including a 44% increase in the rate of lean tissue deposition, but no change in the rate of fat deposition. Feeding RAC resulted in a 13% increase in the rate of weight gain, consisting of a 29% increase in the rate of lean tissue deposition and an 18% reduction in the rate of fat deposition. The effects of ractopamine on the rates of fat and lean tissue deposition were similar for pigs continuously fed ad libitum and those experiencing compensatory growth. Both compensatory growth and the addition of ractopamine to the diet resulted in an improvement in efficiency of protein deposition, however, ractopamine also resulted in a reduction in the efficiency of energy deposition. For both growth rate and lean tissue deposition there was an additive effect for ractopamine and compensatory growth. Thus, feeding ractopamine will enhance growth and body composition during compensatory growth in swine.