Submitted to: Symposium on Energy and Protein Metabolism and Nutrition
Publication Type: Proceedings
Publication Acceptance Date: 8/10/2007
Publication Date: 9/13/2007
Citation: Mitchell, A.D., Scholz, A.M. 2007. Efficiency of energy and protein deposition in swine during compensatory growth measured by dual energy X-ray absorptiometry (DXA). Proceedings of the International Symposium on Energy and Protein Metabolism. EAAP 124:487-488.
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 the level of protein in the diet and by feeding the beta-adrenergic agonist, ractopamine. The purpose of this study was to examine the effects of controlled intake, dietary protein level, and 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. Limiting the dietary intake level prevented compensatory growth, consistent with the role of enhanced intake on compensatory growth. Even at limited intake, a low protein diet resulted in more fat and less lean growth and improved efficiency of protein deposition. 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 additive effects of compensatory growth and ractopamine are consistent with different mechanisms of action.
Technical Abstract: A study was conducted to examine the effects of controlled intake, dietary protein (CP) level, and 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. Seven groups of pigs (58 pigs in total) were scanned by DXA for body composition analysis at a starting weight of 61.4 kg and at a final weight of 100.9 kg. Three groups of pigs were fed at continuous intake levels from 60 kg: ad libitum (A) the basal diet (186 g per kg CP and 13.58 MJ per kg ME), ad libitum plus 20 mg per kg ractopamine (R), and limited at calculated NRC energy intake level (C). Four groups of pigs were maintained at 60 kg for 56 d, scanned by DXA again, and then fed: 200 g per kg CP (13.73 MJ per kg ME) diet at C intake (M-HP), 120 g per kg CP (13.79 MJ per kg ME) diet at C intake (M-LP), ad libitum intake (M-A), and ad libitum intake plus R (M-R). There was no difference in the growth rate (0.95 kg per day) during the final phase for pigs were fed at the calculated energy intake level (C). Feeding R resulted in a 13% increase in the rate of weight gain compared to A (1.15 vs. 1.02 kg per day), consisting of a 29% increase in the rate of lean tissue deposition (0.86 vs. 0.67 kg per day) and an 18% reduction in the rate of fat deposition (0.27 vs. 0.33 kg per day). Total body fat and protein deposition were based on the differences between the 60-kg and 100-kg DXA measurements of fat and lean. Energy deposition was calculated as the sum of fat deposition (39.6 MJ per kg) and protein deposition (23.7 MJ per kg). The efficiency of energy (kg) and protein (PE) deposition was affected by diet and compensatory growth.