Efficiency of energy and protein deposition in swine measured by dual energy X-ray absorptiometry (DXA)

Authors: Mitchell, Alva; SCHOLZ, A. - UNIVERSITY OF MUNICH

Submitted to: Archives of Animal Breeding
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/5/2008
Publication Date: 1/5/2008
Citation: Mitchell, A.D., Scholz, A.M. 2008. Efficiency of energy and protein deposition in swine measured by dual energy X-ray absorptiometry (DXA). Archives of Animal Breeding. 51:159-171.

Interpretive Summary: Valid measurements of energy and protein deposition based on changes in body composition requires accurate determination of body composition at both the beginning and end of the experimental period. Traditionally, these changes in body composition have been determined by the comparative slaughter technique. A series of studies were conducted using dual energy X-ray absorptiometry (DXA) to measure energy and protein deposition in pigs. In an initial validation study it was demonstrated that DXA was comparable to slaughter analysis as a method for measuring body composition and energy deposition in pigs. In subsequent studies it was demonstrated that DXA could be used to determine differences in energy and protein deposition in pigs of different genetic backgrounds and pigs that were subjected to different dietary treatments. Based on these studies it was concluded that DXA can be used to replace the comparative slaughter technique for measuring energy and protein deposition in pigs, thus providing a more direct measurement that requires fewer animals.

Technical Abstract: A series of studies were conducted using dual energy X-ray absorptiometry (DXA) to measure energy and protein deposition in pigs. In an initial validation study DXA was compared directly with slaughter analysis as a method for measuring body composition and energy deposition in pigs. Mean values for the total energy content of the carcass calculated from the amounts of protein and fat were 493 MJ for the chemical and 494 MJ for the DXA measurements. During growth from 30 to 60 kg the mean value for carcass energy deposition measured by DEXA was 251 MJ compared to 249 MJ by chemical analysis. Subsequently it was shown that both compensatory growth and the addition of ractopamine to the diet resulted in an improvement in efficiency of protein deposition (PE), however, ractopamine also resulted in a reduction in the efficiency of energy deposition (kg). Another study was conducted to compare the efficiency of utilization of dietary energy and protein by control (C) and IGF-I transgenic (T) pigs in response to dietary conjugated linoleic acid (CLA) versus corn oil (CO). The kg was higher for the C-CO pigs compared to the C-CLA or T-CLA pigs, while the T-C pigs were intermediate. The kg was higher for pigs fed the CO diet compared to those fed the CLA diet. There was no difference in kg based on genotype or sex. The PE was higher in the T-CO and T-CLA pigs compared to the C-CO and C-CLA pigs; hence there was a significant genotype effect. DXA was also used for in vivo assessment of body composition and energy deposition in pigs that were either homozygous stress non-sensitive (NN), heterozygous (Nn) or homozygous stress sensitive (nn). During growth from 30 to 60 kg, the nn pigs deposited less fat than the NN pigs, while Nn were intermediate. This pattern continued during growth from 60 to 90 kg, resulting in the nn pigs having less fat and less total energy than the other two genotypes. There were no differences in protein deposition during these periods. Furthermore, based on the DXA results and measurements of energy intake during these periods, there were no differences among genotypes in the efficiency with which dietary energy was retained.