Abstract
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 energy deposition in pigs. During growth from 30 to 60 kg the mean value for carcass energy deposition measured by DXA was 251 MJ compared to 249 MJ by chemical analysis (R2=0.94). 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 and IGF-I transgenic pigs in response to dietary conjugated linoleic acid (CLA). Addition of CLA to the diet resulted in a reduction in kg, though there was no difference in kg based on genotype or sex. The PE was higher (P<0.05) in the IGF-I transgenic pigs. DXA was also used to assess 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 or 60 to 90 kg there were no differences in the efficiency of either energy or protein deposition. In conclusion, DXA can be used to replace the comparative slaughter technique for measuring energy and protein deposition in pigs, thus this approach is useful for identifying differences in energy and protein deposition in pigs of different genotypes or when subjected to various dietary treatments.
Highlights
Valid measurements of energy and protein deposition based on changes in body composition require accurate determination of body composition at both the beginning and end of the experimental period
It has been shown that dual energy X-ray absorptiometry (DXA) can be used in conjunction with genetic and nutritional studies in swine to evaluate differences in body composition (MITCHELL and SCHOLZ, 1997; MITCHELL et al, 2002: OSTROWSKA et al, 2003; MITCHELL et al, 2005; SCHOLZ and FÖRSTER, 2006)
Studies were conducted 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
Summary
Valid measurements of energy and protein deposition based on changes in body composition require accurate determination of body composition at both the beginning and end of the experimental period. The purpose of the studies reported here was to validate the use of DXA for measuring energy and protein deposition and to apply this approach to pigs of different genetic backgrounds and exposed to various nutritional treatments. Studies were conducted 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. A part of this study aimed at the measurement of the efficiency of energy and protein accretion in control and IGF transgenic pigs fed diets with or without CLA added. Evidence of alteration in energy metabolism under resting conditions is suggested by higher plasma glucose concentrations (OTTEN et al, 1993) and higher intramuscular concentrations of
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