Measured and calculated fat during growth in the pig and beagle
Sheng, H.P.; Kamonsakpithak, S.; Naiborhu, A.; Chuntananukoon, S.; Huggins, R.A.
Growth 41(2): 139-146
1977
ISSN/ISBN: 0017-4793 PMID: 892580 Document Number: 110660
In 55 pigs fat increased from a mean of 6% of bodyweight at birth to 12% at 1 week old and was from 11 to 17% between 1 and 12 weeks. Fat in 42 beagles increased from 6% of bodyweight in the first 2 weeks of life to a mean of 15% in beagles over 1 month old. The percentage of fat was calculated using the equation 100-% total body water (TBW)/0.732 for 18 beagles from 3 months to 1 year old and for 55 pigs and was then compared with measured fat; TBW was measured with tritium or by desiccation. With both desiccation and tritium when 73.2% (water in fat-free body) was used, the differences between calculated and measured fat were so large as to make an estimate of fat valueless. TBW as a percentage of fat-free wet weight was stable during the 12 weeks of growth in the pig, and in the beagle from 3 months to 1 year. In the pig the mean for this period was 83.7% for desiccation and 88.6% for tritium, and in the beagle 62.9% for desiccation and 78.7% for tritium. Fat was recalculated substituting the appropriate mean for the "coefficient of hydration" in the fat-free body in the equation. In the pig, agreement between calculated and measured fat was good with both desiccation and tritium, but the coefficient of correlation for the desiccation method was better than that for tritium. For the beagle, agreement was good between calculated and measured fat when TBW was measured by desiccation but the correlation for the tritium method was poor. Possible reasons for the variability in calculation of fat with tritium are discussed. Fat percentage was measured in 55 pigs ranging in age from birth to 12 wk and in 42 beagles from birth to 1 yr. In the pig, fat increased from a mean of 6% body weight at birth to 12% at 1 wk of age. Thereafter, it increased up to 17% at 12 wk. The percentage of fat was calculated using the equation 100 - percentage of total body water/0.732, and was compared with measured fat. Total body water was measured with tritium or by desiccation. With both tritium and desiccation, the differences between calculated and measured fat were so large as to make the estimates valueless. Total body water as a percentage of fat-free wet weight was stable during the 12 wk of growth in the pig, the mean for this period being 83.7% for desiccation and 88.6% for tritium. Fat was recalculated substituting the appropriate mean for the "coefficient of hydration" in the fat-free body in the equation. Agreement between calculated and measured fat was good with both desiccation and tritium, but the correlation for the desiccation method (0.79) was higher than that for tritium (0.42). Similar data are also given for beagles.