Applicability of some of the assumptions used to estimate the weight of the skeleton in the growing pig and beagle.

Assumptions used in indirectly estimating skeletal weight were tested on 55 pigs (ages day 0-week 12) and 42 beagles (ages day 0-1 year). One of the assumptions was that skeletal weight constitutes a constant proportion of lean body mass (fat-free wet weight). In the beagle the skeletal weight was not constant, but a decreasing proportion of LBM during growth. In the pig there were no significant changes comparable to those in the beagle, probably because only a small part of the growth period was studied. Also, the assumption that bone mineral was 65% of fat-free dry weight of the skeleton was not applicable to the beagle, where it increased from 55% (day 0-week 12) to 70% (mouth 4-1 year). In both species skeletal growth was a function of total fat-free dry weight (FFDWt), but in the beagle the ratio Kt/FFDWt increased from 130 (day 0-week) 12) to 160 (month 4-1 year) and reflected changes in the contribution of body cell mass and skeletal to FFDWt.