Studies of dietary restriction and rehabilitation. I. Interrelationships among the fat, water content and specific gravity of the albino rat

Quantitative estimates of lamb carcass composition 2. Specific gravity determination

Relationships between specific gravity and carcass tissue were studied in 83 purebred Clun Forest lambs slaughtered at approximately 80 lb. liveweight and ranging in carcass weight from 29 to 42 lb. Carcass specific gravity accounted for 86·1% and 78·1% of the respective variances in carcass fat percentage and muscle percentage. Specific gravity determinations on a single joint were also highly correlated with the carcass tissues. Correlation coefficients between loin specific gravity and carcass fat and muscle were −0·89 and 0·82 respectively; corresponding figures for best-neck specific gravity were −0·86 with carcass fat percentage, and 0·76 with carcass muscle percentage. In partial correlation analyses, muscle/bone ratio failed to have a significant effect on these relationships. The usefulness of estimates of carcass composition based on specific gravity determinations is discussed in relation to the maximum probable errors associated with predicted values and with reference to the accuracy of these estimates under different experimental conditions. The magnitude of the confidence limits (P = 0·05) on individual predictions varied from ±2·98% to ±3·48% for fat and muscle respectively and for group (n = 12) predictions, from ±0·88% to ±1·01% respectively. This suggests that little confidence can be placed in specific gravity determinations as a reflection of real individual differences or small treatment differences.

Deposition in and release of vitamin D3 from body fat: evidence for a storage site in the rat

Vitamin D in all body tissues was radio-labeled by supplementing completely vitamin D-deficient weanling rats with oral vitamin D(3)-4-(14)C for 2 wk. All vitamin D was then withheld, and radioactivity and vitamin D content in a variety of organs and tissues were measured. Adipose tissue was found to contain by far the greatest quantity of radioactivity throughout the 3 month experimental period. Immediately after supplementation, half of the total radioactivity in adipose tissue corresponded to unaltered vitamin D(3), and the other half to polar metabolites and esters of vitamin D(3) and unidentified peak II. 1 month later there was approximately the same proportion but a decrease in the total quantity of each form. We conclude that adipose tissue is the major storage site for vitamin D(3) in its several forms. Unaltered vitamin D(3) was the principal storage form observed and presumably a source available for conversion to other metabolites during deprivation.