Some biological aspects of partial starvation. The effect of weight loss and regrowth on body compsition in sheep

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Abstract
1. A study of the effects of four dietary treatments on body-weight and the water, protein, fat and energy content of the empty bodies of forty-three Suffolk ewes is reported. The treatments were as follows: T1,ad lib. food intake from a full-body-weight (FBW) of 40 kg to 71 kg; T2, partial fasting with a resulting weight loss from 71 kg to 50 kg FBW; T3, realimentation and regrowth from 50 kg to 71 kg FBW; T4, a slight food restriction producing a reduced growth rate from 40 kg to 50 kg FBW followed byad lib. food intake from 50 kg to 71 kg FBW. On all treatments sheep were slaughtered in groups of three at 7 kg intervals between 50 kg and 71 kg FBW.2. The whole body, with the exception of several body organs and glands, wool and the contents of the gastrointestinal tract, was minced and analysed for water, protein, fat and energy. Adipose tissue samples were removed at slaughter from subcutaneous and internal fat depots for histological examination. Regression analysis was used in comparing treatment effects on body composition.3. No significant differences were observed between the results of T1and T4. In consequence these results were pooled and are referred to as T1. At 40 kg FBW the empty (ingesta-free) bodies of the lambs contained approximately 52% water, 14 % protein and 29% fat. Through normal growth to 71 kg FBW on T1these values had changed to 40, 11.5 and 45 %, respectively. Following weight loss to 50 kg FBW on T2the water, protein and fat contents of the empty bodies were 47, 13.5 and 35 %, respectively. Regrowth on T3to 71 kg FBW resulted in little change in these components, the respective values being 46, 13 and 36 %. The sheep which had undergone weight loss and regrowth retained significantly more water and less energy than normally grown controls and tended to deposit less fat and more protein.4. Gastrointestinal tract contents accounted for 11 % of FBW at 71 kg in T3animals. In T1, the value was 7.1 % at a similar FBW. Thus there was an average increase of over 56 % in contents in the realimented animals.5. Mean adipocyte diameter at 50 kg FBW on T1was 134 ± 3 μm. At 71 kg FBW the mean diameter had increased to 152 ± 9 μm. Weight reduction (T2) and regrowth (T3) resulted in mean diameters of 122 ± 4 μm and 143 ± 4 μm at 50 kg and 71 kg FBW, respectively.