Published online by Cambridge University Press: 27 March 2009
The effects on the body composition of Corriedale wethers of weight loss, compensatory gain and constant body weight are described. Three groups of sheep were grown from 35–63 kg by different paths. The first grew continuously (fed ad libitum). The second and third groups lost 20% and 28% of body weight (restricted intake), respectively, from 48 kg and were then fed ad libitum until they reached 63 kg. Pairs of animals were slaughtered at intervals in each group. A fourth group of sheep was maintained at 48 kg. Analyses of covariance comparing regression equations were used to determine differences in body composition between the first three groups.
The compensatory growth rates of both groups which had lost weight were 1·5–2 times those during continuous growth. These increases were associated with an increased gut content of these animals and a concomitant reduction in the proportion of empty body weight (EBW) and carcass weight (CW) in t he full body weight (FBW). Thus, the apparent dressing percentage (CW/FBW x 100) was reduced by 2% during compensatory growth. The carcass length was not reduced during weight loss and its growth in relation to the CW was not affected by treatment. Thus compensatory growth animals had longer carcasses. Similar increases in gut contents and carcass length were found for animals maintained at constant body weight.
During developmental growth the proportions of the external offals, organs and gut tissue decreased in relation to the EBW; notable exceptions were the large intestine and caul fat where the proportions remained constant and increased, respectively.
The growth of the CW, lungs, large intestine and head were not reversed during weight loss whilst the liver, heart, hide and gut tissues (except the large intestine) all lost more weight during weight loss than they had gained during the growth phase. The proportions of these latter components were increased in relation to the EBW during the ensuing compensatory growth.
In general, the composition of animals held at constant body weight was similar to that of animals experiencing compensatory growth at the same weight and age.