Two groups of weaned sheep weighing about 30 kg, one born in March and the other in September, were each divided into two and given ad libitum one of two pelleted diets, ruminant diet A or ruminant diet AA6. The March-born sheep commenced experiment in July and those born in September in January. The experiment continued for 4£ years. At intervals sheep were killed and the fat protein and ash contents of their digesta-free bodies determined.The voluntary intake of feed showed a seasonal periodicity with minima in the winter and maxima in summer. The amplitude was 30 % in the 1st year and in subsequent years averaged 13%. Those given the higher quality diet (AA6) consumed slightly less than those given the poorer one.Mean daily feed intake averaged over 6-month periods from January to July and July to January was invariant with age during 4 years of observation. In this time the sheep increased in weight from about 30 kg to about 130 kg. There were, however, considerable differences between individual sheep in the amount of feed they habitually consumed.The body weight of the sheep increased and eventually plateaued. The asymptotic weight defined as A in the equation W = A -Be~k t , where W is weight at time t and B and k are constants, was related to the mean daily feed intake averaged over 6 months; mean daily feed intake measured over 6 months was proportional to a fractional power of body weight indistinguishable from 0-75, the interspecies power to which metabolism is proportional. Growth of wool during successive 6-month periods did not vary with age of animal but differed significantly between animals.Fasting metabolism of the sheep was 316 kJ/kg W 0 ' 76 for wethers and 336 kJ for rams.Analysis of the bodily composition data showed that over a range of digesta-free body weight from 46 to 130 kg it was not possible, on statistical grounds, to distinguish between linear relationships between body weight and its fat, protein, ash and water content, and allometric ones. The linear relationships had marginally smaller residual standard deviations and the regression coefficients show that the gain of the empty body in these sheep consisted of 68 % lipid, 8 % protein, 1 % ash and 24 % water. The lipid in the carcass accounted for 88 % of the total lipid gain and half the accretion of protein and ash was in the carcass. These results confirm those of Searle, Graham & O'Callaghan (1972) based on tritium dilution which showed that post-puberal growth in sheep is of constant composition.The results of the metabolic studies are shown to be consistent with the growth studies.Growth to maturity, as affected by different hypotheses related to the determinants of maintenance energy expenditure and the regulation of appetite, was examined algebraically. It is shown that mature weight is the rate of feed intake divided by the rate of maintenance metabolism per unit weight, and for defined feeding systems the rate constant for the approach to mature weight is the rate of maintenance metabolism divided by the feed equivalent ...
Twenty-seven North Country Cheviot ewes, each carrying twin foetuses and having a mean body weight at 6 weeks prior to parturition of 81 kg were individually penned and offered a constant daily intake of 16-75 MJ metabolizable energy during the last 6 weeks of gestation. At parturition the ewes were allocated to one of three dried grass/concentrate diets containing (1) 10-3, (2) 13-6 or (3) 16-9 % crude protein (CP) and 10 MJ metabolizable energy (ME) per kg. The mean daily CP intakes for diets 1 to 3 were 273, 340 and 415 g respectively and the mean daily ME intake was 25 MJ. Within each level of dietary CP intake the lambs were weaned at either 25, 35 or 41 days of age. There were no significant diet x stage of weaning interactions in milk yield or ewe body-weight change during lactation. The mean daily levels of milk production were 2-4, 2-9 and 3-1 kg for diets 1 to 3 respectively. The corresponding values for ewe body-weight loss were 118, 170 and 265 g per day. When the diet contained 13-8% CP the incremental increase in milk production per unit increase in protein intake was 4-2 g/g. This gave an incremental increase in lamb growth rate of 0-79 g/g and was equivalent to the associated incremental increase in ewe body-weight loss. A reduction in the concentration of CP in the ewes' diet when the lambs are 3 weeks of age may be a useful practical procedure for decreasing milk production and for reducing the body-weight loss of the ewe in a frequent breeding system.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.