Differences amongst breeds of sheep in food requirements for maintenance and live-weight change

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Abstract
SUMMARY In a series of experiments, each of 6 weeks' duration, non-pregnant Romney, Scottish Blackface and Tasmanian fine-wool Merino ewes were individually penned in an outdoor environment and allocated a constant ration within a range from 8 to 30 g of a standard dried-grass pellet per kg live weight. Maintenance requirements were calculated from the regression of live-weight change per unit weight on intake per unit weight. Comparable values for the three breeds were computed as 8·4, 9·2 and 14·0 g DOM (digestible organic matter)/kg/day for Romney, Blackface and Merino respectively, the latter being significantly higher than for the two British breeds. Estimates of requirements per unit change in live weight, after allowing for maintenance, were 5·1, 4·6 and 3·0 g DOM/g live-weight change for the three breeds. Methods of estimation of energy requirements and the reasons for differences between breeds are discussed.