The effect of different dietary energy concentrations on the voluntary intake and growth of intensively-fed lambs

Abstract

In a comparative slaughter trial which covered growth from about 16 kg to 40 kg live weight, five groups of six Romney x Swaledale lambs were offered ad libitum five pelleted diets (A to E) in which rolled barley was gradually replaced by an 80 : 20 mixture of rolled oats : oat husks to the extent that the calculated metabolizable energy (ME) concentration fell from approximately 2-9 (A) to 2-5 (E) Mcal/kg DM. Although daily live-weight gains did not differ significantly between treatments, the daily carcass gain fell from 143 g/day on A to 105 g/day on E (P<0-05) whereas gut contents increased from 9-9% of live weight to 16-1% (P< 0-001) from A to E. Differences in efficiency of utilization of ME above maintenance were variable but for gross efficiency (i.e. retention/total ME intake), there was a significant decline from A to E. Dry-matter intakes for the whole experimental period were similar for all five diets, but initially intake was lower for diet E than for A (780 v. 927 g/day) and ultimately it was higher for E (1410 v. 1150 g/day). In a second experiment, involving diets A and E and a third diet of chopped dried grass, the pattern of intake and growth changed with live weight in a similar manner to that described above, except that appetite and growth on dried grass were consistently poorer. Daily variation in intake and rumen pH tended to be greater on the concentrate diets. It is suggested that, amongst other factors, the stage of maturity of an animal may influence the point at which the digestible energy content of the diet restricts dietary intake in preference to physical limitations.

Energy Nutrition in Ruminants

“…As quoted above, Andrews et al (1969) showed that even the intake of oats can be physically restricted in early-weaned lambs weighing less than 40 kg. This is vividly illustrated in earlyweaned calves and lambs, where the rumen is insufficiently developed for the consumption of sufficient roughage for survival.…”

“…Animals receiving poor-quality diets, which impose physical limitations to intake, also often consume more under such circumstances, as a result of metabolic From Andrews et al (1969). Animals receiving poor-quality diets, which impose physical limitations to intake, also often consume more under such circumstances, as a result of metabolic From Andrews et al (1969).…”

Energy balance studies with weaned lambs

“…Andrews et al (1969) found that weaned lambs used the ME of concentrates with an efficiency of 50% for growth. This paper describes an experiment designed to measure the efficiency of utilisation of lucerne by lambs weaned at 5 weeks of age.…”

The effect in an intensive production system of type of cereal and time of weaning on the performance of lambs

“…It has been shown, furthermore, that inclusion of fibrous material such as oat husk in the barleybased diets reduced intake in the early stages of growth and that only after reaching about 35 kg live weight were the lambs capable of compensating, by consuming more, for the reduction in digestibility caused by including oat husk (Andrews, Kay and 0rskov, 1969). If, however, the oat husk was ground, lambs were able to achieve earlier compensation in intake (Owen, Davies and Ridgman, 1969;Andrews and 0rskov, 1970c).…”