Effect of altering nutrient density (concentrate to roughage ratio) and restricting energy intake on rate, efficiency and composition of growing lambs.
Two hundred ninety-eight Rambouillet ewe and wether lambs approximately 9 mo old from Texas were allotted to pens (29 to 30 lambs/pen). Two replicate pens were fed each of five diets. Two methods of restricting energy intake were evaluated: altering nutrient density (55% vs 72.5% vs 90% concentrate levels) and restricting intake of the 90% concentrate pelleted diet (92.5% or 85% ad libitum intake). Daily gains were highest with the 72.5% concentrate level and feed efficiency was poorest with the 55% concentrate diet fed ad libitum. Altering nutrient density did not reduce energy intake because lambs compensated by increasing feed intake at the lower nutrient densities. Actual feed intake was 89.5% of ad libitum for the 92.5% of ad libitum intake level and 84% of ad libitum at the 85% of ad libitum intake level due to refusal to consume some fines from the 90% concentrate diet. Feed refusal was greatest for lambs with ad libitum access to feed. Average daily gain was depressed by 8% at the 85% intake level. However, feed efficiency was improved (P less than .01) by 20% when intake was restricted to 92.5% of the ad libitum intake level. Differences in carcass traits were small, but consistent; carcass fat content was reduced slightly by restricting feed intake at constant slaughter weight.
Glimp
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HA
U.S. Department of Agriculture, El Reno, OK 73036.
Hart
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SP
VonTungeln
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D000821:Animal Feed; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D004435:Eating; D002149:Energy Intake; D005260:Female; D005508:Food Deprivation; D008297:Male; D009751:Nutritional Requirements; D012756:Sheep / Q000502:physiology*; D015430:Weight Gain