Response of Immature Sheep to Partial Starvation

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Abstract
Individual feeding experiments with a poor quality straw ration and group feeding experiments on dry range feed were designed to investigate further the added stress of partial starvation on immature sheep being maintained at a constant weight. Partial starvation was submaintenance by a reduction in energy, protein or total feed intake. Realimentation was also studied. A change from maintenance to submaintenance by reduced energy, protein or total feed intake decreased body weight, carcass weight and wool production. Height at withers did not appear to be influenced by a reduction in protein or total feed intake, but reduced energy intake decreased height at withers. Partial starvation for 42 days apparently did not influence the relative proportions of fat and protein in the carcass in any treatment. Both carcass protein and fat were lost. A nitrogen balance confirmed these observations. The greatest nitrogen loss occurred with the low protein intake. The nitrogen balance was negative, however, with the lowered energy intake. Adaptation to submaintenance feeding of energy or protein occurred as measured by nitrogen balance because progressive decreases in urinary nitrogen resulted as partial starvation continued. Energy or protein improved response of immature sheep on submaintenance feeding. One of the primary effects of energy addition as starch was its nitrogen sparing effect in spite of a decreased organic matter and nitrogen digestibility. It was concluded that protein is one of the primary requirements to alleviate the stress of partial starvation on a submaintenance intake of highly lignified mature roughage containing from 4.0 to 6.7% crude protein. Partial starvation for 148 days under range conditions was primarily a protein deficiency although response to an energy supplement was obtained. Realimentation for 150 days on adequate pasture removed all significant differences in body weight and carcass fat. Carcass weight however, was smaller for those not previously supplemented on the energy and protein deficient range. The maintenance requirement under barnfed conditions for total digestible nutrient (TDN) and digestible energy (DE) requirement in pounds and kilocalories respectively were: TDN=0.042 W ¾ and DE=84 W ¾ where W is body weight in pounds, TDN is in pounds and DE is in kilocalories. Copyright © . .

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