Body Composition and Efficiency of Growth of Suckling Lambs as Affected by Level of Feed Intake

Abstract

An experiment was conducted to study: (1) the efficiency with which single and twin lamb pairs convert milk and supplemental feed energy and protein into weight gains, as well as the energy and protein of these gains at different levels of milk intake, and (2) to compare the chemical composition of the lamb bodies at 90 days of age as affected by level of nutrient intake. Thirty lambs, 10 singles and 10 pairs of twins, all sired by Hampshire rams, and suckling Rambouillet × Columbia dams were used in a 2 × 2 factorial experiment. Treatment factors consisted of different levels of milk intake and twin vs. single lamb comparisons. Different levels of milk intake were obtained by feeding 94% and 111% of the digestible energy (DE) requirements recommended by the N.R.C. (1957) to ewes with single lambs and 97% and 114% to ewes with twins. The following results were obtained: The lambs consuming more milk, due to the higher DE levels fed to their dams, were significantly heavier at 90 days of age than those suckling ewes fed the lower levels and single lambs were heavier than twin lambs. No interaction was observed between level of milk intake and number of lambs suckled. There was a 12% increase in body energy gain favoring the lambs consuming the higher milk level. Combined twin lamb gains were significantly greater than single lamb gains. Protein gain was significantly greater in lambs consuming the higher milk levels and in twin lambs. The body composition of the lambs was not significantly changed due to milk intake levels, but the single lambs were composed of less water and protein and more fat than the twin lambs. It was estimated that the lambs utilized 77% of the energy of the milk consumed and 19.4% of supplemental feed energy for body energy gain and maintenance energy. On an energy gain basis only, single and twin lambs utilized milk gross energy with an estimated efficiency of 43.8% and 37.4%, respectively. Estimated creep feed utilization was 13.2% for single lambs and 8.8% for twin lambs. Efficiency values did not differ due to level of intake. Gross energy in the pelleted ration fed to the ewes was converted to milk and thence to lamb gain with an average estimated efficiency of 8.3%. The estimated utilization of milk protein for body protein gain and wool growth was 43.3%. Estimated creep ration protein utilization was 19.9%. Treatment differences were small.