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The use of dehydrated grass in rations for early weaned lambs and some physiological effects of a rapid ration changeover France, Robert Thomas

Abstract

A study was conducted to evaluate dehydrated grass pellets (Orchard grass — Ladino clover) as a feed for early-weaned lambs. Three groups of 8 Polled-Dorset lambs were weaned at 8 weeks of age and were fed either a) the dehydrated grass, b) a 50-50 mixture of the grass and protein-supplemented barley or c) a protein-supplemented barley ration. All rations were pelleted. Digestibility trials were also conducted and the effect of level of feed intake on nutrient digestibility investigated. The dehydrated grass resulted in rates of gain comparable to those produced by the pelleted barley ration. Feed conversion efficiency was lowest for the grass and highest for the barley ration. An interaction between the dehydrated grass and barley was observed in nutrient digestibility. Increasing the level of feed intake from approximately maintenance to appetite tended to result in slight depressions in the digestibility of energy and protein of all rations. It may be concluded from this experiment that dehydrated grass can be used successfully for intensive feeding of early weaned lambs and little nutritional advantage appears to be gained from combining dehydrated grass with barley. A second study was undertaken to measure the changes occurring in five parameters when the ration of lambs was rapidly changed from all-roughage to all-concentrate. The five parameters were blood plasma glucose, rumen lactate concentration, rumen ammonia level, rumen protozoa population and rumen pH. The main effect of the change over from roughage to concentrate was the accumulation of lactic acid in the rumen. This accumulation resulted in a lowered rumen pH and a decrease in protozoa numbers. During the change over an initial increase in rumen ammonia level was followed by a decline in this parameter. It is postulated that this may have been due to the increased nitrogen intake and a subsequent adjustment in the rumen microbe population leading to increased ammonia utilization. An increase in plasma glucose level was observed which was probably due to one of two factors, either the availability of lactate as a carbohydrate source in the rumen or to glucose formed by hydrolysis of starch in the intestine. From the latter part of the study it may be concluded that when ruminant rations are changed from high roughage to high concentrate the change should be slow enough to prevent a large accumulation of lactic acid. This would mean a period of 3 to 4 weeks under normal circumstances.

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