Investigations into the use of indicator methods of estimating the digestibilities of feeds by ruminant animals

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Abstract
Summary: This paper describes a comparison of acid insoluble ash (AIA) and acid detergent lignin (ADL) ratio techniques for estimating digestibility with the conventional total collection method using sheep fed a range of feeds. In only two of 17 digestibility trials were the results obtained by AIA ratio techniques significantly different from those obtained by the total collection method. In the case of ADL no significant differences occurred between the results obtained by the ratio technique and total collection method.In a trial using sheep in metabolism cages the AIA and ADL contents of faeces excreted in consecutive 4 h periods covering 48 h did not show any significant variation either within or between the two 24 h periods.The results obtained from ‘grab’ samples of faeces (25–40 g) taken per rectum or from faeces bags attached to sheep fed communally can be expected to give acceptable agreement with total collection provided the marker concentration in the faeces represents a number of sheep sampled on several days, since variation between individual samples of faeces may be high.