Experimental sheep in nutrition trials are commonly housed individually in slatted, unbedded pens and receive a concentrated, pelleted ration. Under these conditions a number of abnormal oral activities are performed including bar-biting, slat-chewing and wool-eating (Marsden and Wood-Gush 1986, Cooper et al 1994). These have been described as a functionless, stereotypic response to a restrictive or frustrating environment. They may, however, be the redirection of feeding motivation to apparently inappropriate substrates, when presented with a diet which does not satisfy all the sheep's nutritional needs. In this experiment the effect of a fibrous diet, which provides a substrate for chewing and/or rumination, on the performance of abnormal oral activities was examined, since pellated rations are usually low in effective fibre.