1. Twenty-seven Large White pigs from three litters were involved in a 33 factorial experiment in which they were given three pelleted diets containing 0, 10% and 20% of dry sawdust during each third of an experimental period ranging from 29·5 to 118 kg live weight. The effects of these treatments on dry-matter intake and rate of growth in each sub-period and on the final carcass quality of the pig were studied.

2. The results confirmed a previous finding that pigs developed a compensatory increase in intake in response to diets containing increasing amounts of sawdust, but that in small pigs this operates very poorly and leads to much retarded growth on the high sawdust diets.

3. The compensatory intake mechanism took some time to develop after the pig had been put on to the sawdust diets, the delay being much longer in the smaller pig. Similarly, when the pigs were returned to high energy diets some time elapsed before intake returned to normal. During this time lag the pigs grew faster, as with compensatory growth, than when they had not previously been subjected to low energy diets.

4. It is concluded that long-term observations must be made in order to investigate the nutrition of pigs fed ad libitum.

5. Although energy intake can be restricted by giving low energy diets for a short period, this does not seem to improve carcass quality.