Results are reported of an experiment made under commercial conditions on the effect of the level of meal fed in conjunction with an unrestricted supply of whey on the performance and carcass quality of pigs.

All the pigs received the same meal mixture and had continuous access to an unrestricted supply of whey. The four treatments were: (1) 3 lb meal per pig per day reduced to 2 lb at 13 weeks of age; (2) 3 lb meal per pig per day throughout; (3) 2½ lb meal per pig per day throughout; and (4) as (1) but the daily allowance of meal increased to 2½ lb/pig at 20 weeks of age. There were five pens of nine group-fed pigs on each treatment, involving a total of 180 pigs. The pigs were on experiment from 8–9 weeks of age to bacon weight. Comprehensive carcass measurements were made on all the pigs.

Mean differences in rate of growth, efficiency of food utilization and carcass quality between the four groups of pigs were small and were not statistically significant. The significant differences in the proportions of meal and of whey consumed by the pigs on the different treatments during the growing period are discussed in relation to relative prices of the two foods. It is concluded that where unrestricted whey feeding is to be used, the feeding system employed in treatment 3 could be recommended in most of the environmental and economic situations likely to be encountered in practice.

The superior performance of the pigs in the experiment compared with that in earlier trials is discussed in relation to the stock improvement work and concurrent improvements in housing and management carried out during the intervening years on the Cow and Gate farm in Dorset where the experiments were conducted.