The efficacy of three sources of vitamins A and D supplements was tested in an experiment with fattening pigs involving the following four treatments :

• (1) Control—basal meal.

• (2) As control, but at one week of age the pigs had been given a single intramuscular injection of a commercial preparation, supplying 500,000 i.u. of vitamin A and 100,000 i.u. of vitamin D3.

• (3) Basal meal + 1 % cod-liver oil (containing 500 i.u./g. of vitamin A and 68 i.u./g. of vitamin 3), supplying 2,270 i.u. of vitamin A and 309 i.u. of vitamin D3 per lb. of diet.

• (4) Basal meal + synthetic vitamins A and D concentrate (containing 50,000 i.u./g. of vitamin A and 5,000 i.u./g. of vitamin D3), added to supply 2,250 i.u. of vitamin A and 300 i.u. of vitamin D3 per lb. of diet.

The basal meal which was the standard fattening diet used at Shinfield consisted of: fine miller’s offal 50, barley meal 30, flaked maize 10, white fish meal 10, all parts by weight. It should be noted that the diet contained a precursor of vitamin A, and it was calculated that this would provide about one-third of the recommended allowance of vitamin A for fattening pigs.