Further studies on various aspects of the use of highcopper supplements for growing pigs.

The growth-promoting effect of the addition of 0-1 yo copper sulphate (supplying 250 p.p.m. Cu) to a growing-pig diet, reported by Barber, Braude, Mitchell & Cassidy (1955), has since been confirmed in many experiments both in Europe and America. In the present paper results of four further experiments are given dealing with: ( I ) the optimal level of copper sulphate to include in the diet; (2) comparison of copper sulphate and copper carbonate, in diets given at two different levels; (3) comparison of the effect of copper sulphate in diets containing dried skim milk as the protein supplement in place of white-fish meal; and (4) effect of system of feeding (‘semiad lib.’, wet, or ‘fully ad Zib.’, dry) on the response to copper sulphate.