The reasons for the declining trend in pigmeat production since 1940–41 must be examined in any attempt to evaluate efficiency in producing pigmeat. The table clearly sets out the change in composition and the reduction in quantity of dairy by-products available for pig feeding.

Approximately one-third of the skim milk, and all the buttermilk from buttermaking, is used for making milk powder or casein. The skim milk available for pigs has decreased by 175 million food units (gallons). Meantime, whey available has increased by 83 million food units. The whey is not so valuable a food as skim milk, and not as readily available to the farmers; therefore it is not all being used. It is thus clear that efficiency has increased in terms of pigmeat produced from the shrinking, basic dairy-by-product feed supply. This could be improved especially by better farm husbandry and by wasting less whey.