The potential for eliminating maize and fish meal, and reducing the levels of cereals in diets for finishing pigs was examined.
Non-conventional feedstuffs are now being included in formulations to an increasing extent. However, the relationships between their chemical composition and book values and the nutrients which are actually available to the animal are much less predictable. In addition, the fatty acid profile of some by-products may have an adverse effect on carcase fat quality.
Four diets, ranging from one containing a proportion of maize and fish meal through to cereal contents from 70% to 20% were formulated and fed to 320 finishing pigs from 40 kg to slaughter. Growth performance and feeding behaviour were monitored over the finishing period and skatole (boar taint) and economic analyses were carried out.
Finishing pigs can perform equally well whether maize and fish meal are included in the diet or not. No significant diet effects on palatability or feeding behaviour were found. However, a non-significant trend towards reduced performance was observed when the cereal content of the diet was reduced to 30% even though a similar content of DE was maintained in the ration.
Killing out percentage and fat depths at the P2 position tend to be reduced when by-product diets are fed.
Pig fat tends to follow the fatty acid profile of the diet and this resulted in the pig fat having a higher proportion of unsaturated fat when the by-product diets were fed. This is beneficial in terms of human health but negative in terms of feed processing, presentation and storage.
The incidence of skatole was not affected by the range of diets used in this study. At today’s prices (1997), cereal/soya diets, without maize or fish offer best opportunities. By-product diets must be bought competitively to be cost effective.