Digestible and metabolizable energy values of ten feed ingredients in growing pigs fed ad libitum and sows fed at maintenance level; comparative contribution of the hindgut

Abstract Digestible (DE) and metabolizable (ME) energy values of 14 diets were measured in three groups of pigs: sows fed at a maintenance level; 45-kg growing pigs fed nearly ad libitum; and ileo-rectal anastomized (IRA) growing pigs. The energy digested in the hindgut was calculated as the difference between DE values in intact growing pigs or sows and DE measured in IRA pigs. Diets were prepared from ten ingredients (wheat, corn starch, soybean meal, rapeseed oil, meat and bone meal, corn gluten feed, wheat bran, wheat middlings, wheat straw and sugar beet pulp), the inclusion levels of ingredients being independent. The DE and ME values of ingredients were calculated by regression of DE or ME values of diets on levels of inclusion of ingredients. The DE values of ingredients were higher in sows than in growing pigs, the difference being greater for high-fibre diets. Apart from wheat straw, which contributed negatively to DE in growing pigs, the largest difference was obtained for sugar beet pulp, for which the DE value in growing pigs represented 60% of the value obtained with sows. No difference was observed for wheat and corn starch. The contribution of the hindgut was higher for sows than for growing pigs and more pronounced for high fibre ingredients (sugar beet pulp, soybean meal). Rapeseed oil was totally digested in the small intestine. Comparison of measured and tabulated DE values shows a good agreement for wheat, corn starch and soybean meal. But tabulated values overestimate the DE values of fibrous ingredients and rapeseed oil for growing pigs and underestimate the DE values of the same ingredients (except rapeseed oil) for sows. Conclusions are equivalent for ME. The consequences of these digestive interactions on the energy evaluation of pig diets are discussed.