Heat processing of cereals in mash or pellet diets for young pigs

The influence of heat processing (HP) of the cereal on performance and component digestibility in piglets fed on diets offered in mash or pellet form was determined. In trial one, there were eight treatments arranged factorially with two cereals (barley or maize), two HP of the cereal (raw or cooked-flaked) and two forms of the diet (mash or pellets). Piglets were fed on the experimental diets from weaning at 22 to 42 days and then on a common pelleted starter diet until 52 days of age. At 42 days, piglets fed on maize-based diets had better feed conversion ratio (1.20 versus 1.41; P<0.01) than piglets fed on barley-based diets. Heat processing of the cereal improved growth rate at 32 days (0.135 kg per day versus 0.114 kg per day; P<0.05) but no differences were detected thereafter. Pelleting improved feed conversion at all ages (P<0.01) but not daily gain. At 52 days of age, the only differences remaining were for daily gain (P<0.05) between maize and barley diets and for feed conversion (P<0.001) between pellet and mash diets. Coefficient of total tract apparent digestibility of components were higher for maize than for barley-based diets and were improved by both HP of the cereal and pelleting (P<0.05). In trial two, the coefficient of ileal apparent digestibility of starch, the volatile fatty acid concentration at the caecum and the pH of the gut content were measured in piglets fed on the mash diets tested in trial one. Starch digestibility tended to improve with HP (0.985 versus 0.977; P<0.10). Processed cereals gave lower propionic and butyric acid concentrations and higher caecal pH than raw cereals (P<0.05). In summary, maize diets gave better performance and digestibility than barley diets; HP of the cereal improved digestibility and growth rate only for the first 10 day post-weaning and pelleting of the diet improved digestibility and feed conversion but not growth rate.