The digestible energy and net energy content of two varieties of processed rice in pigs of different body weight

An experiment was conducted to examine the effects of two varieties of extruded rice (medium-grain variety Amaroo and long-grain variety Doongara) on the digestible energy (DE) and net energy (NE) content in pigs of two body weight groups (8 and 55 kg). Diets contained 857 g rice/kg, 50 g meat and bone meal/kg, 82 g fish meal/kg and other trace ingredients. Diets were fed at 0.05 proportion of body weight for 8 kg pigs (≈400 g/day) and at 0.0375 of body weight for 58 kg pigs (≈2175 g/day). Digestibility of gross energy (GE) was determined using titanium dioxide as an indigestible marker, and the DE content of rice was calculated by subtracting the DE content of ingredients other than rice. The mean (±S.E.M.) coefficient of total tract apparent digestibility (CTTAD) of GE and DE content (MJ/kg air-dry basis) of rice were 0.92 (0.003) and 15.1 (0.06), respectively. The rice variety did not influence the DE content. However, the body weight of the pig significantly influenced the DE content of rice such that weaner pigs extracted less energy from a given rice than grower pigs (up to 0.5 MJ/kg, P<0.001). In the second experiment, the CTTAD of GE and DE content (MJ/kg DM) of cooked medium-grain rice Amaroo (autoclaved for 20 min at 120 °C; rice:water ratio of 1:2, w/w) was examined in 10 kg pigs. The mean CTTAD of GE and DE values (±S.E.M.) were 0.918 (0.001) and 15.10 (0.031), respectively. The estimated mean NE content of rice using CVB and INRA formulae was 11.5 MJ/kg (air-dry basis).