Digestibility of energy in four cereal grains fed to barrows at four body weights

This study was conducted to determine the digestible (DE) and metabolisable energy (ME) content and the coefficient of apparent total tract digestibility (CATTD) of gross energy (GE) in 4 cereal grains (corn, wheat, barley and sorghum) fed to barrows and to quantify the effect of body weight (BW) on the digestibility of the 4 cereal grains. Twenty-four weanling barrows (13.3±0.8 BW, stage 1), 24 growing barrows (31.6±1.5 BW, stage 2), 24 finishing barrows (56.7±1.8 BW, stage 3) and 24 fattening barrows (111±3.8 BW, stage 4) were individually housed in metabolic crates and allotted to 1 of 4 diets with 6 pigs fed each diet at each BW in a completely randomized design. The 4 diets consisted of 973.4g/kg of a cereal grain and 26.6g/kg of vitamins and minerals. Faeces and urine samples were collected for 5 d following a 10 d adaptation period. The DE and ME content and the CATTD of GE in corn and wheat were greater (P<0.05) than in barley and sorghum for barrows weighing 13.3 and 31.6kg. Wheat had higher (P<0.05) DE and ME values than barley and sorghum, but these were lower (P<0.05) than corn when fed to barrows weighing 56.7 and 111.4kg. Pigs weighing 111.4kg had the highest (P<0.05) DE and ME values and CATTD of GE when fed corn, wheat or barley. The DE and ME contents and CATTD of GE in sorghum were unaffected by increasing BW of pigs. There was a significant interaction in ME content and CATTD of OM between cereal grain and BW with ME content and CATTD of OM increasing with BW in the corn, wheat and barley and not changing with BW in sorghum (P<0.05). Overall, DE and ME values and CATTD of GE were greater for pigs fed corn and wheat than barley and sorghum and the digestive ability of pigs fed any of the cereal grains excluding sorghum was increased with increasing body weight. Therefore, differences in the DE and ME content of different cereal grains for pigs of different BW indicate that the effective energy values of various ingredients for pigs at different physiological stages should be considered in order to accurately and economically formulate diets based on these cereal grains.