Effect of chemical content and physical characteristics on nutritional value of wheat, barley and oats for poultry

Abstract

Five wheat, barley and oat varieties were grown on two locations in Norway in 1998 and 1999. These 60 batches of wheat, barley and oats were analysed for chemical contents and physical characteristics. Diets with and without enzyme addition containing 770 g cereals of each batch per kg DM were fed to broiler chickens from 7 to 21 days of age. Apparent metabolisable energy (AME) value of the diets without enzyme added was also determined using adult cockerels. Overall, no major difference in AME value determined with broilers existed between wheat, barley and oats diets when enzymes were not used. AME value of the wheat diets was negatively ( P<0.05) correlated to feed intake. Enzyme addition gave a consistent increase in broiler performance and AME value. Composition varied considerably among batches of wheat. Starch and fat content was positively ( P<0.05) correlated to AME value, while protein content was negatively ( P<0.05) correlated. Falling number was also negatively ( P<0.05) correlated to AME value. A negative relationship between baking quality characteristics and nutritional value of wheat for poultry therefore seemed to exist. Viscosity of the wheat was not closely associated with nutritional value. Considerable variation in nutritional value, which was largely caused by variations in viscosity of the grain, was found among barley varieties. Nutritional value increased ( P<0.05) and variation between batches of barley decreased when enzymes were added to the diet. Water extract viscosity and in vitro digestion viscosity were equally well suited as predictors of nutritional value of barley to poultry, while acid extract viscosity was poorly correlated to nutritional value. Considerable variation in nutritional value was found among oats varieties. Nutritional value increased ( P<0.05) and variation between batches of oats decreased when enzymes were added to the diet. Fibre content was negatively ( P<0.05) associated with nutritional value, while fat content was positively ( P<0.05) associated with nutritional value. When enzymes were not used, viscosity of the cereal also tended to be negatively associated with nutritional value. AME value was consistently higher when determined with adult cockerels than with growing broiler chickens. It is therefore concluded that AME values determined with adult cockerels may have limited value for evaluation of nutritional value of cereals for growing broiler chickens.