Effect of pelleting and enzyme supplementation on variation in feed value of wheat-based diets fed to broiler chicks

The effect of wheat cultivar, pelleting, and enzyme supplementation was measured with a broiler chick bioassay comparing differences in feed intake, growth, FCR and metabolisable e nergy (ME) level. Samples of two wheat cultivars from each of six classes were ground and were either unpelleted or pelleted and ground before including (80%) in mash diets with or without enzyme (Avizyme 1302). Two common control diets were fed in the two bioassay series required to evaluate the 48 diets. Each diet was fed to four cages of six male broilers from 4 to 17 d of age. Apparent metabolisable energy (AME) was determined on excreta collected at 16 d of age. There was more than a 25% difference in feed intake among the 48 diets; the largest contribution of the variation was due to wheat cultivar. Feed intake was significantly increased by enzyme addition and decreased by pelleting. Variation in feed intake explained more than 70% of the variation in body weight and had only a minor association with determined AME. The AME of all wheat samples, except the two Durum wheats, was increased by both enzyme supplementation and processing. The increase in AME with processing may represent an anomaly of using different bioassay series to measure unpelleted and pelleted wheat samples or it may represent changes in AME of all wheat samples, except Durum wheats, with storage after harvesting. The relative AME and FCR measurements for the 12 wheat samples were similar whether the wheats were pelleted or not. However, there was no relationship between measurements of feed intake when the different cultivars of unpelleted and pelleted wheat were compared. The marked variation in feed intake and growth rate of broilers fed different cultivars of wheat continues to be a concern as it suggests that other factors may limit intake and prevent the broiler from obtaining the required levels of nutrients from the diet.