Whole grain feeding promotes energy utilisation more in sorghum- than wheat-based broiler diets

Abstract

Wheat and, to a lesser extent, sorghum are the two commonly used feed grains in Australia for chicken-meat production. Whole grain feeding (WGF) is becoming increasingly accepted in countries where wheat is the dominant feed grain so, for this reason, the present study compares responses of broiler chicks to 12.5% whole versus ground barley in diets based on wheat, sorghum and a wheat-sorghum blend. Six nutritionally equivalent diets were offered to 7 replicate cages (6 birds per cage) of male Ross 308 chicks from 7 to 28 days post-hatch. These treatments were offered as an intact pellet containing 12.5% ground barley or as a mix of 12.5% whole barley and a balancing pelleted concentrate. The effects of dietary treatments on relative emptied gizzard weights, contents and pH, excreta dry matter and energy utilisation were determined. WGF increased relative gizzard weights by 22.5% (16.96 versus 20.77 g/kg; P < 0.001) but reduced their contents by 13.7% (8.32 versus 9.64 g/kg; P < 0.025). WGF reduced the incidence of dilated proventriculi from 4.76% to zero (P < 0.03). WGF increased excreta dry matter by 13.3% (25.08 versus 22.13%; P < 0.005) in birds offered wheat-based diets, which should aid in the prevention of wet litter. There were significant treatment interactions (P < 0.001) for parameters of energy utilisation (AME, AME:GE ratios, AMEn). For example, WGF did not influence AME:GE ratios of wheat-based diets (P > 0.75) but improved those of sorghum-based diets (0.729 versus 0.697; P < 0.001) WGF notionally increased AMEn of wheat-based diets by 0.08 MJ (12.23 versus 12.15 MJ/kg) but by 0.70 MJ (11.52 versus 10.82 MJ/kg) in sorghum-based diets. The greater responses of sorghum to WGF reflect its inherently poorer energy utilisation relative to wheat, which is an underlying problem that needs to be addressed. However, the quality of ground sorghum for chicken-meat production may be enhanced by its incorporation into WGF regimes.