Pre- and post-pellet whole grain inclusions enhance feed conversion efficiency, energy utilisation and gut integrity in broiler chickens offered wheat-based diets

Abstract

In order to investigate whole grain feeding strategies seven dietary treatments were offered to 8 replicates (6 birds per cage) of male Ross 308 chicks from 7 to 28 days post-hatch. A steam-pelleted, wheat-based diet in which the wheat had been ground through a 3.2 mm hammer-mill screen served as the control. Whole wheat was added at 4.5, 9.0 and 18.0% of the diet in substitution for ground wheat and whole wheat was incorporated into the ration either pre- or post-pelleting. For post-pelleting additions, whole wheat and pelleted concentrate were blended. The effects of dietary treatments on relative gizzard and pancreas weights, gizzard contents and their pH and the incidence of dilated proventriculi were assessed. Treatment effects on growth performance and nutrient utilisation (AME as MJ/kg and MJ/day, ME:GE ratios, N retention and AMEn) were determined. Effects of treatments on starch and protein (N) digestibility coefficients and disappearance rates in the distal ileum were investigated on the basis of inherent AIA dietary concentrations and starch concentrations in the distal ileum were considered. Feed and water intakes and dry matter of excreta over the total excreta collection period were determined. Post-pellet inclusions of whole wheat had greater impacts on bird performance than whole wheat additions prior to pelleting. Relative to the ground grain control diet, post-pellet whole wheat inclusions increased relative gizzard weights, reduced gizzard digesta pH, reduced the incidence of dilated proventriculi, improved feed conversion ratios, ostensibly increased starch digestibility coefficients and disappearance rates in the distal ileum and reduced residual starch concentrations in the distal ileum. Additionally, post-pellet whole wheat inclusions unequivocally enhanced all nutrient utilisation parameters. Collectively, post-pellet whole wheat inclusion increased relative gizzard weights by 26.1% (18.35 versus 14.55 g/kg; P < 0.001), reduced the incidence of dilated proventriculi from 8.4 to 0.7% (P < 0.02), improved FCR by 4.25% (1.442 versus 1.506; P < 0.003), increased AME by 0.81 MJ (12.88 versus 12.07 MJ/kg; P < 0.005)) and enhanced ME:GE ratios by 6.14% (0.743 versus 0.700; P < 0.005). The 18.0% pre-pellet inclusion of whole grain increased relative gizzard weights by 13.0% (16.44 versus 14.55 g/kg; P < 0.005), improved FCR by 5.51% (1.423 versus 1.506; P < 0.001) and enhanced AME by 0.59 MJ (12.66 versus 12.07 MJ/kg; P < 0.005). This study confirms the advantages of whole grain feeding in the context of broiler chicken performance which appeared to be driven by greater extents of starch digestion allied to heavier relative gizzard weights.