Influence of partial replacement of ground barley with whole barley and exogenous enzyme supplementation in pelleted diets on growth performance, nutrient utilisation and foregut development in broiler starters

Abstract

A 3 × 2 factorial arrangement of treatments, evaluating three inclusion levels of whole barley (WB; 0, 141, 282 g/kg) in a barley-based diet and two levels of carbohydrase (Carb; 0 and 0.15 g/kg of feed), was used. The AMEn and standardised digestible amino acid contents of the test barley were used in formulating the basal diet. Whole barley was added to the diet at the expense of ground barley (GB; 3.0 mm sieve size). The diets contained 5.0 g/kg titanium dioxide as an inert marker. Each of the six experimental diets was pelleted and offered ad libitum to six replicate cages (eight birds/cage). Body weights and feed intake were recorded weekly throughout the 21-d trial. The AMEn was determined using the classical total excreta collection method (17–20 d). On d-21, ileal digesta were collected from the terminal ileum to determine the coefficient of apparent ileal digestibility of nutrients. Jejunal digesta were collected for the determination of intestinal digesta viscosity. There was no significant (P > 0.05) interaction between WB and Carb for any measured parameter. Compared to the birds fed GB diets, those fed WB at 141 g/kg had a higher (P < 0.05) weight gain by 36 g/bird, with no effect on the feed intake or feed efficiency. The inclusion of WB tended (P = 0.058) to enhance N digestibility from 0.741 in GB diets to 0.775 in diets with 282 g/kg WB. Irrespective of Carb supplementation, compared to the GB diet, WB inclusion at 141 and 282 g/kg improved (P < 0.001) starch digestibility (by 3.6 % and 5.7 %, respectively) and AMEn (by 1.85 % and 2.89 %, respectively). These improvements were not associated with any impact (P > 0.05) on gizzard development. Jejunal digesta viscosity was not influenced (P > 0.05) by WB inclusion. Adding Carb increased starch digestibility and energy utilisation by 2.24 % and 0.12 MJ/kg, respectively, possibly due to 0.35 cP reduction in jejunal digesta viscosity (P < 0.05) by the supplemental Carb. Overall, WB could be included in barley-based broiler starter diets up to 282 g/kg of diet with no adverse effects on performance.