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The influence of barley particle size and enzyme supplementation on performance, nutrient and energy utilization, and intestinal morphometry of broiler starters (day 1–21) fed pelleted barley-based diets was evaluated. Two barley particle sizes (fine and coarse) and 4 enzyme treatments (nonsupplemented [control], carbohydrase [0.15 g/kg of feed; Carb], phytase [0.10 g/kg; Phy] and combination of carbohydrase and phytase [0.15 and 0.10 g/kg, respectively; Carb + Phy]) were evaluated in a 2 × 4 factorial arrangement. Fine and coarse barley particles were achieved by grinding whole barley in a hammer mill to pass through 2.0 and 8.0 mm screens, respectively. A total of 384, 1-day-old male broilers (8 birds/cage; 6 cages/treatment) were used. Supplemental enzymes tended ( P = 0.056) to increase the weight gain of birds with a synergetic effect from Carb + Phy. The response of feed intake to supplemental enzymes interacted ( P < 0.05) with barley particle size, as Phy increased feed intake only in fine barley diets. Both coarse particles and supplemental Carb, either individually or in combination with Phy, reduced feed per gain ( P < 0.001). Digestibility of DM, nitrogen, and fat was greater in birds fed coarse barley diets ( P < 0.05). Dry matter, starch, fat, and phosphorus digestibility values were improved by supplemental enzymes ( P < 0.05). Coarse barley ( P < 0.05) and Carb ( P < 0.001), either individually or in combination, increased the AMEn. Coarse barley reduced the gizzard pH ( P < 0.001). Birds fed diets with supplemental enzymes had shorter jejunum ( P < 0.05). Neither the barley particle size nor supplemental enzymes ( P > 0.05) affected the jejunal digesta viscosity. In summary, feeding coarse barley particles and supplemental Carb improved the feed efficiency and nutrient and energy utilization. The effects of barley particle size on measured parameters suggest that the particle size effect was preserved even after pelleting. The combination of Carb and Phy tended to improve the weight gain but caused no further improvements in nutrient utilization.

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The influence of the method of barley inclusion (fine, coarse and whole barley) in a wheat-based diet and protease supplementation (0 and 0.20 g/kg) on growth performance, nutrient utilisation and gastrointestinal tract development of broilers (d 1 to 21) was evaluated in a 3 × 2 factorial arrangement. Whole barley (WB) grains were ground in a hammer mill to pass through the screen sizes of 2.5 and 8.0 mm to achieve fine (FB) and coarse (CB) barley particle sizes, respectively. A total of 288, one-day-old male broilers were allotted to 36 cages (6 cages/treatment; 8 birds/cage). There was no significant ( P > 0.05) interaction between barley inclusion method and protease for any growth performance or nutrient utilisation parameters. Birds fed diets containing CB and WB showed higher ( P < 0.05) weight gain, and digestibility of dry matter, nitrogen, calcium, gross energy, and ileal digestible energy compared to those fed FB diets. Compared to the birds fed FB diets, feed per gain was lower ( P < 0.05) in birds fed diets made of WB. Fat digestibility of the birds fed CB was higher ( P < 0.05) than those fed FB and WB birds. Compared to FB and CB diets, inclusion of WB resulted in heavier ( P < 0.05) gizzards but reduced ( P < 0.05) gizzard pH. Supplemental protease, however, had no effects ( P > 0.05) on growth performance and nutrient utilisation, most likely due to the well balanced digestible amino acids and high inherent digestibility of protein in the basal diet, and/or the presence of exogenous carbohydrase and phytase. In conclusion, the present results showed that the inclusion of coarsely ground and whole barley in a wheat-based diet can enhance nutrient and energy utilisation and is beneficial to the growth performance of young broilers.