Effect of enzyme supplementation of a diet based on barley, and autoclave treatment, on apparent digestibility, growth performance and gut morphology of broilers

Abstract

An experiment was conducted with 270 chicks to investigate the autoclaving stability (0, 50, 70 or 90°C for 10 min) of a commercial poultry feed enzyme (β-glucanase) on the performance and gut morphology of birds fed a barley-based diet over 28 day period. Digestibilities of fibre, fat and starch were also determined on Days 12 and 28 of the experiment. The addition of the enzyme (heated and non-heated) significantly improved the performance (body weight and feed to gain ratio) and reduced the relative intestinal length (duodenum, jejunum, ileum and caeca) of the birds compared with those fed the non-supplemented diet (P < 0.05). There were no differences in the apparent digestibility of fibre among the different treatments and age of the birds. However, the ileal coefficients of fat and starch were reduced significantly (P < 0.001) in the birds fed the non-supplemented diet compared with those fed corn-soy and barley-based diets with enzymes heated and non-heated at both ages. Autoclaving treatment (70 and 90°C) improved significantly (P < 0.001) the performance of the birds fed the barley-based, enzyme-supplemented diet during the first week of age, without affecting the intestinal length and the digestibility of the nutrients studied. Histological observations on the small intestine epithelium of barley-fed birds indicated morphological changes in the jejunum compared with birds fed the corn-soy diet (shortening, thickening and atrophy of the villi and an increment in the number and size of globet cells). The addition of enzymes, heated or non-heated, to the barley diet improved these histological alterations. The enzyme was found to maintain its activity through conditioning temperatures, manifested by a positive effect on performance digestibility of nutrients and gut morphology.