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Abstract
1. The objective of this experiment was to study the influences of xylanase and citric acid on the performance, nutrient digestibility, digesta viscosity, duodenal histology, and gut microflora of broilers fed on a wheat based diet.
2. The experiment was carried out as a 2 × 3 factorial arrangement with two concentrations of xylanase (0 and 200 mg/kg) and three concentrations of citric acid (0, 20 and 40 g/kg). A total of 408 one-day-old chickens with similar body weight were distributed into 24 pens with 17 birds/pen. Each dietary treatment was given to 4 replicate pens from 0 to 24 d of age. To determine the apparent nutrient digestibility, chromic oxide (3 g/kg) was added to the diets as an indigestible marker.
3. Xylanase significantly increased body weight gain at 24 d of age by 1·4% and improved gain-to-feed (G:F) by 3·6%. The inclusion of 40 g/kg citric acid decreased feed intake and body weight gain by 15·4% and 11·8%, respectively. The inclusion of 20 g/kg of citric acid decreased feed intake, but it did not affect body weight gain of broilers at 24 d of age. The inclusion of 20 and 40 g/kg citric acid improved G:F by 3·8 and 4·3% respectively. Xylanase significantly decreased the viscosity of digesta and improved retention of DM, CP, and energy.
4. Xylanase and citric acid did not have any effect on the histo-morphology of the duodenum and intestinal microbial population.
5. In conclusion, citric acid at 20 g/kg decreased feed intake, did not have a negative effect on body weight gain, and improved G:F. Xylanase decreased digesta viscosity, increased nutrient retention and consequently improved performance of broilers fed on a wheat based diet.
Acknowledgements
The authors would like to thank Novozymes A/S (Bagsvaerd, Denmark) for supplying xylanase enzyme, and the Kimia Gharb Gostar Company (Kermanshah, Iran) for providing citric acid.
