Effects of Graded Levels of Xylanase-Treated Rice Husk on Nutrient Digestibility and Growth Performance of Broiler Chickens

This study investigated the feeding value of Aspergillus tubingensis xylanase-treated rice husk in broiler chickens. The objectives of the study are (I) to investigate the effect of xylanase treatment on the utilization of rice husk in broiler chickens and (II) to determine the optimum level of xylanase-treated rice husk that can be tolerated by broiler chickens. Xylanases are hydrolytic enzymes that degrade xylan and hemicelluloses located in plant cell walls, into xylose which is a reducing sugar and enhancing nutrient digestibility in animal feeds. The production of extracellular xylanase by a locally isolated Aspergillus tubingensis was conducted using solid-state fermentation. The selected isolate was identified by cultural techniques and verified by molecular identification. Conventional feed ingredients such as maize is the primary cereal as source of energy in broiler diet. High cost, availability and competition existing among man, industry and livestock has necessitated the need to find cheap and available alternative feedstuffs for maize in poultry diet. Rice husk is one of the alternative feedstuffs but characterized by high fibre content and Non-Starch Polysaccharide (NSP) (Dalibord, 2006). Thus, addition of the xylanase enzyme breaks the NSPs resulting in plant cell wall destruction after releasing the trapped nutrients such as starches and proteins within fibre-rich cell walls (Gade et al., 2017). Crude xylanase produced was used for enzymatic degradation of rice husk to improve its nutritional value. The rice husk was initially subjected to physical pre-treatment by soaking in water for 24 hours or ground to increase the surface area. Pre-treated rice husk was treated by spraying xylanase onto the rice husk at 100g/ 0.2mL representing the concentration level that recorded the best degradation of fibre content in the treated rice husk. Xylanase-treated rice husk (XTRH) was used with other ingredients in formulating a broiler chicken diet at different inclusion levels. The experiment was a complete randomized design with five experimental diets containing xylanase-treated rice husk at different inclusion levels 0, 5, 10, 15 and 20 kg/100kg. The control diet contained no xylanase-treated rice husk (XTRH). There were five (5) treatments each with three (3) replicate cages of eight (8) broiler chicks totalling 120 birds for the feeding trial. One hundred and twenty (120) day-old chicks with an average weight of 54.85g were randomly allotted to five dietary treatments formulated with 0 (control), 5%, 10%, 15% and 20% (XTRH), and fed for eight weeks. There were three replicates of eight (8) birds per treatment. Results showed that the performance of Broiler chickens such as feed intake, and weight gain feed fed diet containing a 20% inclusion level of xylanase-treated rice husk was significantly higher (p<0.05) compared to other treatment diets. This showed an improvement in the utilization of a high-fibre diet, nutrient digestibility, growth performance, and carcass characteristics which can be beneficial to farmers in reducing the cost of feed, and increasing savings and profit margin. Conclusively, the application of xylanase produced by Aspergillus tubingensis on rice husk may have enhanced efficient enzymatic hydrolysis of its fibre fractions and improved its nutritional values. Supplementation of rice husk treated with xylanase at 100g/0.2mL concentration level and included at 20% in broiler chicken may enhance nutrient digestion and utilization and improve the growth performance of broiler chickens.