Application of enzyme technology to improve the nutritive value of high-fibre feedstuffs for broiler chickens
Waititu, Samuel Mwangi
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Feed accounts for over sixty per cent of the production costs in the commercial poultry sector. Maize and its by-products are the major ingredients used by the industry in making diets for poultry and other non-ruminants. Maize is also the staple food for most Kenyan communities and there is competition between humans and animals for the same commodity. This makes poultry feeds expensive which limits the development of a vibrant livestock industry. Many studies have been done to evaluate alternative ingredients with less competition. Use of enzymes has the potential to facilitate the use of non-conventional ingredients thereby lowering the current feed costs. A study was done to determine the effects of supplementing high and low fibre basal diets with blends of multicarbohydrases on growth performance and nutrient utilization in broiler chickens. The ingredients used to make the high fibre diets were obtained from U.S.A and Canada but were feedstuff that are locally available in Kenya, and were selected to mimic a practical Kenyan poultry diet. Two basal diets, a low (LF) and high fibre (HF) diet were formulated to meet NRC (1998) nutrient specifications for broiler chickens. The ingredients of LF basal diet were wheat, corn, soybean meal, distiller's dried grains with solubles (DOGS) and canola meal, whereas those of HF basal diet were sorghum, brewers' dried grains, cottonseed meal and sunflower meal. Titanium oxide (0.3%) was added to the diets as a marker to determine nutrient digestibility. The basal diets were formulated with or without enzyme blends A, B or C to give 8 dietary treatments, in a factorial experimental design with two basal diets and three enzyme blends, A, B, and C. The enzyme blends contained cellulase, pectinase, mannanase, galactanase, xylanase, glucanase, amylase, protease, invertase and phytase at different enzyme activities. Four hundred male broiler chickens were divided into 10 groups of five birds each and fed the 8 diets in mash form from 1 to 21 days of age. The HF basal diet had a higher content of non-starch polysaccharides (NSP) than the LF diet (13.3% vs. 10.5%). Birds fed on the HF diets had lower (P< 0.05) feed intake and body weight gain, and higher gizzard-to-body-weight ratios compared to those fed the LF diets, but their feed conversion ratios were similar (P> 0.05). Enzymes improved (P < 0.05) body weight gain, nitrogen corrected apparent metabolizable energy (AMEn) content of diet, apparent ileal digestibility (AID) of neutral detergent fiber (NDF), and degradation of NSP in ileal digesta of broilers in both diet groups. Enzymes improved (P > 0.05) feed intake and feed conversion ratios of the birds. Enzymes improved (P< 0.05) the apparent total tract digestibilities (ATTD) of phosphorus and calcium. Enzymes decreased (P < 0.05) viscosity of jejunal digesta with greater effects observed in broilers fed on the LF diets. Enzymes improved AID of crude protein and amino acids. Diet*enzyme interactions (P< 0.05) were observed for AID of glycine, serine, asparagine and threonine. Generally, enzyme blend C had the highest activities of multicarbohydrases and also showed better effects on most of the measured responses for broiler chickens in both diet groups but more so for those fed LF diets. It is evident from the present study that the addition of multicarbohydrases improved growth performance and nutrient utilization of broiler chickens fed on the low and high fibre diets.