| dc.description.abstract | An experiment was conducted to determine the effect of supplementing a high fibre
diet with combinations of NSP-degrading enzymes on growth performance and
nutrient utilization of broiler chickens. The ingredients of the high fibre diet were
obtained from U.S.A and Canada but are feedstuff locally available in Kenya, and
were chosen to formulate a diet representing a practical Kenyan poultry diet, whereas
those of the low fibre diet represented a standard Canadian poultry diet. Proximate
analysis was done on the feedstuff comprising the high fibre diet to determine their
nutritional values and non-starch polysaccharides (NSP) profile to aid in feed
formulation and selection of enzymes, respectively. Two basal diets, a standard low
fibre diet, LF, and a high fibre diet, HF, were formulated to meet NRC (1998) nutrient
specifications for broiler chickens except for metabolizable energy and crude protein
content of both diets, which were 94% and 97% NRC, respectively. The LF basal diet
was composed of wheat, corn, were soybean meal, DDGS and canola meal, whereas
the HF basal diet was composed of sorghum, brewers’ dried grains, cottonseed meal
and sunflower seed 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, which were analyzed as a 2 X 4
factorial arrangement to determine the main effects of diets and enzymes, and
interactions between the diet type and enzymes. Enzyme A provided 1,100 units (U)
of cellulase, 100 U of pectinase, 50 U of mannanase, 40 U of galactanase, 1,000 U of
xylanase, 250 U of glucanases, 10,000 U of amylase, 1,000 U of protease, 600 U of
invertase and 500 U of phytase per kilogram of diet. Enzyme B provided 3,000 U of
cellulase, 800 U of pectinase, 300 U of mannanase, 40 U of galactanase, 850 U of
xylanase, 600 U of glucanases, 2,000 U of amylase, 150 U of protease, 600 U of
invertase and 500 U of phytase per kilogram of diet. Enzyme C provided 5,000 U of
cellulase, 1,000 U of pectinase, 400 U of mannanase, 1,400 U of galactanase, 1,500 U
of xylanase, 1,500 U of glucanases, 6,000 U of amylase, 600 U of protease, 600 U of
invertase and 500 U of phytase per kilogram of diet. 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. Compared with the LF basal diet, the HF basal diet had
higher content of NSP (13.3% vs. 10.5%) and neutral detergent fibre (NDF) (18.8%
vs. 12.4%). Birds fed 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). Supplementation of
multicarbohydrases improved (P < 0.05) body weight gain, AMEn content of diet,
digestibility of NDF, and degradation of NSP in ileal digesta of broilers in both diet
groups. Feed intake and feed conversion ratios improved (P < 0.05) in birds fed
enzyme supplemented diets. Supplementation of phytase improved (P < 0.05)
digestibility of phosphorus and calcium with greater effects observed in birds given
HF treatments. Supplementation of multicarbohydrases decreased (P < 0.05) viscosity
of jejunal digesta with greater effects observed in broilers fed the LF diets. Enzymes
improved (P > 0.05) digestibility of crude protein and amino acids and significant
diet*enzyme interactions (P < 0.05) were observed for digestibilities of glycine,
serine, asparagine and threonine. Generally, enzyme blend C had the highest activities
of multicarbohydrases showed better effects on most 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 appropriate combinations of carbohydrase enzymes
to target cell wall polysaccharide structures could further improve growth
performance and nutrient utilization of high fibre diets by broiler chickens. The
improvements in growth performance and nutrient utilization observed in broiler
chickens fed the enzyme supplemented high fiber diet likely resulted from the cell
wall degrading activity of the enzyme supplements and, to some extent, the reduction
of digesta viscosity. However, more research is needed using similar ingredients from
Kenya, and to determine the best combinations of multicarbohydrases and their
optimum activities when feeding such diets in order to obtain maximum beneficial
effects. | en |
