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Performance of layers fed xylanase, phytase or both in low phosphorus diets
Due to the lack of endogenous phytase enzyme in chickens to hydrolyse dietary phytate bound phosphorus, only 30-40 per cent of the phosphorus from plant sources is freely available for digestion and absorption by poultry. A conventional source of phosphorus for chicken feed is inorganic phosphorus in the form of dicalcium or monocalcium phosphate.
Undigested and unutilised inorganic phosphorus and phytate phosphorus residues are excreted. High phosphorus levels in excreta cause a major environmental problem when animal waste is used as a manure for growing crops.
It has been shown that phytase supplementation of the feed improves phytate phosphorus utilisation in laying hens. In addition to the phytic acid, soluble non-starch polysaccharides are one of the factors inhibiting the growth and production performance of broilers and layers fed wheat or barley based diets.
It has been demonstrated that anti-nutritional effects of non starch polysaccharides in broiler and layer diets can be counteracted by supplementing the diet with xylanase or beta-glucanase enzymes
This study was undertaken to compare the effects on egg production of adding xylanase or phytase or both to a standard phosphorus or a low phosphorus sorghum-wheat/ soybean meal based layer diet.
A total of 504, twenty seven weeks old, ISA Brown layers, were allocated three to a cage in a standard layer housing facility. There were two basal diets, a standard phosphorus diet and a low phosphorus diet.
The major difference between these two diets was the available phosphorus content. The standard-P and low-P diet had an available phosphorus content of 0.31 and 0.12 %, respectively. Each basal diet was supplemented with no enzyme, xylanase, phytase or both, and the enzyme activity of each experimental diet was analysed. Each diet was offered to 21 replications of three hens per cage.
The eight experimental mash diets were fed for a period of 27 weeks. Daily egg production was recorded for the twenty seven weeks of the trial and all eggs laid in the day were weighed once every four weeks.
The production performance of the hens fed the standard phosphorus diets and the low phosphorus diets with or without enzyme supplements. Hen housed and hen day egg production of hens fed the standard-P diet was significantly higher than those fed the low-P diets. Supplementation of the standard-P diet with xylanase, phytase or both had no significant effect on hen housed or hen day egg production. In contrast, supplementation of the low-P diet with phytase significantly improved hen housed and hen day egg production compared with those fed the unsupplemented low-P diets.
However, the addition of xylanase to these diets did not significantly improve the hen housed or hen day egg production. Hens fed low-P diets supplemented with xylanase alone did not have a significantly improved egg production over those fed the unsupplemented low-P diets.
Egg weight was not significantly affected either by level of phosphorus in the diet or supplementation of xylanase and/ or phytase. Egg mass was significantly (P<0.05) higher in groups fed the standard-P diet compared with those fed the low-P diets without enzyme supplements. Egg mass produced by the hens fed the low-P diet supplemented with phytase was significantly higher than those fed the unsupplemented low-P diets.
There was no significant improvement in egg mass produced by adding xylanase to phytase supplemented low-P diets.
Feed intake was not significantly influenced either by phosphorus concentration in the diet or enzyme supplementation of these diets. Feed conversion ratio was not significantly different between the groups fed standard-P or low-P diets. Xylanase or phytase supplementation of the standard-P diet had no significant effect on FCR.
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Article made possible through the contribution of the Australian Poultry Science Symposium (APSS) 2006.
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