A total number of 480 Bovans White laying hens 21 weeks of age
were used to study the effect of dietary crude protein (CP), methionine (M)
and microbial phytase (Phy) levels on laying hen performance, egg shell
thickness, nutrient digestibility coefficients and economic efficiency.
Hens were randomly divided into 8 equal groups with four replicates of
15 hens each. Two levels each of crude protein, methionine and microbial
phytase were used in a 2X2X2 factorial design. The two levels of crude
protein were the optimum level, 18% (CP1) and low level, 16% (CP2);
methionine levels were the optimum level, 0.42% (M1) and low level,
0.31% (M2) and microbial phytase levels were 0.0 (Phy1) and 500 FTU
/Kg of the diet (Phy2). The diet contained CP1 and M1 without microbial
phytase supplementation represents the control. Hens were kept in
cleaned and fumigated cages of wire floored batteries in an open system
house under similar conditions of management up to 40 weeks of age.
Water and feed were offered ad-libitum under a total of 16 hours light
/day regimen.
The overall results showed that laying hens fed diets containing the
optimum level of crude protein (18%) recorded significantly (P<0.05)
higher egg production and egg weight and better feed conversion ratio
compared to those fed low level of crude protein (16%). While, the
average values of feed intake significantly (P<0.05) increased with
feeding laying hens diets containing the lower level of crude protein.
Feeding laying hens diets containing the optimum level of methionine
(0.42%) significantly (P<0.05) increased egg production values
comparing to those fed diets containing low level of methionine (0.31%).
While, the average values of egg weight, feed intake and feed conversion
ratio were not affected by using different levels of dietary methionine. At
the same time, supplemental microbial phytase at 500 FTU/Kg of laying
hen diets significantly (P<0.05) improved the average values of egg
production, egg weight and feed conversion ratio. Laying hens fed diets
either containing optimal levels of crude protein or supplemented with
microbial phytase recorded significantly (P<0.05) higher values of egg
shell thickness. Also, either the optimum level of dietary crude protein or
microbial phytase addition to laying hens diets significantly (P<0.05)
improved digestibility coefficient of organic matter, crude protein and
ether extract. Economic efficiency values improved by feeding laying
hens diets containing lower levels of either crude protein or methionine
with supplemental microbial phytase. Accordingly, the results of this
study indicated that adding microbial phytase can spare part of dietary
crude protein or methionine in laying hen diets without adverse effects on
laying hen performance, egg quality or economic efficiency.