Performance and Egg Quality of Laying Hens Affected by Different Sources of Phytase

MATERIALS AND METHODS

Ninety 46 week-old white Leghorn laying hens were housed in 30 cages at the research center of Bu-Ali Sina University, Iran. Hens were weighed individually and divided into six groups of five replicates (cages). Groups were arranged in a factorial of 2x3 with Wheat Bran (WB) in two levels of 0 and 5% and phytase (NataphosV®) in 3 levels of 0, 150 and 300 phytase units (FTU kg^-1) and fed as part of isocaloric and isoprotein diets containing 12.13 MJ ME, 165 g CP, 35 g Ca and 1.2 g Av P kg^-1 (Table 1).

Hen-day egg production and food intake were measured over an 8-week experimental period and Feed Conversion Ratio (FCR) was calculated per cage. Eggs from each replicate were collected on two consecutive days every fortnight. Each egg was weighed then broken out onto a flat surface. The yolk was separated from the albumen and weighed. Shell thickness was measured. Egg shells were washed, dried and weighed. Albumen weight was calculated. Data were analyzed by ANOVA using the general linear models procedure of SAS software. Comparison between means was done using Duncan Multiple Range Test method. Significance was assumed at p<0.05.

RESULTS AND DISCUSSION

Egg production, egg weight, feed intake and Feed Conversion Ratio (FCR) w ere not affected by WB (Table 2). Egg production and feed intake were significantly higher in phytase supplemented groups than the unsupplemented group. FCR differed significantly between dietary treatments as phytase supplementation significantly decreased FCR. There were no significant interactions between WB and phytase supplementation for all the parameters.

Table 1:	Composition and nutrient level of experimental diets
*WB: Wheat Bran, **PE: Phytase Enzyme, †Supplied per kilogram of diet: Cu: 12 mg, Fe: 80 mg, Mn: 100 mg, Zn: 75, Se: 0.3 mg and I: 1 mg, ‡Supplied per kilogram of diet: vitamin A: 9600 IU, vitamin D3:3120 IU, vitamin E: 36 IU, vitamin K3: 1.0 mg, riboflavin: 7.2 mg, niacin: 60 mg, pantothenic acid: 14.4 mg, folic acid: 0.72, mg, thiamin: 4 mg, pyridoxine: 6 mg, vitamin B12: 0.08 mg, biotin: 0.15 mg

Table 2:	Effect of endogenous and exogenous phytase on laying hen performance
a-cMeans within a main effect in raw with different superscripts are different using Duncan`s multiple range test

Table 3:	Means of egg size and egg components weights affected by endogenous and exogenous phytase
a-cMeans within a main effect in raw with different superscripts are different using Duncan`s multiple range test

Inclusion of WB in the diets had no effect on egg size, albumen weight shell weight and shell thickness (Table 3). Yolk weight was significantly affected (p<0.02). There was a significant main effect of phytase supplementation on egg characteristics (Table 2). Egg size was not significantly affected by phytase supplementation. Albumen weight was significantly higher for 300 FTU kg^-1 phytase. Phytase supplementation generally improved shell weight and shell thickness. There was no significant interaction between WB level and phytase supplementation.

Although WB is one of the best sources of endogenous phytase it did not affect egg production and other measurements of hen performance (Table 2). The amount of active phytase present in cereals will vary depending on the cultivar, age and storage conditions (Cavalcanti and Behnke, 2004). Supplementation of diets with exogenous phytase caused significant differences in egg production, feed intake and FCR between dietary treatments. The significant increase in egg production observed in the present study is in the agreement with the investigation on the effect of microbial phytase on egg production (Keshavarz, 2000). In the absence of phytase, feed intake was significantly decreased. Similar results were reported by Punna and Ronald (1999). The higher feed intake in enzyme supplemented groups may be the result of higher egg production. FCR was significantly lower in phytase supplemented groups. Liebert et al. (2005) found that microbial phytase significantly improved feed conversation ratio whereas Boling et al. (2000) reported that FCR was not affected by phytase supplementation. Present results for egg production are in agreement with those of Boling et al. (2000), who reported that addition of 100 FTU kg^-1 phytase was adequate in a P-unsupplemented corn- soy bean meal-based diet.

Inclusion of WB to the diets had no main effect on egg and egg components weights. Although Cavalcanti and Behnke (2004) reported that endogenous phytase resulting from inclusion of WB to a low available phosphorous (Av P) diet was able to improve P utilization, we did not see any effect of WB on layer hen performance. This might be due to the fact that, in the present study, Av P was similar for all the diets. Phytase supplementation significantly affected shell and albumen weight. Keshavarz (2000) also reported that phytase supplementation significantly increased egg size in laying hens.