EFFECT OF DIETARY NPP LEVEL AND PHYTASE SUPPLEMENTATION ON THE LAYING PERFORMANCE OVER ONE YEAR PERIOD

Our trial was aimed to study the effect of different dietary non-phytin phosphorus (NPP) levels with and without phytase enzyme supplementation on laying performance and eggshell quality of Tetra SL-LL in the last 25 weeks of the long-term (17 months) egg production. A total of 69 Tetra SL-LL layers were allocated into 3 dietary treatments. Two diets with different levels of NPP (2.45 or 2.15 g/kg, HP and LP, respectively) were formulated, and 0 or 300 FTU/kg phytase enzyme was added to low NPP feed (LP and LP+E, respectively). Dietary Ca was uniformly adjusted (38.2 g/kg) to feed in each treatment. In the course of the trial, intensity of egg production (%), egg weight (g/egg), number of the broken eggs and feed intake (g/d/bird) were recorded. Every 2 weeks 20 eggs per treatment were broken to determine the shell strength and thickness. Our results show that low NPP diet had detrimental effect on the intensity of egg production (P <0.05). However, dietary treatments had no effect on weight of eggs. They significantly affected eggshell thickness (P<0.05), but not egg shell strength (P>0.05) and phytase added to the LP diet resulted the lowest number of broken eggs (P<0.05). In conclusion, NPP content of the layer diet can be reduced from 2.45 to 2.15 g/kg in the last 25 weeks of the elongated laying term (12-17 month of laying), if supplemented with 300 FTU/kg phytase enzyme without compromising the egg production, and in the same time it can improve eggshell quality and reduce the number of broken eggs.