Phosphorus (P) requirement of laying hens has been the subject of numerous investigations for many decades. However, the requirement for this nutrient has not been adequately established. Published data shows that the values are considerably lower than the recommendation made by National Research Council (NRC) and the values currently used by the poultry industry (1994). This experiment was conducted to evaluate the non-phytate phosphorus NPP requirement of Hy-line brown laying hens fed on wheat and sorghum based diets with or without phytase supplementation. It aimed to determine the effect of phytase supplementation with different concentrations of dietary non-phytate phosphorus on egg quality and laying hens performance. In addition it provides a safety guideline and more cost effective NPP requirements for laying hens.
A total of 720 Hy-line Brown layer hens at 18 weeks of age were weighed then randomly allocated into 120 cages with 6 birds per cage. The birds were housed in an environmentally controlled shed with 16-hour lighting and temperature maintained at approximately 22-26 ℃ . Experimental diets contains the same levels of calcium (Ca 42 g/kg diet), phytate-P (2.6 g/kg diet) and graded concentrations of NPP (1.5, 2.0, 2.5, 3.0, 3.5 and 4.5 g/kg diet). They were prepared with or without supplemental of phytase (450 FTU/kg) which gave twelve diets. Each experimental diet was fed to 10 replicate cages. There were two phases in this experiment, phase 1 from 21 to 50 weeks of age and phase 2 from 51 to 80 weeks of age.
The flock conditions were checked twice daily and monitored carefully. Dead birds were examined and details were recorded. Egg production and eggs with defective shells (crack or soft) were recorded daily. Body weight and feed intake were measured very four weeks. Three eggs from left to right in every cage were collected every four weeks for testing egg quality. Egg weight, specific gravity, yolk colour, Haugh units, albumen height, shell colour and shell quality (shell breaking strength, shell weight and shell thickness) were measured from 24 to 80 weeks of age.
Egg production is one of the most important economic targets in the egg industries. Dietary NPP level had no significant effect on hen-day egg production, feed intake and feed weight to egg weight conversation ratio. Body weight of layers fed on diets containing NPP of 1.5 g/kg tended to be smaller than the rest of treatments. Egg weight, specific gravity, egg shell breaking strength, albumen height, egg yolk colour, egg shell weight and thickness, Haugh Unit, egg shell weight, egg shell surface area and egg shell weight per unit surface area did not show significant differences between the treatments although the layers fed diets containing NPP of 4.5 g/kg produced more defective shelled eggs. Phytase had no significant effects on all the parameters measured. However, it appeared to improve hen-day egg production of layers fed on diet containing NPP of 1.5 g/kg at the beginning of lay and a negative impact on egg shell quality of layers fed on diet containing NPP of 4.5 g/kg. The proportion of albumen and yolk were not affected by treatments. Dietary NPP concentrations of 2.0 and 2.5 g/kg were slightly superior to other NPP concentrations (1.5, 3.0, 3.5 and 4.5 g/kg) in terms of egg production and egg shell quality.
The results indicated that egg production and egg shell quality parameters in layers fed diets containing 1.5 g/kg NPP with or without phytase supplementation were comparable to hens fed diets containing higher NPP concentrations; and suggest that dietary NPP requirement can be substantially reduced. The NPP requirement results obtained in this study refer to one dietary scenario and bird response may need to be determined for diets containing different levels of Ca. It is strongly suggested the commercial industry that the 4.5 g/kg NPP concentration not to be used in the Hy-line brown laying hens fed wheat and sorghum diets. This is because it gave high numbers of eggs with effective shells and poor shell quality which could pose a food safety issue and also be an economic cost and pollution concern.