Performance, Egg Quality and Mineral Utilization of Dokki-4 Laying Hens Fed Diets Containing Three Levels of Nonphytate Phosphorus in Absence or Presence of Microbial Phytase, Citric Acid or Both

摘要

The present study was conducted to determine the effects of single and combined addition of Citric Acid (CA) and Microbial Phytase (MP) on performance, egg quality and mineral utilization of hens fed graded levels of nonphytate phosphorus (NPP). The NPP levels were 0.40, 0.30 and 0.20% without and with MP (0.05%), CA (2.0%) or both. Twelve groups of both 28 weeks old hens and cockerels were fed their respective experimental diets. Criteria evaluated were feed intake, egg production, egg weight, egg mass, feed conversion ratio, egg components, shell thickness, Haugh units, yolk index, tibia ash, tibia Ca, P, Mg, Cu and Zn and apparent retention of these minerals. Feeding the 0.2% NPP diet adversely affected (p<0.01) egg production, egg weight, feed intake, egg mass, feed conversion, percent eggshell, yolk index, shell thickness, tibia ash content and retention of Cu and Zn compared with their positive control. Although birds fed 0.3% NPP gave comparable performance and egg quality to their positivecontrols, tibia bone ash, tibia contents of Ca and P and retention of P, Cu and Zn of the former were significantly lower than the latter. The poor productive performance and egg quality due to feeding 0.2% NPP diet were completely corrected by MP but CAwas not effective. Added MP can effectively prevent the reductions in performance and egg quality and either microbial phytase or citric acid may partially alleviate the depression of mineral utilization in birds fed the low NPP diets, without a synergistic positive effect for their combination.