The Effects of Microbial Phytase on Serum Calcium and Phosphorus Levels and Alkaline Phosphatase Activities in Broilers Fed Diets Containing Different Levels of Phosphorus

Background: Addition of the phytase enzyme to the diet of monogastric animals is an effective and practical method for both utilization of phytate-P and P disposal. Besides hydrolytic effects on phytate, phytase may also improve the availability of minerals. Alkaline phosphatase (ALP) plays an important role in bone mineralization. Since dietary P levels decrease, serum ALP level has been shown to increase. It was reported that pigs and broilers fed phytase had lower serum ALP level. The present study aimed to investigate the effect of microbial phytase on serum calcium (Ca), inorganic phosphorus (Pi) levels and ALP activities in broilers fed diets containing different P levels. Materials, Methods & Results: A total of 144 one-day-old male broiler chicks (Cobb 500 stain) were used in this study. The birds were housed in metabolic cages (33 cm × 33 cm × 40 cm) under environmentally controlled conditions for 42 days. The fluorescent lights were on for 24 h each day. Diets and water were provided ad libitum. Starter diet was given in the first three weeks of the study, and grower diet was given from the beginning of the fourth to the end of the sixth week. The study was designed as a 3 × 2 factorial arrangement with three levels, low, medium and high, of nonphytate phosphorus (nPP) (0.18, 0.30 and 0.45 %), and two levels of phytase (0 and 600 U/kg diet). Blood samples were collected from 5 broilers in each group on days 21 and 42 and analyzed for serum Ca and Pi levels and ALP activities. Serum Ca concentrations were affected only by dietary P levels between 0-21 days (P < 0.05), but there were no differences between groups for serum Ca concentrations for 22-42 days. Phytase supplementation had no effect on serum Ca concentrations. During the experiment, serum P concentrations increased linearly depending on dietary P levels. Phytase supplemented groups fed low (0.18%) and medium (0.30%) P diets had higher serum P concentrations than those of unsupplemented groups (P < 0.05). However, serum P concentrations were not affected by phytase supplementation in group fed high (0.45%) P diet. In unsupplemented groups, dietary P levels and ALP activity were inversely proportional and serum ALP activities were significantly decreased by the increase in the dietary P levels during the experiment (P < 0.05). When it was compared to unsupplemented groups, ALP activities were significantly lower in phytase supplemented groups (P < 0.05). In phytase supplemented groups, there were no difference for ALP activities between groups fed low and medium P diet, but group fed high P diet had significantly lower ALP activities than other supplemented groups (P < 0.05). Discussion: Serum P concentrations were affected by dietary P levels and increased linearly depending on dietary P levels. Although phytase supplementation significantly increased serum P concentrations during the study, serum Ca levels were affected only in first three weeks of the experiment. ALP is a metalloenzyme that plays an important role in bone mineralization. As expected, dietary P levels and serum ALP activity were inversely proportional in this study. The decrease in serum ALP activity in groups supplemented phytase was a response to increasing P levels in diets in supplemented phytase groups and this result can be accepted as an indicative of the increase in phytate-P utilization in broilers fed low-P diet. Similar results have already been observed in prior studies with chickens and turkeys.