Reducing The Amount Of Inorganic Phosphorus Supplementation In The Diet Of Broilers

Two experiments were conducted to determine the phytase requirement of broilers and the level of available phosphorus with optimum phytase supplementation in this paperIn experiment1, the experiment with different levels of phytase was conducted to estimate optimum phytase supplementation of broilers from1to42d. A total of3601-day-old Ross308broilers were randomly divided into4groups with3replicates and30broilers per replicate (15male,15female). The treatments were fed with basal diet supplemented with0,500,1000and1500U/kg phytase. The results were as follows:1. Phytase supplementation had significant effects on body weight of broilers from1to6weeks (P<0.05), and phytase supplementation linearly (P<0.05) and quadratically (P<0.05) influenced body weight, with the highest body weight when1000U/kg was supplemented. While phytase supplementation had no significant effect on average daily feed intake and feed conversion ratio (P>0.05).2. Phytase supplementation had significant effects on eviscerated carcass ratio and leg muscle ratio (P<0.05), both eviscerated carcass ratio (P=0.031) and leg muscle ratio (P=0.021) significantly increased linearly with increasing phytase supplementation, while phytase supplementation had no significant effects on breast muscle ratio and abdominal fat ratio (P>0.05).3. Pyhtase supplementation had significant effects on liver, spleen and gizzard weight (P<0.05), liver, spleen and gizzard weight significantly increased linearly with increasing phytase supplementation (P=0.019, P=0.055and P=0.000, respectively). Phytase supplementation had no significant effect on heart and proventriculus weight (P>0.05).4. Phytase supplementation had significant effects on jejunum, rectum weight and ileum length (P<0.05), jejunum, rectum weight and ileum length significantly increased linearly with increasing phytase supplementation (P=0.013, P=0.001, and P=0.049, respectively). Phytase supplementation had significant effects on duodenum weight and jejunum length (P<0.05), and phytase supplementation quadratically influenced duodenum weight and jejunum length (P-0.037and P=0.046, respectively), with the highest duodenum weight when1000U/kg phytase was supplemented, at the same time, with the longest jejunum when0U/kg phytase was supplemented.5. Phytase supplementation had significant effects on serum calcium and phosphorus (P<0.05), and serum calcium decreased linearly with increasing phytase supplementation (P=0.002), but serum phosphorus increased linearly with increasing phytase supplementation (P=0.000). In contrast, phytase supplementation had no significant effect on albumin, total phosphorus, alkaline phosphatase, blood urea nitrogen and growth hormone (P>0.05).6. Phytase supplementation did not affect the apparent metabolizable energy and the utilization of calcium, phosphorus, crude protein and ether extract (P>0.05). According to the above analysis, the results of the group with1000U/kg phytase supplementation were optimum. Consequently, the optimum supplementing level of phytase was1000U/kg whose diet was made up according to the nutrient standard of broilers.In experiment2, the experiment with different levels of available phosphorus was conducted to estimate level of available phosphorus in different period of broilers from1to42d when the diet was supplemented with1000U/kg phytase. Three experiments corresponding starter (0to10d), grower (11to24d) and finisher (25to42d) periods were conducted with1080Ross308broilers. For each trial, a total of360broilers were randomly divided into4groups with3replicates and30broilers per replicate (15male,15female). Broilers were fed a diet supplemented with phytase [0.30%,0.35%,0.40%and0.45%nonphytate phosphorus] in each experiment respectively. The diet in treatments were supplemented with1000U/kg phytase in the experiment. The results were as follows:1. The body weight increased linearly with increasing level of available phosphorus when1000U/kg phytase was supplemented (P=0.05) and different levels of available phosphorus with1000U/kg phytase supplementation did not affect the average daily feed intake and feed conversion ratio in starter period (P>0.05).2. Different levels of available phosphorus with1000U/kg phytase supplementation did not affect the body weight, average daily feed intake and feed conversion ratio in grower and finisher period (P>0.05).3. Different levels of available phosphorus with1000U/kg phytase supplementation had significant effects on the utilization of phytate phosphorus and calcium (P <0.05), and both the utilization of phytate phosphorus and calcium increased linearly with increasing the level of available phosphorus (P=0.000and P=0.000, respectively) from21to24d and from39to42d.4. Different levels of available phosphorus with1000U/kg phytase supplementation had no significant effect on slaughter performance and serum biochemical parameters of broilers (P>0.05). According to the above analysis, the optimum available phosphorus with1000U/kg phytase supplementation of broilers in starter period was0.35%.