| The present study concentrated on the properties of phytase and its effect on the performance of chicken in different stage by in vitro and in vtvo experiment respectively. The in vitro experiment studied the influence of temperature pH, feed processing, and storage on the activity of microbial phytase. The ability of phytase to liberate phytate phosphonis from corn, soybean meal and wheat bran was studied also. The animal trials were conducte~ at rearing, growing and laying stage in order to determine the effect of phytase on performance, nutrient utilization, serum merits, tibia measurements and on histological structure. The in ~ itro experiments showed that the activity of microbial phytase is affected by pH, temperature, processing and storage. At 37C the optima] pH is 5.0. Significant interact existed between temperature and pH. The optimal temperature is 45C for pH6.2 and 55扖 for pH5.4 and pH4.6 The activities of phytase at optimal temperature for different pH are much higher than the relative activity at standard condition. Pellet and extrude decreased phytase activity by 39.8% and 73.2%.The phytase activity in powder. pelleted and extruded feed decreased by20 4%, 12% and 18% after a 2-month period of storage. The degradation experiment showed that 300U/kg phytase liberated 16.83mmol/kg and 14.S6mmol/kg inorganic phosphorus in 64 minutes from corn and soybean meal, the amount of inorganic phosphorus liberated fram ~~heat bran in 45minutes is 89.4mmol/kg, accounting 3 7.4%, 20.5% and 62.9%. of phytate phosphorus.Rearing control diet (diet 1) components were as followings: corn 63.1%, soybean meal 29%, wheat bran 4%, dicalcium phosphate 1.9% limstone mill 1% and premix 1%. 35013/kg phvtase were supplemented to a reduced 1% dicalcium phosphate level(diet 2), or replaced all dicalcium phosphate with 0.8% phytic acid and 35OUikg feed phytase(treatment 3). the decreased Ca were supplement with limestone mill and sand to fulfill the decreased component. Last treatment were pelleted based on diet 2. At age week 9 metabolic test and slaughter test were carried out. With 350U/kg feed phytase , the low P or high phytate groupreach or surpass the control group in all the following measurements including: weight gain, feed intal%e, feed/gain ratio, serum Ca level, serum P level, serum AKP activity, tibia breaking strength1 tibia ash and Ca, P, mineral element in tibia ash. The average daily gain and feed efficiency of treatment 2 & treatment 3 significantly higher than that of control. Phytase supplementation increasd utilization of Phytic P, Cu, Fe, Zn and Mn significantly , the only e抴eption is that high phytic acid diet treatment with lower crude protein and dry matter utilization than that of control. For tibia tested factors there were no difference among treatment in yield force, breaking force, elastic parameter and ash content.The growing test dietary (treatmentl) were composed of: corn 63.6%, soybean meal 2(2/o, x抙eat bran 13%, CaHPO4 1.5%, limestone mill 1.0% and additives 0.9%. Reduce the (IaHPO4 level to 0.6%a and adding phytase OUIkg feed(treatment 2) or 350U/kg feed(treatment 4). or with 350U/kg feed replaced all CaHPO4 (treatment 3) and using CaCO3 to supplement Ca level and sand to fulfill the decreased component. Treatment 5 was pellet diet 4. The trial last from 12 to 18 wk. A restricted feeding program were used from week 14. It can be conclude fl-orm the results that the gain and feed efficiency are similar to or higher than the control抯 when treated with phytase. and higher than treatment 2 which without phvtase. It means that the slow growth should be caused by P deficiency is effectively got out by phytase supplementation. Serum measurements phytase supplemented treatmens matched the control. Only treatment 4 had a lower serum P. Phytase decreased the utilization of minera~s and P !ncreased excretion in Feces.Laying test ages were week 20-50 with 12 treatment. The basic ration was as follows: corn 61.9%, soybean meal 27% and wheat bran 1%. The CaHPO4 levels included in... |
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