Effect Of Phytase With Different Dose And Dosage-form On The Performance And Nutrient Utilization In Laying Hens

This study was conducted to evaluate the effects of maize and soybeen meal based diet supplemented with different dose and dosage-form phytase on the performance and the nutrient utilization in laying hens. The performance, blood biochemical parameters, tibia quality, nutrient utilization, as well as the tissue structures of small intestine and ovary were determined. The object of this study was to supply a laboratory basis for health cultivation and proper use of phytase in practice. The thesis fell into three parts and the results were stated as follows:In the first part, an experiment was designed to evaluate the effects of phytase with different dose and dosage-form on the performance and blood biochemical parameters in laying hens. A total of eight hundred and forty18-week-old laying hens were randomly allocated into7groups with6replicates of20birds each. Group Ⅰ, as the positive control, was fed with the basal diet; Group Ⅱ, as the negative control, was fed with low-available phosphorus (LAP) diet, while group Ⅲ, Ⅳ and Ⅴ, as trial groups, were fed with LAP diet adding coated dosage-form phytase at three levels (300,1000and10000U/kg, respectively), and group Ⅵ and Ⅶ were supplemented with300U/kg phytase with powdery and granular dosage-form, respectively. The results indicated that:(1) Compared with the negative control, the addition of phytase to the LAP diet as the only variable had no effect on egg weight, broken eggshell rate and feed intake (P>0.05), but enhanced the laying rate (P<0.05) by2.40%～2.80%, and significantly reduced feed conversion rate (P<0.01) by3.80%～5.06%in group Ⅲ, Ⅳ, Ⅵ and Ⅶ, there were no differences among the positive control and the trial groups (P>0.05);(2) Compared with the negative control, phytase supplementation did not affect eggshell strength and thickness (P>0.05), but both of them had been improved slightly;(3) Supplementing diet with phytase increased the concentration of P (P<0.05) in blood and reduced the activity of serum AKP (P<0.05), the levels of the rest serum indexes were not changed (P>0.05). It was concluded that the effect of coated dosage-form phytase with300U/kg was better to meet the nutrient requirement of laying hens for growth and production.In the second part, according to the first part’s results, an experiment was conducted to study the effect of phytase with different dose and dosage-form on the activity of digestive enzyme, tibia quality and nutrient utilization in laying hens. Treatments were the same as in the first part. The results showed that:(1) Compared with the negative control, the activity of amylase and disaccharidase of trial groups were not increased significantly (P>0.05), but that of trypsin in group Ⅳ had been improved significantly (P<0.05);(2) The contents of tibia Ca and P of trial groups had been increased to a greater extent (especially tibia P), although not affected significantly (P>0.05);(3) Compared with the negative control, the apparent digestibility of Ca (group Ⅲ, Ⅳ and Ⅶ), P (group Ⅲ, Ⅶ) and protein (group Ⅳ) were increased (P<0.05), and the apparent digestibility of P in group Ⅳ and Ⅴ were enhanced significantly (P<0.01), while the apparent digestibility of dry matter, ash and energy were also improved slightly (P>0.05). There were no differences among the positive control and the trial groups (P>0.05).In the third part, according to the first and the second parts’results, the effects of phytase on the tissue structure of small intestine and the development of the follicle were studied. Treatments were the same as in the first part. The results showed that:(1) Compared with the negative control, the jejunum villus height in group Ⅳ was increased significantly by26.03%(P<0.05), while Ⅲ, Ⅴ, Ⅵ and Ⅶ were not improved significantly (P>0.05) by16.49%,21.80%,15.73%and17.29%, respectively. The crypt depth, villus height/crypt depth (V/C) and mucosal thickness in trial groups did not differ significantly (P>0.05) compared to the negative control;(2) The numbers of primary follicle and secondary follicle were not affected significantly (P>0.05) compared to the negative control, while the rate of atretic follicle in group Ⅳ and Ⅶ were significantly reduced (P<0.05) by40.63%and40.41%, respectively. There were also no differences among the positive control and the trial groups (P>0.05).In conclusion, the study showed that the supplementation of phosphorus-inadequate diet with phytase at300,1000and10000U/kg respectively resulted in an increase in performance, the activity of digestive enzyme, tibia parameters and the apparent digestibility of Ca and P, and the phytase with300U/kg was enough to meet the nutrient requirement for growth and production. Besides, the effect of coated dosage-form phytase with300U/kg trended to be better than the granular and powdery dosage-form, and adding phytase with large dose (10000U/kg) had no negative effects on the performance, nutrent utilization, the tissue structures of small intestine and ovary.