低锌饲粮添加植酸酶对1～4周龄鹅生长性能、胫骨发育、免疫性能及抗氧化能力的影响

本试验旨在研究低锌饲粮添加植酸酶对1~4周龄鹅生长性能、胫骨发育、免疫性能及抗氧化能力的影响,探索饲粮添加植酸酶能否提高锌生物学效价和有效降低锌的添加水平。选用1日龄五龙鹅360只,随机分为6组,每组6个重复,每个重复10只鹅(公母各占1/2)。Ⅰ组为正对照组,饲喂基础饲粮,添加80 mg/kg硫酸锌,未添加植酸酶;Ⅱ组为负对照组,饲喂基础饲粮,添加1 200 U/kg植酸酶,未添加锌;Ⅲ~Ⅵ组在负对照组的基础上分别添加16、32、48、64 mg/kg硫酸锌。试验期28 d。结果表明:1)通过二次曲线拟合分析,在饲粮添加1 200 U/kg植酸酶的条件下,饲粮锌添加水平为34.00~44.70 mg/kg时可获得最佳平均日增重与料重比。2)Ⅳ、Ⅴ组的骨密度(BMD)显著高于Ⅱ组(P0.05);Ⅳ、Ⅴ组的骨矿含量(BMC)和血清碱性磷酸酶(AKP)活性显著或极显著高于Ⅰ、Ⅱ组(P0.05或P0.01)。通过二次曲线拟合分析,饲粮锌添加水平为51.38 mg/kg时,血清AKP活性最大。3)Ⅳ组的血清和肝脏总抗氧化能力(T-AOC)显著高于Ⅱ组(P0.05),与Ⅰ组差异不显著(P0.05)。通过二次曲线拟合分析,饲粮锌添加水平分别为50.24和47.49 mg/kg时,血清和肝脏的T-AOC最大。4)Ⅲ~Ⅵ组的胸腺指数和法氏囊指数均显著或极显著高于Ⅰ、Ⅱ组(P0.05或P0.01);Ⅳ~Ⅵ组免疫前后的血清新城疫抗体水平均显著或极显著高于Ⅰ、Ⅱ组(P0.05或P0.01)。由此可见,饲粮中添加植酸酶可以提高1~4周龄五龙鹅的生长性能,促进胫骨发育,增强机体抗氧化能力和免疫性能,有效提高锌利用率,降低饲粮中锌添加水平,增加锌的生物学效价。在饲粮添加1 200U/kg植酸酶的条件下,锌适宜添加水平为44.70~51.38 mg/kg。

Effects of Phytase Supplementation in a Low Zinc Diet on Growth Performance,Tibial Development,Immune Performance and Antioxidant Capacity of Geese Aged from 1 to 4 Weeks

This experiment was conducted to study the effect of phytase supplementation in a low zinc diet on growth performance, tibial development, immune performance and antioxidant capacity of geese aged from 1 to 4 weeks, and to explore whether phytase could effectively reduce the zinc supplemental level and increase the biological availability of zinc. A total of 360 Wulong geese were randomly divided into six groups with six replicates per group and ten geese per replicate ( half male and half female) . Geese in the group Ⅰ ( positive control group) were fed the basal diet supplemented with 80 mg/kg zinc sulfate, and without phytase;geese in the group Ⅱ ( negative control group) were fed a basal diet supplemented with 1 200 U/kg phytase, and with?out zinc sulfate; and the others in the groups Ⅲ to Ⅵ were fed the diets supplemented with 16, 32, 48 and 64 mg/kg zinc sulfate based on negative control group, respectively. The experiment lasted for 28 days. The results showed as follows:1) by quadratic curve fitting analysis, in the condition of dietary supplemented with 1 200 U/kg phytase, when dietary zinc supplemental level was 34.00 to 44.7 mg/kg, the average daily gain and feed to gain reached the best. 2) The bone mineral density ( BMD) of groupsⅣ and Ⅵ was significantly higher than that of group Ⅱ (P<0.05); the bone mineral content (BMC) and serum alkaline phosphatase ( AKP) activity of groups Ⅳ and Ⅵ were significantly higher than those of groupsⅠ and Ⅱ ( P<0.05 or P<0.01) . By quadratic curve fitting analysis, when the dietary zinc supplemental level was 51.38 mg/kg, the ser?um AKP activity reached the strongest. 3) The total antioxidant capacity ( T?AOC) in serum and liver of groupⅣ was significantly higher than that of groupⅡ( P<0.05) , and were no significant difference compared with group Ⅰ (P>0.05). By quadratic curve fitting analysis, when the zinc supplemental level was 50.24 and 47.49 mg/kg, respectively, the T?AOC in serum and liver was the highest. 4) The thymus index and bursa of Fabricius index of groups Ⅲ to Ⅵ were significantly higher than those of groups Ⅰ and Ⅱ ( P<0. 05 or P<0.01) , while the level of serum antibody against avian influenza of groups Ⅳ to Ⅵ was significantly higher than that of groups Ⅰ and Ⅱ before or after immunization ( P<0.05 or P<0.01) . In conclusion, diet adding phytase can enhance the growth performance of Wulong geese aged from 1 to 4 weeks, promote development of tibia, enhance the antioxidant capacity and immune performance, improve the utilization rate of zinc, reduce the dietary zinc supplemental level, and increase the biological availability of zinc. It is suggested that the opti?mal zinc supplemental level is 44. 70 to 51. 38 mg/kg when the diet adding 1 200 U/kg phytase.