ABSTRACT

The objective of this study was to investigate the effect of variation in wheat-derived phytase activity on myo-inositol 1,2,3,4,5,6-hexakis (dihydrogen phosphate) (InsP₆) degradation, inositol phosphate (InsP) isomer concentration and phosphorus (P) digestibility in pigs fed wheat-based diets. Additional effects of a microbial phytase supplementation were also studied. Three wheat genotypes (W1-W3) with an analysed phytase activity between 2760 and 3700 FTU/kg were used to formulate four experimental diets that included soybean meal and rapeseed meal but did not contain a mineral P supplement. DietW1-DietW3 only differed in the included wheat genotypes (W1-W3) at an inclusion level of 400 g/kg. DietW3+ contained W3 and a commercial 6-phytase supplementation at 500 FTU/kg diet. Eight barrows with an initial body weight of 27 kg were fitted with a simple T-cannula at the distal ileum and assigned to the four dietary treatments in a completely randomised row column design. The experiment included four periods of 12 d each. The first 5 d of each period were for diet adaptation, followed by collection of faeces (4 d), ileal digesta (2 d), and blood (last day). In DietW1-DietW3, the mean precaecal (pc) InsP₆ disappearance was 48% and the mean pc P digestibility was 37% without a significant effect of the wheat genotype. The InsP₆ disappearance measured in the faeces was close to complete in all treatments, and faecal P digestibility was not significantly affected by the wheat genotype (36% overall). The addition of microbial phytase caused a significant increase in pc InsP₆ degradation (to 79%) and pc and total tract P digestibility (to 53% and 52%, respectively). The concentration of InsP₆ degradation products in ileal digesta was not significantly affected by the wheat genotype, except for that of Ins(1,2,3,4,6)P₅ and myo-inositol, which were higher in DietW3 than in DietW1 and DietW2. The added microbial phytase significantly reduced the concentration of InsP₅ isomers in the ileal digesta and increased the concentrations of lower InsP isomers and myo-inositol. There were no significant effects of the added microbial phytase on pc amino acid digestibility; however, the wheat genotype exerted significant effects on the pc digestibility of Cys, Gly and Val. It was concluded that an increase in the intrinsic phytase activity of wheat achieved by crossbreeding was not reflected in InsP₆ degradation and P digestibility in pigs fed wheat-based diets.

摘要

本研究的目的是研究小麦来源的植酸酶活性变化对肌醇1,2,3,4,5,6-hexakis（磷酸二氢盐）的影响（InsP ₆) 降解、磷酸肌醇 (InsP) 异构体浓度和饲喂小麦基日粮的猪的磷 (P) 消化率。还研究了补充微生物植酸酶的其他效果。三种小麦基因型 (W1-W3) 的植酸酶活性分析在 2760 至 3700 FTU/kg 之间，用于配制四种实验日粮，包括豆粕和菜籽粕，但不含矿物质 P 补充剂。DietW1-DietW3 仅在包含水平为 400 g/kg 的小麦基因型 (W1-W3) 上有所不同。DietW3+ 含有 W3 和 500 FTU/kg 饮食的商业 6-植酸酶补充剂。八只初始体重为 27 公斤的手推车在回肠末端安装了一个简单的 T 型套管，并以完全随机的行列设计分配给四种饮食治疗。实验包括四个阶段，每个阶段 12 天。每个时期的前 5 天用于饮食适应，随后收集粪便（4 天）、回肠食糜（2 天）和血液（最后一天）。在 DietW1-DietW3 中，平均 precaecal (pc) InsP₆消失率为 48%，平均 pc P 消化率为 37%，小麦基因型没有显着影响。在所有处理中，粪便中测量到的 InsP ₆消失接近完全，并且粪便 P 消化率不受小麦基因型的显着影响（总体为 36%）。添加微生物植酸酶导致 pc InsP ₆降解率显着增加（至 79%）以及 pc 和全肠道 P 消化率（分别为 53% 和 52%）。回肠食糜中InsP ₆降解产物的浓度受小麦基因型影响不显着，除Ins(1,2,3,4,6)P ₅和myo外-肌醇，在DietW3中高于在DietW1和DietW2中。添加的微生物植酸酶显着降低了回肠食糜中 InsP ₅异构体的浓度，并增加了较低 InsP 异构体和肌醇的浓度。添加的微生物植酸酶对pc氨基酸消化率没有显着影响；然而，小麦基因型对 Cys、Gly 和 Val 的 pc 消化率有显着影响。得出的结论是，通过杂交获得的小麦内在植酸酶活性的增加并未反映在饲喂小麦基日粮的猪的 InsP _{6降解和 P 消化率中。}