Morgan Natalie K, Walk Carrie L, Bedford Michael R, Scholey Dawn V, Burton Emily J
School of Animal, Rural and Environmental Science, Nottingham Trent University, Nottingham NG25 0QF, UK.
AB Vista Feed Ingredients, Wiltshire SN8 4AN, UK.
Anim Nutr. 2016 Mar;2(1):33-39. doi: 10.1016/j.aninu.2016.01.002. Epub 2016 Feb 4.
Measurements of total phytate phosphorus content of diets may be deceptive as they do not indicate substrate availability for phytase; it may be that measurements of phytate susceptible to phytase effects are a more accurate measure of phosphorus (P) availability to the bird. To verify this hypothesis, an experiment was conducted to compare diets formulated to contain either high or low susceptible phytate, supplemented with either 0 or 500 FTU/kg phytase. Susceptible phytate was determined by exposing the feed samples to conditions that mimicked the average pH of the proximal gastrointestinal tract (pH 4.5) and the optimum temperature for phytase activity (37 °C) and then measuring phytate dissolved. Ross 308 birds ( = 240) were fed one of 4 dietary treatments in a 2 × 2 factorial design; 2 diets with high (8.54 g/kg, 57.90% of total phytate) or low (5.77 g/kg, 46.33% of total phytate) susceptible phytate, containing 0 or 500 FTU/kg phytase. Diets were fed to broilers (12 replicate pens of 5 birds per pen) from d 0 to 28 post hatch. Birds fed diets high in susceptible phytate had greater phytate hydrolysis in the gizzard ( < 0.001), jejunum ( < 0.001) and ileum ( < 0.001) and resulting greater body weight gain (BWG) ( = 0.015) and lower FCR ( = 0.003) than birds fed the low susceptible phytate diets, irrespective of phytase presence. Birds fed the high susceptible diets also had greater P solubility in the gizzard and Ca and P solubility in the jejunum and ileum ( < 0.05) and resulting greater tibia and femur Ca and P ( < 0.05) content than those fed the low susceptible diets. All the susceptible phytate was fully degraded in the tract in the absence of added phytase, suggesting the assay used in this study was able to successfully estimate the amount of total dietary phytate that was susceptible to the effects of phytase when used at standard levels. No interactions were observed between susceptible phytate and phytase on phytate hydrolysis. Hydrolysis of phytate was greater ( < 0.05) in the gizzard of birds fed the diets supplemented with phytase, regardless of the concentration of susceptible phytate in the diet. Phytase supplementation resulted in improved BWG ( < 0.001) and FCR ( = 0.001), increased P solubility ( < 0.001) in the gizzard, Ca and P solubility ( < 0.001) in the jejunum and ileum and Ca and P concentration ( < 0.001) and strength ( < 0.001) in the tibia and femur. Pepsin activity was higher in birds fed the diets supplemented with phytase ( < 0.001) and was greater ( = 0.031) in birds fed the high susceptible phytate diets compared with the low susceptible phytate diets. Findings from this study suggest that there may be a measure more meaningful to animal nutritionists than measurements of total phytate.
日粮中总植酸磷含量的测定可能具有误导性，因为它们并未表明植酸酶可利用的底物量；或许对植酸酶作用敏感的植酸的测定，是衡量禽类可利用磷（P）的更准确方法。为验证这一假设，进行了一项实验，比较配制的含有高或低敏感植酸的日粮，并分别添加0或500 FTU/kg的植酸酶。通过将饲料样品置于模拟近端胃肠道平均pH值（pH 4.5）和植酸酶活性最佳温度（37℃）的条件下，然后测量溶解的植酸，来确定敏感植酸。罗斯308肉鸡（n = 240）采用2×2析因设计，饲喂4种日粮处理中的一种；2种日粮分别含有高（8.54 g/kg，占总植酸的57.90%）或低（5.77 g/kg，占总植酸的46.33%）敏感植酸，并分别添加0或500 FTU/kg的植酸酶。从孵化后第0天至28天，将日粮喂给肉鸡（每栏5只鸡，共12个重复栏）。无论是否添加植酸酶，饲喂高敏感植酸日粮的鸡，其肌胃（P < 0.001）、空肠（P < 0.001）和回肠（P < 0.001）中的植酸水解程度更高，体重增加（BWG）更大（P = 0.015），饲料转化率（FCR）更低（P = 0.003）。与饲喂低敏感植酸日粮的鸡相比，饲喂高敏感日粮的鸡，其肌胃中的磷溶解度更高，空肠和回肠中的钙和磷溶解度更高（P < 0.05），胫骨灰分和磷含量更高（P < 0.05）。在不添加植酸酶的情况下，所有敏感植酸在消化道中均被完全降解，这表明本研究中使用的分析方法能够成功估计在标准水平使用时，日粮中对植酸酶作用敏感的总植酸量。在敏感植酸和植酸酶对植酸水解的影响方面，未观察到交互作用。无论日粮中敏感植酸的浓度如何，添加植酸酶的鸡的肌胃中植酸的水解程度更高（P < 0.05）。添加植酸酶可提高BWG（P < 0.001）和FCR（P = 0.001），增加肌胃中的磷溶解度（P < 0.0
