Ren Zhouzheng, Yan Jiakun, Hu Qianli, Liu Xinshuai, Pan Chong, Liu Yanli, Zhang Xiaozhen, Yang Xin, Yang Xiaojun
College of Animal Science and Technology, Northwest A&F University, Yangling, China.
Front Physiol. 2020 Feb 14;11:85. doi: 10.3389/fphys.2020.00085. eCollection 2020.
Dietary phosphorus oversupply wastes non-renewable natural resources and raises environmental concerns in animal agriculture. We hypothesized that laying hens do not need large safety margins for dietary phosphorus because of the existence of fibroblast growth factor 23 (FGF23). In experiment 1, a total of 504 Hy-Line Brown laying hens (40-week-old) were randomly assigned to seven diets (for each diet, six replicates of 12 hens), containing 0.12, 0.17, 0.22, 0.27, 0.32, 0.37, and 0.42% non-phytate phosphorus, respectively, for 15 weeks. In experiment 2, a total of 14 Hy-Line Brown laying hens (40-week-old) were randomly assigned to two diets: (1) phosphorus restricted ( = 7) diet containing 0.14% non-phytate phosphorus, and (2) regular phosphorus ( = 7) diet containing 0.32% non-phytate phosphorus, for 21 days. Laying performance and egg quality were investigated in experiments 1 and 2. Phosphorus excretion and physiological changes were determined in experiment 2. It was found that dietary non-phytate phosphorus levels had no effects ( > 0.05) on laying performance and egg quality in either experiment. In experiment 2, laying hens fed 0.14% non-phytate phosphorus had decreased phosphorus excretion (by 52.6%, < 0.001) when compared to those fed 0.32% non-phytate phosphorus. In response to the 0.14% non-phytate phosphorus diet, laying hens in experiment 2 exhibited: (1) suppressed calvaria mRNA expressions of (by 57.8%, < 0.001) and fibroblast growth factor receptor 1 (, by 52.8%, = 0.012), (2) decreased serum levels of FGF23 (by 41.7%, = 0.011) and phosphorus (by 40.3%, < 0.001), (3) decreased kidney mRNA expressions of (by 66.0%, = 0.040) and (by 63.3%, = 0.012) and decreased kidney protein expression of type 2a sodium-phosphorus co-transporter (NPt2a, by 51%, = 0.025), (4) increased duodenum protein expression of NPt2b (by 45%, = 0.032), and (5) increased excretion of calcium (by 22.9%, ≤ 0.024). Collectively, decreasing dietary non-phytate phosphorus by up to 0.12% had no negative effects on egg-production performance but significantly decreased phosphorus excretion in laying hens. The laying hens adjusted to low-phosphorus diets by increasing intestinal NPt2b protein production, which was associated with decreased serum FGF23 concentration. Decreasing dietary non-phytate phosphorus is suggested to laying-hen nutritionists.
日粮磷供应过多会浪费不可再生的自然资源，并引发畜牧业中的环境问题。我们推测，由于成纤维细胞生长因子23（FGF23）的存在，蛋鸡日粮中不需要很大的磷安全裕量。在实验1中，将总共504只海兰褐蛋鸡（40周龄）随机分配到七种日粮中（每种日粮12只鸡，设6个重复），日粮非植酸磷含量分别为（质量分数）0.12%、0.17%、0.22%、0.27%、0.32%、0.37%和0.42%，实验为期15周。在实验2中，将总共14只海兰褐蛋鸡（40周龄）随机分配到两种日粮中：（1）7只鸡饲喂磷限制日粮，非植酸磷含量为0.14%；（2）7只鸡饲喂常规磷日粮，非植酸磷含量为0.32%，实验为期21天。在实验1和实验2中均对产蛋性能和蛋品质进行了研究。在实验2中测定了磷排泄量和生理变化。结果发现，在两个实验中，日粮非植酸磷水平对产蛋性能和蛋品质均无影响（P＞0.05）。在实验2中，与饲喂0.32%非植酸磷日粮的蛋鸡相比，饲喂0.14%非植酸磷日粮的蛋鸡磷排泄量降低（降低了52.6%，P＜0.001）。对于0.14%非植酸磷日粮，实验2中的蛋鸡表现出：（1）颅骨中klotho mRNA表达受抑制（降低了57.8%，P＜0.001）和成纤维细胞生长因子受体1（Fgfr1）mRNA表达受抑制（降低了52.8%，P = 0.012）；（2）血清FGF23水平降低（降低了41.7%，P = 0.011）和血清磷水平降低（降低了40.3%，P＜0.001）；（3）肾脏中klotho mRNA表达降低（降低了66.0%，P = 0.040）和NaPi-IIa mRNA表达降低（降低了63.3%，P = 0.012），且肾脏中2a型钠-磷共转运蛋白（NPt2a）的蛋白表达降低（降低了51%，P = 0.025）；（4）十二指肠中NPt2b的蛋白表达增加（增加了45%，P = 0.032）；（5）钙排泄增加（增加了22.9%，P≤0.024）。总体而言，将日粮非植酸磷含量降低多达0.12%对产蛋性能没有负面影响，但显著降低了蛋鸡的磷排泄量。蛋鸡通过增加肠道NPt2b蛋白产量来适应低磷日粮，这与血清FGF23浓度降低有关。建议蛋鸡营养学家降低日粮非植酸磷含量。
