Prediction of Fecal Nitrogen and Fecal Phosphorus Content for Lactating Dairy Cows in Large-scale Dairy Farms

• Main Authors: QU Qing-bo, YANG Peng, ZHAI Zhong-wei, LI Ai-xiu, ZHANG Ke-qiang
• Format: Article
• Language: zho
• Published: Agro-Environmental Protection Institute, Ministry of Agriculture 2017-05-01
• Series: Journal of Agricultural Resources and Environment
• Subjects: lactating dairy cows; fecal nitrogen; fecal phosphorus; dietary nutrient composition; prediction models
• Online Access: http://www.aed.org.cn/nyzyyhjxb/html/2017/3/20170305.htm
• ISSN: 2095-6819; 2095-6819

To facilitate efficient and sustainable manure management and reduce potential pollution, it's necessary for precise prediction of fecal nutrient content. The aim of this study is to build prediction models of fecal nitrogen and phosphorus content by the factors of dietary nutrient composition, days in milk, milk yield and body weight of Chinese Holstein lactating dairy cows. 20 kinds of dietary nutrient composition and 60 feces samples were collected from lactating dairy cows from 7 large-scale dairy farms in Tianjin City; The fecal nitrogen and phosphorus content were analyzed. The whole data set was divided into training data set and testing data set. The training data set, including 14 kinds of dietary nutrient composition and 48 feces samples, was used to develop prediction models. The relationship between fecal nitrogen or phosphorus content and dietary nutrient composition was illustrated by means of correlation and regression analysis using SAS software. The results showed that fecal nitrogen(FN) content was highly positively correlated with organic matter intake(OMI) and crude fat intake(CFi), and correlation coefficients were 0. 836 and 0. 705, respectively. Negative correlation coefficient was found between fecal phosphorus(FP) content and body weight(BW), and the correlation coefficient was -0.525. Among different approaches to develop prediction models, the results indicated that determination coefficients of multiple linear regression equations were higher than those of simple linear regression equations. Specially, fecal nitrogen content was excellently predicted by milk yield(MY), days in milk(DIM), organic matter intake(OMI) and nitrogen intake(NI), and the model was as follows:<i>y</i>=0.43+0.29&#215;MY+0.02&#215;DIM+0.92&#215;OMI-13.01&#215;NI (<i>R</i>²=0.96). Accordingly, the highest determination coefficient of prediction equation of FP content was 0.62, when body weight(BW), phosphorus intake(PI) and nitrogen intake(NI) were combined as predictors. The prediction equation was as follows:<i>y</i>=22.97-0.026&#215;BW-4.02 &#215;NI+14.63 &#215;PI. Using the testing data set, including 6 kinds of dietary nutrient composition and 18 feces samples for the external validation, the relative error between predicted value and measured value of fecal nitrogen and fecal phosphorus content were 1.62% and 3.81%, respectively; the standard error of prediction were 0.70 mg&#183;g^-1 and 0.68 mg&#183;g^-1, respectively. The results indicated the equations had good accuracy for predicting fecal nitrogen and fecal phosphorus content.