Estimation of Excretion of Nitrogen and Phosphorus With Manure From Dairy Cow Based on Ingestion of N and P With Feeds

Through monitoring of ingestion and excretion of nitrogen and phosphorus by dairy cows of an on-scale dairy farm in summer and winter,analysis was done of relationship between the ingestion and excretion and a model was established for estimation of discharge of N and P from the farm in summer and winter.Results show that in water and summer,averagely,an adult dairy cow excretes 31.14 and 13.90 kg·d-1of feces per day,respectively,and a lactating cow excretes 270.71 g·d-1N and 66.67 g·d-1P with feces and urine,16.4% and 19.2% more than a dry cow does,and 150.7% and 174.0% more than a heifer does,respectively.Daily ingestion of nitrogen and phosphorus with fodder of a dairy cow varies sharply from cow to cow different in physiological stage(P0.05),displaying an order of lactating cow drying cow heifer.Daily excretion of nitrogen and phosphorus with feces and urine from a cow also varies sharply from cow to cow different in physiological stage(P0.05).The cows excrete with feces and urine more than 50% of the nitrogen and phosphorus ingested.Positive relationship was found of N and P ingestions with fodder and N and P excretions with feces,urine and milk in summer and winter.A model can hence be built up by fitting with a regression equation for estimation of N and P excretions with feces and urine based on N and P ingestions with fodder.The model may provide references for feces management and pollution prevention in dairy farms.