title: Prediction of urinary and fecal nitrogen excretion by beef cattle.
abstract: An analysis of predicting urinary and fecal N excretion from beef cattle was conducted using a data set summarizing 49 published studies representing 180 treatment means for 869 animals. Variables included in the data set were initial BW (kg), DMI (kg/d), dietary CP content (% of DM), N intake (g/d), apparent total tract N digestibility (%), and urinary and fecal N excretion (g/d). Correlation analysis examined relationships between animal and dietary variables and N excretion. A mixed model regression analysis was used to develop equations to predict N excretion in urine and feces and the proportion of urinary N in total N excretion as a function of various animal and dietary variables. Of the single animal and dietary variables, N intake was the best predictor of N excretion in urine and feces, whereas apparent total tract N digestibility was best to predict the proportion of urinary N in total N excretion. Low prediction errors and evaluation of the equations using cross-validation indicated the prediction equations were accurate and robust. Urinary and fecal N excretion can be accurately and precisely predicted by N intake, whereas the proportion of urinary N in total N excretion was best predicted solely using apparent total tract N digestibility.
authors.affiliation: College of Animal Science and Technology, China Agricultural University, State Key Laboratory of Animal Nutrition, Beijing 100193, China Agriculture and Agri-Food Canada, Lethbridge Research Centre, Lethbridge, AB T1J 4B1, Canada.
authors.forename: R L
authors.initials: RL
authors.lastname: Dong
authors.affiliation: College of Animal Science and Technology, China Agricultural University, State Key Laboratory of Animal Nutrition, Beijing 100193, China.
authors.forename: G Y
authors.initials: GY
authors.lastname: Zhao
authors.affiliation: Agriculture and Agri-Food Canada, Lethbridge Research Centre, Lethbridge, AB T1J 4B1, Canada.
authors.forename: L L
authors.initials: LL
authors.lastname: Chai
authors.affiliation: Agriculture and Agri-Food Canada, Lethbridge Research Centre, Lethbridge, AB T1J 4B1, Canada karen.beauchemin@agr.gc.ca.
authors.forename: K A
authors.initials: KA
authors.lastname: Beauchemin
mesh_terms: D000818:Animals; D001835:Body Weight; D002417:Cattle / Q000378:metabolism*; D004032:Diet / Q000662:veterinary*; D004044:Dietary Proteins / Q000008:administration & dosage / Q000378:metabolism; D004063:Digestion / Q000502:physiology; D005243:Feces / Q000737:chemistry*; D008954:Models, Biological; D009584:Nitrogen / Q000032:analysis* / Q000652:urine*; D012044:Regression Analysis
chemical_list: D004044:Dietary Proteins; D009584:Nitrogen
keywords: apparent total tract N digestibility; beef cattle; crude protein; nitrogen excretion; nitrogen intake; prediction