title: Aspects of nitrogen metabolism in sheep-fed mixed diets containing tree and shrub foliages.
abstract: Data on N utilisation by sheep-fed diets containing foliages were analysed to develop prediction equations for N excretion in faeces (FN) and urine (UN), and to determine endogenous N excretion. Overall, 218 dietary treatments from forty-four publications were compiled in the database. This database was split into three subsets: without foliage in the diets (FL-0); foliage levels (FL) in between 0 and 310 g/kg (FL-L); FL in between 310 and 800 g/kg diets (FL-H) to study the effects of foliages on metabolic faecal N (MFN) and endogenous urinary N (EUN). Nitrogen intake (NI) as single independent factor was the best predictor of FN (R2 0.75), UN (R2 0.81) and total N excretion (R2 0.86). Addition of dietary N concentration and FL for FN (R2 0.82), dietary N concentration and foliage NI for UN (R2 0.85), and FL and foliage NI for total N excretion (R2 0.92) as supporting predictors to this relationship slightly increased R2 values. The monomolecular and exponential models slightly improved the prediction of N excretion with NI as a predictor compared with the linear model. The excretion of MFN was greater for FL-H compared with FL-0, but was similar between FL-0 and FL-L, and FL-L and FL-H. However, EUN decreased in FL-H compared with FL-0 and FL-L, but was similar between FL-0 and FL-L. In conclusion, using NI as the primary predictor produced an accurate prediction of N excretion. Inclusion of foliages in the diets may shift N excretion from urine to faeces and increase the excretion of MFN and EUN.
authors.affiliation: Department of Animal Nutrition, West Bengal University of Animal and Fishery Sciences, Belgachia, Kolkata 700037, India. patra_amlan@yahoo.com
authors.forename: Amlan K
authors.initials: AK
authors.lastname: Patra
mesh_terms: D000821:Animal Feed / Q000032:analysis*; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D004032:Diet / Q000662:veterinary*; D005243:Feces / Q000737:chemistry; D008954:Models, Biological; D009584:Nitrogen / Q000737:chemistry / Q000378:metabolism*; D018515:Plant Leaves / Q000737:chemistry* / Q000378:metabolism; D012756:Sheep / Q000378:metabolism*; D014197:Trees / Q000737:chemistry*; D014556:Urine
chemical_list: D009584:Nitrogen