title: Short communication: Supplementing grape marc to cows fed a pasture-based diet as a method to alter nitrogen partitioning and excretion.
abstract: The inclusion of the grape marc into livestock rations provides an opportunity not only to use a waste byproduct resourcefully, but also to induce beneficial metabolic changes in animals. Grape marc contains condensed tannins that could alter N metabolism, which would be beneficial from an environmental perspective. The objective was to determine if dietary grape marc could decrease urinary N excretion from nonlactating dairy cattle. Eighteen multiparous cows were randomly divided into 2 equal groups, receiving either (1) pasture+2 kg of dry matter (DM)/d energy pellet per cow (control group) or (2) pasture+2 kg of DM/d energy pellet per cow+3 kg of DM/d grape marc per cow. Urine, fecal, and blood samples were collected at baseline (d 0) and at d 9. Cows receiving grape marc excreted 22% more N in feces compared with the control group. Cows offered grape marc had lower plasma urea nitrogen concentrations (2.42 and 2.97±0.1 mmol/L from treatment and control cows, respectively), but had no significant difference in urine urea concentration compared with control animals (84.24 and 114.1±17.62 mmol/L from treatment and control cows, respectively). Overall, the potential exists to alter N metabolism in dairy cows using dietary grape marc. The exact mechanisms causing this shift in N metabolism require further investigation.
authors.affiliation: Department of Agricultural Sciences, Food and Molecular Biosciences, Lincoln University, Lincoln 7647, New Zealand. sabrina.greenwood@lincoln.ac.nz
authors.forename: S L
authors.initials: SL
authors.lastname: Greenwood
authors.forename: G R
authors.initials: GR
authors.lastname: Edwards
authors.forename: R
authors.initials: R
authors.lastname: Harrison
mesh_terms: D000818:Animals; D001806:Blood Urea Nitrogen; D002417:Cattle; D004032:Diet / Q000662:veterinary; D019587:Dietary Supplements; D005243:Feces / Q000737:chemistry; D005260:Female; D005638:Fruit; D009584:Nitrogen / Q000032:analysis / Q000378:metabolism* / Q000493:pharmacokinetics; D027843:Vitis
chemical_list: D009584:Nitrogen