title: Nitrogen partitioning and milk production of dairy cows grazing simple and diverse pastures.
abstract: Research was conducted to examine the effects of a diverse pasture mix on dry matter intake, milk yield, and N partitioning of lactating dairy cows. A pasture containing only ryegrass and white clover (RG), or high-sugar ryegrass and white clover (HS), was compared with a diverse pasture mix (HSD) including chicory, plantain, lotus, high-sugar ryegrass, and white clover. The experiment was conducted over a 10-d period using 3 groups of 12 cows in late lactation. No difference was observed in dry matter (14.3 kg of dry matter/cow per day) or N (583 g of N/cow per day) intake between treatments. The cows grazing the HSD pasture had an increased milk yield (16.9 kg/d) compared with those grazing the simple RG and HS pastures (15.2 and 14.7 kg/d, respectively). However, no differences were observed in milk solids yield for the 3 treatments. A tendency toward greater milk protein yields in the HSD group resulted in improved N use efficiency for milk of 20.4% from the cows fed HSD, compared with 17.8 and 16.7% from cows in the RG and HS treatments, respectively. Urinary N excretion was lower from the cows fed HSD, at 353.8 g/d, compared with 438.3 and 426.6 g/d for cows fed RG and HS, respectively. These results suggest that the use of pastures containing chicory, lotus, and plantain can contribute to the goal of reducing N losses from cows in late lactation.
authors.affiliation: Department of Agricultural Sciences, Lincoln University, Lincoln, New Zealand 7647.
authors.forename: V K
authors.initials: VK
authors.lastname: Totty
authors.forename: S L
authors.initials: SL
authors.lastname: Greenwood
authors.forename: R H
authors.initials: RH
authors.lastname: Bryant
authors.forename: G R
authors.initials: GR
authors.lastname: Edwards
mesh_terms: D000818:Animals; D002417:Cattle; D003404:Creatinine / Q000032:analysis / Q000097:blood / Q000652:urine; D003612:Dairying / Q000379:methods*; D004032:Diet / Q000662:veterinary*; D005243:Feces / Q000737:chemistry; D005260:Female; D007774:Lactation / Q000378:metabolism / Q000502:physiology*; D008129:Lolium; D029903:Melilotus; D008892:Milk / Q000378:metabolism; D009584:Nitrogen / Q000097:blood / Q000378:metabolism* / Q000652:urine; D014508:Urea / Q000032:analysis / Q000097:blood / Q000652:urine
chemical_list: D014508:Urea; D003404:Creatinine; D009584:Nitrogen