Investigating the effect of synthetic nitrogen application rate on the milk production, intake, digestion and nitrogen excretion of dairy cows fed perennial ryegrass or perennial ryegrass-white clover herbage

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dc.contributor.authorWims, E.
dc.contributor.authorO'Callaghan, Tom F.
dc.contributor.authorMcCarthy, B.
dc.contributor.authorFlynn, D.
dc.contributor.authorSerra, E.
dc.contributor.authorDillon, P.
dc.contributor.authorRyan, D.
dc.contributor.authorMurphy, J.P.
dc.contributor.authorDineen, M.
dc.contributor.funderAnimal and Grassland Research and Innovation Centre
dc.contributor.funderDepartment of Agriculture, Food, 2021R482
dc.contributor.funderHealth Products Regulatory Authority, AE19132-P150
dc.date.accessioned2026-10-21T10:59:01Z
dc.date.available2026-10-21T10:59:01Z
dc.date.issued2026-06
dc.description.abstractThe objective of this experiment was to investigate the effect of synthetic N application rate on milk production, intake, digestion, and N excretion of dairy cows fed perennial ryegrass (PRG) or PRG-white clover (WC) herbage. Twelve ruminally cannulated multiparous Holstein Friesian dairy cows averaging (mean ± SD) 66 ± 12 DIM and 492 ± 41 kg BW were initially enrolled during spring in a 14-d acclimation period. Cows were then randomly assigned to 1 of 4 dietary treatments (DT) in an incomplete crossover design with two 22-d experimental periods. This experimental schedule was repeated during autumn when the cows were averaging 216 ± 12 DIM and 512 ± 37 kg of BW. The 4 DT were as follows: (1) PRG receiving 25 kg of synthetic N/ha per cut (G-L); (2) PRG receiving 50 kg of synthetic N/ha per cut (G-H); (3) PRG-WC receiving 0 kg of synthetic N/ha per cut (GC-L); and (4) PRG-WC receiving 25 kg of synthetic N/ha per cut (GC-H). We observed a DT by season interaction effect on milk yield and milk solids yield. In spring, cows fed GC-L had lower milk yield when compared with cows fed G-H (23.4 and 26.8 kg/d, respectively), and lower milk solids yield when compared with cows fed G-L and G-H (1.53, 1.92, and 1.99 kg/d, respectively). In autumn, cows fed GC-H had greater fat yield when compared with cows fed GC-L (0.89 and 0.78 kg/d, respectively) and had greater milk solids yield when compared with cows fed GC-L and G-L, but were similar to cows fed G-H (1.70, 1.53, 1.53, and 1.58 kg/d, respectively). We observed a DT by season interaction effect on DM and OM intake and on OM digestibility (OMD). In spring, DM and OM intake was similar among DT, whereas in autumn cows fed GC-H had greater DM and OM intake when compared with cows fed other DT. Cows fed GC-L had lower DM digestibility when compared with cows fed other DT in both spring and autumn. In spring, cows fed GC-L had lower OMD when compared with cows fed other DT, whereas in autumn, cows fed G-L had lower OMD when compared with cows fed G-H and GC-H. We observed a DT by season interaction effect on N intake, urinary N concentration, and urinary N output. In spring, cows fed G-H had greater N intake, urinary N concentration, and urinary N output when compared with cows fed other DT. In autumn, cows fed GC-L and GC-H had greater N intake and urinary N output when compared with cows fed G-L and G-H (800, 818, 608, and 626 g/d, respectively, and 447, 439, 265, and 247 g/d, respectively). Urine output did not differ among DT in spring, whereas in autumn, cows fed GC-L and GC-H had greater urine output when compared with cows fed G-L and G-H (66.0, 64.6, 47.3, and 46.8 kg/d, respectively). Overall, reducing synthetic N application rate on PRG-only swards by 25 kg of N/ha per cut generally had no effect on animal performance, intake, or digestibility, and it improved N excretion profiles during the spring. However, these N excretion benefits were not evident during the autumn period. Similarly, cows fed PRG-WC herbage receiving reduced application rates of synthetic N exhibited more favorable N excretion profiles during spring, whereas due to excessively high WC proportions during autumn, cows fed PRG-WC herbage had greater N intake, urinary N output, and urine output when compared with cows fed PRG-only herbage. These results indicate that additional strategies will be required to effectively mitigate urinary N excretion during periods of elevated nitrate-leaching risk.en
dc.description.sponsorshipAnimal and Grassland Research and Innovation Centre
dc.description.sponsorshipDepartment of Agriculture, Food|2021R482
dc.description.sponsorshipHealth Products Regulatory Authority|AE19132-P150
dc.description.versionPublished Version
dc.format.extent14
dc.format.mimetypeapplication/pdfen
dc.identifier.authororcidWims, E.
dc.identifier.authororcidO'Callaghan, Tom F.§0000-0003-2684-7253
dc.identifier.authororcidMcCarthy, B.
dc.identifier.authororcidFlynn, D.
dc.identifier.authororcidSerra, E.
dc.identifier.authororcidDillon, P.
dc.identifier.authororcidRyan, D.
dc.identifier.authororcidMurphy, J.P.
dc.identifier.authororcidDineen, M.
dc.identifier.citationWims, E, O'Callaghan, T F, McCarthy, B, Flynn, D, Serra, E, Dillon, P, Ryan, D, Murphy, J P & Dineen, M 2026, 'Investigating the effect of synthetic nitrogen application rate on the milk production, intake, digestion and nitrogen excretion of dairy cows fed perennial ryegrass or perennial ryegrass-white clover herbage', Journal of Dairy Science, vol. 109, no. 6, pp. 6156-6169. https://doi.org/10.3168/jds.2025-27895
dc.identifier.doi10.3168/jds.2025-27895
dc.identifier.endpage6169
dc.identifier.issn0022-0302
dc.identifier.issued6
dc.identifier.journaltitleJournal of Dairy Science
dc.identifier.otherRIS: urn:A1168881A2B2EB20C70084DB108A7EBF
dc.identifier.otherORCID: /0000-0003-2684-7253/work/230883317
dc.identifier.startpage6156
dc.identifier.urihttps://hdl.handle.net/10468/19475
dc.identifier.volume109
dc.language.isoen
dc.publisherElsevier Inc.
dc.relation.urihttps://www.scopus.com/pages/publications/105039831332
dc.rights© 2026, authors. Published by Elsevier Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY license (https://creativecommons.org/licenses/by/4.0/)
dc.rights.accessrightsopen access
dc.rights.licensenameAttribution 4.0 International
dc.rights.urihttps://creativecommons.org/licenses/by/4.0/
dc.statusPeer reviewed
dc.subjectIn vivo digestibility
dc.subjectNitrogen excretion
dc.subjectPasture-based
dc.subjectUrinary nitrogen
dc.subject[SEFSOffice]
dc.subject[FoodNutritionalSciences]
dc.titleInvestigating the effect of synthetic nitrogen application rate on the milk production, intake, digestion and nitrogen excretion of dairy cows fed perennial ryegrass or perennial ryegrass-white clover herbageen
dc.typeArticle (peer-reviewed)
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