Investigating the effect of Lolium perenne L., Trifolium repens L. and Plantago lanceolata L., with varying synthetic nitrogen application rates, on the milk production, ruminal metabolism, digesta kinetics and nitrogen excretion of lactating dairy cows

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dc.check.date2027-12-31
dc.check.infoControlled Access
dc.contributor.advisorO’Callaghan, Tom F.
dc.contributor.advisorexternalDineen, Michael
dc.contributor.advisorexternalMcCarthy, Brian
dc.contributor.authorWims, Éoinen
dc.contributor.funderTeagasc
dc.date.accessioned2026-10-01T08:22:20Z
dc.date.available2026-10-01T08:22:20Z
dc.date.issued2026-03-02en
dc.date.submitted2026-03-02
dc.descriptionControlled Access
dc.description.abstractReducing nitrogen (N) losses to the environment is a major challenge for agriculture, with the urine patch representing a key pathway for N loss in pasture-based dairy systems. This thesis investigated strategies, such as pasture species and synthetic N application rate, to reduce N excretion in pasture-based systems and evaluated their effects on animal performance, rumen digesta kinetics and fermentation characteristics. Chapter 1 reviewed the literature and identified research gaps relating to the effects of pasture species and synthetic N application rate on animal performance, rumen function and N excretion. In Chapters 2 and 3, perennial ryegrass (PRG) and PRG-white clover (WC) swards were evaluated in spring and autumn under contrasting synthetic N application rates. Moderate reduction in synthetic N application rate on PRG-only swards generally had no effect on milk production, intake or in vivo digestibility. In spring, lowering synthetic N application rate within the PRG-only swards reduced N intake, urinary N concentration and urinary N excretion; however, these effects were not observed in autumn. In PRG-WC swards, synthetic N application rates could be reduced without compromising animal performance but could not be eliminated. In spring, PRG-WC swards supported a favourable urinary N excretion profile; however, in autumn, high WC proportions increased N intake and urinary N excretion, relative to PRG-only swards. Rumen measurements in Chapter 3 indicated that synthetic N application rate had minimal effects on rumen digesta kinetics within PRG-only swards. However, in spring, the lower synthetic N application rate reduced rumen ammonia-N concentration, providing a mechanistic basis for reduced urinary N excretion observed in Chapter 2. In autumn, cows fed PRG-WC herbage receiving synthetic N exhibited a faster rate of digestion of potentially digestible fibre, while rumen ammonia-N concentrations were greater for cows fed PRG-WC swards when compared with PRG-only. These findings demonstrate tightly integrated relationships among N intake, rumen ammonia-N, and urinary N excretion, indicating that effective mitigation requires strategies that better control N intake, improve rumen N utilisation and redirect N partitioning away from urine. Accordingly, Chapters 4 and 5 examined alternative pasture species strategies in late-lactation by comparing PRG, PRG-WC and PRG-WC–plantain (PL) swards in autumn. Inclusion of PL in PRG-WC swards maintained intake and milk yield, but reduced milk fat yield and in vivo digestibility. Cows fed PRG-WC-PL herbage had lower urinary N concentration and urinary N excretion, with a greater proportion of dietary N partitioned to faeces. These responses occurred alongside lower N intake and increased urine output, including more frequent urinations and greater urine event volume. Chapter 5 demonstrated that these effects were accompanied by faster rumen turnover and digesta passage, and lower rumen ammonia-N concentration, explaining the shift in N partitioning towards faeces and the reduction in urinary N excretion. Furthermore, milk urea-N was strongly associated with urinary N excretion, supporting its use as a practical on-farm indicator of urinary N excretion in pasture-based systems. Overall, this thesis demonstrates that moderate reductions in synthetic N application rates on PRG-only swards can be achieved without compromising animal performance, but reductions in urinary N excretion were confined to spring and were not evident in autumn. In PRG–WC swards, synthetic N could be reduced but not eliminated, and high WC proportions in autumn increased N intake and urinary N excretion. In contrast, inclusion of PL in PRG–WC swards reduced urinary N concentration and urinary N excretion and shifted dietary N partitioning towards faeces, although milk fat yield was reduced. Future research should test the robustness of these responses under grazing conditions and quantify water quality impacts.en
dc.description.statusNot peer revieweden
dc.description.versionAccepted Versionen
dc.format.mimetypeapplication/pdfen
dc.identifier.citationWims, É. 2026. Investigating the effect of Lolium perenne L., Trifolium repens L. and Plantago lanceolata L., with varying synthetic nitrogen application rates, on the milk production, ruminal metabolism, digesta kinetics and nitrogen excretion of lactating dairy cows. PhD Thesis, University College Cork.
dc.identifier.endpage245
dc.identifier.urihttps://hdl.handle.net/10468/19390
dc.language.isoenen
dc.publisherUniversity College Corken
dc.rights© 2026, Éoin Wims.
dc.rights.urihttps://creativecommons.org/licenses/by/4.0/
dc.subjectIn vivo digestibility
dc.subjectNitrogen excretion
dc.subjectPasture-based
dc.subjectUrinary nitrogen
dc.subjectDigesta kinetics
dc.subjectRate of passage
dc.subjectRumen pool size
dc.subjectPlantain
dc.subjectWhite clover
dc.subjectRumen fermentation
dc.titleInvestigating the effect of Lolium perenne L., Trifolium repens L. and Plantago lanceolata L., with varying synthetic nitrogen application rates, on the milk production, ruminal metabolism, digesta kinetics and nitrogen excretion of lactating dairy cowsen
dc.typeDoctoral thesisen
dc.type.qualificationlevelDoctoralen
dc.type.qualificationnamePhD - Doctor of Philosophyen
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