Sustainability & efficiency

Assessing the Potential to Enhance Nitrogen Use Efficiency in Holstein Dairy Cows

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Abstract

Nitrogen losses from dairy cattle significantly contribute to environmental pollution through processes such as eutrophication and greenhouse gas emissions, highlighting inefficiencies in dietary protein utilization. Improving nitrogen use efficiency (NUE) can mitigate these environmental impacts while enhancing the economic sustainability of dairy production. Milk urea nitrogen (MUN) in dairy cattle serves as an indicator of nitrogen surplus relative to the animal's physiological requirements. Urea, synthesized from ammonia in the liver, is either recycled into the rumen for microbial protein synthesis or excreted via urine, feces or milk. Consequently, MUN might be associated with dry matter intake (DMI), enteric methane production (MP), energy corrected milk (ECM), metabolic body weight (MBW), and beta hydroxybutyrate (BHB). The objective of this study was therefore to investigate the feasibility of defining a novel NUE-related trait for genetic evaluation. Genetic and phenotypic correlations between MUN, DMI, ECM, MBW, MP, and BHB were estimated to characterize their relationships and to define a novel NUE-related trait. Subsequently, a recursive modeling approach was employed to estimate genetic parameters for the NUE-related trait. A dataset comprising 74,314 records from 2,428 first lactation Canadian Holstein cows was analysed using multivariate repeated-record models to estimate genetic, permanent environmental and residual variance components for all traits. Models included fixed effects of herd-year-season and first calving age, and fixed lactation curves. Results indicate that MUN might be genetically and phenotypically independent of ECM, MP, and BHB, with weak genetic correlations ranging from -0.27±0.11 to 0.24±0.14 and phenotypic correlations ranging from -0.04±0.02 to 0.21±0.02. Based on these findings, a NUE-related trait was defined using MUN as a nitrogen-output trait corrected for the input-trait DMI and the energy sink MBW via a structural equation model. Heritability estimates were moderate to high for NUE-related trait (0.21), MUN (0.24±0.04), DMI (0.32±0.03), and MBW (0.51±0.04). Repeatability estimates were 0.28 for NUE-related trait, 0.28±0.02 for MUN, 0.50±0.01 for DMI, and 0.72±0.01 for MBW. Genetic correlations between MUN and MBW were low (-0.01±0.10), while those between MUN and DMI were negative (-0.16±0.11). Due to the relatively high standard errors associated with these estimates, further research using larger datasets is warranted to validate these relationships. Results of this study provide insight into the potential of genomic selection for improving nitrogen use efficiency, which could contribute to both environmental and economic sustainability of the dairy industry.

Keywords: 2026

How to Cite:

Alcantara, L., Baes, C., Fleming, A., Jahnel, R., Makanjuola, B., Miglior, F., Schaeffer, L. & Schenkel, F., (2026) “Assessing the Potential to Enhance Nitrogen Use Efficiency in Holstein Dairy Cows”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2286550. doi: https://doi.org/10.31274/wcgalp.24046

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