Review: Economic evaluation of cow comfort interventions in dairy production systems - A systematic synthesis of literature from 2005 to 2025.

Cow comfort interventions may improve animal welfare and farm productivity, but evidence about their costs, consequences and returns is fragmented and inconsistently reported, limiting comparison and transferability across production and income settings. In this systematic review, we synthesised and critically appraised economic evidence of cow comfort interventions in dairy production systems published from 2005 to 2025. We searched four bibliographic databases (PubMed, CAB Direct, IngentaConnect and Web of Science) for peer-reviewed studies reported in English. We narratively synthesised the included evidence by cow comfort domain and income setting; categorised the evaluations as either full or partial; recorded the role of economics in stated aims; and appraised methodological and reporting quality using a modified Drummond checklist. Forty-seven studies were included: 32 from high-income settings, nine from low- and middle-income settings, and six that were regional or did not report a specific economic setting. Eighteen studies were primarily economic, 16 had economic and non-economic co-primary aims, and 13 had non-economic primary aims with a secondary economic component. Twenty studies were full economic evaluations while 27 were partial evaluations. Studies commonly addressed housing and management, lameness or foot and claw disorders, and mastitis or udder health, with less attention to bedding, stall design and dimensions, and flooring. Economic evidence was largely heterogeneous, commonly using milk yield as an economic proxy, while cost analyses and estimates of net returns or profitability were common; formal cost-effectiveness and longer-term investment analyses were uncommon. Evidence from low- and middle-income settings was sparse and focused more often on pragmatic, bundled upgrades or hygiene strategies evaluated through budgeting or simulation. Reported economic benefits were context-dependent and could not be meaningfully pooled or used to rank interventions. Standardised modified Drummond quality scores ranged from 33.3 to 90.6% with a median of 58.3%. Recurring limitations included unclear analytical perspective, incomplete cost valuation and price-year reporting, absent time horizons and insufficient discounting or uncertainty analysis when applicable. In conclusion, the evidence supports the potential for context-specific economic gains from improving cow comfort but is insufficient for generalised claims about which intervention offers the greatest return. Future evaluations should transparently report incremental costs and consequences, analytical perspective, time horizon, price year and uncertainty. More context-grounded and longer-term evidence is particularly needed in low- and middle-income dairy systems.