Dairy cow longevity has been defined as total lifespan or duration of productive life (Schuster et al., 2020; Vredenberg et al., 2021). Societal expectation of livestock life expectancy will influence the demand on acceptable productive lifespan, especially as early culling is most likely to occur due to disease (De Vries and Marcondes, 2020). Increased longevity has been associated with sustainability of the industry, particularly in the areas of environmental emissions, economics and societal license to produce (Hansen Axelsson, 2013; Barkema et al., 2015; Grandl et al., 2019; Vredenberg et al., 2021; Gambonini et al., 2022). There is a current trend of longevity being shorter in high production systems due to involuntary culling, which is a problem for sustainability and welfare (Dallago et al., 2021). The sustainability link with longevity exists largely through the reduced need for the rearing of future replacements (Buonaiuto et al., 2024; Clasen et al., 2024). Technical change and productivity growth on farms has been associated with improved longevity, indicating adoption of new information has had positive impacts in these areas (Ali, 2021). Production performance efficiency is not directly linearly related to longevity, with cows later than sixth parity having lower production outputs, therefore there is a balance to be struck between efficiency associated with longevity and economic performance (Owusu-Sekyere et al., 2023). It is important to consider how to sustainably improve metrics such as longevity and production using methods that are both seen as positive by society and based on evidence for management of livestock; it is also important to consider that a longer life does not necessarily translate into a better life, especially when accounting for welfare, profitability and production efficiency (Farm Animal Welfare Council, 2009; Schuster et al., 2020).

The productive life of a dairy cow centres around performance in the areas of milk production, reproduction, and health status (Hu et al., 2021). Together these factors can be used to assess the overall resilience of an individual to their environment and farm management practices (Röcklinsberg et al., 2016). Analyses regarding factors which influence longevity have shown that investments into farm buildings are significant contributors to longevity, with a likely synergistic effect with welfare improvements (Owusu-Sekyere et al., 2023). The economics of dairy farming (and the sustainability of a dairy business) relies heavily on the survivability of individuals within a herd (Kerslake et al., 2018; Vredenberg et al., 2021). To be profitable to a business a cow must produce sufficient milk to more than cover input costs during its lifetime on the farm; this links longevity with production efficiency (Boulton et al., 2017).

The primary reasons reported for replacing dairy cows in a herd are infertility, disease or poor production (Compton et al., 2017; Bugueiro et al., 2019). The way in which primiparous cows are managed around their first calving and lactation is likely to be associated with lifetime performance metrics (Brickell and Wathes, 2011; Sawa and Bogucki, 2017; Puerto et al., 2021) and overall longevity (Dallago et al., 2021). Current common management practices will mean that first lactation animals are often managed within an indoor housed environment (for at least part of a year); the nature of these environments can be highly variable, particularly in terms of total space availability (Thompson et al., 2020). A recent study showed that there was a distinct variation in the housing supplied to dairy cows in Great Britain, with the average total space available per cow being a mean of 8.3m² from a range between 5.4 to 12.7m² (Thompson et al., 2020). This variation was associated with cubicle stocking density, farm location, farmer attitude and outdoor access (Thompson et al., 2020). This research led to a new definition of an area within dairy cow accommodation: Living space. Living space describes the area within dairy cow accommodation which is greater than that considered a baseline requirement per cow, excluding lying areas (Thompson et al., 2020). The mean living space was 2.5m² (range: 0.5m² - 6.4m²). Although total space per cow is a current standard metric within the industry, the novel term “Living Space” provides a more nuanced detail about shed design as it accounts for cubicle dimensions for different breeds and fluctuations in cubicle stocking density. It then standardises the excess passageway or loafing area space above a minimum baseline during housing. Increased living space in high yielding Holstein dairy cows has been shown to lead to increased milk production for primiparous compared to multiparous cows (Thompson et al., 2022). Other research has assessed the impact of primiparous-cow-only groups based on improvements to welfare (Bøe and Færevik, 2003) and production (O’Connell et al., 2008) and reported that variables such as facility design have the potential to impact upon risk of culling and milk production.

A stochastic simulation model was created to further explore the potential economic impacts of these results. The estimated direct financial comparison over cow’s lifetime dependent on living space scenario showed a median increase in financial return of +£87.61 per cow per year when provided high living space (Thompson et al., 2024). The associated return on the initial investment was deemed to be dependent on method of providing additional space, interest rates, and the duration of loan repayments (Thompson et al., 2024).

The aim of this research was to provide insight into whether there are long-term effects of providing additional living space to primiparous dairy cow in terms of milk production. Our null and alternative hypotheses were:

This work follows on from a series of publications linked to the exploration of housed environments for dairy cows. A year-long randomised controlled trial (RCT) to explore the effects of living space on all year-round housed Holstein dairy cows was previously undertaken (Thompson et al., 2022). That RCT explored this question by pairing dairy cows based on parity and calving date, and randomly assigning each individual into a different pen environment for the remainder of the lactation. This was undertaken for primiparous and multiparous animals in the original study. The two scenarios tested were:

In the original study there were the same number of cows present in each group (35 of mixed parities at any one point in time); a total of 75 animals entered each trial group over the trial duration, of which 38 were primiparous heifers). Cow entry initially occurred at any day in milk (DIM) during lactation, then only new cow pairs (<14DIM) entered once the trial commenced (Thompson et al., 2022). All other aspects of the environment, management and animal husbandry remained identical between groups. These animals completed one lactation in either the control or high space group and then resumed life back in normal management conditions in the herd.

This research provides the first preliminary evidence that there are associations between space allowance within the housed environment for primiparous dairy cows and lifetime milk production. It appears housing conditions of primiparous cows has potential to lead to increases in milk production for a period longer than during the first lactation. This has implications for cow productivity as well as welfare, which could help to facilitate more sustainable approaches to managing dairy cows and improving dairy businesses.

The difference in first lactation milk yield for individual cows, described in Thompson et al., 2022, showed important yield differences during the time of exposure to different space allocations. The findings in this research indicate that differences in milk yield continued beyond the initial study of the first lactation. Lifetime performance traits have been previously associated with high first lactation yields but poorer reproductive performance (Fahim et al., 2025). This study identified a similar outcome but used randomised matched pairs that reduced the impact of potential confounding factors.

There are a number of plausible biological reasons for our results, although there is limited evidence to support a causal pathway. Reasons for a prolonged impact of additional living space beyond the time the additional space was provided include; epigenetic changes (Ratan et al., 2023), behavioural changes (feeding patterns or lying time differences as shown in the original study), or long-term metabolic changes. It is unclear which, if any, of these factors played a role in the alteration of lifetime milk yield. Epigenetics have been shown to be associated with diet (Lesta et al., 2023), and since the first parity animals in this study produced more milk, it is possible they consumed more food which led to epigenetic change. Similarly, mammary gene expression has been related to behaviours such as milking frequency and milk yield in short term trials (Wall et al., 2013), therefore another potential carry over effect to enhance future milk yields could be associated with such mammary gene expression. The exact biological mechanism of the effect identified in this research remains unknown however and would benefit from further research.

When assessing the productive days alongside production data to calculate total lifetime yields, at group-level data the combined lifetime milk production in the high space group was 6057 L more than the control space group, produced over 1, 019 fewer lifetime days. This does not account for the potential yield gain that would be achieved when replacing these lost days with a replacement primiparous cow. Based on an average daily production for the high space cohort in this study (38.92L), additional replacement heifers would potentially produce 39, 659 litres over the additional 1, 019 days. However, the payback from this opportunity would also need account for additional replacements costs to rear heifers in the high space group.

There appeared to be no difference between the survival of the two cohorts as no clear patterns emerged in survival times between space allocation groups. However, the small sample size means this could be due to a lack of power in the analysis and more work is needed in this area for further understanding. A study which assessed survival, comparing whether primiparous animals were housed separately from the main milking herd or not within the first month after calving, showed little difference between the groups within the first 580 days after calving, before a divergence in the survival of the two groups (Østergaard et al., 2010).

Due to the complexity of the original trial a limited sample size was available for the current study, which limited the analytic power; there is a risk of type-1 errors within this analysis. However, these were a valuable cohort of cows, given the control placed around their original recruitment and housing conditions. A further limitation was the potential for variation in future living conditions post-trial due to non-standardisation of cow groups without the control of trial conditions, for example cows moved in and out of groups continuously meaning stocking density for each resource would change continuously throughout lactations. However, this variability was the same for both living space groups and since cows were managed with no knowledge of first lactation circumstances, any differences were at random and should not produce a systematic bias. Another limitation was that the data were from a single farm using Holstein cows that were housed year-round, thus the generalisability of the results is unknown.

In conclusion, results from this research provide provisional evidence that there may be long term effects on dairy cows dependent on their living space environments in first lactation. Thus, optimisation of the housed environment at this time could impact future outcomes in terms of lifetime milk production. Future work should be centred around whether there is an equivalent effect of living space allowance in different farm types and management systems. Additionally, more work should be done to evaluate whether a variety of different living space allowances provide additional benefits for milk yield and longevity. It is also unknown how living space provision for older cows compares to outcomes from primiparous only groups; again, this warrants future research.