The post-weaning period in dairy heifer rearing is often underappreciated; however, it is a crucial phase in developing future productive dairy cows. It begins around 8–10 weeks of age, when calves fully transition from a milk-based diet to solid feed, and, as this author refers to it, extends until the first calving. Insufficient management during this period can lead to stunted growth, delayed puberty and ultimately, an increase in the age at first calving (AFC) beyond the desired 23–24 months. Conversely, effective post-weaning management enables producers to meet key growth benchmarks, positioning heifers to calve on schedule and perform optimally as dairy cows. Veterinary engagement in heifer rearing frequently declines post-weaning because of the reduced ease of handling and because animals may potentially reside in locations that are harder to access. As a result, implementing timely interventions to optimise AFC becomes more challenging. However, by leveraging data readily available through milk recording systems, a targeted report has been developed to appraise and enhance the efficiency of on-farm heifer rearing, focusing on three primary key performance indicators (KPIs): AFC, survivability and first-lactation productivity.
The importance of early-life management and age at first calving
Veterinary practitioners often find it easier to engage with calf management during the pre-weaning phase, when calves are more accessible and manageable. Many practices now host dedicated calf clubs, where regular activities such as weighing, monitoring daily liveweight gain (DLWG) and tracking morbidity and mortality provide valuable insights. Blood sampling often complements these efforts and is typically analysed using a Brix refractometer to evaluate passive immunity transfer. Sherwin et al (2016a) provide a detailed overview of the importance of these data and strategies for effective collection. Increasing proficiency in thoracic ultrasound in young calves offers another valuable tool for data collection and decision-making (Olivett, 2018).
Emphasis on the pre-weaning period is well justified, as research demonstrates its critical influence on long-term productivity; Soberon et al (2012) reported that each additional kilogram of DLWG before weaning (approximately 49 days) corresponds to an increase of 970 kg of milk in a heifer's first lactation.
Maintaining engagement with heifer management post-weaning can be challenging for veterinary practitioners, but achieving calving by 23–24 months remains a key objective, supported by substantial evidence of its benefits. Research shows that heifers calving at this age produce more milk over their lifetime (Froidmont et al, 2012; Wathes et al, 2014; Eastham et al, 2018) and have greater herd retention rates (Froidmont et al, 2012). Sherwin et al (2016b) further noted that an AFC over 24 months is ‘significantly associated with an increased risk of being culled’. Delayed calving increases the need to rear additional heifers to maintain herd size, leading to higher stocking densities and elevated risks of disease transmission (Tozer and Heinrichs, 2001). Moreover, older heifers are more likely to become overfat, contributing to calving difficulties (Wathes et al, 2014).
From an economic perspective, reducing AFC significantly lowers production costs. Boulton et al (2017) estimated that costs rise progressively, reaching up to 25.2% higher for an AFC of 30 months or more. This cost reduction is primarily due to savings in feed, labour and infrastructure, which outweigh the increased daily feed requirements needed for heifers to reach target weight by 24 months (Tozer and Heinrichs, 2001).
More recently, attention has turned to the environmental implications of AFC. Research indicates that optimising AFC reduces greenhouse gas emissions, particularly methane. Dall-Orsoletta (2019) observed that decreasing the AFC from three to two years of age was possible and reduced emissions by 2.2 tonnes of CH₄/year. Grandl et al (2019) further reported that cows failing to complete their first lactation exhibited unfavourable emissions per unit of product and often did not recover their rearing costs. Therefore, efficient heifer development not only enhances productivity and economic performance but also aligns with environmental sustainability goals.
Current performance and the value of data-driven insights
Data reveal that current heifer-rearing practices often fall short of the 23–24 month AFC target, with a UK study reporting mean and median AFC to be 29.1 and 28 months respectively (Eastham et al, 2018). The target first-lactation culling rate is <10% (Breen et al, 2012), but Brickell and Wathes (2011) cited a rate of almost twice this at 19%, while Sherwin et al (2016b) found a mean culling rate of 16.9%. These trends present a tangible opportunity for practitioners to influence on-farm practices that can enhance animal welfare, business profitability and sustainability.
The primary challenge lies in engaging producers with post-weaning heifers, given the logistical difficulties of managing larger animals that are often housed off-site or in less accessible areas. Targeted data collection focused on three key performance indicators—AFC, survivability and first-lactation production—offers a pragmatic approach to stimulating producer interest and action.
Key performance indicators for heifer development
1. Age at first calving
While average AFC is commonly reported, it offers limited insight and may create a false sense of security regarding heifer performance. A more informative approach examines the distribution of AFC, which highlights costly delays, as illustrated in Figure 1. With the cost of rearing a heifer increasing by £2.87 for every day past 24 months at calving (AHDB, 2024a), the financial impact for animals to the right of the green line is substantial. Furthermore, heifers calving beyond the blue line are over 5 times more likely to be culled within 50 days in milk (Fodor et al 2020), underlining the importance of managing AFC effectively.
Examining the percentage of heifers achieving the target AFC of 23–24 months provides further clarity on herd performance. In some UK herds, over 80% of heifers meet this benchmark, but as shown in Figure 2, only 23% do so in the example presented. This stark contrast highlights considerable opportunities to improve heifer management and enhance both productivity and economic outcomes.
2. First-lactation production
First-lactation production metrics offer valuable feedback on the success of heifer rearing. Heifers are expected to produce approximately 80% of the yield of mature cows (Bailey and Currin, 2009). Production was measured over a 305-day period to minimise distortion from extended lactations in heifers with delayed conception, and compared with average 305-day yields from second-lactation animals and above (Table 1). Consistently achieving this target suggests that rearing programmes are supporting productive adult performance, though outcomes are also influenced by subsequent management within the milking herd.
| Year born | Lact 1 | Lact 2 plus | Percentage heifer yield |
|---|---|---|---|
| 2016 | 7157 | 8242 | 86.8% |
| 2017 | 7097 | 8613 | 82.4% |
| 2018 | 6530 | 7449 | 87.7% |
| 2019 | 6030 | 7155 | 84.3% |
| 2020 | 6442 | 7212 | 89.3% |
3. Survivability and economic payback
Survivability is arguably the most compelling metric for producers, as it directly affects profitability and sustainability. Heifer rearing accounts for around 20% of total dairy farm expenditure (Sherwin, 2023), and the economic breakeven point is typically reached midway through the second lactation (Boulton et al, 2017). First-lactation culling therefore represents a significant financial and environmental loss. When faced with the figures presented in Table 2, producers can evaluate the true cost of early exits. Animals culled prematurely not only fail to recover rearing costs but also contribute to a notable carbon debt. These insights are often an ‘eye opener’ for producers, reinforcing the financial and ecological benefits of optimising heifer development.
| Year born | Number calved | L1 exits |
|---|---|---|
| 2016 | 41 | 17.07% |
| 2017 | 40 | 32.5% |
| 2018 | 53 | 37.74% |
| 2019 | 54 | 33.33% |
| 2020 | 30 | 26.67% |
| 2021 | 13 | 23.08% |
Methodology for data collection and analysis
Data for this analysis were sourced from milk recording systems and integrated into the Total Vet platform (https://www.total-vet.co.uk/). A bespoke report was generated within Total Vet, with the template saved to allow for future reproduction. The dataset for each animal included:
The data were further analysed using a statistical programming language (https://www.r-project.org/). The Tidyverse package collection (https://www.tidyverse.org/) was used to manipulate the dataset, including grouping animals by birth year and calculating key descriptive statistics. An R Markdown file compiled the results into a structured, reproducible report (Schubert, 2023).
These metrics provide valuable insights into individual heifer performance and contribute to herd-wide assessments, supporting informed decision-making in dairy herd management.
Next steps
Once producers are engaged in discussions about post-weaning heifer performance and the need for improvement within the herd, a range of topics can be explored before deciding where to focus efforts. While the pre-weaning and weaning periods may emerge as priorities, these fall outside the scope of this article. When focusing specifically on the post-weaning phase, discussions typically centre on four key areas.
Post-weaning nutrition
Adequate nutrition is critical for post-weaning growth. Rations containing approximately 16% crude protein at 100 days, reducing to around 12% crude protein at 350 days, are optimal to support skeletal and muscular development during this phase (National Academies of Sciences, Engineering, and Medicine (NASEM), 2021). Overfeeding protein should be avoided, as excess is excreted as urinary nitrogen, contributing to ammonia and nitrous oxide emissions (Schrade et al, 2023). Common challenges include insufficient concentrate feeding and poor forage quality, which may result in underweight animals (Table 3) with suboptimal DLWG. This is particularly problematic, as the post-weaning period offers the lowest-cost opportunity for weight gain (Bach et al, 2021). Failing to capitalise on this opportunity creates a false economy, as compensatory growth later in life requires significantly higher input costs (Figure 3). Overfeeding energy should also be avoided, as this can lead to undesirable fat deposition rather than lean tissue growth (Sherwin and Remnant, 2018).
| Age | Stage | Body weight (kg) | % Mature weight | % Mature height |
|---|---|---|---|---|
| 0 | Birth | 41 | 6 | |
| 1 | 55 | 8 | ||
| 3 | Post-weaning | 116 | 17 | 63 |
| 6 | 185 | 27 | 74 | |
| 9 | Puberty | 274 | 40 | |
| 12 | 343 | 50 | ||
| 14 | Pre-breeding | 377 | 55 | 87 |
| 24 | Pre-calving | 582 | 85 | 96 |
| Mature weight | Adulthood | 685 | 100 |
Grazing management is another critical consideration, requiring careful planning to avoid growth checks when heifers are at grass. Target growth rates are well established: 55% of mature bodyweight before breeding and 85% before calving (Van Amburgh, 2004). These and other benchmarks are presented in Table 3 (AHDB, 2024c). While regular weighing may not be practical for all producers, it should be encouraged to ensure heifers meet the target DLWG of 0.8 kg/day (Akins, 2016). At minimum, withers height markers drawn on handling systems can provide a simple but effective method of monitoring progress.
Health management protocols
Effective health management during the post-weaning period is essential for maintaining growth and achieving key reproductive milestones. Respiratory disease is a frequent challenge, with bovine respiratory disease (BRD) being particularly significant. BRD affects nearly 50% of pre-weaned calves (Johnson et al, 2017) and is associated with reduced milk production during the first lactation (Buczinski, et al, 2021). Vaccination protocols should be discussed early, ideally during the pre-weaning stage, to ensure protection is in place (Sherwin and Down, 2018). However, vaccination must be supported by sound nutrition, hygiene and general management.
Digestive health is another key focus, with most post-weaning issues linked to coccidiosis or helminth infections. For grazing animals, lungworm control is also essential to prevent growth checks and long-term health impacts (Sherwin and Remnant, 2018). An integrated parasite management strategy—including pasture rotation, targeted treatments and monitoring—is vital (Sands et al, 2024). Proactive approaches in these areas are fundamental to optimising health and productivity.
Stress minimisation and behavioural management
Environmental and social stressors must also be addressed. Avoiding frequent regrouping, preventing overcrowding and maintaining uniform age groups all help reduce stress. Good lighting and comfortable flooring conditions improve welfare, encourage natural behaviours and enhance oestrous detection. Visibility and identification of heifers are critical for timely service, particularly when animals are grazing. Handling logistics must be carefully considered.
Locking head yokes and synchronisation programmes can support reproductive management. A UK study reported a net benefit of £88.55 per heifer using a 6-day progesterone fixed-time artificial insemination protocol with sexed semen in spring block-calving herds (Kerby et al, 2021). However, it should be noted that routine synchronisation is not permitted by some milk processors.
Genetic selection
Genomic testing offers a powerful tool to identify heifers with strong genetic potential for traits such as milk yield, fertility and health. According to AHDB, herds genotyping 75–100% of their dairy heifers achieved an average profitable lifetime index (PLI) of £430 in the 2023 calf crop, compared to a PLI of £237 in herds testing only 0–25% (AHDB, 2024b).
Conclusions
The post-weaning period represents a pivotal stage in heifer development, with long-term consequences for growth, fertility and future milk production. Current performance data indicate that many farms fall short of the optimal age at first calving (AFC) target of 23–24 months, underlining the need for improved engagement with post-weaning heifer management. Leveraging data-driven metrics—AFC, survivability and first-lactation production—can empower veterinary practitioners and producers to make informed decisions that improve productivity, profitability and sustainability.
Future strategies should focus on innovative solutions, including automated systems for growth and health monitoring, to overcome the logistical challenges of managing larger, dispersed heifers. Integrating these tools with proactive veterinary input and sustainable management practices will help ensure that post-weaning heifers transition successfully into productive roles within the herd.