Lameness remains one of the major welfare challenges facing the dairy industry because it is painful (Whay, 1997), often severe and long-lasting (Leach et al, 2012; Groenevelt et al, 2014), and highly prevalent (Griffiths et al, 2018; Randall et al, 2019). Historically, much of the focus has been on proactive treatment and care of the very lame cow (Bell and Main, 2011). However, increasingly the published evidence shows that by delaying treatment until the condition has progressed, cure rates are lowered (Thomas et al, 2016), recurrence rates are higher (Groenevelt et al, 2014) and lesions are more severe (Groenevelt et al, 2014). This means a primary focus on treatment of severe lameness may be the most unrewarding and costly approach to lameness, despite being the most common scenario.
Research in the last 20 years shows the pathology associated with the most commonly reported claw horn lesions causing lameness (namely sole ulcers, heel ulcers and white lines) is, in most instances, severe and irreversible by the time we observe them. The pathology associated with thes claw horn lesions has been shown to involve digital cushion (Newsome et al. 2017a), bone (Newsome et al, 2016) and/or chronic infection of the corium (Evans et al, 2011). Involvement of deeper structures, such as joints and tendon sheaths, are the extreme cases. Evidence shows these disease processes can start with events as heifers (Offer et al, 2000), even though lameness is often perceived as a condition of older cows. This means lameness management strategies with a focus on heifers could have significant implications for lesion prevalence and associated, irreversible pathological change to bone and soft tissues, in later life. Recent research has quantified this impact by demonstrating that repeated bouts of lameness can make a very large contribution to the total number of lameness events within herds (Randall et al, 2017). Furthermore, these changes have measurable impacts on milk production and longevity (Randall et al, 2016). This article therefore reviews lameness risk factors and interventions in dairy heifers.
Methods and materials
A descriptive review of the literature was conducted using the Cattle Lameness Literature database (www.cattle-lameness.org.uk), the RCVS library Discovery database, ScienceDirect and Google Scholar. Search criteria included terms related to heifer lameness and reported intervention, with terms outlined in Table 1.
Table 1. Search criteria for literature relating to heifer lameness
| Database | Journals and papers included | Search terms |
|---|---|---|
| www.cattle-lameness.org.uk | Liverpool systematic review (Hirst et al, 2002a) | Heifer |
| ScienceDirect | Extensive journal publications | Dairy heifer lamenesslameness AND ‘heifer group’lameness AND ‘cubicle training’ |
| RCVS Knowledge Discovery database | Extensive journal and grey literature publications — only peer-reviewed papers included | |
| Google Scholar |
Papers were included when there was reference in the title to heifers or cohort studies starting with heifers. Papers were excluded when papers involved conditions other than sole ulcers, white line lesions and digital dermatitis or were not focused on lameness control. Consequently, papers that described surgical or diagnostic procedures in clinical case reports were excluded.
Significance of lameness in first lactation
Prior lameness events or lesions in first lactation have been shown to be an important risk factor for future lameness events (Hirst et al, 2002b; Randall et al, 2016), as well as having adverse effects on milk yields and culling risk (Randall et al, 2016). Consequently, most research involving lameness interventions in late 1990s and onwards involves first lactation heifers to remove any history of lameness as a confounding factor to a large degree (although clearly lameness does occur before first calving). This has generated a useful body of evidence on lameness in first lactation which can be applied to on-farm assessment. This is particularly important for investigations, as herd lameness prevalence can be heavily influenced by replacement rates, which in turn are influenced by heifer availability (or cost), barren cow value and availability of local outlets for lame cows. Furthermore, bovine tuberculosis can decimate herds including young-stock, with major ramifications on unplanned culls and availability of replacements, meaning lame cows are retained for longer than planned. Using heifer lameness prevalence to benchmark performance can therefore improve the plotting of progress by removing these confounders during investigations.
Prevalence of lameness
The Cattle Health and Welfare Group (CHAWG) report (2018) presented the trend in cross-sectional surveys in the UK where there has been reporting of lameness prevalence in dairy cattle (Anon, 2018). Figure 1 plots these data to show the trend in lameness prevalence in the UK over the last 25 years.
In contrast, reports of lameness prevalence in dairy heifers are in short supply (Table 2). Within the Defra-funded heifer lameness project (Bell, 2006) farm level prevalence of lameness ranged from 0–55.6% with a herd level mean prevalence of 16.0% (median 12.5%). More alarming is the Danish report which found 90% of heifers were lame in one cohort examined at 201–300 days in milk (DIM). Mahendran et al (2017) reported lameness period prevalence of 41.1% through first lactation for a cohort of heifers on two dairies during an intervention trial, but showed point prevalence peaked at just over 12.2% at 29–42 days into lactation and fell to 1.1% at around 295–322 days into lactation, revealing the transient and dynamic nature of lameness events in first lactation.
Table 2. Prevalence of lameness in primiparous heifers in two surveys
| Survey start year | Study design and lameness definition | Lameness prevalence | Sample characteristics | Dairy herds | Dairy heifers | Location | Reference |
|---|---|---|---|---|---|---|---|
| 2003 | Cross-sectional survey | Clinically lame 15.0% | 60–120 DIM | 60–120 DIM Any DIM | 60–120 DIM | SW England, Wales and Midlands | Bell (2006) |
| Unsound 39.5% | |||||||
| Clinically lame 15.8% | Any DIM | Any DIM | |||||
| Unsound 44.6% | |||||||
| 2002 | Cohort prospective survey using Sprecher score ≥3 | 25% | Pre-calved | 1 | 147 | Denmark | Capion (2009) |
| 50% | 0–100 DIM | ||||||
| 66% | 101–200 DIM | ||||||
| 90% | 201–300 DIM | ||||||
| 70% | >300 DIM |
DIM = days in milk
Software is also available that allows separate analysis of lameness prevalence by parity. A useful target for lameness prevalence in first lactation is <6%, with suitable adjustments for stage of lactation in seasonally calved herds (Mahendran et al, 2017).
Interventions to reduce lameness in first lactation
There are a number of management practices which may help to prevent or slow progression of foot pathology in heifers. While the evidence base is weak, there is a growing acceptance that more focus applied to heifers has the potential to increase productive, pain-free lifespan, and reduce the likelihood of long-term pathological changes within the hoof structure. A number of studies have evaluated risks and interventions for lameness prevalence in first lactation. Table 3 summarises the evidence supporting each intervention.
Table 3. Interventions to minimise the development of lesions causing lameness in heifers and later life (order according to typical stages applied in the heifer's life)
| Foot health intervention | Examples of practical applications and rationale | References |
|---|---|---|
| 1. Genomic selection of resilient heifers | Applying genomics to weaned heifers to cull (or sell for beef) heifers with a higher risk of lameness | Surprising there are no peer-reviewed publications on genomic selection for lameness in dairy heifers. Liverpool University are currently investigating this. AHDB provide a sire selection index called Lameness Advantage, which is based on an average heritability of 4% (Anon, 2020) |
| 2. Rearing heifers free from digital dermatitis | Keeping rearing facilities biosecure so heifers do not encounter digital dermatitis prior to first calving. This might involve ensuring no mature animals are brought to the heifer rearing site, using automatic scrapers, making sure no trimming equipment is shared and people wear dedicated personal protective equipment for the heifer rearing site | Bell (2006) Gomez et al (2015) |
| 3. Cubicle training prior to first calving | Rearing heifers on cubicles. Sand could predispose to acquired corkscrew claws | Logue et al (2004) von Keyserlingk et al (2011) O'Connell et al (1993) Kjæstad and Myren (2001a, 2001b) |
| 4. Developing the digital cushion with exercise and hard floor/track surfaces | Scraped concrete feed passage during rearing period. Housing autumn block calving heifers 2 months before calving or housing when over 8 weeks into lactation | Gard et al (2014) Bergsten et al (2015) |
| 5. Feeding high dry matter rearing diets | Rearing diets based on straw/hay and concentrate reduces claw horn lesions | Webster (2001) Webster and Tarlton (2001) Offer et al (2001) Logue and Offer (2001) Offer et al (2003) Leach et al (2005) |
| 6. Trimming pre-calving | Trim heifers with long toes 7–8 weeks prior to expected calving | Mahendran et al (2017) found trimming increased prevalence of lameness compared with no trimming. However, initial trimming took place as heifers entered transition and the lactation environment was a high risk for high wear rates |
| 7. Heifer transition and fresh group | Parity 1 transition and milking groups | Cross et al (1999) |
| 8. Protecting the weakened laminar attachment around first calving with a heifer straw yard group for 12 weeks (C-4 to C+8) | Straw yards for 4 weeks before calving until 8 weeks after calving would appear to be the gold standard, but deep bed cubicles with appropriate dimensions could achieve a comparable level of lying time and behaviour. Rubber matting (like quarry belting) along feed barrier to cushion feet. Small fresh group for short pen times for milking and other activities | Webster (2002) |
| 9. Trimming heifers 60–100 days in milk | Conservative foot check at 60 days in milk. Focus mostly on the large and deep model (Stoddard, 2018), and treatment of lesions causing lameness | No good evidence supporting this. There have been two trials which found no reduction in lameness with a 100 day check (Mahendran et al, 2017) or improvement in productivity with an 80 day foot check (Maxwell et al, 2015). Liverpool research suggests this may have been too late in lactation to have a protective or corrective benefit (Griffiths et al, 2018) |
| 10. Fortnightly mobility scoring with prompt, effective treatment | Every 1–2 weeks the person responsible for cow health and welfare watches milking groups walk past them at a milking and selects animals for trimming and treatment. Best practice for claw lesions involves the proactive use of a block and non-steroidal anti-inflammatory drug for claw horn lesions and topical antibacterial treatment with or without a bandage | While trials have not reported heifer groups separately, this intervention would appear to apply well to heifers (Groenevelt et al, 2014; Thomas et al, 2015). Mahendran et al (2017) used the fortnightly scored heifer group as their control group which performed better than the trimmed groups |
Genetic selection
Foot lesions show a small but sufficient level of heritability for the creation of breeding indices such as Lameness Advantage (Anon, 2020). These heritabilities and indices are only as good as the lesion data acquired. Scandinavian countries incorporating hoof trimming data at a national level use much tighter quality control than currently in the UK. Perhaps more promising is the genomic technology which has already shown a number of single nucleotide polymorphisms associated with digital dermatitis susceptibility or resistance (Scholey et al, 2010) and digital cushion thickness (Oikonomou et al, 2014). These have yet to be translated into specific lameness selection indices, but this is only a matter of time. These management tools will become useful for identifying high risk heifers and potentially culling of these heifers prior to first breeding.
Heifer rearing free from digital dermatitis
Heifers acquiring digital dermatitis during the rearing period is an important risk factor for digital dermatitis in first lactation (Bell, 2006). It also appears to influence prevalence in the herd in general. Gomez at al (2015) found heifers that were infected prior to first calving had more cases in first lactation and lesions developed earlier in lactation. Heifers with a single infection produced 199 kg less milk, and heifers with repeated lesions produced 335 kg less milk in first lactation, with the latter group also having a lower conception rate. Randall et al (2016) found heifers with digital dermatitis lesions remained within the herd for a shorter period, and that despite positive associations between digital dermatitis and yield, digital dermatitis was associated with a lower lifetime yield. Ensuring heifers are reared in a biosecure site on the farm to minimise the risk of acquiring infection is therefore important. However, removal of infection from a heifer rearing unit is more challenging, but may be possible with robust detection, treatment and disinfection protocols (Yeruham and Perl, 1998), although eradication with blanket use of antibiotics as used in one case study (Bell, 2011) is not ethically justifiable.
Heifer ‘comfort’ groups
At calving the physiological upregulation of matrix metalloproteinases reduces the strength of the suspensory apparatus (Webster and Tarlton, 2001; Tarlton and Webster, 2003; Knott et al, 2007). The weakening of the laminar attachment lasts several weeks before and after calving (Tarlton et al, 2002). This vulnerability makes the rationale for a heifer transition and fresh group compelling. Webster (2002) tested this hypothesis with the use of straw yards for a period starting 4 weeks before anticipated calving, until 8 weeks after calving. There was a significant reduction in lesion score, which persisted after re-introduction into cubicles, with complete prevention of sole ulcers compared with the control group with sole ulcers. The use of straw yards for 12 weeks (4-week transition and 8 weeks in early lactation) is unpopular for a variety of reasons including mastitis risk and cost. The concept of the heifer comfort group has been broadened to describe the heifer group in comfortable deep bed cubicles for this critical period. Deeply bedded cubicles with smaller group sizes and short milking times is likely to contribute to some of the beneficial effect described by Webster (2002). The use of heifer groups in general is likely to reduce the level of bullying and displacement of heifers from feed and cubicles by dominant older cows and perhaps improve lying times, thereby reducing some of the known potential risk factors for lameness.
Digital cushion development
Research into the digital cushion over the last 20 years has revealed its importance for dissipating concussive forces through the foot (Räber et al, 2004). The volume or thickness of the healthy digital cushion is influenced by a number of management factors including age (Räber et al, 2004), genetics (Oikonomou et al, 2014), exercise on hard surfaces (Gard et al, 2014) and body condition score (Newsome et al, 2017b). Approaches to maximise digital cushion volume, such as rearing heifers on scraped concrete and ensuring they are optimal body condition score, would appear logical but challenging in some situations. This has greatest relevance to autumn block calving herds, when heifers are traditionally managed at grass until calving.
Cubicle training
Cubicle training is a widespread but not universal practice, often introduced once bedding materials such as straw are in short supply. However, there is a strong rationale for having heifers trained to cubicles prior to first calving. When heifers are initially introduced to cubicles, lying times have been shown to drop 2.9 hours and 4.2 hours per day in a pair of experiments conducted in Canada (von Keyserlingk et al, 2011). However, this may not be visible to the farmer, unlike total refusal resulting in lying-out (Kjæstad and Myren, 2001a, 2001b). Cubicle training can result in large differences in foot lesion score in heifers prior to first calving (Logue et al, 2004). In this study, the effect of training far exceeded any difference in lesion score induced with accidental and severe clinical acidosis following a feeding error. The combination of weakened laminar attachment and under-developed digital cushion with a degree of cubicle rejection at calving is associated with higher lesion scores.
It is common for cubicle training to occur for 6–8 weeks around the time of first breeding or as in-calf heifers, but many farmers are able to train heifer from weaning age. Whenever training is under-taken, best practice involves a comfortable cubicle bed (e.g. a mattress well-bedded), well-bedded with a bedding material the heifers are most familiar with (e.g. straw) so as to provide a comfortable bed, which is appealing to lie on (O'Connell et al, 1993). Further work on cubicle acceptance is currently underway at SRUC on this subject. Cubicle training has an added benefit of exposing hooves to harder surfaces, which may have additional protective benefits for lameness (Bergsten et al, 2015) and digital cushion development (Gard et al, 2014). This might explain why sole haemorrhages before first calving appear beneficial to heifer foot health (Randall et al, 2016).
Dietary factors
Historically a lot of unfounded emphasis was placed on acidosis and associated nutritional causes resulting in a subclinical form of laminitis in dairy cattle (Randall, 2018. Laminitis is a condition difficult to diagnose accurately. It is experimentally induced with oral oligofructose, with associated ruminal acidosis, which results in a self-limiting, transient polysynovitis affecting all four limbs (Danscher et al, 2010). However, currently no evidence exists to demonstrate this triggers the onset of the common claw horn lesions causing lameness in dairy cattle. Long-term ruminal acidosis may be associated with reduced biotin synthesis. It has been demonstrated that feeding hay can increase natural ruminal synthesis of biotin (Abel et al, 2001). When natural biosynthesis of biotin is compromised then supplementing biotin at 20 mg/head/day was found to decrease lameness incidence as a result of white line disease by approximately 50% (Hedges et al, 2001), although no benefit was recorded in first lactation. Some of this reduced benefit may be because most heifers are reared on dry diets based on straw or hay supplemented with concentrates, with a carry-over effect a result of the good quality horn laid down during the rearing period lasting through early lactation. Numerous studies have now shown the benefit of the straw- (or hay) based diet over cheaper grass silage diets (Livesey et al, 1998; Offer et al, 2001; Webster and Tarlton, 2001; Leach et al, 2005). The mechanism is still unknown, with drier dung, greater rumen biotin synthesis or better macromineral status all being possible explanations. Zinc status could be particularly relevant to the relatively poorer diets of some youngstock compared with adult dairy cows, although there is no conclusive research evidence to support the measurable reduction in lameness as a result of the major claw lesions in the short-term. Another plausible explanation for the apparent association between poor nutritional management and claw horn lameness could be explained in relation to the depletion of the digital cushion when animals mobilise fat during negative energy balance or with poor feed management (Green et al, 2014; Lim et al, 2015; Randall et al, 2018a).
Hoof trimming
Routine hoof trimming is a widely adopted practice although the evidence supporting the optimal timing and technique is still relatively debatable. Foot checks mid-lactation and at around dry-off would appear beneficial to dairy cows in general (Manning et al, 2016). Given the possible adverse consequences of poor foot angle on development of tendons and heifer conformation, corrective trimming of heifers with long toes at least 8 weeks prior to calving would seem a rational approach.
Only one study has examined trimming before first-calving with a negative effect reported (Mahendran et al, 2017), although heifers were presented for trimming as they entered the transition group and the heifers were managed in a high claw wear environment (sand-bedded cubicles, areas of new concrete long walking distances). Five step method has the strongest evidence-base at present (Mahendran and Bell, 2015). Another study (Maxwell et al, 2015) investigated associations between an early lactation foot trim in heifers at 80 days post-calving and production outcomes in a randomised controlled trial. While no significant differences between the trim and control groups were identified, heifers that were lame at trimming were producing significantly more milk than the non-lame and untrimmed heifers. Targeted trimming of lame or higher yielding heifers at risk may provide most production benefit. This study also identified a high prevalence of lesions in heifers, as other studies have done, indicating regular assessment and early treatment in heifers are both important. Therefore, routine foot checking may be justified on welfare grounds alone.
Early detection, prompt, effective treatment
Finally, even with the best management, heifers will bruise claws. However, the early first lactation heifer may appear to cope with lameness and compensate for this by virtue of their smaller size and general fitness. However, the early detection and prompt, effective treatment of lameness in heifers is likely to contribute to quicker recovery, better recovery, less recurrence and better lifetime productivity. Groenevelt et al (2014) demonstrated the reduction in recurrence and chronic lameness when fortnightly mobility scoring was applied to dairy herds. In a follow-up study, Thomas et al (2015) showed the best 5-week cure rate for claw lesions in acutely lame cows came with the combination of a block applied to the healthy claw and non-steroidal anti-inflammatory drug (NSAID) for 3 consecutive days. This superior cure rate was lost when treatments were delayed by 2 weeks (Thomas et al, 2015), with contralateral limb lameness a complicating factor in identifying cure rate at cow level. Further work is needed to demonstrate the effectiveness of this approach applied consistently over the lifetime of the animal starting as a heifer, but the evidence demonstrating the deterioration (Offer et al, 2000) and consequences for the heifer's performance in later life is compelling (Randall et al, 2016). One of the biggest challenges is showing the producer that the apparent mild lameness observed in heifers is translating to the severe or chronic lameness seen in later lactation. Much work in recent years has focused on methods to positively engage farmers on lameness prevention, with traditional health planning proving disappointing (Bell, 2006; Bell et al, 2006, 2009) and marketing approaches proving more successful (Main et al, 2012; Ritter et al, 2017).
Conclusions
The heifer is vulnerable to lameness in the first few weeks before and after first calving by virtue of physiological changes happening with-in the foot, the under-developed digital cushion, disturbed lying times and the bullying associated with integrating into the milking herd. Although widely recognised, the impact of this often manifests many weeks, months or years later and so the association is rarely made. How the heifer is reared and managed can greatly interact with this vulnerability, providing an opportunity to manage the risk and prevent a lifetime of lameness. There appears to be a number of measures that, when effectively applied, will minimise the progression of foot disease, with consequential benefits to life-time productivity and welfare.
KEY POINTS
- The largest deterioration in foot health occurs in first lactation, leading to chronic lesions in subsequent lactations.
- Ensuring heifers do not acquire digital dermatitis prior to first calving is a high priority for disease control and productive heifers in first lactation.
- Heifer rearing environment can determine digital cushion development and foot robustness in first lactation, particularly with regards to training to use cubicles and exercise on hard surfaces.
- Protecting heifers from long standing times from 4 weeks before calving until 8 weeks after calving appears to be critical for reducing bruising and visible sole/white line haemorrhage.
- Early detection of mild lameness combined with prompt effective treatment, ideally with anti-inflammatory drugs, will protect the digital cushion and PIII from irreversible injury.