Understanding Abnormal Behaviour in Dairy Calves – A Narrative Review

Definitions and framework of abnormal behaviours

Animal behaviour science suffers from imprecise definitions (Levitis et al., 2009), a problem rooted in its long intellectual history, evolving methodologies and changing social norms. Abnormal behaviour may include patterns never observed in typical contexts, but it can also include otherwise normal actions performed out of context (e.g., displacement activities) or directed towards inappropriate stimuli (redirected behaviours) when animals experience motivational conflict (Manning and Dawkins, 2012). Unwanted behaviours encompass both entirely novel patterns absent in natural settings and normal behaviours exhibited with abnormal frequency or without an apparent function (Phillips, 2008; Neja et al., 2017; Johanssen et al., 2024). Such behaviours can become pathological and deviate from species- and sex-typical repertoires that are normally considered adaptive (Mason, 1991; Mason and Rushen, 2006; Radkowska et al., 2020).

Abnormal behaviours in animals include oral and motor activities, many of which resemble adaptive responses arising from drive conflict – a state in which two incompatible internal motivations are activated simultaneously. According to the disinhibition hypothesis, two active drive systems inhibit one another and thereby allow a third to control behaviour (Barrows, 2001). Redirected behaviour is an intact action chain directed towards an alternative, often irrelevant, stimulus. It is also associated with drive conflict because the behaviour can circumvent the conflict (Harré and Lamb, 1986). When displacement or redirected behaviours become compulsive and repetitive, they indicate maladaptive functioning.

Stereotypies are repetitive, persistent and often purposeless behaviours that occur across species when environmental conditions fail to meet animals’ needs. They can harm the animal, but may also function as coping responses to stress or frustration. With prolonged maladaptation, stereotypies intensify and may disrupt physiological regulation (Mason, 1991; Mason and Rushen, 2006; Neja et al., 2017; Radkowska et al., 2020). Environmental enrichment can reduce the development of stereotypies and may protect animals even after transfer to poorer conditions (Mason, 1991; Mason and Rushen, 2006; Radkowska et al., 2020).

Calf normal behaviour

It is generally assumed that when referring to a calf of domestic cattle (Bos taurus), we mean the animal from birth (previously also considered the foetus) until it reaches sexual maturity, typically around 8–10 months of age, depending on the animal’s genetic makeup and environmental factors, particularly nutrition (Perry, 2016; Adamczyk, 2018). During this period, the animal undergoes intensive changes at the morphological, physiological and behavioural levels. A newborn calf is a monogastric animal, adapted to limited social interactions. In natural or semi-natural conditions, the mother cow usually leaves the calf isolated during the first days after calving, visiting it from the herd only for the feeding period. Calves also prioritise restricted movement (dairy calves typically spend up to 18 hours per day lying down) and display distinct expressions of instinctive behaviours relative to learned behaviours. In contrast, a calf approaching sexual maturity is a ruminant, social animal (during this period, animals learn social ties within a herd or group intensively), actively explores the environment and exhibits high daily motor activity (Phillips, 2002; Camiloti et al., 2012; Wang et al., 2022 b). According to Adamczyk (2018), at least two groups of behavioural needs should be maximally satisfied during the predominant period of “being a calf”: sensory pleasure needs (e.g., grooming, nutritional satisfaction) and the need for bonds between conspecifics.

It appears that, as a rule, the sensory abilities of calves (at the receptor level) are similar to those of older cattle (Adamczyk et al., 2015). The most important senses for cattle – vision, olfactory and auditory – primarily serve to identify other individuals, especially the mother cow (Fericean et al., 2010). The changes in the calf’s life are initially driven mainly by instinctive reactions, gradually giving way to abilities and behaviours acquired through learning. This includes, for example, recognising tastes and learning to chew as calves transition from milk to solid feed, independently using pen or bedding-area equipment (e.g., automatic feeders and waterers), and developing social relationships (Bouissou et al., 2001; Costa et al., 2016). Across these domains, physical development can have lasting effects on later productivity, relationships with conspecifics, interactions with humans, and overall welfare (Broucek et al., 2020).

In a natural setting, a calf initially maintains close contact with its mother. Over the following days and weeks, it gradually spends less time suckling and increasingly engages in social interactions with other calves (Lv et al., 2021; McKay et al., 2025). In commercial dairy farming systems, calves are separated from their mothers immediately after birth and housed individually (Costa et al., 2016; Broucek et al., 2020; Whalin et al., 2021; Lv et al., 2021). Within the EU, calves may remain in individual pens for up to eight weeks of age (Lv et al., 2021). Early separation from the mother cow negatively affects the calf’s social competence. Nevertheless, alternative approaches exist, such as various cow–calf contact (CCC) systems (Bailly-Caumette et al., 2023). CCC systems in dairy farming have gained increasing attention from multiple stakeholders and enjoy growing public support (Johanssen et al., 2024; Marin et al., 2024). Moreover, farmers implementing CCC on pasture have reported several benefits, including the expression of natural behaviours and improved growth rates (Johanssen et al., 2024).

From the perspective of behavioural needs, the period of “being a calf” can be divided into three main stages closely associated with nutritional and social behaviours: 1) the neonatal period (up to 28 days after birth), particularly the first days after birth (and even during foetal life); 2) from about one month after birth until the onset of sexual maturation, and 3) the period of sexual maturation (Table 1). The first month after birth is a particularly challenging and demanding period for both the breeder and the calf. This is primarily due to rapid environmental changes (from prenatal to neonatal conditions – especially in large-scale dairy farming) and their interaction with the calf’s limited anatomical and physiological predispositions, which also influence behavioural responses at this stage. The most important behavioural and cognitive needs in the neonatal period usually include those requiring positive responses from the environment to the calf’s imprinting (Orihuela et al., 2021); instinctive behaviours (e.g., the need to suckle the udder) (Phillips, 2008); requirements for comfort of life, including rearing conditions and nutrition (EFSA, 2023); a sense of security (in the context of gradually forming bonds with the mother cow, herd and/or humans) (Beaver et al., 2019); the development of social behaviours towards other calves (Gygax et al., 2010; Raussi et al., 2010; Duve and Jensen, 2011); and cognitive abilities, including responses to changes in routine management and housing (Wechsler and Lea, 2007; De Paula Vieira et al., 2010; Gaillard et al., 2014).

Unfortunately, despite numerous studies conducted under experimental conditions, it is difficult to define universal ranges for calves regarding their natural behavioural needs, primarily due to the complexity of environment–calf interactions (Whalin et al., 2021). Additionally, the time spent performing various behaviours is not evenly distributed throughout the day for several reasons, such as circadian rhythm, feed availability and environmental conditions (e.g., ambient temperature, light) (Pempek et al., 2017; Wagner, 2021; Doyle et al., 2024).

As a rule, when examining animal behaviour patterns in the context of ensuring their well-being, we refer to natural needs while attempting to account for the considerable individual variability that typically occurs. However, for farm animals, including calves, this can be further complicated for at least two reasons: 1) defining natural behavioural needs in domesticated animals subjected to intensive breeding, and 2) recognising that some natural behaviours may negatively affect animal well-being (Špinka, 2006; Whalin et al., 2021).

According to Whalin et al. (2021), natural behaviour is more fully expressed by cattle, including calves, in extensive living conditions on rangeland or pasture than in barns. These authors, seeking patterns of natural behaviour in Bos taurus calves due to a lack of comparable scientific studies within this species, also examined behaviours in other wild ungulates (e.g., Rangifer tarandus L., Bison bison and Bubalus bubalis). They suggest that, under practical barn-farming conditions, approaches aimed at supporting the natural lifestyle of calves primarily include nipple feeding with higher milk allowances, social housing, gradual weaning and access to grazing opportunities. From the perspective of optimising living space and supporting social needs, including play behaviour, attention should be given to the recommendations in the EFSA (2023) scientific opinion. This report advises housing calves in small, stable groups (2–7 animals), which facilitates the expression of social behaviours, enhances learning ability and promotes more positive affective states. The space available for locomotor behaviours during play depends on group size; however, the benefits of social housing are consistently emphasised (EFSA, 2023).

Physiological response of calves related to abnormal behaviour

Behaviour is a complex biological phenomenon primarily governed by the central nervous system (the brain and spinal cord) and modulated by endocrine factors. Key brain regions involved in behavioural regulation include the hypothalamus, amygdala, limbic system, basal ganglia and hippocampus (Visha and Sejian, 2023).

The ability of an organism to adapt to changing environmental conditions is a fundamental mechanism of adaptation (Mery et al., 2010; Zhang et al., 2024). This capacity allows animals to adjust their behaviour based on experience and environmental conditions (Zhang et al., 2024), but can also lead to the development of abnormal behaviours. Abnormal behaviours, including stereotypies, often function as a defence mechanism that reduces emotional arousal and modulates endocrine responses, such as cortisol secretion (Dantzer, 1991; McBride and Cuddeford, 2001), thereby altering the physiological effects of environmental adaptation and decreasing the risk of psychosomatic disorders. Stereotypic behaviours may serve as an attempt to alleviate the physiological symptoms of stress (Ursin and Eriksen, 2004; Li and Gu, 2024). However, research findings are variable. For instance, studies on horses indicate a relationship between oral stereotypies and decreased cortisol levels following their occurrence (McBride and Cuddeford, 2001). In contrast, studies on calves have not found significant differences in cortisol levels between animals displaying stereotypies and those that do not (Webb et al., 2017).

Abnormal motor behaviours are closely associated with the functioning of brain structures such as the basal ganglia, which are responsible for motor coordination (Radkowska et al., 2020). Dysfunction in these structures, particularly due to disturbances in the secretion of neurotransmitters such as dopamine, serotonin, gamma-aminobutyric acid (GABA) and opioids, plays an essential role in the development of abnormal behaviours (Harris et al., 2016; Tatemoto et al., 2022).

Opioids also contribute significantly to the development of these motor disorders by acting within the limbic system and enhancing the occurrence of repetitive behaviours (Low, 2003). Zanella et al. (1996) indicate that opioid antagonists, such as naloxone, disrupt stereotypic behaviours, supporting this hypothesis. Evidence suggests that endogenous opioids have a key regulatory role in the direct and indirect pathways of the basal ganglia, and increased inhibition of the indirect pathways may promote the occurrence of spontaneous stereotypic behaviours in animals (Hemmings et al., 2018).

Engaging in stereotypic behaviours for prolonged periods may lead to reduced physical well-being and metabolic dysfunction in animals (Roche et al., 2009). The hypothalamic-pituitary-adrenal (HPA) axis is a key system regulating the stress response (Li and Gu, 2024). Chronic stress, resulting from prolonged HPA axis activation due to factors such as inadequate housing conditions, can induce behavioural changes in calves. Under suboptimal environmental conditions, stereotypic behaviours may develop as potential coping responses to stress and frustration (Webb et al., 2017; Lyu et al., 2023).

This concept aligns with the “coping hypothesis” (Li and Gu, 2024; Jurkovich et al., 2024) and is potentially supported by a study conducted by Lyu et al. (2023). Their research, performed after regrouping calves, showed elevated cortisol levels and the occurrence of stereotypic behaviours, such as increased self-grooming frequency (Lyu et al., 2023). The emergence of stereotypies may be associated with increased cortisol levels and could function as a compensatory mechanism. However, this hypothesis is not confirmed by other studies (Webb et al., 2017; Li et al., 2024 a).

Stereotypies were historically considered a pathological outcome associated with dysfunctional activity of the dopaminergic system, resulting from excessive dopamine production or hypersensitivity of its receptors (Nakamura et al., 2000; Charlolf et al., 2001; Tatemoto et al., 2022). Elevated dopamine levels in brain structures such as the striatum often lead to hyperactivity and the manifestation of stereotypies (Nakamura et al., 2000). When dopamine levels decrease, dopaminergic neurons function linearly and impulses are transmitted via GABA, which acts on motor neurons and results in motor stereotypy (Harris et al., 2016).

Serotonin plays a similar role: its increased secretion leads to higher catecholamine levels, which can also contribute to the development of stereotypies (Binev, 2023). Cattle exhibiting stereotypic behaviours, such as tongue rolling, have elevated serotonin levels and likely experience pleasure (Binev, 2023). Additionally, serotonin levels are inversely proportional to dopamine levels (Binev, 2023), suggesting that serotonin influences stereotypies both directly and indirectly by increasing catecholamine synthesis.

A study by Sun et al. (2022) found that cows exhibiting increased tongue-rolling behaviour had elevated cortisol and norepinephrine concentrations. Catecholamine levels were positively correlated with cortisol levels (Sun et al., 2022), which can be explained by the fact that glucocorticoids, particularly steroid hormones such as cortisol, can modify behaviour in the short term while also affecting energy mobilisation in cattle (Jurkovich et al., 2024). However, prolonged stress in dairy cows can lead to inflammation, which is also associated with abnormal behaviours (Sun et al., 2022).

Non-nutritive oral behaviours (NNOBs)

Foraging behaviour is a key component of the behavioural repertoire of herbivores, including young ruminants, and provides an important reference point for assessing their behavioural needs (Miller-Cushon et al., 2015; Meagher et al., 2017; Neave et al., 2018). Calves naturally transition from dependence on milk to the consumption of solid feed, gradually expanding their feeding repertoire as they mature (Miller-Cushon et al., 2015; Neave et al., 2018). Although maternal and peer interactions can facilitate this transition (Hessle, 2009; Pullin et al., 2017), the developmental progression towards grazing is well established and typically occurs within the first weeks of life (Whalin et al., 2022; Xiao et al., 2023). Rumination behaviour stabilises by approximately six weeks of age (Peng et al., 2023), with calves spending around five hours per day ruminating (Margerison et al., 2003). Importantly, limited access to fibrous feed can lead to NNOBs such as sham rumination, whereas providing hay reduces the occurrence of these behaviours (Downey et al., 2022; Webb et al., 2014). This developmental context is relevant because restrictions in natural feeding opportunities may exacerbate NNOBs. On many dairy farms, however, calves experience limited environmental diversity, receive restricted milk diets and have an insufficient supply of fibre (e.g., hay). In general, multiple factors affect calves, and the cumulative impact of environmental limitations increases boredom and frustration.

Dairy calves exhibit abnormal repetitive behaviours (ARBs), which are inappropriate and repetitive motor patterns that occur when natural food options are limited (Downey et al., 2022; Downey and Tucker, 2023 a; Daigle et al., 2023). Young cattle show a strong motivation for foraging and using their mouths to collect food, despite some breed differences (Downey and Tucker, 2023 a). Abnormal feeding behaviours are referred to as NNOBs and are defined as oral behaviours other than feeding, drinking or milk drinking. Licking includes non-functional licking of equipment, such as bars, buckets, troughs or any other part of the pen (Peng et al., 2023). Cattle are predisposed to oral stereotypies classified as NNOBs, especially when confined and provided a concentrated diet that reduces rumination time (Ridge et al., 2020) (Table 2).

Abnormal behaviours also include tongue rolling, allogrooming, self-grooming and cross-sucking (Ridge et al., 2020; Veissier et al., 2002; Peng et al., 2023; Welk et al., 2023). Tongue play/rolling refers to the turning, rolling and unrolling of the tongue, either extended outside or inside the mouth (Peng et al., 2023). NNOBs are thought to occur in response to frustration or as a coping mechanism when the environment and/or management practices limit an animal’s ability to meet behavioural needs (Welk et al., 2023). A related category of behaviour is known as non-nutritive oral manipulation (NNOM). Among these behaviours, Downey et al. (2022) include licking, chewing or sucking directed towards a non-nutritive item (such as bars, hutch, bedding or empty bottles), excluding the calf’s own body or that of a neighbouring animal.

The time budget for individual behaviours varies by breed (Riley et al., 2023). Rumination, standing and NNOB time increase with age, while lying time decreases (Webb et al., 2012; Peng et al., 2023). Additionally, the behaviour of calves kept in hutches may vary by day, sex and time of day (Ugwu et al., 2021). Pre-weaned calves often exhibit abnormal, repetitive behaviour or behaviours that appear inappropriate when natural food intake (milk or solid feed) is limited (Garner, 2005; Horvath and Miller-Cushon, 2019 a). Calves increase NNOBs with age, particularly during weaning, with earlier weaning potentially intensifying behavioural signs of weaning stress (Horvath and Miller-Cushon, 2019 a; Eckert et al., 2015; Downey et al., 2022). However, these behaviours stabilise or even decrease in intensity as solid feed intake increases (Babu et al., 2004; Downey et al., 2022; Peng et al., 2023).

Abnormal feeding behaviour in calves is predominant during the day (Downey et al., 2022; Peng et al., 2023), although it can also occur at night (Peng et al., 2023). Behaviours such as self-grooming and tongue licking occur periodically in short bursts lasting less than five seconds (Peng et al., 2023), which complicates the practical assessment of their severity (Downey et al., 2021; Peng et al., 2023). A considerable number of stereotypies have been observed in fattening cattle, most commonly object manipulation, followed by tongue playing and manipulation of conspecifics (Schneider et al., 2019). Some studies report that only 3% of calves exhibit tongue rolling (Nielsen et al., 2008; Leruste et al., 2014), while other studies indicate tongue rolling can occur 5.5 to 10 times per six hours of observation, depending on the number of calves in the pen (Roth et al., 2009 a).

Behaviours such as NNOM are often observed in calves raised under conditions of social isolation, restricted natural feeding behaviours and a lack of appropriate environmental enrichment (Horvath et al., 2017; Leruste et al., 2014; Doyle and Miller-Cushon, 2023; Peng et al., 2023). The specific types of abnormal oral behaviours (e.g., tongue rolling, rod licking, excessive licking) may have different aetiologies (Daigle et al., 2023). The prevailing view is that these behaviours result from an unmet motivation to suck, as some decrease when calves are provided with larger milk volumes, slow-flow teats or roughage (Horvath and Miller-Cushon, 2017, 2019 a; Salter et al., 2021; Riley et al., 2023). A review by Ridge et al. (2020) indicates that ingredient type, particle size, total feed amount, feeding method or mineral supplementation influence NNOB performance. Increasing the time spent chewing may help reduce the occurrence of NNOMs (Babu et al., 2004; Peng et al., 2023), while sham chewing may serve to increase stimulation in a barren environment (Downey et al., 2022).

Hay intake reduces abnormal behaviour and stimulates rumination (Horvath and Miller-Cushon, 2017; Horvath et al., 2020; Downey and Tucker, 2023 b). Ridge et al. (2020) indicate that NNOB performance depends on the inclusion of roughage. Feeding calves hay from two weeks of age provides behavioural and performance benefits, including increased total feed intake and reductions in pen-directed sucking (Horvath et al., 2019). Some feeding methods involving the introduction of fibrous feeds, such as corn stalks, show no clear effect on reducing NNOB (Daigle et al., 2023). In general, hay supplementation from birth onward increases the occurrence of appropriate behaviours and significantly reduces oral stereotypies (Horvath and Miller-Cushon, 2017, 2019 b; Downey et al., 2022). This effect may result from increased environmental enrichment, reduced hunger or the ability to satisfy sucking motivation (Miller-Cushon et al., 2013; Zhang et al., 2021; Phillips, 2004; Downey et al., 2022). Bulk feed provides more chewing and ruminating activity due to larger, longer, stiffer and more fibrous particles compared with grain (Morrow et al., 2023; Downey et al., 2022). Feeding grass hay to milk-fed calves can improve solid feed intake and average daily gain during weaning, leading to higher body weight and fewer signs of hunger post-weaning compared with calves fed only cow’s milk (Welk et al., 2022).

Tongue protrusion can trigger tongue rolling, which is widely considered abnormal behaviour (Garner, 2005; Downey et al., 2022). Tongue rolling usually occurs after weaning, but studies indicate it can also occur before weaning (Downey et al., 2022). According to Downey et al. (2022), tongue rolling occurs in almost all calves within the first eight weeks of life but accounts for only 2.9% of the observation time. Other studies report a lower frequency of tongue rolling (Veissier et al., 2013). Tongue rolling and oral hyperactivity are signs of a compromised social environment and reflect dissatisfaction due to the inability or limited opportunity to express natural behaviours (Webb et al., 2017; Binev, 2023). In such cases, these behaviours may reflect a desire to forage. The provision of roughage before weaning can significantly influence subsequent feeding behaviour and facilitate rapid adjustment to processing novel fibrous feed, reducing neophobia towards unfamiliar feed (Castells et al., 2013; Costa et al., 2014; Morrow et al., 2023).

It has been suggested that intensively reared calves may engage in grooming behaviours to replicate the contact and stimulation they would naturally receive from maternal grooming. Licking may also provide comfort or induce a calming effect in barren or stressful environments (Downey et al., 2021). Hair licking can provide oral sensations similar to manipulating grass or hay, so calves deprived of access to feed may redirect this behaviour towards self-licking or cross-sucking. The interpretation of self-grooming is more complex and likely reflects a motivational conflict due to unmet species-specific needs (Downey et al., 2022). However, grooming is also positively correlated with tongue rolling in heifers and excessive water drinking, particularly when natural feeding behaviours are restricted (Downey et al., 2022). Allowing calves to eat hay provides more stimulation and reduces self-grooming (Downey et al., 2021, 2022). Similarly, a reduction in self-grooming was observed when calves were bottle-fed compared with bucket-fed (Pempek et al., 2013). On the other hand, access to brushes stimulates grooming and may reduce frustration (Pempek et al., 2017; Whalin et al., 2021). It was also found that calves spent more time performing NNOBs when housed individually than when pair-housed (Pempek et al., 2013).

Although cross-sucking by calves is not often classified as a stereotyped behaviour, it shares many similarities with other stereotyped oral feeding behaviours (Rushen et al., 2008). Cross-sucking is defined as sucking any part of another calf’s body. The most common sites include the ears, navel, muzzle, tail and scrotum (for bulls) or the udder (for heifers). Cross-sucking usually begins before weaning (Mason and Rushen, 2006; Vaughan et al., 2016; Salter et al., 2021). The timing is often a few minutes after milk feeding from a bucket, although this is not an absolute rule.

This behaviour is harmful in breeding practice because it has negative health and welfare consequences. When performed repeatedly over time, it is considered an ARB (Mason and Rushen, 2006; Salter et al., 2021; Downey et al., 2022; Welk et al., 2023). These behaviours result from a lack of an appropriate outlet for the calves’ motivation to suckle and are therefore considered abnormal (Jensen, 2003; Welk et al., 2023). The EFSA similarly classifies this behaviour as redirected and abnormal (EFSA, 2023). Calves deprived of feed may redirect their chewing and ruminating motivation to self-licking (Downey et al., 2022). Common consequences of cross-sucking include inflammation of the umbilicus and ears (Mahmoud et al., 2016).

Recent studies have shown the benefits of rearing calves in pairs or groups (Duve and Jensen, 2012; Costa et al., 2016; Abdelfattah et al., 2024), but these housing systems can increase cross-sucking. For example, in Jersey heifers reared in pairs, cross-sucking occurred in 13.5% of animals (Pempek et al., 2016). Other studies report frequencies ranging from 32.12% (males) to 44.15% (females) (Mahmoud et al., 2016). A high frequency (42%) of cross-sucking at weaning and separation has also been reported by Bertelsen and Jensen (2023). However, this is not universal; in small groups of three calves kept from six days to 70 days of age, cross-sucking may occur only sporadically (Abdelfattah et al., 2024).

The formation of stable cross-sucking pairs before weaning may be responsible for the persistence of this behaviour in group-housed dairy calves after weaning (Vaughan et al., 2016). Cross-sucking is also associated with age at weaning; the younger the age, the greater the severity of this behaviour (de Passillé et al., 2010). Cross-sucking may involve only one calf or occur mutually at the same time (de Passillé et al., 2011). Insufficient oral satisfaction is a key factor initiating cross-sucking in calves, which may persist and consolidate into milk-suckling behaviour in adulthood.

Some studies have shown that increased milk and energy intake can significantly reduce the incidence of non-nutritive sucking and cross-sucking (de Paula Vieira et al., 2008; de Passillé et al., 2012; Mahendran et al., 2023; Welk et al., 2023). Feeding large amounts of milk may therefore reduce cross-sucking (Hillmann et al., 2011). Additionally, animals with a positive energy balance performed cross-sucking less frequently, and the timing of cross-sucking bouts was dependent on energy balance (Roth et al., 2009 a). In general, delaying weaning for calves fed high amounts of milk replacer may be beneficial to maintain adequate growth and reduce stress during weaning (Meale et al., 2015).

Other strategies to reduce cross-sucking include avoiding open bucket feeding and using teats (de Paula Vieira et al., 2008; Salter et al., 2021; Welk et al., 2023), slowing milk flow in teats and leaving the bottle in place longer after feeding (Jung and Lidfors, 2001; Jensen and Holm, 2003), providing access to hay or chopped hay and straw (Khan et al., 2020) and implementing appropriate feeding management at weaning (Nielsen et al., 2008; Meale et al., 2015). However, de Passillé et al. (2011) suggested that cross-sucking may not be strongly affected by milk allowance or weaning and could reflect individual calf characteristics or habit formation. A scoping review on pair-housing of dairy calves found that mitigating cross-sucking is most effective when calves are provided with outlets for oral behaviour (e.g., a teat or forage), fed a sufficiently high milk allowance (≥7 L/day) and managed with a gradual weaning strategy (de Passillé et al., 2011; McKay et al., 2025; Plaugher and Cantor, 2025).

Some management solutions do not eliminate cross-sucking but redirect the repetitive behaviour to a more acceptable object, such as a rubber teat (de Passillé et al., 2011). Alternatively, allowing calves contact with their dam (Roth et al., 2009 b) or a foster cow (Margerison et al., 2003) has been shown to reduce or eliminate cross-suckling. Calves reared by their mothers generally show low levels of cross-sucking or do not display this behaviour at all (Margerison et al., 2003; Rademann et al., 2025). In CCC systems, cross-suckling is more likely to occur when contact is restricted (e.g., part-time or foster cow systems), but tends to be very low under full-time contact (Jensen et al., 2024; Rademann et al., 2025). Although partial CCC systems typically limit the occurrence of cross-sucking, these conditions can still promote its development. The effectiveness of CCC systems therefore depends not only on the duration and timing of access but also on implementing a gradual weaning strategy. It remains unclear whether reduced contact alone is sufficient to prepare calves for complete weaning and separation, and further research on gradual weaning is needed (Jensen et al., 2024).

A review of studies indicates that NNOBs are quite common in calves and are difficult to eliminate (Horvath et al., 2020; Downey et al., 2022). A recent study by Doyle et al. (2024) found that farmers perceive inappropriate oral behaviours as problematic for calf welfare, but there is limited clarity in how farmers address behavioural needs and mitigate these behaviours. Feeding milk from teats, providing hay or providing access to natural vegetation can reduce the incidence of such behaviours (Horvath et al., 2020; Downey et al., 2022). Additionally, establishing a positive human–animal relationship improves welfare and reduces fear and anxiety caused by affective states or cognitive appraisal (Lensink et al., 2000; Carulla et al., 2023). Contact with people after milk feeding significantly shortens the duration of non-food-related oral behaviours, reduces mutual sucking and increases resting time (Doyle and Miller-Cushon, 2023). The mechanisms underlying these effects are not fully understood, but human contact may serve as a form of enrichment in the calves’ rearing environment. These aspects remain poorly understood, and further research is needed in this area.

Abnormal locomotion behaviour

Abnormal locomotion in calves refers to deviations from species-typical gait patterns, activity levels and movement rhythms. These deviations may present as reduced mobility, impaired coordination, lameness, asymmetrical gait, excessive restlessness or abnormal motor responses to environmental constraints (Nickles et al., 2021; Bailly-Caumette et al., 2023; Giannetto et al., 2023). Locomotor dysfunction poses significant risks to calf health, welfare and development because movement is essential for musculoskeletal growth, behavioural expression and overall psychophysical well-being (Giannetto et al., 2023; García-Muñoz et al., 2016; Hut et al., 2021). Normal locomotion is characterised by age- and sex-specific gaits, diurnal rhythmicity and behavioural flexibility. Calves typically display higher activity levels than adult cattle and perform dynamic movements such as galloping, bucking and rapid turns, especially during play (Phillips, 2002; Bailly-Caumette et al., 2023). Abnormal locomotion arises when environmental conditions restrict movement or cause discomfort, including limited space, inappropriate flooring, lack of social contact or health issues such as diarrhoea and respiratory disease (Babu et al., 2004; Neja et al., 2017; Sadiq et al., 2017; Webb et al., 2023; Guevara-Mann et al., 2023; Juge et al., 2024).

Numerous studies have reported abnormal locomotion in calves exposed to factors such as restricted movement, inadequate space, flooring type, disease and disrupted social conditions. Genetic predisposition, age, health and personality traits contribute to variability in locomotor patterns (Carslake et al., 2022; Giannetto et al., 2023). Intensive breeding systems can induce stress, limit movement and disrupt circadian rhythms, contributing to abnormal locomotor behaviours (Giannetto et al., 2023). Locomotor activity depends heavily on circadian and seasonal rhythms, with calves being most active during morning and evening hours (Neja et al., 2017; Phillips, 2002; Johanssen et al., 2024). Reduced locomotion, atypical gait or restlessness may indicate discomfort, environmental inadequacy or illness. Conditions such as diarrhoea and respiratory disease significantly impair mobility and disrupt daily activity patterns (Guevara-Mann et al., 2023; Juge et al., 2024).

Play behaviour includes galloping, jumping, kicking, rapid turns, pushing and mounting and is considered a positive welfare indicator (Jensen, 1999; Bailly-Caumette et al., 2023; EFSA, 2023). Play declines sharply under conditions of space restriction, social isolation or uncomfortable flooring (Veissier et al., 1998; Lv et al., 2021; Vázquez-Diosdado et al., 2024). Pair or group housing supports social play, reduces stress and promotes cognitive development (Gaillard et al., 2014; Mandel et al., 2016; EFSA, 2023). Individually housed calves walk less, exhibit more abnormal postures and show fewer play behaviours (Babu et al., 2004; Neja et al., 2017). Several studies show that locomotor play spreads contagiously through a group, stabilising social dynamics and reducing fear (Größbacher et al., 2020; Lv et al., 2021; EFSA, 2023). Males engage in locomotor play and mock aggression more frequently, while younger calves perform rapid gaits such as gambolling and galloping more often (Phillips, 2002; Neja et al., 2017).

Housing conditions strongly influence locomotion. Adequate space is necessary for walking, resting and play, and larger pens or access to outdoor areas significantly increase activity levels (Barry et al., 2020; Marin et al., 2024). In contrast, conventional restricted housing suppresses locomotion, increases stress, limits social interactions and reduces behavioural diversity (Jensen, 1999; Veissier et al., 1998; Lv et al., 2021). When large pens are not feasible, providing evening access to “play pens” can support natural diurnal activity rhythms (Whalin et al., 2021). Flooring type affects gait and comfort: rubber flooring improves stride and muscular effort, while pasture access reduces lameness by providing a softer substrate that encourages exercise and resting (Sadiq et al., 2017; Webb et al., 2023). Environmental enrichment can enhance locomotion by encouraging play through fresh bedding, reflecting calves’ preference for dry sawdust over bare concrete, and by providing brushes that support grooming and may reduce frustration (Pempek et al., 2017; Sutherland et al., 2014; Whalin et al., 2021). Health management is equally important, as diseases such as diarrhoea and respiratory infections significantly reduce locomotion (Guevara-Mann et al., 2023; Juge et al., 2024). Social housing improves behavioural synchrony, reduces aggression and increases locomotor activity (Lyu et al., 2023). Housing calves with their mothers or foster cows supports behavioural development and reduces stress during weaning (Kälber and Barth, 2014). Despite its importance, abnormal locomotion remains under-documented, highlighting the need for further research linking movement disorders to environmental, health and social factors.

Procedures causing pain and altered behaviour

Pain in calves is expressed through a wide range of behavioural changes, including vocalisation, dull eyes, abnormal posture, teeth grinding, tail swishing, altered facial expressions, reluctance to move, reduced appetite and grazing, foot stamping, restlessness, neck overstretching, back hunching, belly kicking, limping and signs of depression (Relić et al., 2012; Gleerup et al., 2015; Steagall et al., 2021). These behaviours arise because pain activates behavioural, autonomic and neuroendocrine responses, functioning as adaptive mechanisms to minimise further injury. As prey animals, however, cattle often mask signs of pain, which complicates recognition and may lead to underestimation of their sensitivity (Tschoner, 2021).

Numerous studies report pain-related behavioural responses in calves during routine husbandry procedures, such as ear tagging, ear notching, nose ringing, branding, castration, disbudding and dehorning (Graf and Senn, 1999; Mirra et al., 2018; van der Saag et al., 2018; Qi et al., 2024). Calves exhibit pain, distress, anxiety and fear during these procedures, although specific behaviours vary with the type of intervention (Silva et al., 2023). Common indicators include increased forward pushing, rearing, redirected behaviours and signs of frustration (Kerr and Wood-Gush, 1987; Graf and Senn, 1999). Leaning the forehead or muzzle against conspecifics or objects is also observed as a sign of discomfort or frustration (Neja et al., 2017). During disbudding and dehorning, calves frequently display tail flicking, head shaking, kicking, ear flicking, stamping, altered feeding patterns and reduced play (Graf and Senn, 1999; Vázquez-Diosdado et al., 2024; Qi et al., 2024).

Pain in calves is assessed using both subjective and objective methods. Subjective approaches rely on the observer’s experience and include tools such as ethograms, visual analogue scales and facial grimace scales (Tschoner, 2021; Gleerup et al., 2015; Mirra et al., 2018). Objective assessments involve biomarkers, including cortisol and substance P (Coetzee et al., 2007; Heinrich et al., 2010), as well as mechanical nociceptive threshold testing, activity monitoring via accelerometers, pedometer step counts and infrared thermography of the eye (Stewart et al., 2008; Heinrich et al., 2010; Gleerup et al., 2015; O’Leary et al., 2020). Other indicators include heart rate, feed intake and body weight (Mirra et al., 2018; Tschoner, 2021). Together, these tools provide a reliable way to detect pain and its behavioural consequences in calves.

Hot-iron disbudding, in particular, induces intense acute pain lasting several hours. It produces burns and open wounds and triggers pronounced behavioural changes, including vocalisation, kicking, falling and avoidance behaviours, alongside reductions in mechanical nociceptive thresholds and increases in cortisol levels (Steagall et al., 2021). Once anaesthetic effects subside, calves often display backward locomotion, persistent head shaking, avoidance of head pressure and reduced feed intake (Graf and Senn, 1999). Some behaviours – such as ear flicking, rubbing, vocalisation and frequent changes in body position – may continue for up to 72 hours post-procedure (Steagall et al., 2021). Castration similarly reduces activity for at least 24 hours (Silva et al., 2023), while ear-tagging increases vocal calls, head movements and tail flicking, and may induce local inflammation; male calves typically produce longer vocalisations (Steagall et al., 2021; Schnaider et al., 2022).

Although pain-related behaviours differ fundamentally from abnormal repetitive behaviours, distinguishing between them is essential for the correct interpretation of calf behaviour. Acute pain can temporarily increase restlessness, redirected behaviours or oral manipulation, which may superficially resemble NNOBs. Therefore, combining behavioural observations with physiological indicators is essential for accurate pain recognition and effective intervention. The literature indicates that these acute behavioural changes are typically temporary and unlikely to result in long-term abnormal behaviours. In contrast, untreated chronic pain can contribute to persistent behavioural and physiological complications.

Conclusion

Distinguishing between “normal” and “abnormal” behaviours can be challenging in husbandry settings. Behaviours that appear typical, such as hygiene-related grooming or meeting physiological needs (e.g., drinking or chewing), may also reflect motivational conflict when animals cannot access sufficient feed. Moreover, suboptimal milk feeding, including insufficient volumes or infrequent feeding, is an important factor contributing to the development of abnormal behaviours in calves, such as cross-suckling or non-nutritive sucking. When assessing calf welfare, it is important not only to focus on individual behaviours but also to take a comprehensive view. Abnormal repetitive behaviours can signal a deterioration in welfare and are often observed in suboptimal environments. Enriching the environment and allowing calves to express a range of natural behaviours helps prevent the development of abnormal and stereotypic behaviours. Providing adequate feed according to nutritional requirements at a given age is important not only to prevent abnormal behaviour but also to support proper growth and productivity later in life. Future research into more complex feeding strategies and improved housing conditions should be pursued. There is limited data on how early symptoms of disorders affect adult health, productivity and behaviour. Integrating scientific knowledge with ethical farming practices not only promotes healthier, more resilient animals but also enhances the overall sustainability of the farming sector.