Animal cognition is a branch of psychology that has not traditionally been considered extensively on farms. It is defined as: ‘all ways in which animals take in information through the senses, process, retain and decide to act on it’ (Shettleworth, 2001: p.277). There is a suggestion that domestication could have led to decreased cognitive abilities in livestock because of reduced brain sizes (Briefer et al, 2014), especially because the domestic environment does not offer the same dynamic environment found in the wild. However, intelligence in animals is difficult to directly observe (Pearce, 2008), and it can be perceived that livestock species are not as complex as other species under human care, perhaps because of how we view their purpose. For example, research from a college in the United States of America as recently as 2005 showed that some veterinary students believed that dogs and cats have more complex cognitive capabilities than livestock species (Levine et al, 2005). This perception may have altered in recent times, but it highlights how production animals have been perceived differently to companion animals in terms of their capabilities. However, it is now known that stimulating the minds of farm animals is an important welfare consideration, and suitable environmental enrichment should be provided to stimulate a positive behavioural response that directly relates to their cognitive capabilities (for review see Bolt and George, 2019). This review summarises the literature on farm animal cognition and provides an overview of specific methods of providing cognitive stimuli for pigs, cattle, sheep and goats, with the goal of minimising stress, promoting positive welfare and increasing productivity through such practices.
Farm animal cognition
The cognitive ability of farm animals has been studied with increasing prevalence and it has become evident that many species have more complex abilities than previously thought (Nawroth et al, 2019). It is difficult to determine whether different domestic species have comparable levels of consciousness and self-awareness, or if they possess such phenomena at all, but it has become clear that domestic farm animals need to be stimulated in their environment to satisfy their needs and reduce boredom and stress (Nawroth and Langbein, 2017). There can be indirect effects on production if cognition is not addressed because it is associated with welfare, and neglecting it can also have direct effects such as triggering aggressive encounters between individuals, as evidenced in pigs (Held et al, 2002). Therefore, enrichment and adequate housing provision linked to the cognitive ability of farm animals is an important tool to use to minimise abnormal and undesirable behaviours (Panchbhai and Thakur, 2016).
Abnormal and undesirable behaviours exhibited by livestock
Good welfare is associated with the display of positive species-specific behaviours by farm animals, but abnormal and undesirable behaviours can arise, especially when conditions are sub-optimal and do not stimulate animals. Stereotypies are a form of abnormal behaviour that are defined as repetitive actions that have no obvious end goal and they occur as a coping strategy by animals in inadequate environments (Mason, 1991). Livestock are particularly susceptible to oral stereotypies, such as sham chewing in pigs (Tatemoto et al, 2019), non-nutritive cross-sucking in cattle (de Passillé et al, 2011), wool-biting in sheep (Lauber et al, 2012) and self-sucking in goats (Battini et al, 2014). Undesirable behaviours may also arise on farm such as aggression with conspecifics (e.g. tail biting in pigs). These abnormal and undesirable behaviours usually occur if animals are not stimulated in their environment with enrichment based on the five main categories (social, occupational, physical, nutritional, and sensory) outlined by Young (2003). Occupational enrichment involves a provision related to cognition and it is an important aspect of providing an adequate environment for animals. It is often combined with other forms of enrichment to occupy an animal's time and reduce boredom and it is likely to provide animals with more stimulation and enhanced control of their environment, which is specifically linked to their cognitive abilities (Mandel et al, 2016). Adopting this approach is likely to reduce the development of abnormal and undesirable behaviours (Sonoda et al, 2013; Panchbhai and Thakur, 2016). It is therefore important to understand the cognitive abilities of domestic species on farms to promote species-typical behaviours.
Domestic pig cognition
It has been suggested that domestic pigs may have the capacity for cognitive complexity because they have a large brain that is well-developed and it appears to have some similarities with the human brain (Jelsing et al, 2006; Gieling et al, 2011). Pigs have social and spatial memory that can be negatively influenced by typical management practices that occur on farm, such as being confronted with unfamiliar situations or housing (Held et al, 2002). Play behaviour is often deemed as an indicator of complex cognitive abilities, and pigs exhibit this behaviour with conspecifics (Marino and Colvin, 2015). This highlights the importance of social buffering in pigs to ensure they are stimulated and exhibit normal behaviour (Figure 1). However, they can also be aggressive with one another and tail-biting is a common issue on commercial enterprises. Providing the correct litter material may reduce the incidence of this undesirable behaviour (Lahrmann et al, 2018), with previous research suggesting that the most appropriate substrates for pigs should be changeable, complex and destructible to satisfy natural exploratory behaviour, and it should also contain edible parts that are distributed sparsely for pigs to root for (Studnitz et al, 2007).
It has been questioned whether auditory stimuli such as music can elicit positive behavioural responses in pigs, and whether individuals can recognise different types of music. de Jonge et al (2008) found that music can stimulate play behaviour and result in less injuries in post-weaned pigs, and Li et al (2019) suggested that the tempo of music is the main factor that can cause a response in some observed behaviours of piglets, with fast tempo music eliciting increased walking, tail-wagging and standing behaviours in comparison to music that is played at a slower tempo. Therefore, music may be a beneficial addition to husbandry routines to stimulate positive behaviours in pigs, and it is a cost-effective technique that can be changed regularly.
Domestic cattle cognition
Cows can learn quickly, and exhibit long-term memory capabilities (Marino and Allen, 2017), but this cognitive development may be inhibited during the early stages of life without the influence of social contact with other calves (Horvath and Miller-Cushon, 2020). There is evidence to suggest that individual housing at a young age has a direct influence on cognitive impairment, which has been shown in cognitive tests and novel object recognition experiments (Gaillard et al, 2014). It has also been discovered that pair-reared calves (Figure 2) will find the location of feed quicker than those reared individually when they are re-grouped at weaning, which suggests more flexibility in modifying their behaviour after being socially housed (Vieira et al, 2010). The impairment of cognitive development and learning is a potential welfare issue, and it is apparent that calves housed individually are more likely to be fearful in novel situations than their socially housed counterparts (Costa et al, 2016). This could make it more difficult to implement changes on farms without eliciting a stress response in these individuals, and resilience of farm animals is a key aspect to consider when managing livestock (Colditz and Hine, 2016). Such evidence highlights how important socialisation is in relation to cognition in cattle.
According to Meagher et al (2020) heifers are motivated to learn when provided with a range of learning opportunities, and it has been shown by Hagen and Broom (2004) that individuals can have an emotional response, including more energetic locomotion, after improving their performance during learning tasks related to food stimuli. Allowing cattle to have control over their own environment may also benefit them and elicit a positive response. For example, there is recent evidence to suggest that domestic cattle adopt contrafreeloading where individuals work to obtain additional food even though it is readily available or already present in their main diet (Van Os et al, 2018), and they have also been shown to find pasture access rewarding, which may lead to improved emotional states (Crump et al, 2021). Therefore, providing individuals with the opportunity to choose how they forage may reduce stress in cattle, although this does have to be balanced with their dietary needs.
Domestic sheep and goat cognition
Evidence of the cognitive abilities of sheep has recently been investigated to understand complexities of cognitive mechanisms, sociality, and individuality (Marino and Merskin, 2019). Horback (2019) argued that although the evidence recently reviewed by Marino and Merskin contains valid points, it does not offer a clear application for sheep as production animals. It is clear that more research is needed to innovate appropriate provisions in a commercial setting, but it is an interesting and potentially important area to consider in terms of welfare, especially as sheep have not traditionally been viewed as intelligent animals. This is especially pertinent because it is believed that sheep may have relatively complex social cognition capabilities and can recognise conspecifics and humans for a number of years, which means that their social environment needs to be appropriately considered on farm (Kendrick, 2008).
Goats also exhibit complex cognitive abilities, can learn quickly and appear to have good long-term memories, although they do not appear to learn through social learning (Briefer et al, 2014). There is also evidence to suggest that personality traits of goats are linked to how individuals perform in various cognitive tasks (Nawroth et al, 2017), so having a comprehensive understanding of the behaviour of individuals will be beneficial. Stockmanship is likely to be a key aspect of reducing stress in goats, with evidence suggesting that individuals are less vocal and agitated in the presence of familiar stockpersons (Boivin et al, 2003), and they also interact for longer periods with people who adopt positive facial expressions (Nawroth et al, 2018). It is not always practically possible to maintain the same staffing on farm to preserve stability for livestock such as goats, but the relationship between humans and animals is a key consideration, and it is important that farm staff adopt a positive attitude when managing these animals to maintain a high level of welfare (Figure 3).
Goats, like cattle, have also been known to exhibit contrafree-loading and will actively work for food by sliding doors open to retrieve forage even when it is readily available through open doors (Rosenberger et al, 2020). This highlights the need for providing stimulating environments for animals such as goats, but Zobel and Nawroth (2020) noted that there is currently very little enrichment in place for supporting the cognitive capability of goats on commercial enterprises. The authors concluded that there should be variable diets and delivery methods, and individuals should have a choice in relation to their social companions, milking schedule, and feeding provision (Zobel and Nawroth, 2020).
Summary
Based on the evidence in this review, it is apparent that pigs, cattle, sheep, and goats have complex cognitive abilities, which means that they can become stressed if certain provisions are not met. This will have implications for their health and welfare and can reduce productivity. Therefore, enrichment is an important provision in their environments.
It is advisable that pig farmers should provide complex substrates where possible, such as straw or woodchip (Figure 4), to stimulate the minds of pigs because of their need to carry out natural rooting behaviour. This will reduce the likelihood of pigs adopting abnormal behaviours. Social buffering will also help to reduce stress, but behaviours should be monitored to assess if stress is developing as a result of interactions in the social group.
It has been identified in this review that sociality is key for cattle, and social stress is a common stressor that may be an issue when cows change groups. Suitable groupings can be assessed using a modern technique called Social Network Analysis (George and Bolt, 2020). It is advisable that cattle are housed with familiar individuals where possible to reduce stress and promote positive health, and careful consideration is needed when integrating new individuals into the herd. Providing cattle with choice of how they forage will also be beneficial, because lack of control can be a stressor for animals.
The evidence in this review suggests that good stockmanship is important for sheep and goats. Poor stockmanship is a stressor, and some individuals may be more prone to stress than others in the flock or herd, especially if they are handled roughly. Efforts should be made to monitor groups of sheep and goats to identify if individuals are showing a change in their normal behaviour, which may indicate that they are being affected by chronic stress. This approach is challenging in larger groups, but it is likely to promote better welfare on farm. Additionally, goats are likely to benefit from complex delivery methods of food, such as puzzle feeders, which will stimulate their minds.
Conclusion
Farm animals have complex cognitive abilities, which means that this should be considered when managing and housing them on farm. Although further evidence is required to understand the full complexities of the cognitive abilities of livestock, it is likely to become an increasingly important factor in the future. Stimulating animals by providing adequate housing and enrichment will benefit them and allow them to exhibit normal species-specific behaviours, thus reducing stereotypes. This approach is likely to benefit animal welfare in commercial enterprises and, consequently, has the potential to enhance productivity.
KEY POINTS
- Evidence suggests that farm animals have complex cognitive abilities that should be considered on commercial enterprises.
- Enrichment can be used to stimulate species-specific behaviours related to cognition.
- Providing adequate conditions and suitable enrichment to stimulate the minds of animals can encourage normal behaviour.
- Providing stimulating environments can reduce abnormal behaviours such as stereotypies.
- Further evidence is required to understand the full complexities of the cognitive abilities of farm animals, but it is likely to become an increasingly important factor to consider on farm.