This article examines the role of olfaction in livestock farming. More specifically, it seeks to understand how farmers mobilise olfaction in support of their work and how this sensory dimension is incorporated into the different livestock management tasks they perform.

Certain aspects of olfaction have attracted attention in rural sociology and in the sociology of human–animal relationships. In addition to research on, for example, odour nuisance (Nicourt et al., 2000 ; Grannec et al., 2017), studies have examined the smell of farm animals as an indicator of poor husbandry conditions and as a socially stigmatising marker associated with livestock farmers (Porcher, 2003). However, beyond these contributions, sociological research on olfaction in farming contexts remains rare.

A small number of studies, particularly in animal science and ethology, have addressed—albeit often implicitly—the role of farmers' sense of smell in decision-making related to animal health and herd management (Schild & Rørvang, 2023 ; Poissonnet et al., 2021). To our knowledge, however, no study has provided a detailed and systematic account of this sensory dimension to date.

The specific contribution of this article is to reconsider the role of olfaction in livestock farming from the farmers' own perspective by analysing its involvement across four major categories of farming activities. The aim is to identify the different ways in which olfaction is mobilised, distinguishing between practices that rely on the farmer's own sense of smell and those that draw upon the olfactory abilities of the animals themselves. The article characterises the various forms of experiential knowledge found on farms and highlights the contribution of sensory knowledge to livestock farming practices. Because olfactory knowledge is not formally institutionalised by the organisations responsible for producing agricultural knowledge, it is generally rooted in practical and empirical experience accumulated by farmers in everyday farming situations. The article also examines how this experiential knowledge interacts with the technical and disciplinary knowledge that informs livestock management methods and practices. More broadly, the study contributes to ongoing reflection on the role of sensory perception in shaping and regulating relationships between humans and animals.

Several studies have explored the role of sensory perception in interspecific interactions. They examine how both human and animal sensory signals, together with the ways in which they are perceived, contribute to the formation, regulation and maintenance of human–animal relationships. On the one hand, analysing how humans perceive animals through the senses encourages us to reconsider animals' social status—that is, the ways in which they are perceived and represented (Doré, 2010). On the other hand, understanding how animals perceive their sensory environment provides valuable insights into their behaviour, thereby influencing the dynamics of human–animal interactions (Collin et al., 2016 ; Schneider & Bräuer, 2024). Such understanding encourages people to adapt their practices and behaviour, thereby strengthening mutual trust and cooperation (Porcher, 2002). Furthermore, this perspective opens new avenues for developing practices that are better suited to animals' sensory worlds (Tallet et al., 2020), while also promoting greater recognition and use of animals' sensory abilities in shared activities like livestock farming, as well as in more recent fields including animal-assisted interventions (Michalon, 2013).

The data analysed in this article derive from a doctoral thesis in the sociology of human–animal relationships. The data were collected during fieldwork conducted with livestock farmers in Brittany, France, and in Namur Province, Belgium. A qualitative methodology was used that combined interviews with on-farm observations. Following an exploratory stage involving livestock farmers and professionals in the agricultural and para-agricultural sectors, interviews were conducted with 24 cattle and pig farmers. The interviews were complemented by on-farm observations, some of which were participatory, thus enabling continuing interactions with the interviewees and a deeper understanding of their practices. The sample was designed to represent the principal production systems used for each species studied: dairy and beef cattle production, together with pig finishing and farrow-to-finish systems. It also reflected the diversity of farming systems by including both conventional farms and alternative production systems, i.e. organic, integrated and agroecological farming.

The first part of the article examines the different ways in which farmers use their own sense of smell to optimise their work and to address a range of farming-related challenges. It explores how olfactory perception is integrated into animal care routines and production management. The second part considers how farmers mobilise the olfactory abilities of their animals to support and facilitate their work. It examines how animal olfaction is used as a management tool in practices relating to animal docility and the regulation of intraspecies relationships.

1. Mobilising the human sense of smell for animal health and production

This section focuses on the human sense of smell. The different livestock farming activities examined here all have one feature in common: they rely exclusively on the farmer's own olfactory perception and not on that of the animals.

Although many farmers acknowledge that their senses are constantly engaged in the course of their work, they most often refer to sight, touch and hearing. However, their sense of smell also plays a significant role. The odours emitted by animals and by other biological materials (animal products and feed) provide crucial information to farmers who are able to interpret them. Through processes of detection, identification and interpretation, odours prompt farmers to respond to farming situations that may require their intervention. Most commonly, the nose serves to detect olfactory anomalies that enable farmers to recognise unusual odours or smells indicative of physical or physiological changes in their animals. Farmers also rely on their ability to establish olfactory reference points against which they can assess whether their farming activities are proceeding normally. They become familiar with recurring odours whose presence indicates a particular state of animal health or provides an indication of future production outcomes. In this way, olfactory information helps guide their decision-making.

1.1. Odours in animal care routines and health protocols

As part of their livestock management practices, farmers establish routines and health protocols to safeguard the health of their animals. These encompass every aspect of animal care, from feeding and maintaining animal housing to health monitoring and the provision of routine care. Although some farmers carry out additional inspections of their animals outside these more or less regular routines, these scheduled activities nevertheless provide privileged opportunities for monitoring herd health. The same applies to production-related tasks such as milking. Livestock farming therefore offers numerous opportunities for farmers to pay close attention to the health status of their animals.

Whether formalised or more informal, monitoring relies primarily on farmers' observation of the animals' physical condition and behaviour. Sight is undoubtedly the main sense involved, as reflected in the frequent use of expressions such as "the farmer's eye" when farmers describe how they monitor the health of their livestock. Nevertheless, some farmers also draw on their sense of smell.

Compared with vision, the use of olfaction as a tool for health monitoring occupies a much less prominent place in farmers' accounts. This observation is consistent with previous research showing that smell is often underestimated and its role poorly recognised. Indeed, olfaction is frequently subordinated to sight and hearing (Tran Bah Huy, 2000). According to some authors, this lower position in the hierarchy of the senses reflects the progressive stigmatisation of certain odours—particularly those associated with waste and working-class environments—which has contributed to the devaluation of olfaction in bourgeois culture (Corbin, 1982). Others argue that smell has been marginalised because it is assumed to offer only limited perceptual information and because odours are considered inherently difficult to describe (Candau, 2016). Nevertheless, for many farmers, smell represents a valuable source of information.

"When one of them urinates, the others come and put their heads underneath—but not to drink. (...) And they do it at any age. They're not drinking it, they're... they just put their heads under like this and end up with urine all over the tops of their heads (laughs). I think they do it to build immunity, or maybe to create a particular smell. Urine is already a marker... of immunity, of territory... (...) Cows do sometimes drink urine, but that's because they're suffering from mineral deficiency. Mine don't drink it—they just stick their heads underneath and let it run over them. Then they come over and give you a cuddle. No, honestly! (laughs). If I can smell urine on the tops of their heads, then I know they haven't been drinking it—they've just been playing in it." (Dairy farmer, alternative farming system.)

This farmer associates the smell of urine on the tops of his cows' heads with the absence of mineral deficiencies. In this case, the odour is not interpreted as an indication of an abnormality. Quite the contrary, it leads him to conclude that the urine has not been ingested but has instead been used for what he believes are immunological and territorial purposes. In his view, the presence of this odour therefore indicates that the nutritional balance within the herd is satisfactory.

This farmer was already aware of the widely held belief that urine consumption in cattle can indicate mineral deficiency. Nevertheless, it should be noted that although farmers sometimes interpret urophagia as a sign of nutritional or mineral imbalance, there is no scientific evidence to support this interpretation. The farmer's reasoning is therefore deductive: because his animals smear themselves with urine rather than drinking it, he concludes that they are not suffering from mineral deficiency. Although smelling the animals' heads is not part of his routine health checks, the repeated detection of this localised urine odour is interpreted as a positive indicator.

Before concluding that a situation requires intervention, olfactory information is most often combined with other sensory indicators.

"Yes, but she was injured, like that little bull over there. (...) The vet had to stitch her up because an artery had been severed. (...) She got her leg trapped between the feed trough and the ground and it got ripped open. (...) It was wide open—it wasn't a clean cut. So we stitched it up, but then... well... she got an infection. I could tell something wasn't right... I could smell the wound, and it smelled bad... Then she became really thin" (gesture indicating an emaciated animal) "...and she eventually couldn't even stand up anymore. At one point it got so bad that I thought we'd probably have to euthanise her." (Dairy and beef farmer, alternative farming system.)

Here, a farmer explains that one of her animals sustained an injury that required suturing, but the wound subsequently became infected, necessitating further veterinary treatment. Basic animal science and veterinary training teaches farmers to recognise several clinical signs of wound infection, including the development of a foul odour. This particular farmer, however, had received no formal training. Instead, she learned "on the job" alongside her farming parents.

She first detected the infection through smell. She described first noticing an unusual odour emanating from the wound before observing a more general deterioration in the animal's condition, including weight loss and immobility. She therefore relied on olfaction to assess the situation, while also using visual observation to confirm her diagnosis that the wound had become infected. Accustomed to the normal smells of animal bodies, she perceived the odour associated with the infected wound as abnormal, and this olfactory cue prompted her to consider the possibility of infection.

Whether used as a standalone indicator or in combination with other sensory cues, odours emitted by animal bodies are interpreted by farmers through forms of knowledge grounded in practical experience. Consequently, their ability to make use of such information depends largely on their familiarity with the characteristic smells of livestock. Ultimately, olfaction proves to be a powerful indicator of animal health, with some farmers fully integrating their sense of smell into their routine health monitoring and animal care practices.

1.2. Odours in production management

Farmers do not limit their use of olfaction to animal care. They also rely on their sense of smell to gather information that is essential for managing the production of marketable products, whether meat or milk. Production management encompasses all the tasks involved in the production of animals or animal-derived products throughout the production process. In meat production systems, this includes activities aimed at improving both the quantity and quality of production, from breeding and genetic selection strategies to the implementation of fattening programmes. In dairy production, the emphasis is placed on optimising both milk yield and milk quality. Consequently, production management also encompasses work relating to animal genetics, as well as the development of feeding strategies and milking practices designed to achieve the desired characteristics of the milk produced. As such, production management provides numerous opportunities for farmers to draw on their sense of smell.

Depending on the breed of cattle or the type of cheese being produced, milk production is sometimes regarded as particularly sensitive. Although some farmers have access to information on milk quality through automated milking systems or milk recording services, those who have developed an olfactory expertise in relation to their production place considerable value on this ability. Several of the farmers interviewed had gradually acquired, through experience, a refined capacity to interpret the olfactory cues associated with their production, and fully integrated this skill into their everyday work. Most often, these olfactory assessments are made before milking and enable farmers to prevent the production of milk they consider to be of unsatisfactory quality. The following interview illustrates how one farmer uses smell to adjust the feed ration of his animals.

"I might have to add some more straw—I don't know. Right now I think it smells quite strong. (...) Yes, I'll add a bit more straw because this mix smells really, really strong. And honestly, I'm always worried about the taste of the milk... (...) Because they're going to be eating this feed all the time, so it really has to be right... (...) I'm glad I did it, because as soon as I walked out I could already smell that... it wouldn't have been right... you can smell it from here... (...) That's really what stresses me now... that's the most stressful part, because once it starts... if the milk turns out bad, that's a real problem." (Dairy farmer, alternative farming system.)

This farmer is able to recognise, by smell alone, a feed ration likely to produce what he describes as "bad" milk. He characterises the odour simply as "strong", without qualifying it further. According to several farmers, "bad" milk has a bitter and acrid taste, which can be corrected by adding straw to the ration in order to produce milk of acceptable quality1.

Through experience, this farmer has learned to assess the feed ration so as to ensure that all the milk produced can be used in his on-farm processing enterprise. The smell of the feed ration therefore functions as an indicator of the expected quality of the final product.

Farmers also rely on other olfactory cues that help monitor the quality of dairy production. These, too, are detected before milking and may originate from the animals themselves.

"I rely enormously on my sense of smell. (...) You'll laugh at me, but even the smell of the [animals'] burps tells me something. It gives me an idea of what the milk is going to taste like. If they smell really, really strong... if their burps smell too strong, then the milk will have a very strong flavour. Mind you... a [cow's] burp always smells bad, but there are different degrees." (laughs) "(...) The good thing is that I've got the calves right opposite, so..." (Dairy farmer, alternative farming system.)

Some farmers therefore rely on the smell of the gases emitted by their animals to anticipate the quality of the milk they are about to produce. If the animals' belches suggest that the milk may be of poor quality, the farmer becomes especially vigilant. After tasting the milk when milking has been completed, he decides whether it is suitable for storage in the bulk tank or should instead be fed to the calves. Unlike the previous example concerning the feed ration, the olfactory cue is not the only indicator on which the farmer bases his decision. It nevertheless constitutes the principal indicator and serves as the first warning signal. Through experience, the farmer has developed genuine expertise in interpreting the smell of his animals' belches, becoming capable of distinguishing subtle differences in their intensity and anticipating their consequences for milk quality.

Olfaction thus constitutes a major indicator in ensuring product quality. Whether the relevant odours originate from the animals or the feed, olfactory assessment before production provides farmers with an important means of monitoring and controlling the quality of their output.

2. Mobilising Animal Olfaction as a Means of Social and Relational Regulation

Whereas the preceding section focused on the use of the human sense of smell to support livestock management, this section is devoted specifically to the use of animals' olfactory abilities. The focus therefore shifts from the act of smelling to that of making use of the animals’ sense of smell—an approach based on animals' capacity to detect olfactory information and respond to it in specific ways.

Although odours continue to be instrumentalised in the service of livestock management, the underlying logic differs from that described above. The emphasis is no longer on experiential knowledge derived from the farmer's detection and interpretation of odours. Instead, it concerns empirical knowledge based on the observation and interpretation of animal behaviours elicited by the odours to which animals are exposed. Consequently, the farmer's analysis no longer relies on olfactory information perceived directly, but rather on the interpretation of the behavioural responses that those odours trigger in the animals.

Furthermore, odours are no longer simply by-products of farming situations. Depending on the context, they are deliberately introduced or generated to encourage animals to behave in ways that agree with the farmer's objectives. Acting as genuine catalysts of animal behaviour, odours become a management tool through which farmers can influence both interspecific and intraspecific relationships within the farm. Rather than functioning solely as indicators, they become active triggers capable of addressing a variety of relational challenges.

2.1. Odours in the cultivation of docility

Farmers also draw on their animals' sense of smell to establish relationships with them, thereby contributing to what can be described as the cultivation of docility within the herd. This process, whether formalised or informal, is undertaken to encourage interactions between farmers and their animals. Its principal objective is to reduce animals' fear of humans while encouraging them to accept handling, thereby facilitating everyday livestock management. Here, handling refers to all procedures that require physical intervention with the animals, including veterinary care, moving the animals around and other routine operations. As with the health routines discussed earlier, the cultivation of docility may involve dedicated sessions or may be incorporated into the different tasks farmers perform with their animals each day. Several of the farmers interviewed described deliberately incorporating animals' sense of smell into this process as a means of fostering familiarity and trust.

"...when they first arrive on the farm, during quarantine, you've got to spend time with them so they learn your smell, so they realise you're not only there to vaccinate them or things like that. (...) I don't need to stay in each pen for half an hour—three, four or five minutes is enough. I squat down in the middle of the pen and just let them come to me. (...) You mustn't move; you just sit there. That's what I do—I sit in the middle of the pen, keep still, and let them come. (...) They'll always come over, they'll smell you, then they'll give you little nudges with their snouts to see how you react. (...) Little by little they'll get used to your smell. So I do that whenever I've got the time—as often as I can. (...) And I enjoy it as well. I stroke them, they come over and smell me, and I really like that..." (Pig farmer, farrow-to-finish system, conventional farming.)

This farmer describes how he begins the process of cultivating docility with newly arrived gilts2.

He routinely incorporates periods during which he allows the animals to smell him freely, thereby enabling them to express their natural investigatory sniffing behaviour. It is primarily through olfaction that this pig farmer seeks to earn his animals' trust. This constitutes the first stage in a process that may eventually allow physical contact such as stroking, and above all, the technical handling required in everyday farming. Sniffing therefore occupies a central place both in the animals' integration into the farm environment and in the relationship established between farmer and animal.

The farmer thus makes strategic use of the animals' sense of smell by deliberately creating situations that encourage sniffing behaviour and thereby promote the development of the human–animal relationship. By allowing himself to be smelled, he elicits behavioural responses that make the animals more willing to accept close physical contact with their stockperson.

However, beyond fostering familiarity, olfaction also helps prevent behaviours that may place the farmer at risk.

"Here" (showing his torch), "I switched the torch on quite early as I was walking over because it's one of the things that tells them I'm coming. Before the last bend, as soon as they can see the light, I switch it on. It's one of the ways... some of them can detect me from quite a distance. My smell, the dog's smell, the sounds, talking to the dog, even talking to myself... all of that is part of it. I try to let them know I'm coming as soon as possible." (Dairy farmer, alternative farming system.)

This farmer describes the precautions he takes when fetching his cows for milking. Still affected by a recent attack from one of his animals, he considers entering the field in darkness, particularly during the calving season, to be a potentially hazardous situation. He consequently seeks to make his presence known as early as possible. To achieve this, he relies not only on his visibility but also on the animals' hearing and sense of smell, allowing them to detect his approach well in advance. Once again, olfaction is not the only sensory modality involved, but is nevertheless an important element of the strategy.

Whether used to foster familiarity or to regulate potentially dangerous behaviours, it is the farmer's own body odour that the animals detect and that the farmer deliberately incorporates into the relationship.

Animal olfaction is therefore regarded by farmers as a genuine tool for managing relationships within the farming environment. They make use of their animals' olfactory abilities to establish, maintain and pacify their interactions with them, thereby facilitating the everyday practice of livestock farming.

2.2. Odours in the stabilisation of intraspecific relationships

Animal olfaction is not only used to improve the relationship between farmers and their animals. It may also be used to establish, maintain and pacify relationships between animals of the same species.

Farmers play a key role in regulating the social dynamics of their herds. This aspect of livestock management consists of creating conditions in which intraspecific relationships can develop and evolve in a stable and harmonious way. Its objective is to maintain an optimal social balance by minimising conflict, respecting the group's natural hierarchy and promoting peaceful interactions, thereby preventing agonistic behaviours that may compromise the animals' physical and psychological well-being. This involves a range of management practices, including the gradual introduction of new animals, continuous monitoring of behaviour and the equitable distribution of resources in order to minimise competition. In addressing these challenges, some farmers also make use of their animals' sense of smell.

For example, farmers may rely on animals' olfactory abilities to stabilise newly formed social groupings. This may involve allowing foster cows and newly orphaned calves time to sniff one another in order to encourage maternal acceptance and ensure that the calf is adopted and suckled by its surrogate mother. It may also involve supporting animals through the loss of herd companions.

"The first thing I looked at wasn't calf separation—it was grief, when an animal dies or has to be euthanised. I'd noticed that if I left the animal in the middle of the herd... whenever it was possible, because we've got a lot of people passing by here and I don't like leaving a carcass where the public can see it... but if I leave the animal there, especially a dead calf, a stillborn calf, or even a cow that was well integrated into the herd, if I leave it there for a day or two so the others can come over, smell it, take their time..." (Dairy farmer, alternative farming system.)

This farmer explains that, whenever circumstances permit, he allows his animals to "grieve" by giving them access to the body of the deceased animal. He has observed that when the carcass remains with the herd, the other animals approach and smell it, which, in his view, enables them to cope better with the separation. According to the farmer, this practice noticeably reduces the stress that such losses normally generate within the herd. He bases this conclusion not only on observations of animal behaviour but also on changes in milk production, noting that the loss of an animal without this opportunity for sniffing is consistently followed by a decline in production.

Although this issue does not yet appear to have received attention in animal or agricultural sciences, several farmers interviewed reported making the same observation, once again attributing a central role to olfaction as a catalyst of animal behaviour: "They'll come over and smell it, and then after about three days... that's it. It's over." (Dairy farmer, alternative farming system.)

Animal olfaction is therefore fully integrated into the management of relationships within the herd. In the previous example, the farmer made use of a naturally occurring biological odour without altering it. In other situations, however, farmers deliberately introduce particular odours in order to influence relationships between animals. They may exploit odours that, through experience, they have found to reduce conflict and lessen the effects of social hierarchy.

"When we mix groups, we use vinegar to mask the smells. Honestly, it's a brilliant product—it costs next to nothing and it works really, really well. (...) I sprayed every one of them with vinegar. (...) We just took a bottle of white vinegar, punched a few holes in the top and sprayed them all. (...) When they get bitten it stings a bit, of course, but because they all end up smelling the same... (...) it stops... because with pigs—I don't know if you've ever seen it—but if you mix groups, they'll fight to the death. Doing this really helps... We've even mixed older animals this way..." (Pig finisher, conventional farming system.)

Farmers may therefore use products with odour-masking properties to stabilise social relationships within groups of animals. By disrupting the animals' olfactory recognition processes, these introduced odours promote the establishment of more peaceful social interactions and thereby reduce injuries resulting from aggressive encounters. In effect, farmers create a shared olfactory identity that helps pacify relationships, particularly in situations known to present a high risk of conflict, such as mixing animals that have previously been housed in separate groups. Vinegar is one option, although commercially available odour-masking products are also used for the same purpose.

Because the social organisation of animal groups can have significant consequences for livestock management while remaining only partially controllable by farmers, for some farmers, the strategic use of animal olfaction represents an important means of influencing and managing their everyday work.

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As this study has shown, olfaction plays an important role in livestock farmers' practices, being mobilised in a variety of ways for livestock management. The sense of smell constitutes a valuable everyday resource, enabling farmers not only to monitor the health of their animals but also to optimise production management and to regulate both human–animal and animal–animal relationships. The use of olfaction in livestock farming is grounded primarily in experience acquired over the course of farmers' careers, giving rise to forms of knowledge rooted in practice.

The functions performed by odours differ depending on whether they engage the human’s or the animal’s sense of smell. They may act as indicators, signalling relevant information, or as triggers, eliciting specific behavioural responses. As such, odours serve as indicators of animal health, production quality and social relationships. Although they may occasionally be used in isolation, they are usually interpreted in conjunction with other sensory cues. Olfaction therefore constitutes an important, albeit complementary, source of information that helps farmers confirm and refine their assessments. The odours mobilised by farmers in the course of their different livestock management activities may be natural, arising spontaneously within the farming environment, or deliberately created or introduced for specific purposes.

Experiential agricultural knowledge sometimes converges with findings from scientific research presented in educational manuals, training materials and advisory documentation intended for current and future livestock farmers. As discussed above, certain animal health training programmes encourage farmers to use their sense of smell to detect infections. Farmers may likewise be advised to allow periods of sniffing between young animals and foster mothers to facilitate adoption, or to employ techniques such as the "pyjama technique", particularly in sheep and goat farming3.

It is difficult to determine whether farming practices derive primarily from academic and disciplinary knowledge transmitted through initial and continuing education, or whether they are mainly the product of farmers' own experience (Petit, 2018). Yet within the dialectical relationships through which the knowledge of farmers, researchers and other agricultural and para-agricultural actors interacts, hybridises and is co-constructed (Compagnone et al., 2018), sensory practices appear, more often than not, to stem from practical and empirical forms of knowledge developed by farmers themselves.

The attention these farmers devote to mobilising their senses in their everyday work may perhaps be interpreted as an attempt to reclaim agency and control over agricultural practice. Reliance on forms of knowledge that are only weakly institutionalised—or not institutionalised at all—and that are not formally legitimised by agricultural organisations and institutions is sometimes viewed as a way of distancing oneself from the scientific and agronomic knowledge that has largely shaped agricultural development since the mid-twentieth century (Nizet, 2019). Because the knowledge considered here is sensory in nature, it arguably reflects this process even more clearly. The senses, as faculties refined only through daily practice and repeated experience, can emerge principally through the accumulated practical experience of livestock farmers (Bouillet, 1997).