France bans the trimming of whiskers

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Vibrissae on the muzzle :: Photo © Astrid Appels

Vibrissae on the muzzle
Photo © Astrid Appels
The French Equestrian Federation (FFE) has followed the example of Germany and Switzerland and banned the trimming of whiskers for horses and ponies competing at FFE endorsed events.

In Germany the trimming of whiskers and ears is prohibited by the German Animal Welfare Law. It states that it does not allow "the trimming the vibrissae around eyes and muzzle as well as clipping or cutting the hairs inside the ears of horses are prohibited." Competitors can be fined if their horses are found unlawfully trimmed or clipped.

France is now following suit. In its 2019 updated version of their general competition rules it has included this stance in section 1.5. titled "The battle against violations on the welfare of ponies and horses"

"Abuse can be defined as intentionally or unintentionally inflicting unnecessary suffering or discomfort to a pony / horse" by "depriving the ponies / horses of their vibrissae, the tactile hairs around the eyes, nose and muzzle." The French rule does not include cutting out the hairs from the horse's ears.

The FFE further considers abuse: the excessive beating of a horse; applying electric shock to a horse; using the whip excessively; giving a blow to the horse's mouth by yanking the bit; compete an exhausted, lame, sick or injured horse; abnormally sensitizing or desensitizing a body part; leaving the horse without food, weather or sufficient work; or using a device and tool that causes excessive pain to a horse when it jumps a pole.

When any type of this abuse is noticed, the president of the ground jury can eliminate the rider. The FFE and Disciplinary committee can impose additional sanctions.

The horse’s vibrissae are often trimmed for cosmetic purposes. However those hairs are critical to a horse's spatial awareness. They alert the horse for objects immediately in front of its eyes of or below its nose. Whiskers guide the horse's muzzle toward edible food and away from other objects. The whiskers near their eyes warn them from bumping into obstacles.

 
Most of the studies into whisker removal have been conducted using rats. The indicate behavioural and emotional changes caused by whisker removal because whiskers serve an important function in sensoro - spatial orientation.

Discussion
In this study, we found that whisker trimming for 10 days after birth caused long-lasting dysfunction of whisker-dependent tactile perception as revealed by the gap-crossing test (Fig 1A), as well as abnormalities in social-related behaviors such as social interaction and social dominance (Fig 1B). Furthermore, neonatal whisker trimming severely affected the development of amygdala circuitry related to fear/anxiety processing as shown by altered c-Fos expression patterns following the height stress compared with that in controls (Fig 2). In contrast, whisker trimming did not alter amygdala circuits related to reward processing as revealed by unchanged c-Fos expression patterns compared with that in controls following whisker-dependent cued training in the radial maze task (Fig 3). These results indicated that the neonatal suppression of tactile perception and experience due to whisker trimming impair the development of emotional systems, leading to long-lasting changes in social behavior.

To what extent did neonatal whisker trimming affect the development of whisker-dependent tactile perception and cognitive systems? In the gap-crossing task, the mean maximum gap distance was only 2.0 cm for the BWT10 mice. For successful gap crossing, mice must decide whether they are able to cross the gap based of whisker information; however, at such short distances, the mice can find the target platform by touching it with their nose as well as with their whiskers [42]. Thus, BWT10 mice may have severe difficulties perceiving the gap distance and/or the shape of the target platform using their whiskers. On the other hand, BWT10 mice could learn the radial maze tactile-cued task with their whiskers, whereas normal adult mice failed to learn this maze task when all whiskers were trimmed prior to the first daily trial and once every three trials thereafter (Soumiya et al., unpublished data). Furthermore, S1BF neuronal activity as estimated by the number of c-Fos-positive cells was significantly upregulated after the 12 daily trials in BWT10 mice but to a significantly lesser degree than that in the control mice. These results suggest that limited sensory processing is sufficient for BWT10 mice to learn the net-guided radial maze task but not the gap-crossing test. Thus, the most plausible explanation is that BWT10 mice lose higher-order sensory and/or sensory-motor integration for whisker-dependent tactile perception. Indeed, it has been suggested that the integration of sensory and motor information is required for learning the gap-crossing test because the information for performance is derived from individual whiskers moving and touching objects synchronically or independently [4345].

Whisker-dependent tactile perception is also important for the social behavior of mice. Adult mice that had their whiskers trimmed immediately prior to testing exhibited reduced aggressive social behaviors against strangers or intruders [6, 46]. Similarly, adult mice with whiskers plucked prior to the test showed no preference for the social chamber in the three-chamber social interaction test (S1 Fig). In the case of mice subjected to whisker trimming as neonates, preference for the social chamber was maintained only in those subjected to bilateral whisker trimming for just 3 days after birth (BWT3) (S2A Fig), whereas the BWT10 mice showed no preference for the social chamber, although their whiskers had fully regrown by the time of testing. Moreover, the BWT10 mice showed social dominancy against controls, while the BWT3 mice did not (Figs 1 and S2B). Similar observations were previously reported in laboratory rats, subjected to whisker trimming during P0–P3 [22]. The difference between the BWT10 and BWT3 mice could result from the duration of sensory deprivation and concomitant effects on neural circuit development. Although there may be multiple causes underlying these abnormalities in BWT10 mouse social behavior, we suggest that impaired neonatal tactile experience and social interaction induces stress that may disrupt the development of emotional systems. This hypothesis is strongly supported by the greater neuronal activation in the amygdala/PVN induced by height stress in the BWT10 mice than in the control mice (Fig 2). Furthermore, social isolation from the dam in the early postnatal period causes emotional dysfunction and abnormalities in social behaviors later in life as well as impaired whisker perception [3338].
Amygdala circuits play key roles in processing different information related to fear/anxiety and rewarding/aversive outcomes, which in turn modulate sensory perception, memory formation, and social behavior [47]. Each neuronal system within the amygdala comprises distinct neuronal subtypes within amygdala and could activate individually. Indeed, some amygdala neurons excited by aversive cue never respond to a reward cue during associative learning in the rat amygdala [48]. Comparing to the relative control, neurons in the amygdala of the BWT10 mice were found to be hyper-reactive against the height-stress but respond normally for the reward processing in the radial maze task (Figs 2B and 5B). These data indicated that the fear/anxiety-related circuit would be more vulnerability against neonatal whisker trimming than the reward relation in the amygdala.

Tactile defensiveness, defined as extreme sensitivity or aversive responsiveness to touch that would be benign to most people (e.g., light touch or clothing texture) is a common feature of neurodevelopmental disorders such as ASD and fragile X syndrome [4951]. The tactile perception system is the earliest to develop among sensory systems. During infancy and early childhood, tactile perception provides important information from the outside world and an opportunity for environmental interactions, particularly with the mother [1]. Therefore, genetic and environmental causes of tactile defensiveness and not only neonatal whisker trimming are likely to impair attachment formation, an early primitive social behavior. Further studies are necessary to elucidate the molecular mechanisms underlying the abnormal development of sensory and emotional circuits caused by neonatal whisker trimming; however, we believe that such studies will have important implications for understanding the pathogenesis of neurodevelopmental disorders.

 
Overview of research into whisker removal. Whiskers are also called 'vibrissae'.

[...]
A literature search was undertaken to determine what is known of the functions of vibrissae, organs that humans and most other primates do not possess, but which are universal in the carnivores and several other mammalian orders. Unfortunately, definitive research on the functions of these organs in common domesticated animals appears to be lacking, although many interesting speculations exist. As might be expected, we know considerably more about their functions in the familiar laboratory rodents. Therefore, in the following paragraphs I cite some of the research findings for rodents and certain other species, followed by presumptive evidence as to the importance of these organs in species as yet unstudied, particularly the dog.

Behavioral and neural approaches to the functions of the vibrissae have been summarized in an excellent review article [Psycho/ Bull 84:477, 1977). Amputation of vibrissae in rats affects locomotor activity, depth perception, swimming ability, shock-induced fighting, emotionality, tactile maze learning, equilibrium, and discrimination of surfaces. Removal of the vibrissae lowers general activity level in cats. The vibrissae of seals are sensitive to vibrations from 50 to 1000 Hz, and it is thought that the animals use these organs to detect prey in dark waters UZoo/ 188:443, 1979).

The length of the vibrissae appears to be correlated with the ecology of the animals. Burrowing mice have vibrissae that are shorter than arboreal species. Among carnivores, the vibrissae of bears are considerably shorter than those of the hunting canines and felines. It is also interesting to note that whales, having forsaken the land for an aquatic environment, lost all body hair except the vibrissae.

While firm evidence of the importance of these organs in dogs is lacking, there is presumptive evidence of their potential significance:

1. The very ubiquity of vibrissae in carnivores suggests important sensory functions. Evolutionary theorists agree that nature is conservative and does not expend energy on the maintenance of useless organs.

2. Vibrissae are constructed differently and are much more heavily innervated than other body hair.

3. The vibrissae in dogs are served by the largest of the twelve pairs of cranial nerves.

4. It is generally recognized that the amount of sensory cerebral cortex devoted to a particular body area is in direct proportion to the importance of that area in the sensory world of the animal. In plotting the sensory areas of the cerebral cortex of the dog it has been determined that "face representation clearly accounts for at least50 percent of somatic area 1 and for a third or more of somatic area 2" UNeurophysio/19:485, 1956). The upper jaw occupies a disproportionately large amount of the face area.
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