The use of pheromones is well known in agriculture to keep some insects away from plants. The so-called pheromonal communication is very strong in this Order. Social life and species recognition are triggered by the emission of the right pheromones. That is why the term of pheromone (from Greek “pheros” meaning far and “horman” meaning to excite) was used, because emitted in a very small amount, pheromones launch from a distance a precise behavior in the animals of the same species. Chemical communication can also involve kairomones and allomones and odors or scents that allow inter-specific, inter-order and sometimes inter-kingdom (e.g., between plants and insects) communication.
In mammals, pheromones have been supposed for a long time to be very active in sexual communication but the difficulty has always been to isolate the effective molecule. Starting with the same ideas as in insects, it could seem impossible to identify in the huge amount of secreted products, the significant part. Pheromones are often monomolecular in insects, but complex in mammals. A new track was found by chromatography analysis allowing isolation of some simple and consistently present elements that, put together in specific proportions, could reproduce the same effect as the natural pheromone. This new method has been initiated by Patrick Pageat and his team at Pherosynthese (France). This lead to discovering the facial pheromonal complex of the cat and to synthesize analogues of pheromones that had clinically very interesting effects.(1)
APPEASING PHEROMONES OF THE MAMMALS
After this first very interesting step, the studies have been directed to the mechanism of attachment. What is known about this very early function indicated there was a chemical communication inducing the first bond. Chemical analysis gives a very fundamental result: all female mammals produce during the first days after the birth of the offspring, a pheromone that induces a good emotional status for the baby. It is a very complex mechanism; there are adoption pheromones on the skin of the newborn and appeasing pheromones on the mother. Obviously, this is part of the root of attachment.
Appeasing pheromone production during nursing exists in all mammals, including human beings. This is another link between our specie and the others ones showing that the “gap” is less wide than we can think. There is a large chemical commonality between all these pheromones. Main compounds are fatty acids, very simple molecules. Only differences in the proportions and in minor compounds make them specific and effective. Classifying the different pheromones according to their composition allows a new observation: dogs, cats, and humans have a very close match, and—maybe—this can explain a little why dogs, cats, and humans can interact so well. As well, it is consistent with how kittens and puppies can switch from a primary attachment to their mother to an attachment of quite similar nature to the adopting human.
How Are They Caught?
As with all pheromones, they are detected by the Jacobson’s organ or vomero-nasal organ (VNO). The existence of this organ has been discussed in many species, including humans. The VNO seems to be more effective in younger animals but VNO have been put in evidence in older animals.
To send air in the VNO, the animal uses a specific behavior called “flehmen.” This has been well described in cats (2) with specific movements of the lips and the tongue, pushing air in the VNO in a series of short gasps.
Flehmen has been seen in horses (just after the birth of the foal) or when mating. It was said that pigs don’t exhibit flehmen, but during the trials about PAP (pig appeasing pheromone), many pigs were doing splendid patterns, raising the upper lip. Goats also do quite the same thing with the lips.
For dogs, it could be a little different and we can see a flehmen analogue when dogs do this curious behavior, panting and lapping at the same time, for example, when they sniff the urine of a female in heat. It could suggest that in certain species, not only VNO is involved in the detection of pheromones. Special gustative cells could be another target for the pheromones. When we taste wine, we keep it in the mouth, back and forth to excite the VNO. In humans, the VNO is closed but the rear opening above the pharynx is open.
Where Are They Produced?
The place where the appeasing pheromones are produced depends on the species. In mammals with many teats, such as dogs and cats, the pheromone is produced by the inter-teat line. In cows and mares, there is a special place at the internal face of the thigh, called “wax zone” without hair and just in front of the udder. In women, the areola of the breast is the producing region.
When Are They Produced?
When samples are taken before and after the birth, we can see the level of production of appeasing pheromone increases very quickly just after the parturition and will last the time of feeding. Active processes of detachment might involve the decrease of appeasing pheromone or the apparition of a new pheromone, triggering specifically the detachment. Further studies are needed to understand better what is going on in that case.
Knowing the powerful effect of the natural pheromone in relaxing the young, it was interesting to wonder whether this effect was found in the adult. Many trials have been made to prove the efficacy of appeasing pheromones in stress situations and we can speak about two different kinds of effects: zootechnical effect and relaxing effect.
During the development of farm animals such as pigs and calves, many factors can prevent them from growing up at their best speed. Atmospheric conditions, diseases, nutritional factors can be part of the problem; It seems very difficult to control perfectly all these elements and it is a hard work for breeders. What we have seen in that case is a very impressive effect on growth on piglets after weaning; the same positive effects were seen in calves. The very important thing is to understand that appeasing pheromones are not hormones and they can’t force the growth but they can eliminate or reduce the effect of negative factors.
So, if you are a perfect breeder and there is no problem in your farm, maybe the difference between treated and non-treated groups will be small—except if you consider the welfare of the animals. We propose that living in contact with appeasing pheromones is smoother. In addition, there are always incidents, sudden cold, epidemics, all factors of risks that are going to decrease the speed and the quality of growth. In that case, you’ll see a big difference between the group with pheromone and the group without.
Effects have been studied both on companion and farm animals.
Pigs: When piglets are ill, they are separated from the others. When they recover, one of the problems is the high frequency of fights between them with a risk of severe wounds. Up to 52 bites have been counted on one piglet introduced again in his group after eight days of separation. Using the appeasing pheromone decreases the level of stress related to the intrusion.
Calves: One use of the pheromone could be to improve the conditions of the death of the farm animals. Their utilization in slaughterhouse could be an interesting welfare issue.
Dogs: By now, in France, the dog appeasing pheromone has been launched under the name of DAP. It is proposed to reduced stress and fears, but also it seems interesting to help the introduction of a new puppy in a house. The system diffuses (as a room scent) and creates an appeasing atmosphere for the puppy. Transportation by car is also a good target for this product. When the animals get relaxed, they exhibited very few autonomous signs as vomiting, panting, or salivating.
Horses: Transportation by van is also a big problem for horses. Many of them have bad experiences climbing in the trailers: they get nervous, they can have sudation, thrill, and increase in heart rate. Pheromones are useful in this case but also for shoeing as that is always a dreadful experience for horses, owners, and blacksmiths.
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