Interpretive review: Semiochemicals in domestic pigs and dogs

Abstract

This interpretive review includes discussion of the available scientific literature with interpretations by the authors. The broad field of semiochemicals can be confusing to scientists and consumers. This review attempts to summarize the known scientific studies for pig and dog semiochemicals while at the same time attempting to refine our use of terminology. The specific objectives of this interpretive review are to summarize and interpret much of the key scientific literature (but not the lay literature) on semiochemicals in pigs and dogs to include (1) definitions of semiochemicals and related molecules including pheromones, (2) to briefly summarize olfactory organs, and (3) and to examine the scientific literature for semiochemical mechanisms and applications in dogs and pigs (two domesticated species with known olfactory acuity). Dogs and pigs have olfactory features that are similar in that they both lack certain olfactory organs (Grueneberg ganglion and Septal Organ) and they have a small vomeronasal organ (VNO) without some major receptors that are found in other species. The primary olfactory organs for both pigs and dogs are the main olfactory epithelium and perhaps the trigeminal nerve. Several examples of pheromones activating the brain via the MOE or Trigeminal nerve rather than the VNO challenge the concept that the VNO is the site of pheromone sensing. We believe it is not appropriate to label something a pheromone when evidence is not available to show that it is a pheromone. We offer definitions for the terms semiochemicals, pheromones, interomones and others and then determine if the evidence is sufficient to call certain semiochemicals a pheromone. Here we review mixed, largely negative, scientific reports of the efficacy of some products labeled as “pheromones” that are more appropriately called semiochemicals. Interomones can have a more powerful effect on dog behavior and physiology than semiochemicals marketed as pheromones. Because marketing of semiochemicals is far ahead of the science, bringing some logic and uniformity to the field will benefit animals and hopefully cause less consumer confusion. Semiochemicals have the potential to offer powerful solutions to behavioral problems using more naturally occurring molecules.

Semiochemical 2-Methyl-2-butenal Reduced Signs of Stress in Cats during Transport

“…Semiochemicals are not drugs and are natural molecules found in animals and plants. They are considered clean, green, and ethical technologies that are favored over conventional drugs [11]. Semiochemical therapy shows promise for improving the lives of cats in a natural way.…”

“…Clearly, the metabolic production of 2M2B and its perception by olfaction are conserved over many species. Generally, 2M2B at low concentrations has a calming effect on animals (as an interomone) in that when animals can smell it, especially during stressful periods, they have behavioral and physiological signs of reduced stress [11]. While the interomone 2M2B has not been shown to be a pheromone in cats, this molecule can reduce aggression and measures of anxiety in paired cats [9].…”

“…Feline facial "pheromones" have been reported for cats [2]. While marketing calls these molecules "pheromones", it is important to point out that studies have not confirmed that they are pheromones according to thoughtful reviews and papers that set criteria for calling a molecule(s) a pheromone [7,11,20]. Here we refer to the cat facial molecules as semiochemicals because they can change behavior but have not been shown to be pheromones by accepted scientific definitions backed by appropriate studies.…”

Behavioural disorder in a dog with congenital agenesis of the vomeronasal organ and the septum pellucidum

“…Carnivora are identified as the mammalian species that have the most developed and varied types of pheromone‐secreting glands 13 . Their secretion plays a critical role in the regulation of socio‐sexual behaviour by mediating physiological and behavioural responses 14 . Moreover, pheromonotherapy based on the application of dog‐appeasing pheromone (DAP) has been used in dogs.…”

“…13 Their secretion plays a critical role in the regulation of socio-sexual behaviour by mediating physiological and behavioural responses. 14 Moreover, pheromonotherapy based on the application of dogappeasing pheromone (DAP) has been used in dogs. It functions as a pheromonal equivalent of the pacifying pheromone secreted by nursing bitches and exhibits effectiveness in a variety of fear-inducing circumstances.…”