Abstract
The impact of health, management, and microbiota on olfactory function in canines has not been examined in review. The most important characteristic of the detection canine is its sense of smell. Olfactory receptors are primarily located on the ethmoturbinates of the nasal cavity. The vomeronasal organ is an additional site of odor detection that detects chemical signals that stimulate behavioral and/or physiological changes. Recent advances in the genetics of olfaction suggest that genetic changes, along with the unique anatomy and airflow of the canine nose, are responsible for the macrosmia of the species. Inflammation, alterations in blood flow and hydration, and systemic diseases alter olfaction and may impact working efficiency of detection canines. The scientific literature contains abundant information on the potential impact of pharmaceuticals on olfaction in humans, but only steroids, antibiotics, and anesthetic agents have been studied in the canine. Physical stressors including exercise, lack of conditioning, and high ambient temperature impact olfaction directly or indirectly in the canine. Dietary fat content, amount of food per meal, and timing of meals have been demonstrated to impact olfaction in mice and dogs. Gastrointestinal (GI) microbiota likely impacts olfaction via bidirectional communication between the GI tract and brain, and the microbiota is impacted by exercise, diet, and stress. The objective of this literature review is to discuss the specific effects of health, management, and microbiota shifts on olfactory performance in working canines.
Highlights
The extraordinary olfactory capability of the canine has long been used by humans for odor identification and discrimination [1]
The mechanisms of pharmaceutical-induced hyposmia include impairment of odorant binding through altered mucus quantity or quality, inhibition of normal turnover/regeneration of olfactory neurons, nasal vasoconstriction, enzyme-associated effects of drugs (ACE-I), altered levels of cyclic GMP, and zinc chelation [76]
Conditioned canines have a lower exercising heart rate compared to their non-conditioned counterparts and this improved cardiovascular condition may contribute to better thermoregulatory performance and subsequently decrease the need for panting [32]
Summary
The extraordinary olfactory capability of the canine has long been used by humans for odor identification and discrimination [1]. The canine’s capacity for odor detection has been reported to be as much as 10,000–100,000 times that of the average human, and the canine lower limit of detectability for volatile organic compounds is one part per trillion (ppt) [2]. This heightened sense gives canines the ability to detect a vast number of chemical compounds containing molecules that display subtle differences in stereoisomeric structures [3]. The objective of this review is to discuss the effects of management decisions related to diet and physical conditioning, medical care, and microbiota shifts on olfaction performance in working canines
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