Serum nerve growth factor (NGF) levels are increased by the external stress in mice, humans and horses; however, similar variations have been unclear in dogs. Since dogs are usually subjected to conditions of work, exercise and activity as important partners of humans, we measured serum NGF levels post-exercise and compared them with serum cortisol levels, as a biomarker of physical stress. Serum cortisol levels were immediately elevated post-exercise and returned to basal levels within 1 hr. On the other hand, serum NGF levels were significantly increased 1 hr post-exercise and gradually returned to basal levels. Further research is necessary; nevertheless, we have demonstrated for the first time that serum NGF levels respond to exercise stress in dogs.

No abstract

Highlights Serum cortisol, NGF, and Mg 2+ levels of the guide dog candidates were evaluated in each stage of their training. Serum cortisol levels were sensitive to the stress caused by the given training load. NGF levels were affected by emotional stress, such as anxiety. Environmental changes at training school caused changes in serum Mg 2+ levels Mental status of the dogs may be visualized precisely by using the 3 parameters.

Magnesium ions (Mg 2+ ) are essential for various enzymatic reactions in the body associated with energy production and activation of the muscles and nerves. Mg 2+ is also involved in blood pressure regulation, maintenance of body temperature, and glucose metabolism. Although various factors including foods and physical conditions have been reported to change serum Mg 2+ status in humans, serum Mg 2+ in dogs exposed to external stress has been unclear. In this study, we examined serum levels of Mg 2+ in dogs at different conditions using the guide dog candidates for the blind. Serum Mg 2+ was decreased in winter and increased in summer. Guide dog candidates in an elementary class of the training showed markedly lower levels of serum Mg 2+ , compared with that of dogs in an advanced class. When healthy adult dogs were subjected to forced exercise using a treadmill, a significant reduction in serum Mg 2+ levels was observed, particularly in winter. These findings suggest that serum levels of Mg 2+ may be influenced by weather fluctuation such as air temperature, nervousness in unaccustomed situations, age, and physical stress induced by exercise. The results indicate that Mg 2+ supplementation should be considered for working dogs, dogs moving or traveling to a new environment, and dogs during winter.

No abstract