Emerging Advancements in Canine and Feline Metabolism and Nutrition

The pet industry continues to grow in both developed and developing countries. According to the 2015-2016 APPA National Pet Owners Survey, 65% of US households own a pet, which encompasses 85.8 million pet cats and 77.8 million pet dogs [1]. In Europe alone, there are another estimated 81 million dogs and 63 million cats, and this market is expected to have a compound annual growth rate of 4.4%, as compared to a 3.5% projected growth rate in the USA [2]. Much of this growth has been stimulated by the increasing appreciation of the value of pets to human health and well-being through both physical and emotional effects. Studies indicate associations between pet ownership and(or) animal-assisted therapy and numerous aspects of positive health outcomes, ranging from improved cardiovascular health to enhanced mental well-being [3, 4]. Humans, reciprocally, are engaged in gaining a deeper understanding of nutrient requirements and the effects of diet and care practices on the health, metabolism, and behavior of cats and dogs of all ages, breeds, and lifestyles. This special issue adds to the primary literature concerning canine and feline metabolism, nutrition, and behavior. Vitamin A has long been known to be essential for life for all vertebrates, and the review by A. S. Green and A. J. Fascetti included in this issue provides a concise summary of the research available to date across multiple species. As the authors point out, we still have much to learn about the metabolism of the most important vitamin A precursor, í µí»½-carotene. Dogs can meet their entire vitamin A requirement through í µí»½-carotene [5]. And although cats require preformed vitamin A, they can efficiently absorb í µí»½-carotene, as evidenced by elevated plasma concentrations after supplementation [6]. Furthermore, í µí»½-carotene may play additional roles in health, including immune response, gap junction communication, and other cellular functions [7], but more research is needed to further elucidate these effects. In addition to companions, dogs long have been employed for work and admired for their athleticism. Ultra-marathon sled dog races are an excellent model for studying metabolism under extreme energy demands. The original research conducted by M. W. Brunke et al. included in this issue reports how concentrations of insulin-like growth factor-1 and its binding proteins fluctuate in response to exercise and negative energy balance. These data give important evidence on how to better fuel these athletes and highlight the need for further research into …