Editor's note: According to the AAEP owner survey, the top three things that horse owners want from vets are 24/7 coverage, a vet who values them and their horse and communicates well, and a practitioner who keeps up with medical advances. With that in mind, regular installments of Keeping Up will headline some recent information to keep you abreast of research, advances and continuing education in the equine medical community in EquiManagement magazine and on EquiManagement.com.
A topic of interest to many equine practitioners was discussed at last year's North American Veterinary Conference (January 2016)—the concept of preventative nutrition. Equine practitioners commonly implement this practice through the use of probiotics, chromium and fatty acids, to name a few.
Meagan Smith, DVM, DABVP (Equine Practice), of the University of Pennsylvania’s veterinary school, delved into facts surrounding these feed materials. A survey of horse owners revealed that 84% feed dietary supplements, and 59% use them to address behavioral and medical conditions. The horse owners surveyed indicate that they depend on their equine veterinarians for information so it is relevant that veterinarians are well informed about supplement choices in order to appropriately counsel clients on what to use.
Regarding probiotics, there are currently no FDA-approved probiotic products for horses. Probiotics are considered as nutraceuticals rather than pharmaceuticals, so probiotics do not go through any kind of drug approval or quality control process. In addition, there are “limited scientific, peer-reviewed studies showing the benefits of these products in horses,” said Smith.
Looking at ingredients in probiotics, it appears that the most common microbiota allegedly contained in the products include Lactobacillus, Enterococcus and Bifidobacterium, none of which are the most commonly abundant microflora found in the equine large colon. It is unknown if these species have any effects on the equine GI tract.
Quality control is also suspect: “All veterinary products tested in one study had less than 2% of the listed concentrations.”
Not only did studies on foals indicate no differences between probiotic-treated or placebo-treated foals with diarrhea, but also there have been reports of adverse effects in foals treated with probiotics. (You can find the PubMed article here: https://www.ncbi.nlm.nih.gov/pubmed/25903509 that is titled, "Effect of a probiotic on prevention of diarrhea and Clostridium difficile and Clostridium perfringens shedding in foals.")
At this time, there are limited or relevant clinical trials testing efficacy of each probiotic and its effects on the equine gastrointestinal environment sufficient to make any conclusions about efficacy. Another concern is the possibility of transference of antibiotic resistance genes, for example by Lactobacillus species, which while screened for in Europe by the European Food Safety Authority, is not in North American probiotic products.
For an in-depth review of probiotics, see A. Shoster, S. Weese, and L. Guardabassi’s article “Probiotic Use in Horses – What is the Evidence for Their Clinical Efficacy” in Journal of Veterinary Internal Medicine, Sept 2014, (http://onlinelibrary.wiley.com/doi/10.1111/jvim.12451/full).
Another product used as a nutritional preventive supplement is chromium, chosen for its reported use in controlling insulin resistance in horses with equine metabolic syndrome. Not only are there no specific chromium requirements documented for horses, but studies comparing insulin and glucose levels in horses fed chromium versus placebo did not identify any difference in effect. Looking to the many different forms of chromium, studies need to be pursued to evaluate bioavailability of each as well as dose.
Omega-3 Fatty Acids
Polyunsaturated omega-3 fatty acids (n-3 PUFA) are a popular supplement to feed for their anti-inflammatory properties, and in particular DHA (n-3 docosapentanoic acid) and EPA (eicosapentaenoic acid), both of which are found in marine fish oil.
EPA is also found in plant oils such as linseed, flaxseed and soybean. The conclusions of studies indicate that “direct supplementation of EPA and DHA through a marine source (algae and fish) results in increased PUFA concentrations in the body, but an ALA-supplemented flax seed does not result in conversion of ALA to EPA and DHA.”
As for effects on insulin sensitivity, horses fed the marine-derived fatty acid supplement responded best.
Supplementation with EPA and DHA have produced favorable results for diminishing inflammatory markers, increasing stride length in arthritic limbs and reducing coughing and respiratory effort as well as improving lung function in horses with inflammatory airway disease and recurrent airway obstruction.