Welcome And Core Question

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Welcome to the Animal Naturopathic Medicine Educatum Podcast, specializing in canine, feline and equine animal health from a biological perspective. Hello everybody, today's audio topic of conversation is how equine species specific feeding from the biological viewpoint of the horse first evolved. The horse has evolved to be a grazing animal, a trickle feeder, feeding on grasses for most of the day while on the move. In early stages of grassland developments, the grasses and shrubs were often not nutritious, low in digestible sugars and starches, and higher in indigestible structural carbohydrates, also known as fibre. The horse's long slow digestive tract developed to deal with the evolving development of grasslands populated with beneficial bacteria that help to break down the fibrous matter and produce volatile fatty acids and nutrients that the horse then used as energy. Although we humans have bred and selected our domestic horses to be somewhat different from their primitive ancestors in many ways, the digestive system of the horse has not changed.

From Forest Browser To Grazer

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So now let's look at the evolving journey. The ancestral horse began as a browser about seventeen to twenty million years ago, the latter part of the early myosin period. A watershed occurred in the development of what would eventually lead to our modern horse. He began moving out of the forest and swampy areas onto the plains as the climate changed to favour conditions for grasslands over dense forest. Paleontologists have been able to determine this occurrence based upon the analysis that grasses are typically much more abrasive than leaves of trees and shrubs, which reflected in a distinct change in the wear of the dentition found in fossil records. The horse's ancestral tree branched significantly after this with different species being split between those that had long teeth and those that retained the shorter ones of previous evolutionary periods. This ensuing period also saw the emergence of a new species of horse that had very long teeth and comparable to what we see now in the modern day horse. This diversity continued until about six million years ago when there was suddenly a large extinction pulse, resulting in a drastic loss of total diversity among all animal species, leaving only the horses with the very longest teeth. The conventional theories have suggested that it was the loss of forestation alone that triggered this extinction due to climate change of turbulent tectonic plate movements. Yet these climate changes were not solely responsible for these dentition changes that were already happening. The climate change

Tooth Wear And Grass Chemistry

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initially began with flora favoring the growth of temperate C three grasses over the forests. Then the climate shifted again favoring warm season C4 grasses over the C three varieties. The distinction of this is that C4 grasses on average have considerably more silica content, about three times as much than the C three grasses, thus causing advanced wear of the teeth. Obviously, without human intervention, if the horse cannot eat then it dies. If they die too young, then reproductive viability is lost in the species. So theoretically only those species with the very longest of teeth would survive. And this is what we have today horses that are very well adapted to grazing, with some limited preference at certain times of the year for browsing depending on what grasses are available. What is interesting to consider in the predomestication times of the horse is that horses had the ability to rank or assess their potential food items according to their net value. This was concluded by scientists referring to horses as selective generalist grazers. Horses are sometimes classified by biologists as gramnivores. They are a herb herbivorous animal who feeds primarily on grass flora, specifically true grasses, which are plants from the Poesia family. Also known as gramminae graminae, which includes tussocks and sedges. You will often find these along the side of a stream or river banks. Horses as hindgut herbivores are gramminoids, often selecting pasture grasses over other species of grass when available, consuming large quantities of low quality forage. Their hindgut fermentation is designed to extract as much of the nutrient compounds as physically possible from low quality foragers compared to other foregut fermenters

Fibre, Microbes, And Hindgut Design

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like cows. Over millions of years the modern equid we know today evolved the most in their anatomical evolution on the world's grassland regions, where it was too dry for most flora species and minimal rainfall. This means their microbiota, which is an ecological community in itself, evolved in low nitrogen habitats. A flora habitat that the modern horses digestive tract has biologically evolved to eat is a diet with the highest plant life fibre, with the lowest protein content within that grazing community. The eggwine species survives in some of the harshest habitats on earth. In later years and with or without the help of humans, horses occupy a wide range of habitats. Whether they thrive it is invariably on forage that is high in fiber, low in protein.

Thrifty Genes In Rich Pastures

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Consequently, biologists claim horses have thrifty genes. They have evolved to be metabolically efficient, an adaptive advantage needed for survival in harsh, nutrient sparse environments, which can be a major disadvantage when your horse in a domestic environment grazing comparatively nitrogen rich pastures that horses were not evolved to consume on a continual basis or in large amounts. So nitrogen rich pastures are naturally high in crude protein levels. Clover, for example, has over 20% crude protein. When combined with other high production species like ryegrass or contained in certain environmental conditions and perhaps the horses fed heavy grain diets, the overall crude protein then can easily rise significantly, contributing to digestive issues and development of nutritional diseases such as laminitis and or bouts of colic. The trouble with high protein diets is that it's not usually the quality of digestible protein that horses need. While some of this nitrogen is part of the makeup of true protein, the rest is what is known as NPN non protein nitrogen or free floating nitrogen, which horses are not designed to eat as a hind gut fermenter. The variety of plants that have too much nitrogen relative to fibre carbohydrate, digestive upsets can happen when the grass is constantly grazed short and doesn't get a chance to grow any structure. Along with the supplemented diet that the horse might be having that's consisting of mainly concentrated grains and legumes. So if the horses were meant to be consuming such short forage or concentrated diets, they would have the ruminant style digestive system like a cow. This is designed for high nitrogen grasses with several stomachs for the body mass and say milk production, rather than the monogastric style of the swift fear-flight-fight responses of a hind gut fermenter we know as our horses. Hmm.

Final Thoughts And Goodbye

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Alright, bye for now. Thanks again.