Physiological Evolution of the Horse

Other than this remarkable jump, the physical features stayed relatively constant over those 1.4 million years(Washburn, McCown 1972). Some anthropologists say that their supra-orbital ridges were slightly more pronounced than previously, cranial bones were heavier and there was still no protruding chin but their molars had decreased in size (Washburn, McCown 1972).

Horse’s have developed into highly specialised locomotor machines. Modified themselves to travel long distances at a moderate speeds and capability of shorter distances at higher speeds. The most efficient running machine that has evolved with many structural adaptions for untiring rapid progress on the ground so that they run long distances efficiently and changing of muscle size and grouping all suggests locomotor adaption (Williams, 2013).

The horse (Equus ferus caballus)[2][3] is one of two extant subspecies of Equus ferus. It is an odd-toed ungulate mammal belonging to the taxonomic family Equidae. The horse has evolved over the past 45 to 55 million years from a small multi-toed creature, Eohippus, into the large, single-toed animal of today. Humans began to domesticate horses around 4000 BC, and their domestication is believed to have been widespread by 3000 BC. Horses in the subspecies caballus are domesticated, although some domesticated populations live in the wild as feral horses. These feral populations are not true wild horses, as this term is used to describe horses that have never been domesticated, such as the endangered Przewalski's horse, a separate subspecies, and the only remaining true wild horse. There is an extensive, specialized vocabulary used to describe equine-related concepts, covering everything from anatomy to life stages, size, colors, markings, breeds, locomotion, and behavior.

Four of the toes had early proto-hooves. The back legs had small hooves on three of the five toes. The toes were padded like a dog’s toes. The Hyracotherium had three incisors, one canine, four premolars, and three grinding molars on each jaw, which was a typical tooth structure of early mammals who were omnivorous browsers (Hunt 4). Eohippus survived for about twenty million years with relatively few evolutionary changes (Wikipedia 7). These animals lived in a sub-tropical climate and ate soft fruits and the leaves of trees.

Percherons and Quarter horses each have different physical features. Both the Percheron and the Quarter horse have straight profiled heads. While the Quarter horse has a short and small refined head, the Percheron has an exceptionally broad forehead, small ears, and large eyes. Both Percherons and Quarter horses have very deep and broad chests. Although the Quarter horse has strong legs and flat knees, the Percheron has clean and heavily muscled feet and legs.

Percherons and Quarter horses each have different physical features. Both the Percheron and the Quarter horse have straight profiled heads. While the Quarter horse has a short and small refined head, the Percheron has an exceptionally broad forehead, small ears, and large eyes. Both Percherons and Quarter horses have very deep and broad chests. Although the Quarter horse has strong legs and flat knees, the Percheron has clean and heavily muscled feet and legs.

From its early stages as a 40 cm tall, 25 kg Eohippus to its current state as a 1.6 meter tall, 500 kg beast, every step can be traced through an abundance of fossils located mostly right here in the United States. While the changes in equids from their beginnings until now are drastic, I found it interesting that it was not necessarily gradual. Most of the changes in size, structure and teeth did not happen until the Miocene, upon which the development was rapid. Figure 5 shows the mass of Equid genera in comparison to when they lived. For the first half of equid development, barely any change occurred. This displays how important environmental factors are in the evolution of species; without the emergence and prominence of open grasslands in the Miocene, horses as we know them today would almost certainly not

Horses are monogstric animals with a relatively small stomach. From the horse’s mouth to their large intestine, their gastrointestinal tract is similar to that of a human’s. However, past the cecum, a horse’s gastrointestinal tract is more similar to a cow’s [3]. A horse’s gastrointestinal tract can be divided into three segments: foregut, midgut, and hindgut [4]. The foregut consists of the esophagus and stomach. Once food has passed through the stomach, it enters the small intestine (midgut): duodenum, jejunum, and ileum, which join the hindgut, cecum, colon, and rectum, at the ileocecal junction. The small intestine and stomach can almost receive a continuous flow of food [3]. The cecum is a large fermentation vat located on the right side of the animal. Carbohydrates fermented by fibrolytic bacteria produce volatile fatty acids, which account for 60-70% of the their energy. However, in modern management practices, horse owners and equine caretakers do not let horses graze like they naturally should; therefore, they substitute the horse’s diet with grains and fats, which the horse is not designed to properly digest. This unbalanced feeding regimen causes numerous digestive disturbances [3].

George G. Simpson George Gaylord Simpson is known as being one of the most influential empirical paleontologist of the twentieth century due to his crucial contributions in the modern evolutionary synthesis. He is known for his expertise in extinct mammals and their intercontinental travels; more specifically, discovering evidence in fossils for the theory of linear evolution in horses. Furthermore, Simpson is an important figure in the studies of paleontology due to his exceptional dedication to his career through his education, which is shown through his many achievements throughout his life. Background Simpson was born in Chicago, on June 6th, 1902, as the youngest child of three and only son. His father, Joseph A. Simpson, was a successful

When Atkin says “the use of drugs”, there are a variety of inhumane stimulates that could be referred to. Medications such as Lasix are highly desirable in the racing as world as they mask the side effects of exercise-induced pulmonary hemorrhage. EIPH occurs when blood escapes the system and penetrates into the horse lungs and airway. While tools like Lasix mask circulatory problems, drugs such as Phenylbutazone are even more disturbing. Typically used as an anti-inflammatory for injured horses, Phenylbutazone temporarily takes away the pain of a minor strain or bruise. However, trainers often administer 12 times the recommended dosage of this medication to all of their racing horses; injured or not. If a horse's injury is too severe, they

Horses are best described as hindgut fermenters with an enlarged cecum and colon that harbors a complex microbial community. These microbes contribute to the digestion processes that enable the horse to extract energy from dietary components that otherwise would be wasted. In addition to hindgut fermentation, extensive fermentation occurs in the stomach when horses consume diets rich in nonstructural carbohydrates. The fermentation in the stomach, however, produces mainly lactic acid and small amounts of VFAs because of the acidic conditions of the stomach that support acid-tolerant bacteria (eg, lactic acid–producing

Exercise represents a physical stress that challenges homeostasis. Its undoubted beneficial effect on the health of the body has been underlined in numerous scientific studies. However, exercise in excess can be deleterious to certain organs and systems of the body. Exercise is a stress situation for which the body must find a new dynamic equilibrium and this requires. among other things, adaptative responses of the hormonal system.

Barefoot trimming is said to be based on the hoof morphology of wild horses, however the climate and habitats of horses have been shown to affect their hoof morphology (Hampson et al. 2010). This

The estrous cycle of the mare has two phases, which are known as estrus and diestrus. Estrus is when the horse is in heat and diestrus is when the horse is not in heat. Generally, the estrous cycle will go for 21 days. 7 of those days are when the horse is in estrus, and the other 14 days are in diestrus. The egg can be released at any time throughout the estrous cycle. The mare will only come into season during certain seasons of the year, usually occurring in spring and summer. In winter, the mare is in anestrus, which means that their reproductive system in not active.

The main goal for many agricultural producers across the country is to annually improve the quality of their stock. For certain companies such as Cargill and JBS who are two of the largest protein distributors across the globe, an improvement for their stock could be reaching their end point faster. For other operations involved in the purebred or show aspect of the industry improving the quality could mean producing better structured animals who are larger framed.