Horse liver (Photo credit onemedicine.tuskegee.edu)
Sorry that I have not posted for a little while, but things have been pretty hectic lately. Today, I will tell you about the functions of a horse liver. The liver plays an important role in digestion. It secretes salty bile to help change the acidity of the food as it enters the gut from the strongly acidic stomach. If bile ever runs low, digestion will be altered. Especially the breaking down of fats. And as a horse has no gall bladder and bile is discharged in response to eating, a horse that is starved for 12-24 hours can accumulate the bile pigments in the blood, giving a false impression of jaundice. The liver also acts as a detoxifier. Poisons absorbed from the gut are removed from the blood by the liver before they can affect the rest of the body. Even naturally produced poisons such as ammonia are converted into safe chemicals that can be excreted. Example: Ammonia is converted into urea for excretion by the kidneys. The liver also manufactures many essential micro-chemicals, such as clotting factors and vitamins. Iron and other essential vitamins and minerals are also stored in the liver until they are required; vitamin and mineral deficiency diseases are a common reflection of liver failure, and when these functional reserves of the liver are exhausted the horse may bleed from the nose, into the gut, or urine. The liver is essential to the horse’s survival. Even though it can look pretty gross.
To see where the liver is located and some more pictures, click here to watch my video.
Horse intestine (photo credit, VETERINARY ONLINE)
Now that I’m done with mouths, let’s move on to a “more interesting” subject, Intestines! Namely, the horse intestines. True digestion begins in the small intestine when it receives liquefied feed material from the stomach. With assistance from the enzymes secreted by the pancreas, the small intestine is the primary site for digestion and absorption of sugar and starch (a complex sugar in plants), protein (that has been initially digested in the stomach), and fat. The small intestine is also the site for absorption of fat-soluble vitamins (A, D, E, and K), calcium, and phosphorous. The large intestine in the horse works like a large fermentation vat in which tremendous numbers of bacteria and protozoa live to facilitate further digestion of plant fiber by their production of enzymes that are capable of breaking down this component of the equine diet (the horse itself does not have these enzymes). This fiber breakdown produces substances called “volatile fatty acids” that can then be absorbed and used by the horse for energy. A second important function of the large intestine is water absorption. This function occurs very efficiently such that by the final step in the small colon, the waste material not used by the horse is formed into fecal balls. These are subsequently passed into the rectum for evacuation through the anus. There, wasn’t that fun? I sure had fun writing it. 😉
To see some horse intestines, click here to watch my video.
Horse mouth (royalty free)
For the next few weeks, I’ll be writing about different animal mouths. Starting with the horse mouth. Horses grasp food using a combination of the lips, tongue, and teeth. Horses’ lips are extremely tactile when it comes to consuming feed. Feeds are mixed with saliva in the mouth to make a moist bolus that can be easily swallowed. There are three pairs of glands that produce saliva – the parotid, the submaxillary, and the sublingual. Horse saliva contains bicarbonate, which buffers and protects amino acids in their highly acidic stomach. Saliva also contains small amounts of amylase which assist with carbohydrate digestion. The mouth contains 36 – 40 teeth. Wolf teeth are not included as not all horses have them. The horse’s upper jaw is wider than the bottom jaw to allow for a chewing motion that is quite complex. The chewing action of the horse is a sweeping action which incorporates both lateral, forward, backwards, and vertical motions. This allows the feed to be effectively ground and mixed with saliva to initiate the digestive process. The texture of the feeds will dramatically influence the chewing rate (jaw sweeps) and rate of ingestion. An average horse will generally take 60,000 jaw sweeps per day when grazing. This amount will be dramatically reduced when confined to a stable and large amounts of grain are fed. When horses chew fibrous feeds such as hay or pasture it is a long jaw sweep action. This is why horses continually out on pasture rarely develop sharp edges on their teeth. Grains are consumed in a shorter sweep which does not extend past the outer edge of the teeth. When large amounts of grain are given, horses chewing action will be changed and the teeth will not be worn evenly. Hooks or sharp edges will start to form on the outside edge of the teeth. Conclusively, mouths are essential for digestion and a discussion about the digestive system would not be complete without them.
To see where the “wolf teeth” are positioned and what a horse’s skull looks like, click here to watch my video
Horse stomach (photo credit, succeed-equine.com)
Now we are going to move on to another kind of stomach, the horse stomach. Interestingly, horse’s stomachs (like their hearts) are relatively small for the size of the animal, this limits the intake and storage of food. An average horse weighs 800 to 1,200 pounds. But their stomach capacity is only about four gallons, and works best when it contains two gallons. Also, their stomachs empty when they are about 2/3 full. Whether or not the stomach enzymes have completed their processing of the food. This inhibits full digestion and proper utilization of food. Continuous foraging or several small feedings per day are preferable to one or two large feedings.
The horse stomach consists of a non-glandular proximal region (saccus cecus), divided by a distinct border, the margo plicatus, from the glandular distal stomach. In the stomach, assorted acids and the enzyme pepsin break down food. Pepsin allows for the further breakdown of proteins into amino acid chains. Other enzymes include resin and lipase. Additionally, the stomach absorbs some water, as well as ions and lipid soluble compounds. The end product is food broken down into chyme. It then leaves the stomach through the pyloric valve, which controls the flow of food out of the stomach. Although not as complex as a cow stomach, horses stomachs serve them well. They do not weigh the horse down or hinder their agility, such as the cow stomach does. Although if a horse eats too much, it can get bloated like a cow. Ultimately, make sure your horse doesn’t eat too much too fast, and remember, if an animal’s gut is not healthy, the animal is not healthy.
To see a horse stomach compared to a cow stomach and what the horse stomach looks like, watch my video at http://youtu.be/n1jUkgmUAts
Discussing the Horse’s Appendicular Skeleton.
The appendicular skeleton is comprised of the fore and hind limbs. The fore limbs do not attach to the spine at all, instead they are suspended with muscles and tendons. Which give the horse more agility so that they can do things like folding up their legs when jumping. The hind legs attach to the pelvis and even though they support only 40% of the horse’s weight, they produce the most forward motion and the stabilization attachments to the spine. So the next time you are with a horse, think about this and don’t forget to have fun!
Concerning Horse’s Diet.
English: A buckskin Dole Gudbrandsdal horse “Norlys” grazing. Français : Un cheval Dole-gudsbrandsdal à robe Isabelle broute. (Photo credit: Wikipedia)
Obviously, the most natural thing that a horse can consume is green grass. It is also the most nutritious thing a horse can ingest. Grass contains Silica, which promotes dental, hoof, and bone health. For most people, it is hard to find fresh green grass in the winter. These people can buy their horses hay. Although good hay can be quite nutritious, it still does not have as many health qualities as fresh grass. Some people supplement their horses with grains, oats being the traditional choice. Horses can also eat (good) corn but grass seed heads are the closest thing to what horses eat in the wild. When it comes to grains (or any other food) fresher is better. With all the processing going on nowadays grains can lose much of their nutritional value such as silica. You can also get your horse concentrate mixes. These mixes contain things like flax, beet pulp, molasses, bran, vitamins, and minerals, usually to make up the shortcomings in your horse’s diet such as in the winter when the horse is not getting much grass or to give the horse energy. It is also a good idea to give this mixture to pregnant mares to keep their health up so that their foals will most likely be healthy. You can also give your horse salts and minerals in the form of a salt block so that your horse can satisfy its cravings whenever it wants. Just for a little fun fact, reports have shown that horses will usually crave salt more in the summer than in the winter. So keep your horse happy, healthy, and content with a good diet and plenty of exercise.
Mounted skeleton of an Arabian horse (Photo credit: Wikipedia)
Regarding the Horse’s Axial Skeleton
The axial skeleton is the part of the horse’s endoskeleton* that contains the skull, vertebrae column, sternum, and ribs. If you are not familiar with the skull, ribs, ect, this is what they are composed of. The skull has 34 bones and 4 cavities, the cranial cavity, the orbital cavity, the nasal cavity, and the oral cavity. The cranial cavity encloses and protects the brain. While the Orbital cavity surrounds and protects the eye, the oral cavity is a passage to the respiratory system and the digestive system, and finally, the nasal cavity leads to the respiratory system and also includes the extensive pericardial sinus. Moving along, the vertebral column has about 54 bones including 7 cervical (neck) vertebrae, the atlas and axis which support and move the skull, 18-19 thoracic (the vertebrae that the spine is mostly made from) vertebrae, 5-6 lumbar (lower back) vertebrae, and 15-16 caudal (tail) vertebrae. Although, the number can be different according to different breeds of horses. The Arabian for example only has 5 lumbar vertebrae, and 16 cervical vertebrae. The sternum is located on the back of the pelvis and is the part that the backbone attaches to, usually having one or two of the lumbar vertebrae fused to it. And ultimately, the ribs, horses usually have 18 pairs of ribs but the Arabian has 17 pairs. The ribs are used to enclose and protect the vital organs such as the heart and lungs. So the next time you see a horse, think about all the interesting things I have told you today and make sure to check out next week’s blog about the horse’s Appendicular skeleton.
*A skeleton on the inside of a creature’s body.
Discussing the Equine Heart.
The frog is triangular in shape. (Photo credit: Wikipedia)
A horse’s heart has a more rounded shape that a human heart and is also smaller compared to the horse’s size than a human’s. The horse heart is composed of four sections, the left and right atria and the left and right ventricles. When a horse reaches maturity its heart usually weighs 7.5 lbs, but it can weigh as much as twice that amount. The horse heart grows until the horse reaches four years of age, but sometimes (usually because of a condition) the horse’s heart might grow a little more. There is a component on the horse’s hoof called a “frog”. Located in the digital cushion, the frog aids the heart by helping to pump the blood up the leg. How this works is when the horse walks, (trots, canters, gallops, ect.) the frog is compressed against the ground and shoots the blood up the leg. That is why a horse can go lame if it stands around all day and doesn’t get enough exercise. The heart is not strong enough to pump all the blood up the horse’s long legs, and consequently the horse will go lame. Usually in the back legs first as horses tend to move their front legs more. So make sure your horse gets enough exercise and ride often to get that frog pumping to ensure your horse’s health.
The sense of touch in an equine.
Wild horses interacting (Photo credit: Wikipedia)
The sense of touch is an important but usually overlooked element in the lifestyle of a horse. Most people think that horses have a thick tough hide. But they really do not. Although tougher than the human epidermis, horse’s skin is rich in nerve endings. If you watch horses interacting, you will see lots of evidence that horses communicate using touch. Mares reassure their foals with a brush of the muzzle, friends scratch each others backs with their teeth, and sometimes horses just stand next to each other for comfort and/or support. When interacting with humans, a rub, pat, or massage in the right place will tell the horse that the human is his friend and sometimes the horse will respond. Which is cute when the horse nuzzles or sniffs you, but is not so cute if the horse bites or stomps you.