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[–]punstersquared 22 points 11 hours ago

Cows have 4 compartments to their stomach, 3 forestomachs and 1 true stomach. They're basically giant fermentation vats on legs. You can literally feed sawdust (for carbon) and urea (for nitrogen) and their rumen bacteria will synthesize amino acids, which is crazy. Some drugs get broken down by the bacteria if you give them orally, which is a bummer, but they're also resistant to some of the toxins that will kill, say, horses, because the rumen bacteria get a first crack at everything that passes their lips. The true, glandular stomach, or abomasum, is last in line, next to the duodenum, and calves which are just nursing and don't need to ferment anything will shunt the milk directly to the abomasum. Evolution is crazy stuff.

Birds are even crazier than you think. They have a crop, a proventriculus, and a gizzard. They have full rings in their trachea and instead of a diaphragm and boring old closed lungs, they have weird lungs which exchange gases as the air is going past and down into their air sacs in the lower part of their body cavity as well as their bones! The air sacs act as bellows, and air passes through tubes called air capillaries in the lungs, allowing cross-current exchange. They have pneumatic bones to make flight easier but then they need a place for B cell maturation because there's less room for bone marrow, so they have a special organ called the bursa of Fabricius.

Turtles and snakes have 1 ventricle.

Since cats are obligate carnivores and don't have to detoxify much plant stuff beyond what's in the gut of their prey, they've lost (through drift) a number of glucuronidation enzymes in the liver. This is why they can't take acetaminophen - they metabolize it halfway, then the toxic metabolites accumulate.

Most quadrupeds don't have a clavicle, and the thorax/vertebral column is suspended between their front legs by muscle, with no bony connection.

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[–]dawardIM NP 12 points 9 hours ago
I would like to subscribe to zoology facts.

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[–]punstersquared 7 points 3 hours ago
Thank you for subscribing to zoology facts. Did you know that an adult horse has roughly 60-70 feet of GI tract? They have a relatively small stomach since they are grazers, but the rest of their GI tract is quite lengthy to allow for digestion and absorption of nutrients from grasses. They are so-called hindgut fermenters, in that their cecum is quite large and possesses cellulose-fermenting bacteria. They also do some fermentation in their large colon, which is shaped like two horseshoes on top of each other, snaking around and back again to fit in 10-12 feet of large colon that normally holds around 20 gallons of semi-liquid proto-poo (technical term). When a horse has a large colon impaction that becomes an immovable obstruction, the large colon, which is mobile for much of its length, is flipped out of the laparotomy incision onto a sloped tray going away from the patient, and a colotomy incision is made so that it can literally be hosed out by an assistant while the surgeon(s) milk the fecal material out of the other parts of the colon. Much of the length is in the small intestine, and it takes a lot of surgery to create a horse with short gut syndrome.

Horses lack the reverse peristalsis mechanism and have a very strong lower esophageal sphincter, so they don't vomit and rarely reflux. This means that gastric rupture is a very real concern when the horse has a mechanical obstruction or ileus, because the LES can withstand more pressure than the gastric wall. One of the first things that is done to a horse presenting with abdominal pain is passage of a nasogastric tube, and if the horse is referred to a surgical center, the nasogastric tube is often left in place. Because of all of those lovely bacteria for fermentation, horses are prone to developing endotoxemia and SIRS from anything that disrupts barrier function in the gut, such as infectious colitis or ischemic events. In adults, this is usually due to translocation of dead Gram negative bacteria or pieces thereof, not from true sepsis. As you might imagine, with a gut that looks like you're playing Tetris with a giant spaghetti noodle, obstructing and strangulating lesions are not uncommon. They can also get bacterial die-off and endotoxin translocation from issues like sudden diet changes.

A horse is actually standing on the highly derived fingernail of its middle digit, so they are always flipping us off. They have a large metacarpal/tarsal bone with small, non-weightbearing bones on either side (MC2-4 and MT2-4), with a single digit. The distal phalanx resembles the shape of the hoof, and P3 is suspended from soft tissue connections called laminae, like the matrix of our nail bed. The sole of the hoof actually can not bear the weight of the horse and if these laminae become too inflamed and separate, P3 will rotate downward (called "founder") and actually penetrate the sole. Laminitis can be caused by a number of factors and is the end result of systemic illness in many cases. Chronic laminitis can be caused by equine metabolic syndrome, pituitary pars intermedia dysfunction (equine Cushing's), etc.; acute laminitis can be caused by endotoxemia, sepsis, or even being forced to bear weight for too long on one limb because another other limb is fractured or otherwise severely compromised. This is what killed Barbaro, the famous racehorse who won the Kentucky Derby and was forecast to win the Triple Crown until he suffered a catastrophic comminuted fracture of P1 during the Preakness.

A bolus for a horse that is severely hypovolemic may be 40 - 100 L. Since there is a limit to how fast you can administer this, even with 10-12 gauge catheters in both external jugular veins, it is common to use 1-2 L of 7% NaCl to borrow fluid from the interstitium to maintain adequate organ perfusion. There is also study/discussion/speculation that this may help stabilize the endothelium and have other benefits that persist after it has been redistributed.

Horses can carry MRSA in their nares and people who work with horses, including equine veterinarians, are more likely than average to be colonized. MRSA can be found in dogs and cats as well, but they are far more likely to get Staph pseudointermedius, which in turn is less likely that S. aureus to be a serious human pathogen.

Despite all that can go wrong with their guts and limbs, horses are the consummate athletes. A fit horse's heart rate can vary from less than 30 while resting to over 240 during maximal exercise. They also have huge spleens and a large RBC storage pool in the spleen, allowing them to double their hematocrit during exercise. They have large, powerful muscles proximally but their digit is greatly extended and fortified, so that their distal limb is entirely bone and sinew. This concentrates mass near their body and makes it easy for a little angular momentum to move their limb, and the strong tendons of the digital flexors and so-called suspensory ligament (around the metacarpophalangeal joint) act as energy reservoirs that stretch when the limb is weightbearing, then snap back as weight is shifted to the other side, like a rubber band storing energy.

They also have a "stay apparatus" allowing them to sleep while standing up; when they lock their legs, muscular contraction is required to move them again but is not required to stay upright.

The fainting goats that periodically show up on social media actually have a form of myotonia congenita.

Dogs have a problem with sporadic, unpredictable renal failure from eating grapes or raisins. The toxin is still unknown and is probably only present in some grapes but not others; it may be due to a fungus infecting the grapes, and there may be host factors that cause some dogs to be susceptible but not others. In the wrong dog with the wrong grape, even one grape can be fatal, despite the fact that many dogs belong to naive owners who feed them grapes on a regular basis.

Lilies are highly toxic to cats, causing renal failure.

Fecal transplants or 'transfaunation' are actually fairly old school in equine practice. I've helped with a couple - we filtered the poop through some gauze to remove the particulates that might clog the pump used, then administered via NG tube. Ruminants whose ability to ferment has been wiped out by ruminal acidosis or other causes get a sample of rumen juice from a healthy cow (acquired and transferred via orogastric tube).

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