Why do cows have such straight backs (parallel to the ground)? Most other animals don’t seem to…
In: Biology
Short answer is they don’t. Quadrupedal land animals can’t have straight backs due to the suspension on their spines.
It appears straight due to selective breeding for cows with larger chucks, rounds, sirloin, etc. So breeding for more back meat.
Look at images of bovine skeletons and you can see that they have curved spines just as other mammals do. I was not able to find a mammal with a straight spine using my google-fu.
In fact, I could not find any images with a cow who had a straight back.
Most four legged animals do have a relatively straight back, but the vast majority of them (cattle included) have a lump on their back where the forelegs and hindlegs join the spine and ribs for support. In humans we call these shoulders and hip bones. In cattle they are called, similarly, the top of shoulder and the hip.
Other animals that are similarly flat back designs are the zebra, fox, donkey, elk, and llama, among others.
Other four legged animals such as the bear, cats, and weasels have bent backs to accommodate their ability to stretch or pounce to get food.
We have selectively bred cattle for a long time. We have selected cattle with straight backs.
This is reflected in the way cattle are officially judged. The TL:DR would be “so the animal doesn’t waddle when they walk because this can cause the animal to go lame.”
A better explanation from wikipedia
>>As with the shoulder blades, all joints in the back should be level with the spine, from the shoulder blades to the hip and the pins of the cow. However, some cows’ pins do sit slightly lower than the spine. This is acceptable, but it is undesirable for any of the joints to drop off from the spine too much. If joints are set too low from the spine, this will affect the angle of the spine, as well as the angle of the ribs and pelvis, and may cause the animal to walk with a slight waddle. This is not desirable in a beef cow. This can also cause problems with the legs, which means that the hooves do not wear evenly on the ground. This can cause permanent lameness and other conditions at some point in the animal’s life.
https://en.wikipedia.org/wiki/Cattle_judging
They are bred to be that way. If you look at wild cows or buffalo they do not have straight backs but the loin and rib (top of back near haunches) is the most valuable steak. So farmers breed cattle to have long, wide, straight backs. It is easier to cut and process and it produces more meat. Look at the limousin cattle breed compared to the holstein. The first is a special breed of beef cow bred to have long backs. The second is a dairy cow bred to be tall for easy access to udders. Artificial selection drives the selection of certain traits.
Edit: limousine cattle is spelled limousin
To help them moo-ve.
But looking at their skeletal structure, the spine actually inclines at an angle as you move towards its tail. This is the thoracic curve. However the way its vertebrae align from the spine give the illusion that it is straight and parallel.
It is thought that this gives better center of gravity, alleviating the weight from rear hips, better front shoulder support, and even act as a “cooling mechanism” in hot weather. Think of it like a computer heatsink displacing heat a CPU generates.
Ummmm, the cows around me (rural Michigan) do not have straight backs. They all seem to have a low arching bow.
A lot of the pictures you see of cows have been “doctored”. In the purebred industries, straighter backs are believed to be more desirable. Long before photoshopping, cows and bulls have been staged to look more desirable. For example, in many purebred publications and advertisements for genetics, hair is combed (and styled with product) and trimmed to show a straight line on the back. Sometimes even yardsticks are taped there and spray painted to match the hair color.
Source: I have personally witnessed this
Animals tend to develop downward curves to their backs as they age. Compare a young deer to a 6-7 year old deer. Beef cattle are generally butchered before they are 36 months old and don’t have time to develop that sway back.
(Obligatory warning: I’m on mobile)
Long story short: it appears straight but technically isn’t. What you see as the line of their back is the line that connects all the spinal processes of their vertebrae. Those do line up to create a straight line. The body of the vertebrae however do form a curve underneath that you can’t see.
Long story long: let’s look at why backs are curved for a second. In 4 legged animals, walking requires the back to undergo a slight side-to-side wave-like motion with each step. It also bends ever so slightly with each step when the hip is flexed to bring the leg forward under the animal. The spine also holds the weight of the innards, which are contained by muscles that are attached to the spine. Basic architecture tells us that an upwards curve is better at holding in weight than a straight line. Hence, the spine curves upwards a bit.
Now let’s compare some behavior and lifestyles to better understand the anatomical differences between species. Take a horse and a cow for example. A horses back is much more curved than a cows. But why is that? One good way to try to backtrack why a feature is the way it is, is to think about its function. A horse has a raised withers (the area between the shoulder blades). In this area, the spinal processes are much longer than in the rest of the back. This is also the area where a lot of the muscles and most importantly, the ligament that runs all the way along the spine from the base of the skull to the top of the tail, are attached. The raised processes give more surface for those muscles to attach to, and allow for a lever effect to take place. This all facilitates the act of raising the head. Horses are nervous prey animals that rely on their senses and their ability to escape a situation quickly to survive. They graze most of the day with their head down, but most of their non-grazing hours are spent with their heads in a more horizontal/upwards position (when they nap while standing or socialize). So they need the raised withers and more curved back to help their muscles raise their heads and support the weight of their belly.
Cows on the other hand, have a generally lower position of the head. Proportionately, they spend less time grazing because they are ruminants. They tend to spend their ruminating time lying on the ground with their legs tucked under and their heads just slightly raised above the ground, but they don’t need to raise their heads above the level of their backs as much as horses do. The fact that they also spend much more time lying down helps them carry the weight of their belly. So they don’t need as much room to attach head muscles to.
As for most carnivores, they have well developed muscles all around, but are mostly developed for motility. They are less likely to spend a lot of time in a specific position so their bones have adapted to give muscles more space. They typically have lighter, finer skeletons as well whereas grass eaters have heavier, less streamlined bones.
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