Why Do Cows Only Eat Grass?

You don’t have to be a cattle expert to know cows eat grass and a LOT of it! 

No matter the breed of cow or its intended use, all cows need to spend a significant amount of their waking hours munching on various grasses and other plant matter to sustain their massive bodies. 

But why do cows seem to only eat grasses? 

Cows are a type of herbivore known as a ruminant. Ruminants’ digestive systems, teeth, and saliva are ultra-optimized for breaking down, absorbing nutrients, and digesting plant matter. While cows technically can eat other foods, it is more nutritious and efficient for them to eat plant matter. 

Let’s look closely at cows’ diets, anatomy, and why they are best suited to eating grasses. 

Although it seems like a bland (and tedious) diet to us humans, it turns out that spending hours each day foraging for nutritious plants is the perfect breakfast, lunch, and dinner for cattle. 

why do cows eat grass

Why Do Cows Eat So Much Grass? 

Bovines like cows, buffalo, and antelopes are, as briefly mentioned above, strict herbivores, so they only eat plants. 

More specifically, these large, hooved mammals are a type of herbivore called a ruminant. 

Digestion in cows and other ruminants differs greatly from how carnivorous or omnivorous animals digest food. 

Essentially, ruminant animals have numerous adaptations that allow them to quickly digest, break down, and pull nutrients from plant material. 

They have long, winding digestive tracts, unique gut/rumen bacteria, complex stomachs with multiple chambers, and even specialized teeth and saliva. 

All these help to process cellulose, grind up blades of grass, and sort of “ferment” the plant material to break it down in a way carnivorous animals’ bodies simply aren’t equipped to do. 

Furthermore, there are three main types of ruminants: 

  • Concentrate selectors 
  • Intermediate types 
  • Grass/roughage eaters 

While concentrate and intermediate selectors eat smaller amounts of much more varied plant material, cows are grass and roughage eaters, so they mostly eat the same type of plant matter: pasture grasses.  

Of the three types of ruminants, grass and roughage eaters are the best suited to eating huge amounts of grass. 

For starters, they have the largest rumens! 

The rumen is one of four stomach chambers cows, and other ruminants use to slowly break down the plant matter they consume. 

In addition to having huge stomachs to hold lots of grass, grass and roughage eaters like cows have longer intestines on average than other ruminants and flat, wide, spade-like teeth perfect for tearing up and grinding down high-fiber plant material like pasture grasses.  

They’re also able to regurgitate, chew, and re-digest their partially-digested food (cud) as part of the breakdown process to further derive every last bit of nutrient content from their meals.

Related Reading: How cows chew and use their teeth

To sum up, cows primarily eat grass because it is the tastiest, most nutritious, and most abundant food to eat in large amounts. 

Their bodies have spent thousands of years evolving to be hyper-efficient at breaking down grass and taking in its key nutrients! 

Do Cows Eat Anything Other Than Grass? 

Cows primarily eat two types of plants classified as grasses. 

First, the main grass they eat is pasture or lawn grass like orchard grass, fescue, and ryegrass. 

They also eat lots of dried grasses like hay and alfalfa. 

Still, as we covered earlier, just because cows are best suited to eating and pulling nutrients from grass doesn’t mean they’re only physically able to eat grass.  

Though eating foods like meat and cheese won’t necessarily kill a cow in one sitting, it’s essential to note cows’ bodies lack certain traits and digestive enzymes to properly break them down. 

Meat- and dairy-eating animals have different digestive tracts optimized for breaking down these foods, just like cows with grasses!  

For this reason, it’s also best to avoid feeding cows any processed, pre-packaged “human” foods. 

This, of course, assumes a cow would even be willing to eat something like a chicken nugget or a slice of processed cheese in the first place.

In most cases, they’ll instinctively turn their noses up at it, as these foods are unfamiliar and unappealing. 

Still, if they manage to eat a bit of meat or dairy by accident, they’re likely to only suffer an upset stomach for a day or two. 

However, many types of plant matter aside from plain old grasses (and animal feed made primarily of grasses) are safe for cows. 

For starters, as we’ll cover in more detail below, they enjoy small amounts of fruit and vegetables as treats!  

What Other Plants Can Cows Eat?

Ideally, for a balanced diet, the majority (at least 90% or so) of what a cow eats will be made up of dried grasses and pasture grasses. 

Aside from these staple foods, it’s always a good idea to add some variety to your cows’ diet with other (plant-based) safe, nutritious, delicious foods like fruits and vegetables.  

Of course, as individuals, you’re likely to notice some cows enjoy variety more than others. 

While some cows are content to stick to eating grasses, others greatly enjoy the taste of other edible plants like sweet fruits and flavorful veggies and greens. 

Experiment with some different types to determine what your herd prefers. 

Some of the best and most nutritious fruits cows love eating include:

  • Apples
  • Watermelon
  • Bananas
  • Blueberries
  • Pineapple
  • Oranges

In addition, dark, leafy greens like kale and turnip greens, a wide range of vegetables also make great supplements to any cow’s diet. 

This is, of course, as long as most of their diet is still made up of dried grasses like hay, alfalfa, and pasture grasses like ryegrass and bluegrass.

Some great vegetables to include in your cows’ diet are: 

  • Carrots
  • Broccoli
  • Cauliflower
  • Zucchini
  • Cucumbers
  • Potatoes
  • Squash (various)
  • Pumpkin

Further reading: Are tomatoes bad or toxic for cattle?

Do Cows Need Vitamins or Supplements? 

In general, cows get most of the vitamins and nutrients they need to thrive from their diet of grass, grass, and more grass. 

However, depending on what you plan on using your cattle for (beef, dairy, leather, etc.), adding certain vitamins and mineral supplements will improve your cows’ health and the product(s) you eventually obtain from your herd. 

For example, beef cattle need more vitamins A, D, and E and macro minerals like calcium and magnesium to stay healthy and produce quality beef. 

On the other hand, dairy cows benefit more from added sodium chloride (salt) and water to their diets to stay properly hydrated while lactating. 

All cows, however, benefit from having a salt supplement (typically a large block of salt and other added minerals) in their daily diet, regardless of whether you plan on keeping them as pets or utilizing them for their resources. 

Salt is an essential nutrient in a cow’s diet, and cows usually need a dedicated sodium supplement to encourage them to drink plenty of water and keep their salt levels within a healthy range to regulate various other bodily processes.

Further reading: Why do cows need a salt lick?

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Growing up amidst the sprawling farms of the South, Wesley developed a profound connection with farm animals from a young age. His childhood experiences instilled in him a deep respect for sustainable and humane farming practices. Today, through Farmpertise.com, Wesley shares his rich knowledge, aiming to inspire and educate others about the joys and intricacies of rural life.

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