Gazette Vet: The Grazers


Recently, as I ran my dogs around a local field, I couldn’t tell if they were more excited to have off-leash exercise or to eat as much grass as possible. As we walked our loop, they had their smiling faces on and their happy tails wagging. But as they ran from smell to smell, they constantly sampled grass.

This is normal for them, so I don’t worry about it much, though I wish they wouldn’t do it. I’d say I’ve got a 50/50 chance then that one of them will wake me up at night puking grass.

Dogs and cats are clearly carnivorous animals, so why grass?

First, I’ve never had a dog or cat tell me why, so all I can do is guess. To my knowledge, there is no good scientific reason why our domestic dogs and cats sometimes (or often) eat grass. Of course I have my own opinions, which I will share here.

Everything that our pets do is based upon instinct. It’s amazing really, that our domestic dogs still do some ingrained instinctual behaviors that the wolves of 10,000 years ago did! Cats, the same. So, let’s go back to those days and consider why wild wolves and cats would ever eat grass?

To help clear out parasites. Being a wild animal is not a romantic life. It’s a hard knock life full of a lot of suffering and challenges. One of those challenges is intestinal parasites. Intestinal worms are extremely common in wild dogs and cats, and believe it or not, an otherwise healthy adult animal can live in a reasonable balance with these parasites. We see this in our domestic dogs and cats with worms. The number one sign of worms in our dogs and cats? Nothing. Most of the pets we see with worms we pick up on a fecal test are not having diarrhea or weight loss (yet!). This is not a healthy or sustainable state, but it shows that there is a balance. But one proposed reason why wild dogs and cats would suddenly consume a lot of grass would be to try and clear or reduce a heavy worm burden. Dog’s belly feels gross, dog eats grass, belly feels better.

To supplement their diet. 10,000 years ago, there were not acres of manicured tall fescue grass, or even our slightly less maintained farm pasture. There were native plants and grasses. It is hard to say what exact nutrients wolves or wild cats would need from grasses that they wouldn’t get by eating the intestines of the animals they hunted, but it’s reasonable to say that there is a difference between fresh prairie grass and prairie grass that has been fermenting in the stomach of an elk for two days. The evolution and creation of all the species we know of today is exceedingly complex and mind-blowing if we really think about it. Suffice it to say, animals have amazing instincts to survive and thrive in the environments in which they live. Grass eating was in there somewhere.

Now let’s go to our pets. They are domestic, friendly, playful, and fully dependent upon us for their survival. Yet their ancestors were wild. Our pets’ instincts have been diluted and mixed up over tens of thousands of years, leading us with some interesting behaviors that are not quite essential for survival while sleeping on a couch! Grass eating is definitely one of these instincts that sometimes has a purpose but often is just a “confused instinct.”

I break it down into two groups:

There are the regular grazers. These dogs and cats somewhat regularly partake in grass eating without any real consequence. They always will when the opportunity presents itself, but are otherwise completely healthy, despite the occasional vomit or interesting bowel movement the grass eating causes.

Then there are the problem grazers. These pets start eating a lot of grass when they are having some sort of intestinal upset. Whether a virus, an ulcer, or some “dietary indiscretion,” their belly feels bad, so their ancient instinct tells them, “Eat tons of grass!” You can tell they are feeling sick. Either they are not eating, or they are vomiting and/or having diarrhea, while also seemingly obsessed about grass. You should consider a vet visit, especially if they are not eating.

Sometimes the grass eating does help, however most of the time it adds fuel to the fire, like treating a stomach ulcer with Texas Pete hot sauce.

So, if your pets are regular grazers like mine, but are overall healthy, consider it an amazing natural wonder and contemplate the mind-blowing complexity of our natural world. But if you pet is acting sick and wanting to eat tons of grass, it’s time to start thinking about why your pet feels sick and consider a call to your vet if it keeps up!


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