Pasture Time and Laminitis

I’m taking a quick break from the Hoof Angles series to comment on a very serious problem with the way we manage our horses: excessive caloric intake. Because of the unusually warm weather we’ve been experiencing here in Ohio, the pastures are especially lush right now. And with that lush grass comes a greatly-increased risk of laminitis and founder – the #2 killer of horses.

Daily Caloric Requirements Chart

Yes, I know what you’re thinking: “My horse has been out on grass pasture his entire life, and he’s never had a problem!” But that’s the same logic people use to rationalize all sorts of destructive behaviors. The odds may have favored your horse in the past, but, overall, they’re against him. And that’s a fact based on data, not just my opinion. I also realize it’s the “horseperson’s dream” to finally own a few acres so he or she can keep their horses on grass without having to buy hay. But it’s simply not good for them, any more than a steady diet of glazed doughnuts is good for you and me.

Last year I wrote a post entitled Laminitis Risk Calculator that included an MS Excel spreadsheet to help you assess whether or not your horse is at risk. That spreadsheet is still available, either under Tools in the Sidebar, or through the aforementioned post, and I strongly encourage you to download the file and do a thorough analysis of your horse’s needs and current consumption. This year I decided to try to make the data more readily understood by creating a pair of charts that will allow you to quickly approximate your horse’s daily caloric requirements versus his intake.

Daily Caloric Intake Chart

The first chart, labeled Daily Caloric Requirements, will let you quickly approximate your horse’s daily needs by locating his desired weight along the bottom, following it up until it intersects with the type of work he’s doing, and then noting the calories required on the left. Remember that the work times are averages, and adjust accordingly. And if you want a more accurate estimate of your horse’s weight than a weight tape provides, see the Instructions page of the Laminitis Risk Calculator for a method based on girth and body length.

Once you’ve determined his requirements, use the second chart, labeled Daily Caloric Intake, to figure out how many calories he’s currently consuming. The items that are typically fed “all at once” (hay and feed) are listed as flat lines per indicated weight on the chart, while grass consumption is shown on a per-hour basis, with and without a grazing muzzle. Don’t forget to multiply the hay and feed numbers by the amounts actually fed. Look up the number of hours on pasture along the bottom, follow it up until it intersects the appropriate sloping grass line, and note the calories on the left. Then, add in the calories from hay and feed, and compare the total with his needs. If it’s higher (or possibly lower), you need to make an adjustment! Note that treats and supplements aren’t included, so consider them as well. And be honest about it; there’s no point in pretending he’s working more than he is, or eating less than he is, just to make the numbers look better. Let’s do an example…

Suppose I have a 900-pound horse whose weight is pretty close to ideal, and I ride her for 45 minutes Tuesdays and Thursdays, and 2 hours on Saturdays and Sundays. That’s a total of 5-1/2 hours per week, or an average of 47 minutes per day. So according to the first chart, her work load is Light and her average daily caloric need is 16,000 calories. She’s out on the pasture for 7 hours every day (with no muzzle), and I give her 20 pounds of grass hay each evening and no feed. That means she’s consuming just over 15,000 calories of grass plus (8,000 x 2) = 16,000 calories of hay each day – nearly twice the number of calories necessary to maintain her weight! So it’s time to make some adjustments. I could cut her hay in half (8,000 calories) and cut her pasture time down to a bit over 2 hours (8,000 calories), and that would be very close. But, being a big fan of keeping horses outside, I’d rather put a muzzle on her (3,800 calories) and cut her hay to 15 pounds per day (12,000 calories). There are lots of ways to end up with the correct diet, and the Laminitis Risk Calculator makes it easy. But you can do a pretty good job with these 2 charts.

For more information on laminitis, be sure to check out the Animal Health Foundation. They have a lot of very useful and interesting information on this all-too-common condition. And remember: the risk of laminitis is very real, and you need to take it seriously! So please share this with your friends and stablemates.

I’ve added a button to make it easy to print both the charts –

Print the Charts

Back to hoof angles soon…


  1. Cathy says:

    Hi There,

    research that is being done here (NZ) suggests that laminitis (and many other problems) is not so much about sugar in the grass or the calorie load but about the potassium/sodium imbalance in the grass at certain times of the year.
    What is your take on this and have you considered it?


    • Steve says:

      Hi Cathy –

      I’m not a nutritionist, and therefore rarely venture comments on nutrition-related issues. This article was based on research done in Australia by Dr. Pollitt’s group, among others, and their method has been proven to be a useful tool in predicting the risk of a laminitic episode. Caloric intake is but one of the 5 factors they use, but it is a significant one. When I’ve looked at the diets of horses that are laminitic, borderline laminitic (sensitivity of the soles), or showing external signs of foot inflammation, they are invariably consuming far more than their required calories: often 2 – 3 times what they need to maintain their weight. So I’m not saying that the potassium/sodium imbalance isn’t an issue; I’m merely saying that I don’t know enough about it to fairly comment on it! And for me, the predictive method I’ve reported on here seems to be working fine – no laboratory analysis needed.

      Best –

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