In a perfect world we would all have access to a scale big enough to properly weight our miniature horses. Many veterinary clinics have scales big enough for a big horse and can easily help you weigh your little horse, but when you don’t have access to a scale what do you do?
There are several formulas out there meant to help with this dilemma, but which one is the most accurate? And why would you need to know the weight of your mini?
One reason it’s a good idea to have an accurate weight for your miniature horse is that it helps you come up with a good feed plan. Some minis are easier keepers and can benefit from being fed a bit less. This, of course, is not ideal as horses are meant to browse and graze for at least 18 hours a day, but for some miniature (and big!) horses this proves their undoing. If you can get an accurate weight measurement then you will have an idea of how obese your horse is and how much you need to feed to help get things under control. The suggested amount to feed a mini is 1.5-2% of their body weight.
**IF you need to monitor how much hay your mini is getting I highly suggest using a slow feed net. As you know I like the Hay Chix nets as they have held up perfectly for me over the years and I find them very easy to fill and manage.
Another reason you want to have an idea of how much your minis weighs is for administering medicine. Banamine, Bute, wormer – all are administered by weight. Miniature horse are extremely sensitive to Bute and if too much is given it can kill a mini quite quickly. So knowing about what your mini weighs, as weight will fluctuate a little bit, will help you make an accurate guess when it comes to giving them their meds.
I have come across several formulas that help us make an educated guestimate of our miniature horse’s weight. Here are a few:
Body weight = (Girth in inches x 9.36) + (Length in inches x 5.01) – 348.53
Body weight = (Girth in inches x 11.68) + (Height in inches x 2.85) – 357.26
Body weight = (Girth in inches x 13.18) – 326.07
For the above measurements —>
- Girth is holding the measuring tape snuggly just behind the front legs and over the top of the wither area.
- Length is measuring from the center of the chest, down the length of the body to the middle of the tail.
- Height is from the ground to the top of the withers.
And then this one which seems to be the most accurate:
Heartgirth x Heartgirth = y
y x length of body = Total
Total / 330 = Body Weight
I have a Facebook friend that shared her findings, measurements versus actual weight using a scale. She said the bottom formula has proven to be quite accurate only being between 5-15 pounds off of the actual scale weight. When she has used a weight tape it has been as much as 50 pounds off – saying the mini weighs more than it does, this could prove deadly when administering meds. My weight tape didn’t seem that far off from the formulas listed so I’m wondering if the brand of weight tape matters? (***this post has been edited below with more information about weight tapes. They are not all created equal!!)
I have measured all my minis and will share that here. I’ll also use a weight tape to compare. This is exciting for me because I love doing experiments!
First up is Zorro. He is going to be three years old in May and is about 39″ tall measured at the last mane hair.
His measurements are:
- girth = 53 1/2″
- length = 49 1/2″
- height = 42″
First formula shown above: (53.5 x 9.36) + (49.5 x 5.01) – 348.53 = 400.225 pounds
Second formula: (53.5 x 11.68) + (42 x 2.85) – 357.26 = 387.32 pounds
Third formula: (53.5 x 13.18) – 326.07 = 379.06 pounds
Fourth formula: (53.5 x 53.5) = 2,862.25
2,862.25 x 49.5 = 141,681.375
141,681.375 / 330 = 429.3375 pounds
When I measured him with a weight tape he measured 411 pounds. Only 12 pounds different than my calculations.
My Facebook friend told me that the fourth formula is typically only 5-15 pounds different than the scale weight. But as you can see these formulas all give very different answers. One idea is to average all of them and then go with that. In this case that would mean Zorro weighs about 399 pounds. I would feel confident giving him meds based on this average. I can be pretty confident that I would not overdose him at least!
Bonnie is up next. She will be 6 years old this year. She’s my little Insulin Resistant mare and is on Thyro-L daily. She’s at the perfect weight as far as looks go right now, we’ll see how she sheds off this spring. She tends to be a bit lean. She’s 38″ tall at the last mane hair.
Her measurements are:
- girth = 51″
- length = 51 1/2″
- height = 42″
First formula shown above: (51 x 9.36) + (51.5 x 5.01) – 348.53 = 386.845 pounds
Second formula: (51 x 11.68) + (42 x 2.85) – 357.26 = 358.12 pounds
Third formula: (51 x 13.18) – 326.07 = 346.11 pounds
Fourth formula: (51 x 51) = 2,601
2,601 x 51.5 = 133,951.50
133,951.50 / 330 = 405.9 pounds
When I measured her with the weight tape she measured 411 pounds. 37 pounds heavier than my calculations indicate.
So her average is 374 pounds. She is a bigger boned mare and used to be stockier than the other two. But the Thyro-L has made it a bit harder to keep weight on her. I do think she looks very good right now though!
And last but definitely not least is Sky. Sky will be 15 years old this year and is 36 1/2″ tall at the last mane hair. She put on a lot of weight this spring and kept it on all summer and fall, even with me driving her as often as I could. She was tested for IR and Cushings and came up with a clean bill of health, other than being over weight. I finally managed to get her to eat some Chaste Berry Powder this winter, disguised by her Excel powder that tastes like Fenugreek, and she has started to slim down a bit. I’m looking forward to really driving her this summer and hoping she will continue to slim down. It’s because of her that my ponies aren’t allowed forage 24/7 anymore. I do try to keep hay in front of them 12 hours a day at least and sometimes it will last longer. But she just couldn’t handle forage all the time, even low sugar low starch forage. She did great on that diet in 2016 but not last year. This is why it’s so important to be FLEXIBLE when caring for horses. If you try to do the same for all your horses someone may end up paying the price. So be willing to adjust to fit what they need. They will tell you if you listen…
- girth = 56″
- length = 51″
- height = 40″
First formula shown above: (56 x 9.36) + (51 x 5.01) – 348.53 = 431.14 pounds
Second formula: (56 x 11.68) + (40 x 2.85) – 357.26 = 410.82 pounds
Third formula: (56 x 13.18) – 326.07 = 412.01 pounds
Fourth formula: (56 x 56) = 3,136
3,136 x 51 = 159,936
159,936 / 330 = 484.65 pounds
When I measured her with the weight tape I got 448 pounds. 13 pounds different than my calculations.
Sky’s average is 435 pounds. I do feel this is a bit light for her, she’s probably closer to the 450 mark. I would love to get her on a scale and will be looking for one locally to borrow. I think 400 pounds is ideal for her body type and age. She has fairly decent bone and is nice and stocky with a nice wide chest. But in her show shape days I’ll bet she was about 360 or so. Very lean.
So just a little over view of figuring out how much your miniature horse weighs. Of course as I stated above, having access to an actual scale is the best way of checking your miniature horse’s weight. Using these formula’s in place of a scale will at least get you in the ball park of your minis weight. And it’s a way to monitor your horse’s weight as the seasons go by as well!
*** I am editing this post with some interesting information about weight tapes. The weight tape I used when I measured my horses for this post is called a Sure-Measure tape. It’s for horses and ponies and I’ve had it for many, many years. Somehow I’ve never lost it even though I have moved many times! It seems that this tape is far more accurate than the Coburn tape that I bought at the local feed store. When I measured the ponies with that tape it was quite a bit off from the formulas above!
This is the Coburn tape and probably what most of you have. It’s what is sold at the local feed stores. However it was the most inaccurate, in my opinion, of the things I did to guestimate my horses weight. The numbers are below!
Zorro’s weight with formulas above was 399. The Sure-Measure tape said he was 411. The Coburn tape said he was 435. That’s 36 pounds difference…
Bonnie’s weight with formulas above was 374. The Sure-Measure tape said she was 411. The Coburn tape said she was 435. The Coburn tape is WAY off for her, 61 pounds off!!
Sky’s weight with formulas above was 435. The Sure-Measure tape said she was 448. The Coburn tape said she was 490. So again it was way off, 55 pounds off for her!!
A friend of mine told me that she went and googled around about weight tapes and found out that different companies use their own formulas for calculations based on the heart girth measurements so the weight tapes will be different! I wish they would put that warning on them so we know that!! These differences are so big that if you were using a weight tape to medicate your miniature horse it could be deadly. So please either find a scale or use the formulas and then average them to come up with a more accurate weight guestimate.