Question
I have a two-year-old Quarter Horse gelding that is HYPP-positive (N/H). He weighs about 1,050 lb (477.3 kg) and he is currently being fitted for halter competition. He is kept in his stall for all but one hour of the day, during which he is allowed to roam a sandy enclosure. He is fed 15 lb (6.8 kg) of feed (14% crude protein, 6% fat), as much alfalfa (lucerne) as he will eat, and a fat supplement. How can I figure the potassium content of my gelding’s ration?
Answer
In order to find the potassium content of your horse’s current diet, it is necessary to know how much potassium is in all the feedstuffs given the horse. Unfortunately, I am not able to calculate this from the information you have given me on your horse’s ration. However, I can walk you through how to calculate this once you get the information you need. Here are some things to think about when trying to figure out what the best diet would be for a horse with the possibility of having HYPP.
Currently, it is recommended to feed a horse with HYPP a grass hay and to avoid alfalfa, because alfalfa and other legumes tend to be forages with the highest potassium content. For example, the average potassium content of alfalfa hay is 2.4% but can range from 1.8 to 2.9%, while the average for Bermuda grass hay is 1.7%, with a range from 1.2 to 2.1% (www.equi-analytical.com). So it may be worth the investment to have your hay analyzed for potassium content to see where it falls in the range, or consider switching to grass hay.
This horse is receiving a large amount of concentrate, which supplies some potassium as well. The feed mill that manufactures that particular feed does not disclose any information about the feed on its website (neither ingredients nor nutrient analysis), so I think you will need to call them directly to ask about the feed. Some of the ingredients in commercial concentrates that have higher potassium content are molasses and soybean meal. Most grains like oats are low in potassium. Mineral mixes used in commercial feeds can have added potassium. Altogether, this means that the potassium content can be quite variable, so it’s best to ask the manufacturer. The manufacturer can also let you know which of its concentrates has the lowest potassium. If the mill has no low-potassium feeds, you can go to feeding oats with a ration balancer (like All-Phase) or a well-formulated vitamin and mineral supplement (like Micro-Max or Gold Pellet).
Ideally, the diet should be as low in potassium as possible, which would be around 1%. Any feeding technique that slows consumption will be beneficial because this will decelerate the rate that potassium enters the bloodstream. Once you know the
potassium content of the hay and the grain, you can figure out what it is in the total diet by the following calculation.
Calculate:
1. Find amount of potassium (noted as “K” here) in concentrate: percentage of potassium in the concentrate x pounds of concentrate = KG
2. Find amount of potassium in hay: percentage of potassium in the hay x pounds of hay = KH
3. Add KG and KH and then divide this by the total pounds of concentrate and hay; this will give you the percentage of potassium in the diet.
Example:
If the potassium content in the concentrate is 1.2% and the amount of concentrate fed is 15 lb, then KG = 18. If the potassium content in the hay is 2.4% and the amount of hay is 15 lb, then KH = 36. So, 18 + 36 = 54 and 15 + 15 = 30. Divide 54 / 30 = 1.8% potassium in the diet.
