I am not over exaggerating when I say that the value I'm going to talk about today is one of the THE MOST IMPORTANT numbers related to feeding your horse, but the funny thing is that you've likely never heard of it. The fact that most of you have never heard of it is proof of how extremely poor education is on the most important part of your horse's diet. But really smart horse feeders know that forage first decisions get the best results over and over again! And that very important choice can be summarized with the Relative Feed Value.
What is Relative Feed Value and Why Is It Important?
The Relative Feed Value (RFV) is a number found on a hay or pasture analysis. It is an end result of forage species, environmental conditions, water and fertilizer, and when a forage grower harvested the product. On a Dairy One/Equi-Analytical analysis it's at the very, VERY bottom of the page. What you need to know about RFV is that it's a calculation. It's not extracted from the forage sample. It is calculated using Digestible Dry Matter as a function of Acid Detergent Fiber (ADF%) and Dry Matter Intake Potential as a function of Neutral Detergent Fiber (NDF%)- All of which are measurements of structural carbohydrates and, ULTIMATELY, the digestibility of the forage in question. The RFV is a rough estimate of HOW the forage will behave in your horse; will it make your horse gain weight, lose weight, or stay the same? It summarizes the fiber values (i.e. cellulose, hemicellulose and lignin) which dictate the health and happiness of your horse's microbiome. It tells you which forage will be best to prevent ulcers! It can even predict how much your horse will like the hay. Are you convinced yet?
Let's consider this absolute, undeniable fact....the number one reason that you feed your horse hay and pasture is to provide calories. Yes, yes, yes, we want hay to do a lot more than that, but first and foremost, we want our hay choice to maintain a good weight on our horses. Just think, if you spent $400 per ton and your horse turned into a skeleton by Halloween, you'd be very unhappy with your forage choice. On the flip side, if you purchased a barn full of hay and all of the horses quickly became pregnant balloons, you'd be equally unhappy. Because this is true, it makes sense to focus on forage analysis values that help us predict weight gain, weight loss, or weight maintenance first!
Here's what I LOVE about the Relative Feed Value number. It offers horse owners, new to forage testing, a simple, uncomplicated number from which to shop by. More importantly, when you get the RFV right for your horse (the forage matches the need), your dependence on additional supplementation and complex management strategies goes way down. Here is RFV in a nutshell explained using an average metabolism, 500 kg (1,100 lb) horse in light to moderate work;
Relative Feed Value Over 100 = Weight Gain Hay
Relative Feed Value Between 90-99 = Stay the Same Hay
Relative Feed Value Below 90 = Weight Loss Hay
Can you pick out the "Maintenance" and "Weight Gain" Hays listed in the chart and forage results below? Which hay sample is the most likely to facilitate weight loss in your horse?
There are other very important, meaningful numbers of a forage test; namely crude protein, digestible energy, and acid detergent fiber. However, the problem that I witness over and over again with those values is that they are complicated by the numbers around them and thus lead to confusion for those who don't look at forage tests every day. So, when I send clients out in the world to shop for a forage source that matches their horses' needs, I tell them to shop for a RFV range. Here are a couple examples for you. See if you can match A, B, and C forage tests below to the horse's need.
A Quarter Horse in Central Oregon with a history of laminitis needs to lose weight. We'll be shopping for hays with a RFV below 90, in addition to being low carb.
A recently imported warmblood has lost a lot of weight. He's competing as an upper level event horse, and show season is in full swing. We'll be choosing forages with a RFV over 100. Maybe even some alfalfa with a RFV of 140-160!
An Arabian mare in Tennessee with a history of tying up needs to maintain the same body condition score on high fat feeds. We'll be looking for forages with a RFV around 95.
ADVANTAGES OF USING RFV
Will appear on most forage analysis
Simplicity- fiber values get summarized into 1 number
Focuses on HOW the forage will behave in the animal
Bridges the gap between weight management and ulcer prevention
Estimates how much hay you will need to buy
DISADVANTAGES OF USING RFV
Designed with cattle in mind!
Best calibrated to alfalfa forages
Only a rough guesstimate
Some nutritionists poo-poo it
I won't bore you with the complexities of the equation in this article, but if you'd like to know more, I will direct you to an extension publication that does [CLICK HERE]. Suffice it to say, the Relative Feed Value is undervalued.
Three Grass Hay Samples from Highest to Lowest Relative Feed Value
If you are daunted by the plethora of numbers populating a forage analysis, then this article is for you. Can't remember what ADF stands for? Unsure if a digestible energy value of 1.0 or 0.98 is best for your horse? Well, start with this question- "Does my Horse need to gain weight, lose weight or stay the same?" If your horse needs to lose weight, then shop for forages with a RFV below 90. If your horse needs to gain weight, look for a primary forage over 100. And, if your horse needs to stay the same, then shop between 90-99 RFV. Easy!
Jeranyama, P. and Garcia, A.D., 2004. Understanding relative feed value (RFV) and relative forage quality (RFQ).
Lawrence, Laurie. 2011. The Relative Feed Value of Hay. Published December, 2011. Accessed on November 7, 2022 from http://equine.ca.uky.edu/news-story/relative-feed-value-hay