Forage Recommendations for your Horses

Relative Feed Value (RFV) of Forage (hay and pasture): The Hay Marketing Task Force of the American Forage and Grassland Council has endorsed the use of RELATIVE FEED VALUE (RFV) as a measure of forage quality and its fiber digestibility.

What is forage RFV?

All forage laboratories can provide you with an RFV number for each forage analyzed. There is a direct relationship between the RFV and the digestibility of the forage. The higher the number, the higher the digestibility and availability of the nutrients found inside the plant cells, and vice-versa.

  • ADF (Acid Detergent Fiber): The less digestible carbohydrates are those found inside the plant cell walls, and include cellulose and lignin.
    • The lower the ADF, the more palatable the forage and the higher the digestibility, and vice versa.
  • NDF (Neutral Detergent Fiber): The total plant cell wall carbohydrates, including ADF plus hemi-cellulose. Often considered an indicator of forage quality and intake potential.
    • The lower the NDF, the easier it is to digest and the greater the intake/day, and vice versa.

Table 1: Lists the different quality standards: Forage Grade and Description, along with their corresponding percentages of ADF and NDF and their resulting Relative Feed Values (RFV).

Forage GradeDescriptionIf the ADF is:If the NDF is:Then the RFV is:
PrimeExcellentUnder 30Under 40Over 151
5RejectOver 46Over 66Under 74

This table is from the veterinary textbook Equine Internal Medicine, 2nd Edition 2004, “Applied Nutrition” Chapter, Donald R Kapper, PAS, guest author, and Stephen M Reed, DVM, editor.

“Good Quality” forage has a Forage Grade of 2, or an RFV above 103. If the RFV is below 102, additional nutrients must be fed per day, due to the lower digestibility/availability of the nutrients in that forage. If the RFV is below 74, we do not recommend feeding it, due to the increased risk of impaction colic.

Nonstructural Carbohydrates in Forage

All horse owners/managers/trainers need to do a better job of understanding carbohydrate components and balancing rations based on them – because all carbohydrates are not created equal!

  • NSC (Non-Structural Carbohydrates): Easily digestible carbohydrate components of feed ingredients. Originally, it was made up of: starch + sugar + fructans, but recently calculated as WSC + starch and ESC + starch.
  • WSC (Water-Soluble Carbohydrates): Carbohydrates that can be extracted with water, including simple sugars and fructans. High WSC might indicate high fructan levels in grasses or high simple sugars in non-grass forages. Beneficial to horses needing extra endurance, but not for horses with laminitis.
  • Fructans: Carbohydrates made up of many fructose molecules (complex sugar) and digested by fermentation, primarily in the hindgut. They are found in “cool season” grasses (Ky Bluegrass, Timothy, Orchardgrass, etc.) and are not found in legumes (Alfalfa, Clover, Peanut Hays, etc.).
  • ESC (Ethanol-Soluble Carbohydrates): Carbohydrates that dissolve in ethanol solution and primarily digested in the small intestine. High ESC generally means a feed will generate a high glycemic (blood sugar) response. Beneficial to hardworking horses that need lots of “short term” energy, but not for horses that are sensitive to blood sugar changes (e.g., insulin-resistant horses).
  • Starch: Found mainly in cereal grains (such as oats, corn, barley, rice, and wheat) and mostly digested in the small intestine where they are broken down and absorbed as glucose (simple sugar).
    • Low starch content means little glucose will be absorbed in the small intestine (low glycemic response). This is good for horses that can’t handle large blood sugar changes (e.g., insulin-resistant horses).
    • High starch content means a high glycemic response. Good for horses needing “quick” energy (fuel for fast-twitch muscles).

Recommended forages (with the supplementation of Progressive Nutrition’s Diet Balancers) for horses with insulin resistance, cushings, equine metabolic syndrome or laminitis, is to keep the nonstructural carbohydrates below 15% in the total diet. Severely affected Insulin Resistant (IR) horses need to be kept below 10% ESC + starch in the total diet, while all Laminitic horses should to be kept below 10% WSC + starch. If the hay NSCs are unknown or higher than recommended, soak in cold water for one hour before feeding it. This will remove about 30% of the nonstructural carbohydrates or the WSC + starch. Remember to discard the water.

Because all cereal grains and molasses are high in NSC or WSC + Starch (45% to 75%), we do not recommend feeding any horse feed that has cereal grains or molasses in its ingredient list to IR, laminitic, cushings or equine metabolic syndrome horses. If extra calories are needed, use vegetable oil and digestible fiber as their calorie sources, not cereal grain. The three best sources of digestible fiber are: beet pulp, soybean hulls, and alfalfa.

BE AWARE – All crude fibers are NOT created equal!

There are “indigestible” sources of crude fiber available today that are very inexpensive and used in feeds to keep the price per bag down. They include Oats Hulls (oat mill feed), Rice Hulls, and Peanut Hulls. They all contain a very high percentage of lignin, which is 100% not digestible to the horse. Read the ingredient list to see if they are listed there. They can also be called “Plant By-Products” or “Processed Grain By-Products.”

How Much to Feed Horses per Day?

For hay, every horse should be fed a minimum of 2% of their body weight per day in hay. That would be equal to 20 lbs of hay per 1,000 lbs of body weight.

The amount of protein, minerals, and vitamins needed per day will depend on the individual horse’s size, age, reproductive status, and/or training level. These nutrients are included in all of Progressive Nutrition®’s Diet Balancers and Horse Feeds. To help you determine how much to feed per day, we have Growth Monitoring and Daily Feed Planner Charts available on the Nutrition Information page of our website.

The number of added calories needed per day to maintain desired body weight will depend on each horse’s:

  • Metabolic rate (metabolism)
  • Calories per pound (or the digestibility, RFV) in their forage (hay and pasture)
  • Exercise level per day
  • Current Body Condition Score (BCS).

Extra calories can be added when needed, with additional vegetable oil sources (Envision® Classic) or Oats when feeding our Diet Balancers, any of our Premium line of feeds, or our extruded feed