Carbohydrate Content of Feed

The important information in the following table is primarily the NSC. This represents the carbohydrate or "energy" content of the feed. As you can see oats, corn and sweet feed are all considered "hot feeds" due to their high sugar content. If we are trying to manage a horse's weight we would tend to not use these feeds and instead we may go to a higher fiber, lower carbohydrate feed. This could be accomplished in a number of ways. If a Timothy based hay was available that could be appropriate by itself. If it was desirable to feed a grain, there are newer pelleted or "complete feeds" on the market that tend to have a lower protein and carbohydrate compound. Depending on the hay quality and the feed source it may be advisable to add a vitamin-mineral supplement to the diet. Besides managing weight gain, carbohydrate limits are important for Cushingoid horses, those prone to founder and horses with EPSM concerns.

The unknown component of most feeds may not be the grains as we can usually determine the carbohydrate content, but the hay remains the variable that requires investigation. The NSC levels for hay may vary due to the type of grasses, which cut is harvested and even what time of day the hay is cut. Fortunately a simple hay evaluation will take the guess work out of this and this can be arranged through my office.

Measuring Weight of Feeds

These conversions may be helpful for those of you that are trying to measure the amount to feed based on volume or weight.

Table 1. Average feed weights in a 1 lb. coffee can

Feed lb./can
Beet Pulp 0.50
Corn 1.40
Extended Feed 0.75
Oats 1.20
Pelleted Grain 1.50
Sweet Feed 1.20
Wheet Bran 0.45

Average Feed Composition

Table 2. Nutrient composition of common equine feeds on an as fed basis (%)

FEEDSTUFF DE (Mcal/lb) Moisture (%) protein (%) fat (%) NDF1 ash (%) NSC2 (%)
timothy hay .80 10.00 8.60 2.30 56.60 5.40 17.10
alfalfa hay .94 90.00 17.02 0.40 42.90 7.80 21.90
wheat straw .67 90.00 3.20 1.80 72.10 7.10 6.80
sweet feed 1.47 14.00 12.60 6.00 14.00 4.30 49.00
pelleted feed 1.5 - 10-14* 4-6* -* -* -*
oats 1.30 10.80 11.50 4.60 24.40 3.10 45.60
corn 1.60 12.00 9.10 3.60 9.50 1.30 64.50
barley 1.42 10.40 11.70 1.80 16.80 2.40 56.90
molasses 1.11 25.70 4.30 0.20 0.40 9.90 59.50
beet pulp 1.18 9.00 8.90 0.50 40.50 4.90 36.20

1neutral detergent fiber

2non-structural carbohydrate

*variable number (evaluate feed tag)

Click here for:  NSC levels for commercially available feeds (PDF ~ 188Kb)

Conversion Factors

Units Multiply By Units Desired
lb 454 g
lb .454 kg
kg 2.2 lb
Mcal 1000 kcal
Mcal/lb 2.2 Mcal/kg
cal 4.184 J
Mcal/lb 9.224 MJ/kg
kcal/lb .00922 MJ/kg
ppm 1 mg/kg
ppm .0001 %
ppm .454 mg/lb
% 10,000 mg/kg
% 4536 mg/lb

Abbreviations

  • g = grams (1 g = 1000 mg)
  • kg = kilograms (1 kg = 1000 g)
  • mg = millograms
  • cal = calories
  • kcal = kilocalories (1 kcal = 1000 cal)
  • Mcal = megacalories (1 Mcal = 1,000,000 cal)
  • J = joules
  • MJ = megajoules (1 MJ - 1,000,000 J)
  • ppm = parts per million
  • IU = International Units

Nutrient Requirements for Horses Using National Research Council (NRC) Information

Table 3. Horses on Maintenance Diets (no-minimal work)

Weight of Horse DE (Mcal Protein (g) Calcium (g) Phosphorus (g) Magnesium (g)
400 kg1 13.4 536 16.0 11.2 6.0
500 kg2 16.4 656 20.0 14.0 7.5
600 kg3 19.4 776 24.0 16.8 9.0

Table 4. Horses in Light Work

Weight of Horse DE (Mcal Protein (g) Calcium (g) Phosphorus (g) Magnesium (g)
400 kg1 16.7 670 20.4 14.6 7.7
500 kg2 20.5 820 25.0 17.8 9.4
600 kg3 24.2 970 29.6 21.1 11.2

Table 5. Horses in Moderate Work

Weight of Horse DE (Mcal Protein (g) Calcium (g) Phosphorus (g) Magnesium (g)
400 kg1 20.1 804 24.5 17.5 9.2
500 kg2 24.6 984 30.0 21.4 11.3
600 kg3 29.1 1164 35.5 25.3 13.4

Table 6. Horses in Heavy Work

Weight of Horse DE (Mcal Protein (g) Calcium (g) Phosphorus (g) Magnesium (g)
400 kg1 26.8 1072 32.7 23.3 12.3
500 kg2 32.8 1312 40.0 28.5 15.1
600 kg3 38.8 1552 47.3 33.8 17.8

1Breed examples + Connemaras, Icelandics, Morgans (smaller)

2Breed examples = Thoroughbreds, Quarter Horses, Appaloosas, Paints, Morgans, Warmbloods (Selle Francais), Welsh Cobs

3Breed examples = Warmbloods (Dutch, Hanoverians, Trakehners, Oldenburgs)

Definitions

As Sampled Basis -nutrient results for a sample in its natural state including the water. Also known as as fed or as received.

Crude Protein (CP) - the total protein in the sample including true protein and non-protein nitrogen. Proteins are organic compounds composed of amino acids. They are a major component of vital organs, tissue, muscle, hair, skin, milk and enzymes. Protein is required on a daily basis for maintenance, lactation, growth and reproduction.

Neutral Detergent Fiber (NDF) - a measure of hemicellulose, cellulose and lignin representing the fibrous bulk of the forage. These three components are classified as cell wall or structural carbohydrates. They give the plant rigidity enabling it to support itself as it grows, much like the skeleton in animals. NDF can be negatively correlated with intake.

Acid Detergent Fiber (ADF) - a measure of cellulose and lignin. Cellulose varies in digestibility and is negatively influenced by the lignin content. As lignin content increases, digestibility of the cellulose decreases. ADF is negatively correlated with overall digestibility.

Starch - a polysaccharide found primarily in the grain or seed and/or root portions of plants. Starch is a good source of energy.

Water Soluble Carbohydrates (WSC) - carbohydrates solubilized and extracted in water. Includes monosaccharies, disaccharides and some polysaccharides (mainly fructan). Fructan is a major storage carbohydrate in grasses.

Ethanol Soluble Carbohydrates (ESC)- carbohydrates solubilized and extracted in 80% ethanol. Includes primarily monosaccharides and disaccharides.

Non Fiber Carbohydrates (NFC) - a mathematical estimate of non-cell wall (non-fiber) carbohydrates consisting of starch, sugar, pectin and fermentation acids that can serve as energy sources for the animal. NFC is calculated as 100% - (CP% + NDF% + Fat% +Ash%).

Fat - Fat is an energy dense nutrient and contains 2.25X the energy found in carbohydrates. Fat is added to rations to boost energy levels when intake may be limiting.

Total Digestible Nutrients (TDN) - denotes the sum of the digestible protein, digestible nitrogen-free extract (NFE), digestible crude fiber and 2.25X the digestible fat. TDN is estimated from digestible energy (DE).

Digestible Energy (DE) - the energy that is apparently digested and absorbed by the animal. It is determined by subtracting the energy contained in the feces from the gross energy. In horses, the fecal energy loss is typically 35 - 40% of the gross energy. The DE is used to balance the energy portion of the equine diet. Energy requirements are expressed as megacalories (Mcal) in the nutrient requirement tables.

Calcium (Ca) - bone and teeth formation, blood clotting, muscle contractions, milk component, transmission of nerve impulses, cardiac regulation, activation and stabilization of enzymes.

Phosphorus (P) - bone and teeth formation, key component of energy metabolism, milk component, body fluid buffer systems.

Magnesium (Mg) - enzyme activator, found in skeletal tissue and bone, neuromuscular transmissions.

Hay Analysis

Now that you may have had your hay analyzed how can you make sense of the information? Making sense of the DE, CP and various minerals will be the easy part. Understanding the breakdown of the carbohydrates and fiber numbers is where a significant amount of confusion develops. Understanding the concept of NSC seems straightforward until you delve into how these carbs can be separarted into several fractions.

Generally the hay analyses will report the carbohydrate information in the following categories: %NSC, %NSC Starch, %NSC WSC and %NSC ECS.

WSC - Water Soluble Carbohydrates include sugar and all the fructans.

ESC = Ethanol Soluble Carbohydrates include sugars and the shorter chain fructans.

Fructans may be a new term for many of you and it is one that deserves some understanding especially for those with horses that are considered higher risk for laminitis and metabolic disease. Fructan is a storage polysaccharide produced by most C3, cool-season grasses (orchard grass, timothy, brome, crested wheatgrass and certain broadleaf plants), they are higher in NSC than C4 warm season grasses (Bermuda, summer prairie grasses, and other grasses of tropical origin). This is because C4 grasses store starch instead of fructan. Starch forms in specialized organelles in the grass. When those organs are full, starch production stops, so starch production is self-limiting. In C3 grasses, fructan is stored in various places all over the plants and can continue as long as conditions are conducive to formation of sugar, while growth is limited.. In plants, fructan production occurs only under certain conditions, generally when growth is limited by some sort of stress, while sunlight continues to create sugars that cannot be utilized. Some kinds of grass are better at making fructan than others, but we still need to acknowledge that environmental conditions are more important than genetic potential. Fructan is good for plants; it gives them energy stores to tap when times get hard. Mammals lack the enzymes to digest fructan, but symbiotic bacteria in the gut readily ferment it. Fructan is good for cows, providing a rapidly fermentable energy source for the microorganisms in the rumen. But cows ferment in the fore-gut, while horses ferment in the hind-gut, and this is where the problem lies.

Connecting the dots to how fructans directly play a role in precipitating a laminitic episode is not exactly clear. There have been several theories and probably it is related to a combination of factors. A metabolic theory is related to an insulin spike after the ingestion of fructans, sugars and starch. A bacterial one relates to the changes in the gut that follows from ingesting more fructans where the acidity increases (pH drops), the microbial population is altered and the lining of the gut is affected.

When analyzing hays fructans will be included and depending on the type of grasses, time of harvesting and other environmental factors the levels will vary.

The average of Non Structural Carbohydrate (WSC + starch) content in straight grass hay is 11 to 15% of dry matter. There is very wide range in NSC content of grass hay, from 2% to over 30% of dry matter. High levels of NSC may occur in hay grown under cold or drought stress, or without adequate fertilizer. Anything that slows growth can increase NSC concentration.

Starch content of grass hay is generally 1 to 3%, while Ethanol soluble sugar content normally runs from 4-11% of dry matter. Again, under unusual weather conditions, sugar may be higher than these averages. If cost effectiveness is a concern, test just for sugar content and skip starch, (unless it is Bermuda or another tropical grass hay, in which case the starch can be high). For a horse with glucose intolerance, keeping the level of NSC (WSC + starch) in hay <10 %, can often alleviate symptoms.

Applying information to horses Now we will go back to the sample hay analysis and try to find some practical information. Some of this depends on your goals. Is the hay being analyzed to see if it's a quality product for your horses? Will it satisfy what is suggested by the NRC seen in Tables 3-5? Do you have horses with metabolic issues and risk of laminitis?

First of all I will start with the question of its quality for two situations: a Thoroughbred that is just being maintained through the winter months and the second being a Hanoverian in moderate work.

For the Thoroughbred we can look at Table 3 and use the 500 kg category and read across to see the appropriate suggested levels. Going back to our hay sample, we can see the DE is .84 Mcal/lb so if the horse eats 25 lbs of hay/day his energy intake from the hay will be 21 Mcal/day. The protein intake with 6.8% protein will be calculated using the conversions. 6.8% X 4536 = 30,845 mg/lb. Using the conversion of mg to g we will get 30.8 g of protein/lb of this hay. Assuming the horse eats 25 lbs the daily protein intake will be 30.8 X 25 = 771 g/day. The Calcium, Phosphorus and Magnesium can be calculated in the same manner as was done with the protein.

Now going back to Table 3 line 2 we will check if the hay is appropriate. The suggested DE is 16.4 Mcal and the hay supplies an excess with 21 Mcal/day. The protein level of 656 g which is recommended will be exceeded with this amount of hay as 771 g/day was calculated. The measured minerals of Calcium, Phosphorus and Magnesium will also exceed base levels with 41 g, 26 g and 13.5 g respectively. For many Thoroughbreds the winter months are the hardest and feeding extra calories is not a bad idea as they often need it to maintain their body condition, while a Morgan on the same hay may put on weight. The extra protein will not be a problem nor the increased minerals. Again this is making the assumption that this horse actually eats 25 lbs hay/day, if the horse is in a group it may be harder to judge and some horses may not eat this amount due to dental issues, palatability/condition of hay or individual preference. This hay would work as a maintenance diet for this type of horse and grain would not necessarily be required. Again it's always important to look at the individual and continually assess body condition, the environmental situation and daily consumption.

For the second horse, the 600 kg Warmblood in moderate work (Table 5), the daily requirements are going to be quite a bit higher. Generally a horse in this situation may be eating less hay than the previously discussed horse. So, let's assume this horse eats 18 lbs hay/day. Our calculations based on the consumption of 18 lbs hay/day of this hay are as as follows: DE 15.1 Mcal, Protein 554 g, Calcium 30.6 g, Phosphorus 18.7 g and Magnesium 9.8 g. Based on this hay the DE is deficient 29.1-15.1=14 Mcal, the Protein is deficient 1164-554=610 g, the Calcium is low 35.5-30.6=4.9 g, the Phosphorus is low 25.3-18.7=6.6 g,and the Magnesium is also low 13.4-9.8=3.6 g. So there are a couple of considerations, in order to make up the deficiencies the horse would need to eat more hay, possibly find a better quality hay to replace or supplement this and/or use grains. As most of you would assume this diet will need some type of grain. If we chose a 14% Protein pellet and sweet feed mixed ration and fed 6 ilbs/feeding would that work?

If we use Trotter that has 14% Protein, 3% Fat, +/- .85% Calcium, .6% Phosphphorus, with an unknown quantity of Magnesium plus Charger with 14% Protein, 6% Fat, +/- .9% Calcium, .6% Phosphorus and an unknown quantity of Magnesium as our grains how will they work? The Calcium levels are estimated because they are listed on the feed tag as a minimum level of .6% to a maximum 0f 1.1% in the case of Trotter. The DE numbers for both are not actually known, but we can use 1.5 Mcal/lb as an approximation for both. The increased fat in the Charger is a more "energy dense" source of calories. In addition if we look at the NSC levels of Charger vs. Trotter you will see the carb content is quite a bit higher for Charger. For this type of horse it may be beneficial, but for a "hotter" horse or one who was on lay-up or perhaps if there were metabolic issues then this would need to be re-considered.

If we went by the company's (Blue Seal) recommendation for amount of Trotter to feed a horse of this size and work level, they suggest 0.65 - 1.00 lbs feed/100 lbs body weight. So for a 600 kg horse that weighs approximately 1300 lbs the range would be 8.5 - 13 lbs feed/day. This seems like a large quantity of grain, but again we have to remember the energy demands of a horse working bat this level. Since we plan on using Trotter and Charger and because I prefer using more of a pelleted ration than a sweet feed, I will start with a diet of 4.5 lbs of Trotter and 1.5 lbs of Charger.

Starting with Trotter fed in this quantity the totals for the day will be as follows: DE 13.5 Mcal, Protein 571.5 g, Calcium 34.7 g, and Phosphorus 24.5 g. The Charger fed at 1.5 lbs twice daily will give the following results: DE 4.5 Mcal, Protein 190.5 g, Calcium 12.2 g, and Phosphorus 8.2 g. The following table will show all the results.

Results of a Typical Hay Analysis

Evaluated on "As Sampled Basis"

Components Levels
DM % 92.4
Protein % 6.8
ADF % 41.5
NDF % 62.9
TDN % 53
Calcium % .37
Phosphorus % .23
Magnesium % .12
Fat % 2.1
NFC % 17.5
% NSC Starch 1.5
% NSC WSC 8.8
% NSC ESC 6.8
% NSC 10.2
DE Mcal/lb .84

Table 8

FEEDS DE (Mcal) Protein (g) Calcium (g) Phosphorus (g) Magnesium (g)
Hay Sample 15.1 554 30.6 18.7 9.8
Trotter 13.5 571.5 34.7 24.5 -
Charger 4.5 190.5 12.2 8.2 -
Totals 33.1 1316 77.5 51.4 9.8
Recommended Levels 29.1 1164 35.5 25.3 13.4
Excess/Deficiency + 4 + 152 + 42 + 26.1 - 3.6

So back to our original question of does this diet work for this particular horse? The answer would be yes, the excesses are not significant issues in this case. We could lower the protein excess by substituting adifferent ration with one that had less than 14% crude protein. The calories will probably work in this horse's favor due to energy demands of the work. Maintaining an appropriate Calcium to Phosphorus ratio is important with all diets. In this case the ratio is 1.4:1. Recommended levels vary, but a range of 1.2-2.1 is appropriate. In order to increase the Magnesium levels without throwing off the Calcium-Phosphorus ratio a mineral suppllement would need to be added to the diet. A trace mineral salt block would be recommended as a good salt source, but the horse will still probably be deficient in Magnesium unless supplemented separately.