Protein Nutrition III: Determining Protein Requirements for Your Horse

Written By Dr. Kris Hiney

In the last two articles we discussed the importance of protein quality, not only in terms of site of digestion in the horse, but also the amino acid composition of that feed.  Now we will try to simplify these concepts into selecting appropriate feeds for horses.

The first task in developing a feeding program for your horse is to identify what class of horse you have.  (For a review revisit: Equine Energy Requirements and Energy Requirements for the Working Class)  The horses with the lowest protein requirements relative to their body size are the mature horses not in work, or maintenance horses.  This does not include geriatric horses which may have altered protein needs due to the lowered efficiency of their digestive system.  We also must assume that the horse is receiving enough calories in the diet.  A horse fed a diet sufficient in protein, but low in calories will lose weight (makes sense right?) but a horse which has adequate calories but not enough protein can also lose weight.  We also make some consideration for the activity level of the horse as well.  Remember the difference in energy requirements  between the couch potato Quarter Horse and the active Thoroughbred mare (Equine Energy Requirements)?  Well a similar relationship exists with protein requirements.  Essentially the more active horse would have more lean tissue/muscle  to support than the lazy horse.   Table 1 lists the actual protein requirements for a  maintenance horse depending on activity level and their body weight.  Remember that this does assume a quality protein source. Lower quality protein (less digestible or poor amino acid profile) can adjust these figures upwards.

Table 1.  Crude Protein requirements for maintenance (grams of CP/d) based on average activity level.

Wt of horse (lb)

Couch potato

Average

Active

900

434

507

579

1000

482

562

642

1100

530

619

707

1200

579

675

772

1300

626

731

835

What percent protein do you need?

But let’s put these numbers into something more people are familiar with, percent of the diet.  Table 2 provides the percent protein of the total diet a horse would need to consume to meet their protein requirements.   Looking at Table 2 shows how easy it is to meet a maintenance horse’s protein requirement.  You can also see that as total consumption goes up, the percent of the protein needed in the diet goes down.  Conversely, if you fed less you would need to increase the percent protein in the diet.  Horses will usually consume between 1.5 and 2.8% of their body weight per day on a dry matter basis.  Typically you will see horses lower their consumption of less palatable hay which often equals poor quality.  However, this can largely be based on the individual, as some horses compensate by lowered feed quality by increasing intake (Edouard et al., 2008).  It turns out that horses are much more variable in their voluntary intake than other domestic species are!  Just like a horse to always want to be unpredictable. If you notice your horse picking through its hay and leaving a good proportion of the hay untouched it may be wise to select a supplement designed to provide amino acids but not to greatly increase the calorie consumption by the horse.  Alternatively it may be time to find a new hay supplier (see Selecting Forages).

Table 2a. Percent total protein required in the diet on a dry matter basis depending on the total consumption of the horse per day.

% of Bwt consumed

Couch potato

Average

Active

1.5

7.2

8.4

9.6

1.75

6.2

7.2

8.2

2.0

5.4

6.3

7.2

2.25

4.8

5.6

6.4

2.5

4.3

5.0

5.6

Table 2b. Percent total protein required in the diet expressed on an as fed basis assuming an average dry matter content of 85%. Note: this can change with the feed fed and is only representative of harvested feeds, not pasture or grasses.

% of Bwt consumed

Couch potato

Average

Active

1.5

8.5

9.9

11.3

1.75

7.3

8.5

9.7

2.0

6.4

7.4

8.4

2.25

5.6

6.6

7.5

2.5

5.1

5.9

6.8

Protein content of common horse feeds

Now let’s look at some typical protein values for feeds.  To be sure of your own feed ideally have your forage tested as well as examine your feed tag.  Corn ranges between 8-9 % CP on a DM basis, oats 12-13%, soybean meal – 43-49%, grass hays – 10-18%, and legumes between 18-25%.   With the range of protein content in forages, one can see how important it is to have knowledge of your nutrient content prior to selecting your concentrate.   Even with these ranges, most maintenance horses will easily meet their protein requirements by forage alone.  If you look at the range of percent protein needed by the maintenance horse in their total diet, it compares quite well with grass hays.  If you are feeding your horse and he is maintaining weight, he should easily be meeting his protein requirements at the same time.  Remember, we assume  the horse is receiving good quality hay.  If you are worried about the horse meeting its amino acid needs, many feed companies make supplements specifically designed to be fed with a strictly forage diet, rather than greatly increasing the concentrate intake.  For example, many feed companies offer protein supplements in the range of 30-35% crude protein.  These are designed to be fed at a minimal rate (only 1-2 lbs per day) in order to simply balance out any deficiencies from an all forage diet.  Clearly not all horses need the extra calories that come from feeding higher levels of concentrates.  This provides a convenient, easy way to ensure that your horse’s nutritional needs are being met.

Next month we continue with protein nutrition in the exercising horse.

Edouard et al.2008. Animal:An international journal of animal biosciences. 102:10:1526-1533.

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