Hay isn't the same from day-to-day, field-to-field or harvest-to-harvest. Since pasture and hay are the forage foundations of your horse's diet, you need to know what nutritional values are in your hay and how pastures can change with weather and season.
Changing seasons and conditions can have a big affect on forage growth and nutrient content/quality, that may necessitate changes in horses’ diets to address seasonal deficiencies. First, it is important to know what a horse’s needs are, and how to meet these with a balanced diet. This may mean supplementing some forages with additional nutrients such as vitamins and/or minerals that can be found in feed and supplements.
Stephen Duren, PhD, of Performance Horse Nutrition, says basic requirements for a specific horse (idle horse, working horse, lactating mare, etc.) won’t change much—except the need for more calories in cold weather to generate body heat or when the horse’s routine has changed.
The real change through the seasons will be in the nutritional levels of the forages you feed and the availability of forage.
How Forage Can Change
“One aspect of seasonal changes is reduction in availability of forages, if horses are depending on pasture,” says Duren. Nutrient content of plants will also change—from early summer when they’re green and growing, or during hot, dry weather when they may be dried out, or winter when they’re dry and dormant.
Hay has different nutrient content if harvested while green and growing, compared to after it’s mature and dry. “Nutrient content of hay and pasture not only changes with the season, but also depends on maturity of plants. As they mature, their structure becomes more fibrous—with higher proportion of non-digestible fiber. Tall pasture or very mature hay has lower digestibility and decreased protein because of the higher fiber content,” said Duren.
Dry or wet extremes in season changes not only affect availability and prices of certain forages, but also their nutrient levels. “In Texas this past year, there wasn’t any forage in some areas of drought,” said Duren, “and the forages that did grow were very stressed. Other regions had too much rain and plants were also deficient in nutrients; extreme moisture can also stress plants.
Without analysis, you might not know the levels of various nutrients in hay or pasture—to know if they are adequate for a particular horse or if he needs a supplement. “The only dietary factor you can see and evaluate is calories—by visual examination of the horse," he explained. "If he’s getting too many calories he’ll gain weight. If he’s not getting enough, he loses weight. But you can’t just look at a horse and say he’s deficient in selenium or protein. It takes awhile before we see symptoms of deficiency.
“Whether a horse has enough protein, calcium, phosphorus, trace minerals, etc., requires a dietary analysis, and these levels will change with seasons,” he stated.
If hay is the major forage portion of a horse’s diet, you don’t always know if it was put up early or late in the season, or know its stage of maturity. Nutrient levels may be different in different batches of hay from the same ranch or same field—in different cuttings or on different years. It depends on growing conditions, and weather conditions at harvest.
“If you buy much hay at a time, the $20 it might cost to have a forage analysis is well worth it. This gives an incredible amount of information, and lets you know if you need to supplement the forage component of diet,” he said. It also lets you know how much of certain nutrients you’d need in your supplement.
“You might not want to analyze every batch of hay if it’s coming from the same farm/same fields every year, but might take a couple samplings each year, or analyze the best forage and the worst—and plan the ration accordingly, based on the worst case scenario," Duren noted. "This enables you to make sure horses’ diets are properly fortified with vitamins and minerals. You can always adjust the calorie content by adding oats or fat.”
Be in the Know
“The biggest service you can do for clients (and keep them happy) is to have a nutrient analysis of forage," he said. "Then you can show how your supplement or concentrate complements that forage at the rate you are feeding it.”
This assures the owner that his/her horse is getting everything it needs. “Putting this information in the owner’s file, along with information on the horse’s weight (based on actual weighing or use of weight tape estimation) can be helpful," said Duren. "You can show the owner that this is what the horse weighs, this is how much hay he’s being fed, and here’s the nutrient analysis of that hay—and this is the supplement being fed, to make up for these specific deficiencies in the hay. You can then ask the owner how much oats or whatever additional feed he/she wants you to add to the diet as an additional calorie source as the horse’s exercise/riding changes.”
There are products that can be added to forage to make up deficiencies that are called ration balancers or supplement pellets. "They are a low-intake product, typically fed at a rate between 1 and 2 pounds per day, for adequate vitamin/mineral concentration," said Duren. "Then you can add any unfortified cereal grains you want, based on the horse’s work if he needs more energy, or if a pregnant mare is thin and needs to gain more weight.”
In the end, it pays to know what your forage contains, and to have a plan to balance that forage. Any nutrient changes in forage can then be accommodated by changing the supplement portion of the diet, keeping your horses and your clients happy.