Horse owners generally reach for high-calorie feeds, vegetable oils and supplements when faced with adding weight to underweight horses. These products, without question, have their place in any weight-gain program, but the quality of pasture and hay should also be a primary consideration.
Pasture. A well-maintained, lush pasture can be a nutritional paradise for an underweight horse, offering plenty of energy and other nutrients to fuel weight gain and boost well-being.
For maximal efficiency, stocking rate should be considered. Using a stocking rate of one to two acres per horse, a five-acre field could easily sustain two to three horses, especially when growing conditions are optimal. On the flip side, stocking rate would decrease for that same pasture if weather patterns preclude pasture growth or if weeds have gained dominance over nutritious grasses. Waves of weeds, no matter how pretty their flowers (think buttercups), have no value in horse pastures and should be eradicated with a thoughtful (and horse-friendly) control program.
Of course, horse owners must introduce even thin horses gradually to pasture, starting with an hour a day and adding an hour each day until they are grazing 10 or 12 hours. Once horses are on pasture for half the day, they can be turned out in the field full-time if the management scheme warrants.
As horses transition to pasture, changes in manure might occur, including a noticeable loose or cowpie consistency. These changes are likely due to an influx of water (remember, grass is chock-full of water) and a modification of the microbial population in the hindgut. This microbial population, which is critical in transforming forages to usable energy, requires time to adjust to any new diet, underscoring the importance of slowly familiarizing horses to pasture.
Pastures with little or no nutritious vegetation offer nothing to an underweight horse, so efforts should be concentrated on finding suitable forage alternatives, such as hay or hay products.
Hay. All hay fed to horses should be good-quality, meaning free of dust, mold, weeds, foreign debris, and over-mature plants. All hay does not, however, provide horses with the same energy, and this is advantageous to horse owners, considering the wide range of body types that must be managed. While a "whale-of-a-Welsh Pony" might live happily and healthily on hay manufactured from nondescript, mature pasture grasses, the same might not hold true for an apprehensive Thoroughbred that requires an upgrade in body condition.
For thin horses on a weight-gain regimen, the highest-quality hay should be sought. What differentiates high-quality hay from middling hay? In this situation, two elements are important: plant type and stage of maturity.
Hay typically contains grass or legume plants, or a mixture of both. To bump up the energy content of a ration, horse owners should consider a legume hay, typically alfalfa (lucerne) but clover or lespedeza are also options. A pure legume hay can be particularly energy-dense, especially if it’s been produced with dairy cattle in mind, so consider this during hay selection.
If a straight legume offers too many calories or is price-prohibitive (in some regions, alfalfa can be expensive), a top-tier grass-legume mix will also provide more energy than an all-grass hay.
To get the most nutrients from hay, it should be harvested at early maturity, as this is when leaves are nutrient-packed and stems are soft and pliable. Over-mature hay often contains stiff or woody stems, which are harder for horses to digest and offer far less nutritive value.
Any hay, regardless of type, that is off-colored, dusty, or foul-smelling should not be fed to horses.
Achieving weight gain in horses is not for the impatient, but choosing a high-quality forage is one way to increase energy consumption. An appropriate feed—one fully fortified to complement the forage—will also help the resident rack-o’-bones gain weight.
Working closely with an equine nutritionist will ensure you’re making the best feeding decisions. Don’t know a nutritionist? Start a conversation with a KER nutrition advisor now.
And really, that Welsh Pony mentioned earlier, he should be managed so he’s maintained in moderate body condition. Now, where’s that grazing muzzle...
KER Note: EquiShure, a hindgut buffer developed by Kentucky Equine Research, stabilizes the pH of the hindgut, which can fluctuate as the microbial population adapts to a pasture-rich diet. Shifts in pH can cause acidosis, which may, in turn, lead to gastrointestinal problems.