Forage, Fermentation

And Why Horses Thrive On Diversity

 

Horses evolved as continuous foragers, moving across landscapes and consuming a wide range of plant species rather than a single dominant grass. In wild and feral populations, this constant dietary variation plays a critical role in how efficiently forage is utilised, not through the plants alone, but through the way the hindgut microbial population adapts and strengthens over time.

 

As a horse transitions between different grazing areas, each with its own mix of grasses, herbs, and forage species, the cellulolytic bacteria within the cecum and colon are repeatedly required to adjust to slightly different fibre structures, lignin profiles, and carbohydrate bindings. This continual process of adaptation does not weaken the system. It strengthens it. The microbial population becomes more resilient, more versatile, and more efficient at extracting nutrients from plant material. In practical terms, this can be thought of as a form of microbial hybrid vigor, where diversity drives robustness.

 

This is one of the key reasons feral horses and pasture-kept horses on multi species grazing often demonstrate better body condition, calmer digestion, and more stable energy than domesticated horses consuming a narrow forage base. The hindgut environment is not static by design. It is meant to respond, adapt, and improve through exposure to variation.

 

 

Hay, by Necessity, Is Always a Compromise

 

Hay plays an important role in domestic horse management, but it must be understood for what it is. A compromise. Unlike living pasture, hay is harvested at a single point in time, typically when grasses are long-stemmed and mature enough to cut and bale efficiently. This means the horse receives a uniform forage profile day after day, often from a single grass species, sometimes from a single paddock, and frequently from a single cutting.

 

While this provides consistency, it removes diversity. Over time, a narrow forage base limits microbial adaptation and can reduce the overall efficiency of fibre fermentation. The horse still eats, and the gut still functions, but it does not develop the same depth of digestive resilience seen in horses exposed to multiple forage types.

 

When feeding hay, the best outcomes are consistently seen with true multi species grass hays rather than single species products. Hays that contain a mix of grasses more closely replicate natural grazing patterns and provide a broader range of fibre structures for the hindgut microbiome to work with. Even though hay can never fully replicate pasture, diversity within hay is one of the most effective ways to narrow that gap.

 

 

Alfalfa Is Not Grass, and It Should Not Be Treated as Such

 

Alfalfa is commonly grouped with grass hays in feeding programs, but biologically and fermentatively it is very different. Alfalfa is a legume, not a grass, and its fermentation profile bears little resemblance to that of true forage grasses.

 

Legumes ferment rapidly, produce a different volatile fatty acid profile, and place a very different demand on the hindgut environment. In practical feeding terms, excessive alfalfa can overwhelm microbial balance rather than support it. This is why high-alfalfa forage diets are frequently associated with digestive instability, excitability, and inconsistent utilisation, particularly when combined with energy-dense feeds.

 

A useful way to conceptualise this is not to think of alfalfa as forage in the traditional sense, but as a highly fermentable input that must be tightly controlled. While that analogy does not imply sweetness or sugar content, the metabolic impact of excessive inclusion can be just as disruptive.

 

For horses consuming Thrive Feed, alfalfa is not recommended as a primary forage source. If it is used at all, it should never exceed 20 percent by weight of the total forage ration, with the remaining 80 percent coming from true grass hay. This ratio preserves the structural and fermentative dominance of grass fibre while limiting the destabilising effects of excessive legume fermentation.

 

 

Feeding for Function, Not Convenience

 

The goal of forage feeding should not be convenience or tradition, but functional digestion. Horses do best when their hindgut microbes are challenged gently, regularly, and intelligently through exposure to varied fibre sources, not overwhelmed by uniformity or excess fermentability.

 

When pasture diversity is unavailable, selecting multi species grass hay, limiting legume inclusion, and supporting efficient upstream digestion allows the hindgut to function closer to how nature intended. This is where forage choice and feed design must work together, not compete.

 

Thrive Feed is built on this principle. Support digestion first, respect microbial physiology, and allow the horse to do what it has always done best when given the right inputs.