A shiny coat gets credited to grooming: the right brush, a good shampoo, maybe a biotin supplement. But look past the coat, and the glow turns out to be a report card. It is the visible result of a process that happens inside the horse's gut, and in Portugal and Spain that process goes wrong more often than most owners realise.
An Organ With a Huge Energy Bill
The horse is a hindgut fermenter. Unlike a cow, which ferments in the forestomach, a horse digests most of its forage in the caecum and large colon, well after the stomach. There, a microbial population breaks fibre down into volatile fatty acids, the horse's most important energy source.
None of this runs for free. Gut tissue is among the most metabolically active tissue the horse carries. The gut wall constantly renews itself, and the protective mucus lining needs a steady supply of protein to keep up. Before a single calorie or gram of protein reaches muscle, coat or behaviour, the gut has already claimed its share. It sits, so to speak, first at the table.
Why This Goes Wrong Here More Often
Across most of Portugal and Spain, turnout is limited. That is not a side detail, it is the core of the problem: hay is not a supplement to grass here, hay is the ration. Where a horse in a wetter climate can make up part of a shortfall at pasture, that safety net largely disappears.
The baseline itself is thin. Most grassland here is not sown, managed pasture like in Northern Europe, but the extensive, semi-natural Mediterranean systems known as Montado in Portugal and Dehesa in Spain: a spontaneous sward on shallow, acidic, low-fertility soil. That farmers across the south-west of the Iberian Peninsula now deliberately oversow with clover and alfalfa to lift protein levels is not a lab measurement, but it is a clear signal from the field: the standard sward has little to offer on its own.
On top of that comes unpredictable drought, which swings both yield and quality year to year, with no fixed pattern of cutting too early or too late, but with the constant that an older crop at cutting time carries less protein.
And there is a third factor, partly human. In the Montado ecosystem, repeated tillage with heavy machinery has been shown to drive soil degradation through erosion. Separately, general soil science holds that the topsoil layer carries most of a soil's available phosphorus and potassium, and that this is exactly the layer that washes or blows away when land is worked too often without time to recover. Together, these two effects mean grass on such land keeps growing from an increasingly poorer base.
Our own lab data makes the outcome concrete. A 550 kg reference horse in light work needs about 770 grams of protein a day. Eleven kilos of our Meadow hay, at 8.1% protein, delivers 784 grams of that: the full daily requirement from forage alone. That same comparative data also includes local hay at 3 to 5% protein, no exception in this region, which from the same eleven kilos delivers only 290 to 485 grams. A shortfall of 285 to 480 grams a day, quietly patched over by an extra scoop of concentrate that was never meant for the job.
The same holds for energy. The reference horse needs about 22 Mcal a day. Our Meadow hay covers 18.0 Mcal of that, or 82%. Overmature, protein-poor hay delivers noticeably less energy per kilo, and because horses also eat less of it by choice, coverage drops well below that 82%, leaving the rest to come from somewhere else.
What a Shortfall Does Over Time
When intake falls short of demand for long enough, there is no sudden crisis. The horse does not collapse. Instead, the body starts setting priorities. Gut maintenance and basic function come first, and anything counted as surplus gets cut. That surplus is exactly where the glow, the topline and the energy come from.
Over the long term, this adds up: a dull, lifeless coat; a topline that sinks while the belly stays round, the familiar hay belly that is actually a sign of undernutrition rather than overfeeding; reduced resilience, since a large share of the immune system sits in the gut. The same signs can also point to something else, such as worms, dental problems or an underlying condition, so persistent symptoms should always go to a vet first. And an often underestimated risk: owners who patch the gap with a lot of extra grain in an uncontrolled way, which disturbs hindgut pH and raises the risk of hindgut acidosis and colic.
The Fix Is Less Exciting Than the Problem
No miracle product is needed. The fix is something old-fashioned: forage of consistent, demonstrable quality, with protein and energy levels that are actually measured, not estimated. Two bales can look identical and still differ by hundreds of grams of protein a day. That difference is invisible to the eye, but not to a lab certificate.
It is a shift from "how much am I feeding" to "what is my horse actually getting". In a region where hay is the entire ration, not just a supplement to grass, that question is not a luxury but a necessity.
And When You Get It Right
Then something almost undramatically good happens. The gut no longer has to economise on itself, and room opens up again for what the owner actually wanted to see: a coat that catches the light without a bottle involved, a back that carries rather than sags, and a horse with energy for the work instead of just for getting through the day.
The glow, then, is not a cosmetic feature. It is a by-product of a gut that no longer has to improvise, in a climate and on a soil that do not make that easy. Curious where your own horse stands? Run the numbers with the free feeding calculator.