What our sheep eat in autumn: new grass, stubble, acorns and olive prunings

There's one image that sums up really well how we work with our sheep: Gustavo, sitting on a hillside as evening falls, with a pair of binoculars, watching them eat. He isn't looking for a lost sheep. He wants to know which leaf they pick, what they leave behind, what they're nosing for in the grass. Gustavo, from Toledo, and Susana, from Madrid, are agronomists who met at university, and today they look after our Manchega sheep and our goats and make the team's goat, sheep and mixed-milk cheeses in the province of Toledo.

When autumn arrives, the countryside changes its menu. New grass peeks through, the stubble is still there, the holm oaks drop their acorns and the olive grove pruning leaves piles of branches. For a flock of 4,200 Manchega sheep grazing across some 600 hectares, every resource counts.

We'll tell you what our sheep eat in autumn and check it against the science: acorns are an extraordinary feed, but they come with some fine print. And the idea of "montanera cheese" deserves an explanation.

Autumn, the most generous season for the flock

Walking around the farm in early autumn, the first thing they told us sounded almost like a celebration:

At this time of year the land is in great shape. See how the grass is starting to come up? This is this year's stubble. And then something really important: the acorns, which are starting to fall. Sheep love acorns. So here they've got a really varied diet.

That variety is the key. After a summer when the pasture dries out, autumn brings several things at once:

• New grass. The first rains wake up the seeds that spent the summer in the soil; out here we call it the otoñada. It's tender, juicy, digestible grass, but scarce at first: the sheep have to walk a lot and be very selective.
• Stubble. Our rotation has one plot of cereal, another of legumes and another resting with the year's stubble, as we told you in sheep among the olive trees: grazing and rotation. Straw on its own is poor and fibrous, but the sheep pick up fallen grain, eat the grass sprouting between the stalks and fertilise the soil along the way.
• Acorns. Holm oaks and Portuguese oaks drop their fruit in autumn, and the sheep love it.
• Olive prunings. It's pruning season in the olive grove, and the thin leafy branches are a treat the flock really appreciates: "they love the olive branch prunings, they absolutely love them".

Acorns: what they really provide

Gustavo and Susana talk about them with enthusiasm: "they pack an amazing amount of nutrients, as everyone understands from Iberian ham". To be precise, the acorn is above all an energy feed, not a complete feed.

A Portuguese study published by CIHEAM (Ferraz de Oliveira et al., 2012) analysed the pulp of holm oak acorns (Quercus rotundifolia, the Iberian holm oak) and cork oak acorns:

More than half is starch, around 10 % is fat and protein barely reaches 4 %. An article from the University of Córdoba in the Revista Forestal (Rey et al., 2022) gives figures of the same order and points out that composition varies a lot from one tree to another. In one of their holm oaks, oleic acid made up around 76 % of the fat.

For a sheep, that's a lot of energy in just a few mouthfuls, right when it needs to get back into condition after summer. But the protein has to come from grass, legumes and forage.

Why a sheep isn't an Iberian pig

The comparison with Iberian pigs is very intuitive, but there's a fundamental difference. A pig has a single stomach, and much of the oleic-rich fat it eats passes almost unchanged into its back fat. That's why the montanera shows so clearly in the ham.

Sheep and goats are ruminants: in the rumen, microorganisms turn a good share of unsaturated fats into saturated ones (biohydrogenation). A review by the French INRA (Chilliard et al., 2007) explains that diet does change milk fat, but far less directly than in pigs. Acorns can influence the milk; they don't "turn" cheese into acorn-fed ham.

Is there such a thing as "montanera cheese"?

During the visit this phrase came up: "Some people make montanera cheese, like with hams". We looked into it carefully, because it's a lovely idea and we wanted to tell it accurately:

• "Montanera" and "acorn-fed" are legal terms for Iberian pigs. The Iberian quality standard (Royal Decree 4/2014) defines the montanera as the feeding regime based on acorns and dehesa pasture, and for "acorn-fed" ham it requires entering the dehesa between 1 October and 15 December and gaining at least 46 kg over more than 60 days. That standard only applies to pigs.
• There's no official category of "montanera cheese" or "acorn cheese". We haven't found any designation of origin, geographical indication or regulation with that name for sheep's or goat's cheese.
• There are cheeses linked to acorns, though. The clearest example is PDO Queso Ibores, a goat's cheese from Extremadura: its specification describes woodland of holm and cork oaks and says acorns are "one of the main sources of food in the winter season" for the goats.

So "montanera cheese" is an expression that makes perfect sense in the countryside, but it lacks the legal backing that ham has: if someone uses it, it's a free commercial name. If you see a cheese with that label, ask what's behind it: how many months in the dehesa, how much of the diet was acorns and when the milk was collected.

Interestingly, PDO Queso Manchego, whose area includes the province of Toledo, describes in its single document a landscape of "holm oaks, kermes oaks and Mediterranean scrub" and links it to the cheese's colour, aroma, flavour and texture. The holm oak has always been part of Manchego's landscape.

Acorns yes, but sensibly: tannins and quantities

Acorns contain tannins, the compounds that give an unripe persimmon that rough, dry feel. In small amounts they're not a problem; in large amounts, they are. The MSD Veterinary Manual, describing Quercus poisoning, gives several key points:

• Sheep and cattle are the most sensitive ruminants. Goats are relatively resistant: their saliva has proteins that bind to tannins and their rumen adapts to break them down.
• It takes a lot. As a general reference, the manual talks about animals getting 75 % or more of their diet from oaks.
• The risk appears when other food is lacking and hungry animals only have acorns, shoots or leaves within reach.

On top of that, the Portuguese study found that tannins drop as the acorn ripens: green ones that fall early are more astringent. And a trial with lambs published in Archives Animal Breeding (Mekki et al., 2022) replaced 40 % of the barley in the feed with holm oak acorns without seeing differences in growth or digestibility, although the authors consider it a feed "to be used with caution" and cite studies where, at 50 %, protein utilisation got worse.

The sensible guidelines are few and clear:

1. Acorns are a supplement, not the base. They're eaten alongside grass, stubble and olive prunings.
2. Never on an empty stomach. A well-fed flock is selective; a hungry one gorges.
3. Introduce them gradually. The rumen needs a few days to adapt to so much starch.
4. Always clean water. In a dry autumn that's no small thing, as we explained in what you don't see behind a cheese.
5. Watch. Exactly what Gustavo does with his binoculars.

Olive prunings

Olive leaves have always been fed to livestock in the Mediterranean countryside. The FAO devoted a chapter to them in its study on olive grove by-products, with plenty of data from Spanish research, and the Feedipedia database (INRAE, CIRAD, AFZ and FAO) sums up the essentials:

• Moderate protein (around 9–10 % of dry matter in fresh leaves) and lots of fibre (40–60 %).
• Better fresh than dry: in sheep, the digestibility of fresh leaves is around 55–60 % and drops to 40–50 % when dry. The FAO advises using them no later than eight days after pruning.
• Sheep choose: they eat the leaves and thin stems and leave the wood, which adds very little.

And one important precaution: sheep are very sensitive to copper. The copper fungicides used in olive groves against peacock spot can leave levels on the leaves that are toxic to them, and Feedipedia puts it bluntly: don't give sheep leaves treated with them. Before putting the flock into a freshly pruned plot, you need to know what treatments it has had.

Gustavo and his binoculars

Back to the hillside. This is what Gustavo told us:

What I usually do is come up here in the evenings with the binoculars, so I can see exactly the mouth, the leaf, and I know what they like and what they don't. I watch the sheep looking for things, and I ask myself: what's she looking for? What's this? I come at different times of day to see how they eat one thing, how they eat another, the direction they graze in, which leaves are the favourites.

Susana calls it his evening "meditative state". But behind that calm there's method. Sheep don't eat at random: they select, their preferences change throughout the day and they seek out certain leaves at certain times. Knowing this helps decide when to go into a plot, how long to stay and what to supplement at the feeder.

The sheep is above all a grazing animal that eats close to the ground; the goat browses more on leaves from shrubs and trees. Our goats live in Ventas con Peña Aguilera, 40 kilometres away, and by nature they make more use of the scrubland and handle tannins better.

Gustavo and Susana sum it up by mixing university and experience:

In the end, it's the people who've observed the problem a huge amount and done loads of trials who can tell you whether what you've studied actually works or not. The ideal is to have both sides: sometimes you know things, but you don't know why.

Can you taste in the cheese what the sheep eat?

Yes, and it's well studied. A classic review in Le Lait by INRA researchers (Coulon et al., 2004) concluded that switching from hay and silage to spring pasture makes big sensory differences in cheese; that the botanical makeup of the pasture affects texture and flavour; and that some compounds pass directly from the plant into the milk, such as carotenes (colour) and terpenes (aroma).

It's the scientific basis of what in wine we call terroir. That's why we care that our sheep eat a varied diet of whatever the land offers each season. We also talk about it in why having your own sheep changes the cheese.

To be honest, flavour depends on many more things: breed, lactation, cheesemaking and, above all, ageing. And the difference between goat and sheep, which we cover in goat or sheep: why goat's cheese is aged less, matters more than one season's diet.

At the end of the afternoon, they left us with a line that explains why someone spends hours watching sheep through binoculars:

That observation, in the fields and in the cheeses, is there all the time. But it all comes from love. If you didn't like this, you wouldn't give it the time and patience you do. First, you have to love it.

Frequently asked questions

Is there such a thing as acorn or montanera cheese?

Not as an official category. "Montanera" and "acorn-fed" are regulated only for Iberian pigs (Royal Decree 4/2014). There are goat's cheeses linked to the dehesa, like PDO Queso Ibores, whose specification mentions acorns as winter feed for the goats, but no regulation defines what an "acorn cheese" is.

Are acorns bad for sheep?

No, if given sensibly. They're very energy-rich and sheep love them, but they contain tannins and little protein. Problems arise when they make up almost the whole diet (the MSD Veterinary Manual mentions, as a reference, 75 % or more) or when the animals are hungry.

Do goats eat acorns the same way sheep do?

Goats handle tannins better thanks to proteins in their saliva and the adaptation of their rumen. They also browse more and eat leaves from shrubs and trees more naturally.

Why are olive leaves fed to livestock?

Because the olive grove produces them every year with the pruning, sheep eat them happily, and it makes use of leftovers that would otherwise have to be shredded or burned. Best fresh, and never if the grove has recently been treated with copper fungicides.

Can you taste in the cheese what the sheep eat?

Yes: pasture and its botanical makeup affect colour, aroma and texture, for example through carotenes and terpenes that pass into the milk. But cheesemaking, breed and ageing matter just as much or more.

From the farm to your table

Every cheese Gustavo and Susana make begins long before the dairy: on a hillside, at sunset, watching which leaf the sheep choose. Our Manchego, our goat's cheese and our mixed sheep and goat cheese carry the seasons of the Toledo countryside inside them. You'll find them alongside seasonal fruit and veg in our shop. From the field to the box, and from the box to your home. That simple, that authentic.

Sources

• Royal Decree 4/2014, quality standard for Iberian meat, ham, shoulder and cured loin. BOE.
• Spanish Ministry of Agriculture, Fisheries and Food. Specification of PDO Queso Ibores.
• Regional Government of Castilla-La Mancha. Single document of PDO Queso Manchego (2025).
• Ferraz de Oliveira MI et al. Acorn chemical composition depending on shedding date and Quercus species. Options Méditerranéennes, CIHEAM, 2012.
• Rey MD et al. La bellota como fuente de alimento con valor nutricional. Revista Forestal, 2022.
• Mekki I et al. Effects of green oak acorn (Quercus ilex) intake on nutrient digestibility, lamb growth, and carcass characteristics. Archives Animal Breeding, 2022.
• MSD Veterinary Manual. Quercus poisoning in animals.
• FAO. Olive by-products for animal feed: olive leaves and prunings.
• Feedipedia (INRAE, CIRAD, AFZ, FAO). Olive forage.
• Coulon JB et al. Relationships between ruminant management and sensory characteristics of cheeses: a review. Le Lait, 2004.
• Chilliard Y et al. Diet, rumen biohydrogenation and nutritional quality of cow and goat milk fat. European Journal of Lipid Science and Technology, 2007.