Acorns for fattening free-range Iberian pigs

The Montanera system is a traditional, sustainable method of fattening free-range Iberian pigs on acorns and grass in dehesa ecosystems across the Iberian Peninsula. Spanning over four million hectares, this high nature value farmland system supports biodiversity and ecological balance. Pigs, at least one year old and adapted to grazing, gain over 40 kg in 2–3 months using only natural forage, with a feed conversion rate of 10.5 kg acorns per kg weight gain. Acorns from Quercus ilex subsp. rotundifolia provide the primary energy source, while grass supplements low protein content. The system relies on natural pig behaviour—peeling acorns to reduce tannins—though this causes a 20% loss of edible kernel. Supported by EcoValia and the Universidad de Córdoba, the practice is part of the EU’s Horizon 2020 OK-Net Ecofeed initiative, promoting low-input, circular livestock systems. The system enhances climate resilience, reduces reliance on external feed, and contributes to rural development and conservation.