How profit-driven inbreeding could bring the world dairy herd to its knees

Known for their distinctive long horns, the Ankole cattle of western Uganda have evolved over millennia to withstand their harsh environment, with its long dry spells and abundance of local maladies such as trypanosomiasis, a disease spread by the tsetse fly. But after flourishing for almost 10,000 years, the Ankole have begun to rapidly disappear.

Farmland is dwindling in Uganda due to the expanding human population, and Ankole requires vast areas to graze. Local herders have responded to the pressure by replacing them, cross-breeding Ankole cattle with industrial species such as the European Holstein. But while these hybrids gain favourable genetic traits from the Holstein, producing more milk and meat, and requiring less land to keep, there is a hidden cost.

The reason why industrial breeds are particularly vulnerable to new bacterial or viral infections is that they have very little genetic diversity compared with local breeds, due to decades of inbreeding. Ginja estimates that for breeds like the Holstein, millions of these cows originate from a mere handful of bulls.