When we picture certain animals a very definite image comes to mind. Dairy cows have black and white spots. Pigs are fat and pink. Chickens are plump, white birds. But what we’re picturing is only a very limited glimpse of these animals. We’re imagining only one of the hundreds of breeds worldwide. Unfortunately, the diversity of our livestock is rapidly becoming as limited as our mental picture of a pig or duck. Overbreeding and preference for certain breeds has led to a dwindling gene pool that could threaten the stability of our entire food system.
Researchers at Penn State made a startling discovery when looking at dairy cows. Virtually every Holstein in the United States is descended from one of just two bulls that lived during the 1960s. Shortly before these two bulls were born, farmers had begun to use artificial insemination to breed their cattle. Not only was it more cost effective and reliable than trading bulls back and forth, but it allowed them to see which bulls produced the most desirable children. Milk production was carefully recorded and compared. When a bull sired a daughter who produced well, his genes were more likely to be chosen again. The preference for certain genetic lines became so extreme that virtually all of the 8 million Holsteins in the US can trace their lineage back to two bulls who were deemed the genetic winners just a few generations ago.
The limited gene pool of Holsteins wouldn’t be quite as alarming if dairies used several breeds of cattle. But Holsteins make up 90% of the dairy cows in the United States. 90% of the country’s milk, cheese, butter and yogurt come from descendants of just two animals. And while the dairy industry is an extreme example, limited genetic variation has become the norm in industrial agriculture. Chickens and turkeys, too, are overwhelmingly just one breed. Pigs have traditionally been more diverse, but that’s changing. Today 75% of pigs raised in America belong to three breeds. And like dairy cows, the other animals we breed for consumption are becoming increasingly inbred with each successive generation.
You don’t have to be a biologist to know why such a limited gene pool is a bad idea. Excessive inbreeding increases the risk of genetic illness with every generation. There was actually a third line of Holsteins from the same era as the two bulls discovered by Penn State. This line died out in the 1990s however when an increasing number of calves were being born with the same genetic illnesses. The recessive genes that caused the conditions were only expressed after several generations of increasing inbreeding. Another risk of inbreeding is infertility. The pregnancy rate for Holsteins was close to 40% in the 1960s but by 2009 was as low as 20%. Fewer breeding animals means even less diversity, and the probability that birth rates will continue downward. Without crossbreeding, the preference for Holsteins in the daily industry could end up causing their extinction.
While these animals have been bred for certain favorable traits, like quick growth, by breeding such a limited population many possibly beneficial traits have been lost as well. One of the greatest concerns scientists have is how well these animals resist disease. Bacteria and viruses are experts at adaptation, and overuse of antibiotics in commercial farming have encouraged strains that are resistant to medications. Should an illness like swine flu or avian flu evolve to target a trait common in the breeds we use for food the entire population could be at risk. With limited genetic diversity, there is less chance for the mutations that would convey resistance. An illness specifically dangerous to American Yorkshire pigs or Holstein cows could easily sweep through the whole population. Not only would our food system be threatened, but many livestock diseases have been known to pass on to humans. Limited diversity endangers us as well as our food.
More diverse and adaptable animals are vital to the future of our food system. But industrial agriculture’s preference for uniformity has already led to a loss of diversity. Experts estimate that at least half of ancestral chicken breeds have been lost since the 1950s. Even well-known breeds like Texas Longhorn cattle are endangered. Overall, roughly a hundred livestock breeds have gone extinct since 2000. But as strange as it may seem, the only way to save these animals is to eat them. The best remaining source of genetic diversity is on small farms raising heritage breed animals. When we buy A2A2 genetic milk, which most Holsteins don’t produce, or multicolored eggs we’re making it profitable for the local farms we work with to keep raising these genetically diverse animals. From the six heritage pork breeds raised by Stryker Farm to the Swiss Brown cows that give Swiss Villa its name, the food we sell at Green Owl helps to maintain healthy populations of heritage breed animals to keep our food supply more diverse and secure.