What to do with animal poop? It's a question that plagues organic and factory farmers alike, and in areas with lots of factory farms (also called concentrated animal-feeding operations, or CAFOs), animal manure is accused of adding high levels of nitrogen and phosphorous to nearby waterways, robbing them of oxygen and killing the fish that call them home.
Animal-farm owners have attempted to solve the problem by selling all that manure off to farmers, who can apply the nutrient-rich manure from CAFOs to their fields as fertilizer. But in doing so, the farmers introduce another problem to the beleaguered streams, according to a new study in Environmental Science & Technology—that of too many hormones.
Find Out Whether You Live Near a Factory Farm
All animal manure is contaminated with naturally occurring estrogen and testosterone, but in many cases, the animals have also been treated with high levels of synthetic hormones to speed their growth.
So the study authors gathered water samples from three streams: one near a farm that applies manure from a beef and dairy cattle CAFO; another from a farm that fertilizes with pig manure and irrigates with water from pig and poultry waste lagoons; and a third from a farm that doesn't use any sort of animal manure on its crops.
Hormones were found in 80 percent of the water samples from the first two streams, despite the fact that synthetic hormones are banned in pig and poultry production. None were found in the third. The hormone-heavy streams also had 50 percent lower fish diversity and 28 percent higher fish death rates than the non-contaminated stream.
The researchers also raised schools of flathead minnows in the two hormone-contaminated streams and found that those fish populations wound up being 60 percent male, compared to 48 percent males in the populations raised in the hormone-free stream. When male-to-female ratios drop like that, the authors wrote, it can lead to a decline in fish populations overall.
Why Women Shouldn't Eat Factory-Farmed Chicken
This is only the second study to look at the effects of CAFO manure runoff on aquatic animals, and, the authors write, there is the possibility that other factors could have contributed to the hormonal changes. Atrazine, for instance, is a pesticide used heavily in Indiana and other Midwestern corn-belt states, and a number of studies have shown the pesticide can cause sex changes in fish, frogs, and other amphibious species. Atrazine was present in all the stream samples tested. But, the researchers concluded, adding heavy loads of both natural and synthetic hormones could be adding to the effects of pesticides or aggravating that damage in ways that aren't yet fully understood. They noted that hormone levels appeared to peak in the spring, just about the time that fish are spawning and hatching, which likely plays a role in damage to the fish's reproductive development.
The solution? Support small-scale farmers who raise small herds and don't have a huge waste problem to deal with. To find ethical meat producers in your area, visit eatwellguide.org.