|Iowa Beef Industry Council photo|
There's a problem with the growing trend of grass-fed beef though: the grass they eat is becoming less nutritious. Researchers at Texas A&M University and Boulder, Colo.-based ecology outfit Jonah Ventures studied cow manure collected from all over the country between 1994 and 2016 and found that crude protein in grass has dropped by almost 20 percent since the mid-90s. That's causing the cattle to gain less weight on grass than they would have in years past. The less-nutritious grass could hurt even conventional cattle, since many are grass-fed before finishing.