A new study found that a large share of male cattle in US feedlots are producing milk, raising questions about hormones, feed, and what ends up in American beef.

• One in five steers in a study of more than 20,000 feedlot cattle was making real milk at slaughter, and the rate is rising.
• Between a quarter and half of young females that had never given birth were also lactating, which should not happen naturally.
• The researcher behind the study blames extreme fat levels, not the hormone implants used on virtually all commercial cattle — but there was no control group of unimplanted animals to test that.
• Merck's own product insert lists udder development as a possible side effect of those ear implants.
• The push for cheap, heavy, high-grade beef has consolidated slaughterhouses, squeezed ranchers, and cost the US 8% of its farms in eight years.

Outlook: Peer-reviewed results are due later this year, and pressure is building for controlled studies comparing implanted, grass-fed, and grain-fed cattle so buyers can choose.