A large amount of beef is mostly grass fed and finished on a grain feed lot the last month of life.

Got a source for "last month of life"?

Penn State University Extension says "...approximately 95% of the cattle in the United States continue to be finished, or fattened, on grain for the last 160 to 180 days of life (~25 to 30% of their life), on average."[1]

Oklahoma State University Extension also cites a study that compares "growth and carcass attributes of calves finished for 98 to 105 days in a grass system or a legume system"[2]

That puts us between 3 to 6 times longer than you stated, and gives us the context for how much of the average cattle's life that is. (USDA Prime, Choice, and Standard are all 30 to 42 months. Select is under 30 months.[3])

1: https://extension.psu.edu/grass-fed-beef-production 2: https://extension.okstate.edu/fact-sheets/finishing-beef-cat... 3: https://www.ams.usda.gov/grades-standards/slaughter-cattle-g...

The world is bigger than US. A minority of the world is US.

Yeah, but outside the US there are also a lot of grain fed cows.

Not a minority in terms of beef.[1] Only Brazil produces more.

But if you have any sources about cattle finishing practices in other countries, I’m keen to read them.

1: https://www.cattlerange.com/articles/2026/04/global-beef-pro...

Around me, 90-120 days on max 60% field corn. If it weren't field corn, it'd be another cereal.

And they are very likely right.

<looks out of the window>

Yup, that's grass they're eating.

All our beef is grass fed, because we don't use grain finishing in New Zealand. Many US people apparently dislike the taste of our beef (grain finishing has a milder flavour). Cattle for beef is mostly farmed on land that is too crappy to grow crops.