* What "they" refers to: Are you asking about humans, a specific population, or a specific animal?
* What "eat" means: Are we talking about the average amount of beef consumed, or the maximum amount possible?
* What "beef cattle" means: Are we talking about the entire animal, or just the meat?
To give you a better answer, I need more information about what you're asking.
For example:
* If you're asking about humans: The average person in the US eats about 22 lbs of beef per year.
* If you're asking about a specific animal: A lion might eat a whole cow in one sitting, while a smaller animal like a fox would only eat a portion.
Could you please clarify your question?