The Roman Military Diet By R.W. Davies
"We've been led to think that ancient Romans were mainly vegetarian and that when the legions came into contact with the European barbarians they had trouble stomaching the meat-rich food. "
"...there is evidence from the Republican period of Roman history for meat consumption by soldiers: "When Scipio reintroduced military discipline to the army at Numania in 134 B.C., he ordered that the only way the troops could eat their meat was by roasting or boiling it." Q. Caecilius Metellus Numidicus made a similar rule in 109 B.C."
In a related discussion, D.C. Reynolds points out, "The tradition about the legions being near vegetarian in camp is very believable for the early Republican era. Scurvy references are reliable, I believe. By the latter half of the 2nd century B.C., the whole Roman world had opened up and almost all aspects of Roman life, including diet, had changed from the 'old days.' My only real point is that Josephus and Tacitus could not accurately chronicle the early or middle Republican diet. Cato is the only source that comes close, and he is at the very end of the era (and a cabbage freak to boot)."
I didn't know Cato the Younger was so fond of cabbage. That may have accounted for his aversion to eating flesh during his "March of the 10,000" as recounted by Colleen McCullough in "The October Horse".