Coiros are beeves fattened at the cratch in ox-stalls
Beeves is the plural of beef, in earlier periods of time eating beef, or meat in general, was a symbol of wealth. Especially with how Rabelais goes into detail of where the beef was raised and describes them as "fat beeves", he is trying to explain their wealth.
Collins Dictionary. HaperCollins Publishers Ltd, 2024. https://www.collinsdictionary.com/us/dictionary/english/beeves Cumming, Nicole. "The relationship between meat consumption and power in late medieval and early modern England" . Animal Society Institute. https://www.animalsandsociety.org/research/sloth/sloth-volume-5-no-1-winter-2019/the-relationship-between-meat-consumption-and-power-in-late-medieval-and-early-modern-england/