Why Would a Wine Producer Have Surplus Egg Yolks?

I was recently offered a whole bucket of egg-yolks by a wine farmer who said they would otherwise go to waste. Why would a wine producer have surplus eggs to throw away?

The farmer was probably using egg whites to “fine” his wines. Fining is a way of removing suspended particles from the wine. About five egg whites are added to a barrel of wine. The egg then absorbs colloids, such as tartrates and harsh tannins, and helps clarify the wine. Obviously a wine producer who has 50 barrels maturing in his cellar will have a substantial number of egg yolks left over after fining them all. Some winemakers sell their egg yolks to local bakeries for use in cakes.