SCOBY, or Symbiotic Culture of Bacteria and Yeast, is a culinary symbiotic fermentation culture consisting of lactic acid bacteria, acetic acid bacteria, and yeast which arises in the preparation of sour foods and beverages. During fermentation it's the scum-like layer that forms over the top of the liquid in kombucha and other fermented foods.

I save the SCOBY from each batch of kombucha that I make. I keep them in a "SCOBY" Hotel in a dark cabinet, filled with kombucha, waiting for my next batch to begin. Over weeks (or months) I "feed: the hotel with fresh sweet tea to keep it going. 

Sometimes I collect too many SCOBYs, or some age and start getting dark. That's when it's time to remove a few but I hate to see them go to waste. 

That's where the girls (chickens) come in. They l o v e SCOBY and it's safe and beneficial for them.

The gelatinous biofilm is rich in probiotics, which supports gut health, improve digestion, and helps to prevent issues like runny poops. It contains proteins, fiber, and vitamins, acting as a nutritious supplement to standard feed. Probiotics in SCOBY can boost immune system function, increase egg shell thickness, and lead to cleaner eggs. 

I only feed the solid SCOBY itself, avoiding the liquid kombucha due to caffeine content which isn't good for chickens. I feed it raw, cut into small pieces but I've heard it can be dried into jerky which sounds interesting. 

Like any food change it should be introduced gradually to your birds diet. I feed it a handful of times per year as a treat or supplement.