The short answer

Only occasionally, in tiny amounts, and unsalted.

Why

Plain wholegrain bread isn't harmful in small amounts, but it offers little nutrition and shop-bought loaves are often salty. Think of it as an occasional filler, not a real food, and never a substitute for veg and pellets.

How to feed it

Offer a crumb-sized piece of plain, unsalted wholegrain bread, ideally dry rather than fresh and doughy.

How much & how often

Rarely, and only a tiny piece.