Yes! Only in small amounts can guinea pigs safely eat ruby chard.
Remember that this vegetable is quite acidic and therefore you should not feed large amounts to your guinea pig or you will harm them.
First of all we should explain what ruby chard is for those who are unfamiliar.
Ruby chard is a red-ribbed type of chard with stems. Depending on the cultivar they range in color from yellow to white to red.
The taste of ruby chard is slightly bitter.
The leafs are usually treated very similar to what the leaves of spinach and the stems is kind of like asparagus.
Usually a common use for ruby chard is a fresh raw salad.