Q:

Can rabbits and guinea pigs eat sparrow grass?

I have a rabbit and a guinea pig kept together in my room. (They come along very well.) 
I also happen to have a bunch of sparrow grass in front of me that I don't have any plans to do with. Could there be any trouble if I just feed it to the little guys?

A:

Sparrow grass is the folk name for asparagus, as mentioned in the relevant Wikipedia article.
A German source Kaninchenwiese.de says:

Spargel kann regelmäßig angeboten werden, wenn er gefressen wird. Akzeptanz: schlecht.

Which, translated to English, means:

Asparagus could be frequently given to your rabbits. But in most cases, it's not well accepted and they do not like it very much.

The links lead to vegetable lists for rabbits ("Kaninchenwiese") and guinea pigs ("Meerschweinchenwiese"). Most vegetables are shown with pictures and all are marked with traffic light system:

red means "do not feed";
yellow means "not optimal" or "not well accepted";
green means "you can feed it without being worried".

Asparagus (Spargel in German) in this system has been assigned a "yellow" according to these criteria.
In every case you should give your rabbit and guinea pig a variety of food to choose from. It is necessary to ensure that they would not eat some inappropriate food in case they are hungry. 

