>>1723340You can do that. It will give them an additional range of things in their diet. Goats are foragers/browsers and need lots of different food types (unlike grazers like cattle and sheep).
You can cut yard grass for making silage and store it double bagged in contractor's trash bags in a metal trash can or 55gal drum. Just compact it by standing on it as you layer it up in the barrel. There's a lot of info on it online. Some people, who run lawn care businesses, will actually harvest the grass they cut for their own silage needs.
There's also "leaf hay" where you harvest the ends of branches from trees that have lots of leaves on them and use that to feed your animals.