Goats living on yard waste from landscaping services

We're planning fencing at the moment-- so a ways away from actually getting goats, but some of our fencing choices will change based on the hope of getting dairy goats, or not.

We live on an urban, 1 acre plot of land and currently have 6 muscovies and 6 chickens who free range, but we're gradually dividing our plot into several areas. Our temp doesn't go below freezing, and our climate is more or less Mediterranean (rain in winter, dry in summer)

With our current setup, about a third of an acre is food forest, with the rest divided into annual beds and paddocks (with overlap and rotation-- including our house in one paddock-- the chickens and ducks can sometimes be in the food forest, particularly as it gets more mature, for example). We wouldn't be growing much goat food ourselves. I'm wondering if anyone has experience getting garden waste from landscaping services (typically this is tree cuttings, brush, etc.-- I'm not too worried about herbicides or pesticides on these) and making this the primary source of food, with very small amounts of grain/hay/mineral blocks.

I've been setting up relationships with some landscaping services who would deliver on different days, instead of going to the dump, and I think I could figure out how to identify most poisonous brush and not feed it to the goats. I'm just not sure if I'd still end up paying quite a bit for goat feed, and if this makes goat ownership prohibitively expensive. Has anyone fed their goats primarily on brush, or have modern breeds been bred to feed primarily on hay?

Thank you for thoughts and advice!

First off, goats are browsers as you know so they will prefer brush over hay but no one has bred a goat to eat primarily hay, they just eat it, and they prefer to have it up off the ground.
In fact they will not eat hay that has fallen to the ground. You can also feed them things like trimmings from your food garden plants and they will even eat some vegetables as long as they are up off the ground.
Occasionally they will eat grass (grazing) but it isn't their preferred food by any means.

Since you will need to depend on Landscape companies it will be best to know if they spray and what they spray.
These guys are in the business of keeping their customers happy and as bug free as possible, that's how they make their money.
In the old days, we used Malathion regularly on trees, shrubs and lawns, this was a monthly application to keep bugs down to a minimum.
It was what the customer wanted, no bugs.
I had to leave my parents nursery to be able to practice no spraying horticulture.

Today it still isn't considered bad by most people, regardless of the new findings being published, people want pretty lawns and landscaping.
Some housing developments even require it and have it in their bylaws of the homeowners association.

goats will not eat something that will poison them, they will use things like poison ivy or oak as a wormer by eating it when they need it.
They will not touch hemlock, or most other poisonous plants especially if there are other, good things available to eat.

Thanks so much Bryant. I had hoped/heard that given abundance, goats won't eat something that is poisonous to them. I'm in South Africa, which is horribly relaxed about spraying, but also in my experience homeowners associations are not as tyrranical about appearances. Thanks for the push to ask companies what they spray, if they spray.