Regarding goats having to be wormed monthly, no, they don't. Nothing does. Not if it's kept in a healthy environment anyway...
I've also kept goats and sheep, and have an orphan lamb now. Before the advent of chemicals, livestock and their owners knew what to use to kill and prevent worms. Wild animals still know what to use; the only time you'll ever see a wild animal dying from worm infestation is when it was already struck down from illness or injury, or confined to an area that does not contain the natural wormers they need. Goats/sheep left to roam in a natural environment will consume the plants and sometimes dirt etc. they need to worm themselves. It's nothing short of a wonder the proponents of 'all things chemical as the only way' never stop to question how people farmed before chemicals, or how wild animals don't die out completely without their miraculous poisons! They go with the incredibly ignorant/history-blind idea that it was an unending deathfest. Must be true because the guy who sells me chemicals said so. Takes science to make chemicals. So it must be true because science is infallible, isn't it? Circular logic failure.
People tend to make much ado about the worminess of soil but DE was discovered because horses running on DE rich pasture just didn't need worming, as an example. On that topic I believe many people use the wrong grade so don't get good results; there are filtering grades as well as coarse grades that work by slicing parasites to death whether internal or external. The relevant discriminator is the size and strength of the diatomites.
I had an orphan merino cross I raised who ate a whole bush of wormwood of the artimissia family. I'd been told a few leaves was potentially deadly; a bush that big (kilos of leaves, bigger than her) would kill her, but she ate the whole lot and was worm free for years; in fact even dirt couldn't touch her, and she was born in and remained in the neighbourhood to truly shocking and abhorrent farming practices. You might not believe me if I told you! I never wormed her or any of my goats or sheep with chemicals. Carrot's a great wormer by virtue of the fibre, and the allium family's a great preventative as well as antibiotic and gentle wormer by virtues of the Allicin and sulfur, and goats if let to browse instead of being forced to graze will often eat such fibrous material the worms suffer and die; it'd be like us trying to eat telephone poles, lol.
In my experience, let the animals eat what is natural to their race's birthland environments, like their wild kin, and they simply do not need worming with chemicals as they are constantly preventing the external and internal parasites from thriving, through diet. A truly healthy animal can't be overrun by parasites. With my chooks, I maintain raw garlic at all times, and every few full moons, before it's full, I give something like tabasco sauce on bread to kill any worms there might be as they emerge from the tissues to breed in the intestines. I've done this for years. I've only seen a few worms in brought in outside stock so far. But I will keep practicing prevention as an ounce of prevention's worth a pound of cure. I've never had lice or mite or worm problems. Also it appears you can't lose chicks to coccidiosis if they have garlic. I swear by it for so many things. I recommend the books of Pat Coleby, and Juliette de Bairacli Levy. Neither of them is 100% right but they sure did know a few things!