Welcome to the world of goats. What a beautiful plot of
land.
It's a long post, so I put in bold the parts that are of vital importance.
I don't know much about your region, so I can't help with how often to rotate your livestock. It depends on so many factors, many of which are specific to your farm that all we could give are generalities at best. The two things I can recommend from personal
experience, are have a great variety of different pasture plants and avoid chemical fertilizers and watering as this makes the
roots grow shallower than pasture plants that have been stressed. If you can get your hands on the book by Pat Coleby, Natural Goat Care, it has some very useful thoughts on the subject. Keep in mind she's writing for a different part of the world, so specific plants and supplements may not apply to you - or it may. The theory behind her opinions is very good however and a great chance to geek out about goat nutritional needs.
Two different kinds of goats living together - In principle this isn't a problem. In practice, it depends entirely on the goats in question. Goats have personality and will definitely get into trouble if they aren't happy with their environment. Quite often if animals come from different flocks, they (this is going to sound silly, I know it, but it's the human interpretation of goat-thoughts) speak a different language. Not knowing the full vocabulary of goats, it's hard to know exactly what's different, be it body language, tone of voice, different calls mean different things, but there is an adjustment time when you introduce animals to each other. They fight for hierarchy, they need to learn each other's language.
This isn't said to discourage you. Some of the best animal 'friendships' on my farm, are between animals from different flocks. It's just shocking the first few times you see it. It's so difficult to watch them sort themselves out, but human interference prolongs this period of adjustment. However if one gets seriously injured, it's time to step in (if you can without endangering yourself).
Fencing:
Goats must be trained to use electric fences - this takes a great deal of time and isn't always successful.
Most important piece of advice for any animal purchase:
Buy the farmer, not the livestock. When you get your goats, a good farmer will be willing to take the goat back if there is problems (often, but not always, offer to refund part or all the price of the animal). If they aren't... double check with yourself that you are confident in the situation - Sounds like you aren't experienced enough to judge the animal, so judge the farmer - if you haven't been breeding and showing goats for a couple of decades you aren't going to know every tiny detail to look for when evaluating a goat. So spend at least as much time looking at the farm and farmer as you do looking at the goat. Ask questions that you already know
the answer to - then see if they know the answer. If they answer something different than what you've heard, then get them to tell you why they think so. If they can, then this is a good sign.
Do you have a local goat guru you can cultivate? This is your number one resource and if you don't do anything else, do this.
Do you know the local parasite, goat STDs and other local issues with goats?
Where are you going to get your buck service? You going to keep your own buck (they are destructive and stink - sometimes a good thing depending on your neighbours)? Do you know what testing your future stud has had for which diseases? How often are they tested? There are a lot of STDs in goats, some places worse than others.
The farmer(s) selling you the goat(s), what is their worming and vaccination practices? Do they worm on schedule or as needed? Are you going to use worming meds? If not, are you willing to let the animal suffer and die if they do get an infestation and it can't be treated by natural means? (
disclaimer: I advocate prevention of parasites and illness, but will treat with meds IF AND ONLY IF the animal needs it, and feel that worming to schedual is one of the biggest causes of parasite resistance - my opinion which I feel a bit too strongly about and know full well I come across that way.)
The one thing I kicked myself most when bringing animals from mixed flocks into my home is the worming meds weren't the same. Animal A came from a flock that was resistant to wormer Z, Animal B came from one resistant to wormer X. Z and X are the main two wormers one can buy here. So now what do I worm with when an animal needs it? X and Y don't work all that well anymore, so I import super-expensive wormer Y. There are a lot of restrictions on what meds can be used locally. Get to know the restrictions for your area - and which ones you are willing to take the risk to break.
What's the closest vet who deals with large animals? Where's the second closest? Do they do house calls? Do they do goats or are they horse only? What's their after hour number? How much are you willing to spend on vet bills in an emergency? Know now that emergencies that require a vet only happen after hours or on statutory holidays (for some reason). Do they castrate? Will you castrate (see note above about Billy being destructive and smelly - also they sexually mature younger than you think)
Sorry, this got kind of long. I can wax poetic about all the things I wish I had known to think about before I got my animals.
One more thing before I go, the breed.
If you aren't fully set on these two breeds, it is worth considering that the quality of the individual goat and the quality of it's care will affect the milk production more than their breed. I personally know quite a few saanens that give higher milk fat content than the standard for any other breed of goat - but that's primarily because of the care these girls receive from their owner (my goat guru). You can make great cheese from almost any goat milk. Another thing to consider is hybrid vigor. Goat crosses often produce better than pure breed (and are more affordable starting place). In the end it's a personal choice, but it is a choice.
Some of my least favourite animals have been pure breed and my favourite have been mixed. My absolute favourite goat is Oberhasli grade. Oberhasli are a very rare breed, so the gene pool is very limited. For that reason, it's okay to take a non-oberhasli and breed it to a Oberhasli buck, take that kid, breed it to an Oberhasli...and so on and so on. The part breed kids are called 'grade' or 'experimental' and once you get to 7/8ths oberhasli (I think) then you can call it pure. Without this breeding up option, the gene pool would be limited to the dozen registered animals (in Canada) they started with when this programme was introduced. I guess my point is, preserving breeds is good, but sometimes it can be too limiting to the gene pool.
Landrace varieties often preform better than pure breeds. Maybe there is a
landrace goat local to your area?
Or if you are already in love with the breeds you have chosen, then don't doubt yourself any longer. Give them a go. It's better to take action than get stuck trying to think out all the best ways - because no matter how much thinking and research you do, the problems you get will probably be completely different than anything you imagined.