If you get guineas, get a flock and make sure you have a bad ass fighting rooster if you have yard chickens. The rooster will drive the guineas out to the perimeter where wild things belong. If your rooster isn't tough enough, the tougher primitive guineas will persecute the chickens to death. Nothing can win a distance run against a guinea.
we been told Lucy was attacked by geese in the 1930s, they can be real mean, or so the story goes, YMMV they can be an effective alarm but they can turn on ya too so plan accordingly a determined intruder or attacker, or group of intruders or attackers can get past them
Geese need watching... The campus I work on is home to a couple dozen nesting pairs of Canadians during the spring. Moma incubates while papa stands guard. The campus security puts out orange cones in a 100' radius around the nests. But people are stupid - there's many photos of "smart" people being chased by a PO'd gander. Absolutely hilarious.
You are being far too conservative with your numbers, sir. Bulls here, require far too much maintenance. For me, it isn't financially feasible to even have one on the farm. We only pay $10 USD, for each cow we get inseminated by a bull. I still say, as others have in this thread - geese. Or, at least one goose, anyway. They will sound the alarm when intruders enter your property. They are quite territorial and will sound the alarm. However, they aren't as much for attacking the intruder. As I replied to sec's post, owning a bull is not a feasible option - here in Cambodia anyway. I would have to hire someone solely to look after the bull. Agreed. Personally, I wouldn't eat geese on the property. In fact, if I had more than one, I would prefer to have them separated - in different fenced areas. In my opinion, if they are alone, they are more valuable as guard animals. Hear, hear! Unfortunately, I have never seen a donkey first hand, anywhere in SEA.
They use donkeys around here to guard sheep, goats, and other tasty, to coyotes, livestock. They will quite literally kick a coyote to death. Alpacas have a similar temperament, but are much more expensive. On the plus side tough, Alpaca wool is quite valuable.
Make some new reliable friends. Get to know the neighbors. everyone wants a big dog, I think feeding such a critter gets old. A small dog has good ears and lets you know about stuff you can't hear. I have heard about ducks as sentries. I would stay away from guineas. I think they are annoying.
So did my G-ma. She used to take target practice on them when the noise woke the baby. Several notches in the stock of her rifle (which I have.)