As general rule a goat can pack about 1/3 of its body weight. If you put way too much on they will lay down. We try to keep their packs at about 50-55 lbs or so. When we are packing something out we might go a bit more but for a good hike 50lbs is about right.
As for body types, I like the goats with longer legs and a strong build.
There is has been some concern about the transmission of diseases between domestic goats and sheep and wild sheep. I have an article from a friend listed below that talks about it in more depth. I dont have a lot of sheep country near where I hike/hunt so its not an issue. We also take very good care of our goats and hit the vet at least twice a year for checkups and shots. The only times that there have been problems that I am aware of is when there are large "groups or herds" of meat sheep/goats up in the same areas. But to play it safe at least until they have more evidence one way or the other I dont plan to take them into the same country as sheep.
With so many places to hike, I try to avoid taking our packgoats to areas
that are known bighorn habitat (particularly known areas of lambing as the
young lambs may try to approach goats). There is a possible transmission of disease (Pasteurella) from goats to sheep.
It is best in my opinion to avoid known Bighorn sheep habitat.
I think that the literature supports that most disease transmission in the
bighorn sheep is believed to be from domestic sheep to wild sheep. I'm not
aware that any biologist or scientist has stated categorically that goats do
NOT transmit disease to bighorn sheep (unfortunately). I believe that they
use words to the effect that there is some risk, though it may be very
small. I think that there is a recorded case where some herd meat goats
(that escaped) caused "pink eye" or something like it in bighorn sheep,
which resulted in loss (death) of some bighorn sheep because they went
From what Iíve read on the topic is that biologists seem to associate free roaming or herd managed
goats (like herds of meat goats) to introduction of diseases (not
packgoats). Biologists seem to make the distinction between herd managed
goats and packgoats. The general public just hears "goats. I'm not aware that any one has
pinpointed a disease transmission from domestic packgoats to bighorn sheep.
It's all about scientific data (or lack of it), and perception.