HI, I'm Dr STeve
The stiff legged part of your description has me concerned about tetanus. THis is a disease that goats are very suscetible to and is difficult to treat.
Tetanus causes the muscles to become rigid and causes stiff legs. It usually progresses and causes death in most animals . THis is truly an emergency and to increase your chances of saving this goat, you should call your local vet as soon as possible to have them examine, confirm and treat this condition.
It is possible that he could have something else like an infection tht is causing a fever and the panting, but the stiff legged part of his problem is very consistent with tetanus. The treatment that I use is penicillin to kill the bacteria that causes tetanus ( clostridium tetani) and tetanus antitixin to reduce the effects of the tetanus toxin that this bacteria produces.
Once clincal signs show up like the stiff leggedness, the prognosis for full recovery goes down quickly.
If he would happen to have another condition, that would be god, but with his young age, it is likely to still be necessary to have a vet treat him before he gets tooo weak and dehydrated.
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The advice was right on, but too late to be useful. I administered anti-biotics, and electrolytes prior to your assesment. I did not read your response until the next morning. 8 hours for an answer is unacceptable. I don't know what your site's situation is but I will not become a subscriber.