Good Morning The best and only way I've found to transport the small number of pigs (assuming these are for slaughter at 60-70Kgs) is to buy, despite the cost, of an Ifor Williams P8 livestock trailer these are big enough to take 7-8 pigs. I've actually had 27 weaners in at one time. Yet when empty easily handled, having a single axle and fairly light but very robust.
I would agree with Bob here we bought one of these last year and it is so easy to handle, before that we borrowed a trailer, sometimes the lights didn't work or a brake would get stuck on, at least with our own we know that it is both legal and safe.