To an extent, it will be what they need to see that will determine how they are placed on the x-ray plate. My pig, Sundae, had an x-ray to check for bladder stones/sludge. She was conscious for it- she tends to freeze when stressed, so essentially they set her on her feet on the plate, pulled their hands away, x-rayed her, and picked her back up. The vet has also said sometimes he will place them in a small box if it helps to keep them still. They did not do a second view, as they were able to see what they needed to see on the first scan which just involved her standing still. As for gas, my understanding is that if they could not get the pics any other way, they would give her a whiff of gas. There is always some risk to using anesthetics, but for what it's worth all three of the pigs I have owned were under anesthesia at one time or another, and all did very well, even those that were very ill at the time.