When I started showing, I took four pigs around about half a dozen shows. One was a January-born gilt who, at the Royal Show (the English one!) won her class and went on to win best female Tamworth and was also one half of the best pair. She did similarly well throughout the season, sold for £300 at the BPA sale, and went on to be an excellent breeding sow.
When the very experienced judge handed me the first rosette, he pointed out that she had a small extra teat. I was genuinely surprised, because, when I checked her at eight weeks, I had not noticed anything. So, being a novice, I asked why he hadn't marked her down for that. He said that everything else about her was perfect - she had "ticked all the boxes" in every other respect.
Since then, several breeders who also judge on a regular basis have also said that they would not mark down a pig with an additional teat. Of course, it's all purely subjective. You may get a judge who is extremely fussy, but most will look for a full set of 12 (or 14, depending on the breed standard - check which applies) fully-formed teats.
I've heard tales of people slicing off additional teats for showing purposes, but I don't know if that's just a myth.
Do have a go at showing. It's great fun and I'm sure you'll enjoy it. The entry forms for most shows are out now, so don't waste any time in getting yours in. Showing is also a good way of getting a professional opinion on how good your pigs really are, so take criticism - good or bad - and use the knowledge to improve your herd in the future.
Where are you thinking of showing? If you want to message or email me for any advice, please do.
All the best
Liz