Pigs like humans come in shape and sizes , when I get a new resident I weigh him/her for weekly for the first 3 /4 weeks to get an average for that individual
then , the rely on the feel of the pig
get to know the pigs body mass feel has always alerted me to any health issues
Long before kitchen scales became affordable we piggy keepers refared to a pig losing weight as going LIGHT
a very good indicator that there was some health issue , and closer observations were needed