Snoopy211: Don't worry la...sometimes bb's appetite will fluctuate like that. Some days, they will drink really well and some days, they prefer to sleep more. Also, every few months, bbs have growth spurts ie they will drink a lot more in those few days. So long as over a week or two, the general intake of milk is normal then you do not need to worry. If you are feeding according to a timetable, I would even suggest that you do not bother to feed the 1 oz after burping so that by the next meal, bb will be a little bit more hungry, so bb will feed better at the next meal.
I agree with MARSHMELLOW. Adults also have no mood to eat sometimes, so do babies and children. Sometimes, they'll suddenly eat more and back to normal again.