My 9 day old baby boys resp rate is around 55.sometimes after a big feed it can be as high as 75,whilst fast asleep it comes down to 45.is this ok?

A bit too high: At that age I expect a RR of 30-40 in sleep and 30-60 awake. Any rate in the 70's is worrisome and it would be dangerous to feed a kid if that was present. However, you need to count the rate over at least 30 sec to a minute to decide the rate. Some newborns are going through a process of setting their breathing pattern and briefly pant fast, stop & go slower.If usually > 50-60, have baby checked

Neonatal respiratory: Normal respiratory rates in newborns less than one month old is 30-60/minute. It is not uncommon for new infants to have very transient increases in respiratory rate, but these are NOT associated with color changes or respiratory distress. Expansion of the stomach after a feeding can cause increased rates due to stomach expansion, but this should not be prolonged.