I was having some steering issues with a Kubota F3080 which just recently got resolved but prior to resolving what was causing the issue Steve Barlow told me to check and see if there were bubbles on the dipstick when the intermittent problem happened on mine. Never any bubbles and have never seen any bubbles on other Kubotas and I've had a few.
First off I wouldn't worry about it, I'd just use the machine like it is perfect. If the bubbles are a real problem then you'll start having issues which will be covered under warranty. It seems possible that air has gotten into the system which could have happened during the original filling and they may work themselves out of the system. If they continue then inform the dealer when you take it in for first service, which I would only do if there are warranty issues or other needs for service or if first service is free.
First 50 hour service is really easy to do and good for owner to do to get better aquainted with your machine.
In my opinion, no, it's not normal to have visible bubbles on the dipstick but it's not something I'd worry about unless it continues after the first 30 to 40 hours. If so, then there is an air leak or open valve letting air into the system. There is an air relief valve which can be heard fairly well when one steers/turn steering wheel which is more noticeable on some Kubotas models more than others.
