Former Bulls loanee Sam Smith is one of six released by Cambridge following their promotion.
The 24 year old leaves after making a surprise appearance for the U's in the Play-Off Semi Final against Halifax - his first U's appearance in over 12 months and only the 12th game he started for the club during his two year spell.
Also leaving the Abbey Stadium are Kevin Roberts, Andy Pugh, Matthew Barnes-Homer, Scott Garner and Blaine Hudson while Rory McAuley and Ashley Chambers have been told they can leave on free transfers despite having deals for next season.