Britney Spears went all out for her 25th birthday yesterday.

The mom of two spent some time with her eldest son, Tater Tot, hitting the Los Angeles Zoo, and later going out to dinner at Mr. Chow’s with some pals and her manager, Larry Rudolph.

The real partying picked up at a bar near the Laugh Factory on Sunset Blvd. around midnight. Birthdaygirl Brit was joined by new BFF Paris Hilton and Fergie too, both of whom had spent the early evening at the Vh1 Big in ’06 Awards.

Lindsay Lohan, who has been attending Alcoholics Anonymous meetings was not part of the birthday festivities, but sources do tell us that the troubled actress was out partying at Teddy’s in the Hollywood Roosevelt Hotel Saturday night.

Back on the Sunset Strip: Paris, Britney and Fergie sat in a corner table, taking over the whole room. “The three of them seemed to be having a great time,” one spywitness tells us. “Though there’s rumored to be some friction between Britney and Madonna, there wasn’t any last night when the DJ played Holiday and the girls went crazy!”

As they’ve been known to do, the girls were walking around hand in hand around the club. Paris departed around 2 AM, while a partying Brit still held court. WHEW!!!
Happy birthday!!!