Dad's got two set-ups where we used  6x6 treated wood, but there is 8 of them(4 down each side)"working chute". (both set-ups are outside in the weather)
There are about 14 foot long and at least 4 feet is in ground. All 8 are tied together(bolted) with 2x4s about 10 feet in the air. 
Concrete only on the inside, where cattle's hooves would be, thus the whole post isn't surrounded by concrete.

The first one, lasted about 25-28 years, then we replaced the posts(rebuilt it the same way) Dad still uses it and the neighbors have "borrowed" that set-up, too (until they built their own fancy hyd. unit, all under one roof, two miles down the road) 

Note: No lag screws; All bolts, large washers and nuts.