In the past 2 years, we've tried three different brands of liquid, and Purina is the first one to actually make a noticeable difference in our cows. The quality of the grass here is very poor, so it is just about a necessity that we supplement. For the first half of last winter we used Mix 30 (it's cheap) and the cows were getting thinner and chasing us to the gate, bawling. We put out Suprlix (32-5) for the rest and they immediately stopped bothering us, and stopped losing condition.
We went to a couple of seminars in the area where a Purina guy gave a talk about the new liquid, and in a trial they did at a ranch near here last winter, they improved the BCS of cows nursing calves by as much as 1.5.