My son only has a few Simbrah cows so room for error is slim, he bred a heifer last year to Rocky Balboa to get a live calf. The heifer looked a little tight and we felt like she could have problems and the information out was he would be calving ease. Well, heifer laid down and spit out a heifer calf that might have been 60lbs wet and looked like a rat. Here she is at 8 months just 7 days after being on halter, Rocky is my choice for calving ease. I know it is only one, but when you only have 5 or 6, everyone counts!