About 25 years ago I inseminated about 20 holstein dairy cows with Charolais and belgium blue semen ie using the charolais as a terminal sire. The holstein/charolais calves produced had double muscling on their rumps and looked impressive but I had to get the vet out several times due to calving problems (massive head of the calves) . They also took along time to mature so had to go through an extra winter before ready to go to the works. There is a reason why most cattle in the cooler areas of OZ and NZ are angus and hereford and thats because they calve easy , are hardy, can forage well for food and are dont have many metabolic problems .