I think 70% of calving ease ability is the length of gestation. Thats what it is. How may times have you heard" well it was a 115# calf but it was 10 days past due". SHAZAM! I kow dad had 5 bulls on over 100 head of cows in 5 pastures. He had one ohlde bull......something like the first 14 calves were from the olhde bull. I don't think you can breed the performance out of the current shorthorn breed......and certainly not in one generation. My average used to be 100# with the bell curve usually ranging from 90-110#. I finally got ticked off and used an extreme Red Angus calving ease special bull and a low weight Shorthorn bull I raised. I don't have the records in front of me but after maybe 6 years my average is down around 90#. I still bang in a calf over 100# but I am getting some 70 some pounders also. Also my older bigger cows are gradually coming out of production. I think the big Shorthorn cows are bred up from the old milking Shorthorns and the bigger Irish genetics. I pulled off a yearling half-shorthorn,half red angus bull calf. He had been out breeding 20 heifers and cows. I put him on show feed to get him ready for a show and he just exploded. I think he grew a foot longer and 4 inches taller in about 4 weeks. I don't think man could destroy mother earth if we tried and I don't think we could breed performance out of Shorthorns if we tried. It will sure take more than one generation. I would think that jpj would increase marbling ability and carcass traits. I think that there is agroup of breeders that fight him cause they have been breeding cattle differently for the past 15 years.jmo