I've got a 5 year old brangus cow that has been obese or borderline since weaning. Even in 1/4 acre of Tifton 9 bahia grass with her calf she stayed fat. Her calves have all been easy keepers as well and her oldest just calved and is already visibly gaining again with startling speed. I swear she could be "normal" weight on drylot getting 2 or 3 pounds of grain a day while nursing. Would this be all genetics or something else?