Remember a few years back, all of the major studs were selling semen off of "Twinners"? They were supposed to be bulls homozygous for twins. I could see it if the conditions were right for the right system, but for us calving in June/July on open ground, ZERO twins is fine by me.
My Dad once had a cow throw a set of twin heifers - purebred Angus here - and those twin heifers had twins every year of their lives. Mind you they were both dead by the age of 7 and 8. Milked like fools and ran themselves into the ground, but it'd be interesting if a person could go back in time, to figure out just how many pounds of calf they weaned in their short life span compared to cows having one calf every year for 14-15 years. Myself, I'll stick to the singles.