My main necropsy experience was with wild grazing animals, especially white-tailed deer, our main study animal, so yes I have had lots of experience with twin births, just not in cattle. I did necropsy several beef calves that had externally observable birth defects including one that died of a set of twins. The sibling lived. All of the 7 beef calves I necropsied had an underbite and all but one had been diagnosed with Weak Calf Syndrome by a veterinarian. I am a biologist, not a vet. All the beef calves I necropsied also had those internal issues I stated above. According to the data on Weak Calf Syndrome, 3 of every 100 calves born in the U.S. each year die of WCS. That is around a million dead calves that can't be sold by the livestock owner, which is why I am trying to help you. That is close to a million cows that are fed for a year, with no return to the livestock owner - seems to me to be a huge, likely preventable waste. Since every calf that I examined that had WCS also had a fairly severe underbite, an underbite might indicate disrupted mineral uptake by the calf as a fetus, and that likely contributes to its mortality soon after birth. Many newborn animals have underbite (overbite is far less prevalent), but do not have the mortality causing internal birth defects, so they live their life unable to bite off foliage efficiently. That also costs the livestock owners money when the animals are sold. If all livestock owners checked the bite on their newborn cattle, equines, sheep, goats and camelids, especially llamas and reported the underbites to their County Extension Agent, maybe steps would be taken to find what is causing this significant and likely unnecessary loss. Also, thank you very much, Travir.