In mix sex bovine twins if the anastomoses placentas before day 45 the female will be a freemartin. If the anastomoses placentas after day 45 the female will be fertile. Cattle twins are also chimeric. Twins are rare in cattle about 1 in 200 births. Of which 1/2 are fraternal. https://beef2live.com/story-cattle-births-make-record-twins-0-110920