I have had a little experience with embryo transfer both from my studies at college and past experience. From what I know the size of the calf is determined by both genetics and the maternal environment. Studies have shown that the calf will develop and grow to the space that is has available in the uterus. For example, putting a full blood mini hereford embryo in a large cow will give the calf plenty of room to grow to a birthweight around what the large cow is used to having, and visa versa. And yes some dairies put multiple embryos in their Holstein cows to increase the # of progeny from that cow each year. I read an article sometime about a Holstein cow that had quadruplets through embryo transfer. Hope that answers your questions!
