09/18/08 Fall calf birth weights

Calves born in the fall usually have lighter birth weights than spring-born calves. There is an explanation. I'm Jeff Keane; I'll be right back to discuss that theory. Just about any one who has calved cows in the fall notice a lot less calving problems than in spring calving cows. Since fall calving is here, it seems like a good time to talk about what might be the reason for lighter birth weights of calves born in the fall. Years ago I asked Buddy Cobb, a pioneer Charolais breeder from Montana about this observation. He said the best explanation he had heard was that fall cow's gestation is during the hot part of the year and that the cow's blood supply is further out in the extremities to aid in cooling the animal and so there is less blood closer to the fetus. With spring calving cows that carry their calves through the winter months, the blood supply is held closer to the cow's vital organs. The fetus then has a more abundant blood supply and gains more weight before birth. I just read an article that pretty much confirmed that theory. Researchers from Oklahoma State University studied same age spring and fall calving cows, artificially bred to the same bulls for five years. The fall calving cows averaged 77.7-pound calves while the spring calving cow's calf birth weight averaged 82.2 pounds. One other side note  Buddy Cobb sold some spring calving cows right out of his herd to a Florida producer and those cows sent to a warmer climate had significantly smaller birth weights that year than the cows left in Montana. I'm Jeff Keane.