Q:  I turned my bull out May 15 with the cows. Last nite (Dec. 8th) I was putting hay out and noticed my bull was following a few cows around and trying to ride them. The cows he was following appear to be heavy bred (vision only). I haven't had them palpated or anything, though. My question is can cows give off a false heat after they are bred? 

A:  The primary hormone of pregnancy for beef females is progesterone. Progesterone is produced by the corpus luteum that is on the ovary. Progesterone does not allow the cow to cycle.

During mid- to late-gestation, there are hormones produced that come from the placenta. Some of those hormones are estrogen or estrogen-like.

So the answer to your question is yes, cows that are pregnant may have some riding activity caused by hormones that are estrogen-like that are being produced by the placenta.