Estrus Behavior

You and I have had this conversation.   This has been my best year for conceptions.  But I still have a straggler.   She was my late calver - December 21, 2019.  I want to move her back.  I set her up on a CIDR and the 7 day protocol.   I pulled the CIDR Tuesday.  I wanted to breed her on observed heat.  The little bulls had her sniffed out by 48 hours post CIDR removal.  But all the cows are bred and they totally ignored her. In this case, I don't have a standing heat to time off of.  I bred her last night at 49 hours.  I know that is early.  I am, as I type this, getting ready to breed her again at 64 hours post CIDR  removal.  This will be the first time this year I have decided to use 2 straws at one breeding.   Here is an excerpt from that publication that deals with heat detection under these circumstances:


Herdmate Status (Stage of Estrous Cycle)
To determine the cause of silent heats or poor expression of heat, consider the overall reproductive status of the herd and compare the ratio of open to pregnant animals in each group of cows and heifers. Pregnant cows are the least likely group of herdmates to mount a cow in heat. Herd managers must rely on the other open cycling herdmates to detect heat. What about the other nonpregnant herdmates? Do herdmates vary in their ability to detect and mount cows in heat? Does the day of the herdmate's estrous cycle influence her interest in the estrous cow?

When Penn State researchers conducted a very controlled study, estrous cows encountered each of 19 cycling herdmates in an isolated barn one-to-one for 10 minutes. The total number of mounts by each herdmate was determined on day 10, day 15, day of heat, and day 5 of the next cycle. Herdmates varied in mounting activity, as did estrous cows in attracting mounts. More important, for the herdmates as a group, the number of mounts differed substantially with the day of the cycle. Herdmates in midcycle (day 10 and day 15) and on day 5 averaged one mount or less during the 10-minute observation period. Some herdmates did not even mount the estrous cow on those days. However, when the herdmate herself was in estrus, the number of mounts averaged 2.5 during the 10-minute period. Thus, taken as a group, cows are poor heat detectors in the middle of their cycle. Since this represents 50 to 60 percent of the estrous cycle and reduces the number of effective heat-detecting herdmates by a similar percentage, managers must rely on cows in or near heat to detect other estrous cows.

In some herd situations, a few open cycling cows may contribute to the problem of silent or missed heats. In small herds, most of the herd may be pregnant at certain times, and the stage of the cycle of the few nonpregnant cows may be such that they are not effective heat detectors. As more animals become pregnant, the number of potential heat-detecting animals is reduced. The situation is similar for herds that freshen on a seasonal basis. After an intensive breeding period, when a high percentage of the herd is pregnant, it becomes increasingly difficult to identify the few open cycling cows in heat. There simply may not be enough herdmates in the proper stage of the cycle to interact with an estrous cow. A third situation may occur frequently in free-stall herds where cows are grouped according to production. Generally, the lower production group contains pregnant cows, but because of low production, some nonpregnant cycling cows may be included in this group. It becomes very difficult to detect the cows in heat because their herdmates are pregnant.