As the end of the calving season nears for many cattlemen, the last few cows in the heavy pen seem to last forever. Those late calvers are doing more than dragging out the calving season. They are costing you money. Their young calves are usually lighter at weaning, late calving cows usually rebreed later or not at all. 

How can you move up a late calving cow in the breeding season? The answer is a CIDR. CIDR stands for Controlled Intravaginal Drug Release device. It is inserted into the cow’s vagina, where it releases the hormone progesterone. CIDRs are a common estrus synchronization tool, but they can also be used to bring cows into heat before she would normally come into heat on her own.

In order for this to work, you should insert the CIDR no sooner than 20 days after calving. The uterus must shrink back to its original size for reproduction to occur. Recovery takes time-imagine something holding a 90 pound calf needing to shrink to the size of a volleyball. Trying to “jump start” the cycle with a CIDR (progesterone device) too early after calving could result in less than desired pregnancy results.

If you plan to use natural service breeding insert a CIDR for 7 days, then remove the CIDR on day 7, and give an injection of prostaglandin. Bulls can be immediately be placed with the cows. There is no need for extra bulls, a bull to cow ratio of 1:25 should be sufficient. However, all bulls should have a breeding soundness exam by a veterinarian. Young bulls may require special attention and a higher bull to cow ratio.

This protocol requires two cattle handlings and will cost around $15 for the CIDR and prostaglandin.

Since the CIDR will synchronize estrus you could also use artificial insemination (A.I.). If you choose to A.I. you need to add a GnRH injection at the CIDR insertion, leave the CIDR in for 7 days, and inject prostaglandin when you remove the CIDR.

If you plan to A.I. it would be worth your time to look over the different estrus synchronization protocols at: or visit with your A.I. representative or Extension Educator. Choose a system that works best for you. Any of the 7-day CIDR protocols will “jump start” the estrus cycle. The “recipe” for each system should be followed exactly- no guessing or giving late injections!  

Cows should be in good condition, a body condition score of 5 or greater at the time of calving, and maintaining or gaining weight after calving through breeding. Cows maintaining or gaining weight are more likely to conceive and sustain a pregnancy than cows losing weight.

It will cost a little money and take some extra work, but it is possible to move those late calving cows up.