I had a meeting last month comparing the costs per pregnancy for natural service and estrous synchronization and AI. After the meeting, a rancher stated to me that he has 8 cows and just purchased a $3,000 bull. He then asked me what his cost per pregnancy was! I said “Darn high!” Actually, his cost per pregnancy is $185.67 plus he has to deal with handling and managing a bull!

Obviously, he asked me what his options were. I suggested that he consider a total AI system. Since he did not know how to AI, he needed a system that did not include simple daily estrous detection and AI. I suggested that he use a program that synchronizes the returns heats of his cows so that he could reduce the number of days an AI technician needed to be on the farm.

Let’s use this rancher’s cows and step through the process of resynchronization. Let’s assume that all his females are mature cows and that his breeding season begins with a fixed-time AI occurring on May 21st. Normally, we would expect the cows that did not conceive to be in heat about 21 days later or about June 11th. To synchronize this return heat, a CIDR device is inserted about 14 days after the first breeding (June 4th in this example). The CIDR is then removed on June 11th and an estrous-detection patch is placed on the cow’s tail head. The cows will be in estrus from 36-96 hours after the CIDR device is removed. Breed these cows about 12 hours after you first observe them in estrus. Cows not observed in estrus conceived to the first AI and therefore are typically pregnant.

Resynchronization: An option for the small cow-calf rancher

The first question most ask is how many cows will I get pregnant using this method? If the conception rate to AI is 60% then after two services 84% of your cows will be pregnant or, in this case, 6-7 of the 8 cows will be pregnant by June 15th. What about the other 16%? Synchronizing one more estrus event will get another 60% of the remaining open cows so after 3 synchronized heats, 94% of the herd will be bred.

Synchronize three heats? That’s a lot of work; 9 times through the chute for some cows. How much was your labor worth? If you use the $3,000 bull, your cost for getting all 8 cows pregnant is $1,485.36 (8 x $185.67). The cost for getting 8 cows pregnant using the Resynch protocol would be $600 (8 x $75); an $885.36 difference. If you spent 8-9 hours extra working your cows, then you “made” about $100 an hour!

The side benefits are harder to calculate. First, using AI you can incorporate highly proven genetics into your herd. This means that you can get more predictable performance if you use a bull with an accuracy that is greater than 90%. Second, all your cows can be bred in a fairly short period of time. In our example, we got 8 cows bred in just 45 days.

Resynchronization of estrus is a viable method for small producers to reduce their costs per pregnancy. It does require more labor but the immediate and long-term benefits are substantial enough for small ranchers to consider resynchronization of estrus and moving to a total AI system.

Source: Dr. Les Anderson, Beef Extension Specialist, University of Kentucky