Getting more cows bred earlier utilizing estrus sync
Labor, facilities and costs main constraints for adopting a synchronization protocol
By Erika Lundy-Woolfolk and Beth Reynolds
Improvements in synchronization technology have reduced the cost and labor expense associated with these protocols, while expanding the applications beyond artificial insemination or embryo transfer use. Implementing a natural breeding programs following estrus synchronization can still reap the benefits but gives producers more flexibility to best match their operation needs.
It’s well understood that cows bred earlier in the breeding season will have a bigger calf, resulting in more pounds to sell at weaning. In natural service breeding seasons, the main advantage of implementing synchronization technology is an added opportunity for more females to conceive in the first 21 days of the breeding season. On average, cows exposed to bulls following estrous synchronization are expected to conceive two weeks earlier than cows that were not synchronized.
If a modest two-pound ADG is assumed, a 28-pound improvement would be expected at weaning. If we apply last year’s monthly average Iowa price for 500 lb steers sold in October at $286/cwt, that equates to an $80 advantage compared to herd mates born two weeks later.
No surprise to anyone, labor, facilities and costs are the main constraints for producers considering adopting a synchronization protocol. In fact, the 2009 USDA National Animal Health Monitoring System (NAHMS) data indicated that only approximately 11% of the U.S. cow herd are artificially inseminated annually. Although we expect these numbers have increased since the 2000’s, it would still be a small percentage of the cow herd that undergoes a synchronization protocol each year.
In order to utilize a synchronization protocol, females will need to be near working facilities at the start of the breeding season. Major advantages to a natural service protocol include fewer products administered and less trips through the chute, resulting in a less labor-intensive process and typically better cow behavior than females undergoing AI following synchronization.
Additionally, there can be consequences of altered conception rates and early embryonic loss associated with hauling females post-AI; however, those risks are reduced with natural service protocols since females are often hauled or moved to breeding pastures immediately following the last step of the synchronization protocol.
While weighing the pros and cons of implementing a synchronization protocol followed by natural service, keep these considerations in mind:
Select the right protocol. There are several synchronization protocols that have been developed for natural service and each have their own advantages and disadvantages. Options include single injection protocols, CIDR insert and removal protocols, or feeding MGA to heifers. Your local veterinarian, semen company representative, and area beef specialist are available to help you weigh the pros and cons of each in your unique operation. Additional information on protocols can be found here.
Synchronize appropriate candidates.Not all females are a good candidate for a synchronization protocol. Late calvers that are less than 45 days postpartum are unlikely to respond. However, one advantage of late calving cows going through a synchronization protocol is a “jumpstart” to estrus cycle and has shown effectiveness as early as 21 days postpartum. Keep in mind, these females must be receiving adequate nutrition and are not expected to breed in the first cycle (21 days) of the breeding season.
Have adequate and healthy bull power.Bull power is key to a successful breeding season. Synchronization protocols are designed to bring females into estrus and ovulate within a certain time frame. When naturally serviced females undergo a synchronization protocol, bulls are often expected to breed twice as many cows over a 7-10 day period as they would in a non-synchronized herd. It is worth noting that natural service protocols result in a wider estrus window than AI protocols, so even though bull power needs increase, it is less than what a timed AI protocol would indicate.
A good rule of thumb for a non-synchronized setting for bull to cow ratio is to use the bull age in months, up to 4 years old to indicate how many females he can service. For examples, a 28-month-old bull at turnout would be expected to service about 28 cows in a 90-day breeding season. When utilizing synchronization protocols for natural service, research has shown no difference in heifer pregnancy rates when mature bull to female ratio ranges from 1:16 to 1:25, suggesting an optimal ratio of 1:20 to 1:25.
Bull age is an important consideration as breeding is considered a learned behavior for bulls. Yearling bulls tend to mount cows in heat 40% more times than 2-year-old bulls and 60% more than older bulls. While there is no difference in the percent of females serviced based on bull age, pregnancy rates for females serviced by yearling bulls tend to be 20% lower than females serviced by mature bulls. Combined, these data suggest mature bulls are better suited to breed synchronized groups.
Finally, it is critical for all bulls to have a full breeding soundness exam (BSE) that covers all three components: physical exam, inspection of reproductive organs, and semen evaluation. Due to more cows cycling in a tighter window when synchronized, ensuring bulls pass their BSE becomes even more important. During active breeding periods, especially in the first cycle, monitor bulls closely to ensure injury, disease, or dominance issues do not interfere with the breeding season.
Lundy-Woolfolk is the Southwest IA Extension beef specialist and Reynolds is the Iowa Beef Center Program specialist, both with Iowa State University.