Before we know it, another breeding season will be upon us. As cattle producers, I think we’re all aware of how uniformity contributes to profitability, regardless of your marketing strategy. Whether you market weaned calves, retain ownership and market finished cattle, or market breeding stock, uniformity pays. While uniformity is certainly influenced by genetics, our management strategies, particularly during breeding season, are key to producing consistent cattle.
Uniformity is a noticeable benefit of using estrus synchronization in beef herds because it allows a greater proportion of females to be bred at the beginning of the breeding season; however, synchronization is typically associated with artificial insemination (A.I.). Across the U.S., the overwhelming consensus in beef operations is the use of natural service breeding programs. In fact, a national survey representing 87% of beef cows found that only 7% of operations utilized estrus synchronization, while 91% of beef females were exposed to bulls only. The clear benefits of estrus synchronization, combined with the majority of cows being exposed only to bulls, have encouraged the development of several options to utilize and benefit from both strategies.
Because estrus synchronization works to control a female’s estrous cycle, utilizing it with your natural service program allows more females to be receptive to breeding around the same time and at the beginning of the breeding season. Without using synchronization, each individual female is going to come into heat (show estrus) at a unique time and be bred by the bull. Given that estrus occurs approximately every 21 days in cattle, it may be weeks after turnout before a female gets bred for the first time. Alternatively, when using synchronization designed for natural service breeding programs, females come into heat over a more defined time frame (around five days). Thus, females have a breeding opportunity at the start of the season and another approximately 21 days later, leading to two breeding opportunities in a 30-day period. This translates directly to more calves potentially being born at the beginning of your next calving season and for older calves at weaning. Not only does age positively impact weaning weight, but more calves born in a concentrated time period improves uniformity.
When asked why an operation does not use synchronization, the same national survey found that labor is the number one deterrent. For synchronization to be an economical addition to a natural service breeding program, the additional labor required must not outweigh the potential benefits for your herd. Because natural service synchronization protocols add either one or two trips through working facilities, estimating this labor demand for your specific operation is crucial. Balance this with the potential benefits of synchronization: females conceiving earlier during the breeding season (research shows 13 to 14 days earlier), improved calf uniformity and more recovery time between calving and the next breeding season. As with any change to management practices, carefully weigh both sides of the equation.
Bulls with synchronization
Beyond considering additional labor, there is often concern over the ability of bulls to service a synchronized herd, where many females are receptive to breeding in a short time frame. Breeding is a learned behavior impacted by many factors, so there is not a one-size-fits-all answer; however, we can learn from research in this area. Studies have shown that yearling bulls mount more frequently without servicing females compared to more mature bulls, and pregnancy rates in synchronized females serviced by yearling bulls are lower compared to synchronized females serviced by 2- or 3-year-old bulls. Generally speaking, bulls efficiently produce sperm, and research shows no differences in sperm morphology or motility of a breeding soundness exam before and immediately after bulls were used in a synchronized breeding period. What a breeding soundness exam fails to measure, and what are extremely important in a synchronized natural service program, are libido and social dominance. Spend some time watching your sires during an unsynchronized breeding season to identify more aggressive breeders. Bulls that actively seek, mount and service females are great candidates for a synchronized natural service program. In multi-sire breeding groups, bulls will create a hierarchy where older and larger bulls are usually dominant over younger and smaller bulls.
Age, libido and social dominance aside, the number of bulls you may need to service your herd should be carefully thought out, regardless of using synchronization or not. Research in this area has compared bull-to-female ratios of 1-to-50 in unsynchronized herds to synchronized herds using ratios of 1-to-50, 1-to-25 and 1-to-16. There was no difference in pregnancy rates using a bull-to-female ratio of 1-to-25 compared to 1-to-16 (83% and 84%) in synchronized herds, which were also equal to pregnancy rates in unsynchronized herds using a 1-to-50 ratio (82%). However, pregnancy rates were slightly lower using a 1-to-50 bull-to-female ratio in synchronized herds (77%). Economically speaking, a bull-to-female ratio of 1-to-25 improves revenue margins compared to a 1-to-16 ratio in a synchronized natural service breeding program, as fewer bulls need to be sourced and purchased.
In a natural service breeding program, it is crucial that females show estrus so bulls can seek out those receptive to breeding. If most females in the herd are newly postpartum or are in poor body condition, they may not be physiologically ready for the breeding season. In those cases, choosing which synchronization method to use is critical. Before implementing synchronization in a natural service breeding program, consider the management of females and sires, as well as the sizes of breeding groups and pastures.
Summary for use of synchronization with natural service
- Use bulls at least 2 years of age that are satisfactory potential breeders as determined by a timely breeding soundness exam.
- Be aware of the pros and cons associated with multi-sire breeding groups.
- Use bull-to-female ratios of approximately 1-to-25 to accommodate pasture size, terrain, etc.
- Find what protocol fits your operation best. More information about synchronization protocols can be found on the Beef Reproduction Task Force website.
