Although artificial insemination (AI) has been around for many years, in recent years fixed timed artificial insemination (FTAI) has gained popularity for use in beef heifers. Dan Goehl, DVM, Canton Veterinary Clinic LLC, Canton, Mo., uses it routinely in his beef cattle practice.
“In beef herds there is a huge savings in labor due to the convenience of being able to predetermine, weeks in advance, what day the herd will need to be gathered for chute work,” Goehl says. “This allows for labor savings and the practicality of using AI.”
Goehl says this tool has allowed him to implement AI in commercial herds that would not have heat-detected and bred after observed heats. He says the convenience factor of AI is seen on both ends of gestation. “It is a huge advantage to have 60% of your cows bred on Day 1 of the breeding season strictly for labor and convenience.”
There are also economic reasons why this is beneficial. If you are able to breed 60% AI (Goehl tells producers to hope for more than 60% but to expect 60% or less) and then if the bull can achieve 60% pregnancy rates on the remaining 40% of the herd, you can have 84% bred in the first 21 days.
“Realistically, what we see is that, especially with low birthweight bulls, the gestation is shortened and often the first round of calving is nearly done by the ‘due’ date,” he explains. Artificial insemination increases the average age of the calf crop which in turn increases the average weight of the calves at sale. Additionally, AI increases the likelihood of getting cows bred back earlier in the breeding season and therefore, increases the continuity of the group.
“We have all seen herds that have semen-checked a bull and found out at preg check that he went bad during the breeding season; this is insurance toward minimizing that risk,” he says. It also allows you to decrease your bull power and increase genetic potential by using proven sires.
Options can be utilized such as using maternal bulls on cows compatible with keeping replacement animals and terminal sires in the others. Another option is to have a strictly terminal bull as a clean-up to maximize profits from these calves while using a maternal bull for AI or a mixture of maternal and terminal bulls for AI depending on the cow. “It’s true that some bulls work better in FTAI protocols than others but it has nothing to do with fertility,” explains Mallory Risley, MS, reproductive physiologist at Goehl’s Canton Veterinary Clinic and research coordinator for Professional Beef Services LLC.
“Semen from reputable AI companies is from proven bulls and should be fertile. The difference lies in the individual rates of capacitation required by the sperm. Some bulls quickly undergo this process and others take longer. Thus, some work better than others in protocols that require insemination at a fixed-time.” It is important to ask about such information on particular bulls prior to purchasing semen from the companies’ representatives. The representatives are very knowledgeable about their products and by asking for further information, producers can ensure they are getting the best matched bull for their herd.
Goehl notes that this process is not to be taken lightly and there is significant financial investment. Care must be taken in setting up all dates, etc. and timing of injections is crucial. “Depending on the facility, we usually limit the herd size to 80 head,” Goehl explains. “With two AI techs we can get these through in a timely manner and our variation of time from injection to AI is minimized. I have found it helpful to print a calendar for the producer and clearly spell out exactly what will be done and at what time. We offer to send laborers to help set up the cows through the first trips through the chute if it is helpful for the producer.”
Synch heifers for first breeding
Risley says estrous synchronization must be implemented to reach desirable conception rates when using AI. “This not only makes AI practical, but it increases the number of females in estrus at one time and helps create a uniform, contemporary group at calving,” Risley says. Females can conceive earlier in the breeding season, thus leading to more time between calving and weaning. Therefore, calves born under strict estrous synchronization management, tend to have higher weaning weights than those born under natural breeding systems. Additionally, females that conceive earlier in the season are given more time postpartum to recover prior to the subsequent breeding season and therefore have a greater chance to conceive to first services.
For estrous synchronization to happen, both phases (follicular and luteal) of the estrous cycle must be manipulated. The latter is done with progestins (melengestrol acetate [MGA] and controlled internal drug release [CIDR]) as well as prostaglandins; whereas, the follicular phase is commonly controlled with gonadotropins such as GnRH. Both progestin products are effective at inhibiting estrus and ovulation.
“CIDRs are beneficial as they ensure that each individual animal receives her required dose amount and can decrease the time and labor during the synchronization period,” Risley explains. She notes that MGA requires adequate bunk space and must be fed at the same time every day, and thus can be more demanding than a
CIDRs are approved for use in both cows and heifers; whereas, MGA is only approved for use in heifers. Prostaglandin is required to regress the endogenous corpus luteum (CL) at progestin removal. Once the CL is lysed and the progestin is removed, estrus and ovulation is allowed to occur. By synchronizing the follicular wave with GnRH (causes ovulation of the dominant follicle and “re-sets” the follicular wave), a newly formed dominant follicle is ensured to be present at time of insemination.
Heifers need to be ready
Risley says it is important that heifers are in good to moderate body condition at time of insemination. “This process is not accomplished in a short week; rather, prior planning is required to make sure animals are in an adequate body condition prior to AI. High energy diets fed leading up to AI can help add weight and potentially increase conception rates during the breeding season.”
View the entire Beef Reproduction Task Force Beef Heifer Protocols 2009.