By Taylor Grussing
It seems that beef producers are always ready for calving season to be done but never ready to pull the bulls from pasture. As the length of the breeding season is directly correlated to the length of the calving season, what can be done to decrease the length of both seasons but still get the same number of cows bred in a timely manner? Implementing an estrus synchronization program such as fixed timed artificial insemination (FTAI) or a natural service synchronization program can help shorten both breeding and calving seasons while increasing calf crop value through older and heavier calves at weaning time. Dr. Lamb and colleagues in Florida have documented added calf and herd value after shortening the breeding season from 120 days to 70 days (Table 1). To do this, they implemented an estrus synchronization and FTAI protocol to all cattle at the research farm. So with results like these in Table 1, why do cow/calf producers hesitate to buy females bred using FTAI or utilize FTAI in their own beef females more? This article will explain what to expect when time breeding and calving cows to ease the anxiety of using estrus synchronization and FTAI.
What to Expect at Breeding
In a normal cycling herd, we expect 5% of cows to come into estrus (be sexually receptive) every day during the breeding season. Therefore, when utilizing a synchronization protocol the goal is to condense the number of head that will show estrus into a shorter period of time for breeding. Conception rates to a FTAI protocols average 55% - 60% but can be better or worse based on cow age, condition, and days postpartum. By setting up the breeding season with FTAI and estrus synchronization, 80% of cows may conceive in the first 30 days or the breeding season and subsequently calve during the first 30 days of the calving season (Hughes, 2005; Shafer, 2005). This can be a daunting number to consider calving at one time, especially if labor is limiting and if calving occurs during the winter time in the Upper Midwest. Yet, with more calves planned to be born at the beginning of calving season that will return more value at weaning time, it may be feasible to hire extra help during calving since it will only be for a short time.
What to Expect at Calving
Calving distribution for cows that conceive on the same day with FTAI will vary by sire and cow genetics. Bader and others (2005), studied gestation length of 5 sires at 3 locations and found cows that conceived to FTAI calved over 16 – 21 days. On average the maximum number of cows that calved on any one of those days was 16%. In addition, depending on the calving ease rating of the sire, cows may begin calving two weeks prior to their anticipated due date and conclude calving one week after the due date (based on 285 gestation). This distribution suggests that use of FTAI will not result in an overwhelming number of cows calving on one day. To best prepare for calving season, setting up calving facilities and scheduling labor to account for peak calving events over those 15 – 20 days will yield best results. For example, if 100 cows undergo FTAI and 60% conceive on one day, the calving barn may need to be set up to potentially house 10 calves that may be born on a single day.