Getting heifers to their first breeding in the right body condition and on time can establish their “reproductive momentum” for a lifetime. An article in the January 2013 Bovine Veterinarian explained why creating this momentum in the herd is important.
To keep a beef herd rolling along reproductively year after year, it’s important to strategically plan the heifer’s first breeding. Creating reproductive momentum so that all cows and heifers breed, calve and re-breed in a timely manner every year starts with the first-calf heifer. On any given operation there may be heifers ready to breed for the first time, and heifers ready to calve for the first time, whether they are home-raised or purchased replacements. Both groups need some attention.
Start with the end in mind
On a herd level, mature cows tend to calve near the same date each year if nutrition and bull fertility are adequate. To keep a beef herd rolling along reproductively year after year, it’s important to strategically plan the heifer’s first breeding.
The goal of at least 80% of the females cycling before the start of the breeding season is a minimum for all heifers, first-calf heifers, and mature cows. The best available estimate is that about two-thirds (65%) of matings between a fertile bull and fertile cow will result in a pregnancy that can be detected at typical preg-check times, says Bob Larson, DVM, PhD, Dipl. ACVPM, Dipl. ACT, Kansas State University.
Successful pregnancy is less likely to occur on the first cycle after calving (or on the first cycle after puberty), therefore, cows that are cycling before the start of the breeding season are more likely to become pregnant at their first exposure to bulls than even cows that resume cycling during the first 21 days of the breeding season. ”Therefore, in order to have at least 60- 65% of cows calving in the first 21 days of the calving season, essentially all of the cows need to be cycling by the end of the first 21 days of the breeding season,” Larson says.
To make sure that the mature cows have a good opportunity to calve in the first 21 days of the calving season throughout their lives, for their first calf they need to calve at least 80 to 100 days ahead of the start of the mature cow breeding season, which places this calving ahead of the start of calving for the mature cows, explains Larson.
Larson’s ideal is for heifers to calve two cycles ahead of the mature cows because on average, first-calf heifers require about 40 additional days to resume fertile cycles compared to mature cows. However, it is important to consider individual herd situations.