How the first-calf heifer performs in the breeding season and beyond begins long before that. Bob Larson, DVM, PhD, Kansas State University, says a goal to shoot for is over 90% of cross-bred heifers pregnant in a 60-day breeding season. If the heifers are examined prior to breeding to remove any questionable breeders, the success should approach 93–95%. “If the breeding season is confined to 45 days, I would expect a lower percent pregnant,” Larson notes.
Dan Goehl, DVM, Canton Veterinary Clinic, Canton, Mo., often artificially inseminates the heifers. “Timed AI has become very popular due to labor issues,” Goehl says. When timed AI is used, he plans to get 60% conception on Day 1. “These rates will vary but 60% is very attainable and often we can get higher conception rates than this. If we can get 60% AI on Day 1 and 70% of the remaining 40% at (or around) Day 21 then we would strive to attain 85–90% in the first 21 days and should have 95% or greater by Day 45.” Goehl notes that this is on optimally managed heifers. They will have been tract scored to remove free martins, marginally mature heifers, etc.
In order to reach those goals, Larson and Goehl offer these 12 ways to help clients improve beef heifer fertility:
1. Select cross-bred heifers from dams with sound feet, legs, and udders that conceive early in the breeding season with minimal supplementation, and have producers by-pass heifers from cows that have had vaginal prolapses and other health issues.
It is important when retaining heifers from within your herd to select animals that are from parentage with the traits you wish to propagate. This can be done with computer records, a notebook or any system that identifies these animals. “Ideally we would have records of conformation, reproductive performance and growth/ performance potential,” Goehl says. Recording birthdates or at least birth week is useful because heifers born early in the calving season will have an age advantage relative to females born at the tail end of the season.
Larson suggests also having producers mark dams (with an ear notch, special colored ear tag, etc.) from which heifers should not be retained.
2. Select heifers that will be at least 13 months of age at the start of the breeding season.
Larson notes that both age and weight are important for reaching puberty. “A tight calving season will result in a high percentage of heifer calves that will meet the target age.”