Fertility in beef herds
Successful beef production relies on achieving key objectives, namely:
Weaning at least 95% of calves from mated cows
Keeping death rate in the herd to less than 3%
Weaning healthy, heavy calves
Keeping pasture quality high
The discussion of all the above objectives is beyond the scope of this article; we'll concentrate instead on factors that can affect low weaning rate. Good conception rate alongside good calving and good calf survival rate are the backbone of a top weaning rate.
Conception rate is influenced by many factors, among them the dam's nutritional status pre-mating (body condition, trace elements), the feed ahead post-mating (research suggests a cow should eat at least 12kgDM/day from calving), the herd's disease status (BVD, Lepto, Neospora) and bull fertility.
Body-condition score of no less than 5.5 at mating: underfed cows will take longer to mate and have a lower conception rate. Research suggests that cows should be within 5% of their autumn body weight at start of mating. Adequate levels of copper and selenium are key aspects to check pre-mating and these can be checked with liver biopsies 3-4 weeks prior to the start of mating.
Neosporosis, alongside leptospirosis, are more likely to affect well developed pregnancies causing abortion, and should be considered if in-calf cows turn up empty at calving time (wet/dry). BVD is emerging as a significant disease affecting herd reproductive performance. A study of 94 heifer herds has found that 65% of herds were infected with BVD. BVD can cause a 5% lower pregnancy rate in BVD-affected herds.
Bull fertility and soundness cannot be emphasised enough and bull failure plays havoc with pregnancy rates. Figures vary but anywhere between 10-15% of yearling bulls are either infertile or sub-fertile. BVD-exposed bulls must be identified and dealt with well in advance of the start of mating. Vaccination can and should be undertaken.
In summary:
- Ensure your cows are in top body condition prior to mating
- Determine the status of copper and selenium and supplement early if needed - liver biopsies can be done at the works or we can take the samples from elected cows on the farm
- Consider vaccination to mitigate the effects of BVD and Lepto in the herd
- Check your bulls for fertility and soundness - ensure all bulls are tested for BVD prior to mating, and vaccinate
Please call Totally Vets and one of our veterinarians will be happy to answer any of your questions.
