Choosing the right bull to enhance production
Calving time is here again and we vets get quite involved in beef farms at calving.
Sometimes more than farmers would like and often at unsociable hours, assisting calvings and performing caesarean sections.
Difficult calvings (dystocia) are inevitable, although some farms are fortunate to have a low incidence of dystocia. Part of the challenge is managing the cows before calving, but sometimes it isn’t until calving starts and there is a higher than normal number of cows needing assistance or Caesareans.
Often this coincides with the purchase of a new bull last year and the genetics of the bull plays a major part of the calving ease of cows.
Purchasing a bull is an expensive process, but the value that he brings to your herd can be worth far more than his initial cost. It is important to do a bit of homework, and choose a bull which will enhance and complement the farm production system.
Estimated breeding values (EBVs) are used to measure a bulls genetic potential.
There are a number of traits measured and some results are combined to given indices to meet specific breeding objectives.
EBVs are designed to give a best estimate of genetic performance of a bull. Priorities for calving ease, low birth weights, and shorter gestation (calving value) are important to reduce costs associated with dystocia and also to reduce calving interval.
For producers finishing stock, 400 day weight is paramount and fat depth must be considered.
Those breeding their own replacements need to look at calving ease of daughters, 200 day milk, and scrotal circumference. Scrotal circumference is related to the fertility of daughters and they reach puberty earlier.
For beef producers selling progeny at weaning, calving ease (direct), birth weight, muscle area and 200 day growth would also be important.
Breeding for specific objectives enables strengthening of current herd genetics, and improvement in areas which are deficient when breeding replacement beef heifers. This will ultimately enhance herd profitability.
A fertile bull should be able to get 90% of 50 breeding cows in calf within nine weeks. Producers with a tight calving period need to know that the bull is going to achieve those targets. A subfertile, infertile or sterile bull will not achieve this and will result in costly extensions to calving interval.
Ask your vet to perform a pre-breeding examination. This usually consists of a thorough physical examination, including assessment of internal and external, sex organs, and a semen test.
Your vet will obtain a semen sample via electro-ejaculation, and will assess the volume, density, motility of the sample and assess sperm for defects.
This should be performed within a few weeks of the start of breeding to reduce the risk of a change of status.
A semen evaluation does not assess libido or mounting ability, and therefore does not confirm the ability of the bull to breed.
Try to avoid bringing in disease. For closed herds this is often the only animal coming onto the unit, and the herd may be relatively naive (susceptible to disease).
Establish from the vendor their Johne’s status. This is difficult to test young animals, so the status with the herd of origin is of more use.
Other infectious diseases, such as Leptospirosis, BVD, and IBR should be tested for, or vaccination status should be established. Campylobacter is a venereal disease causing infertility and is spread by bulls. Have your bull tested or treated for this before he is allowed to serve any cattle.
Quarantine your bull on arrival and treat him for internal and external parasites; fluke, worms and lice, and observe for any signs of disease.
Find out the diet that the bull has been fed to ensure as smooth a transition as possible and promote rumen health.