Cattlemen spend a great deal of effort selecting herd sires. This is as it should be as fertility is the most important economic trait. With that in mind here are some points worth considering if you want to get the most out of your investment during this and every breeding season.
To manage reproductive diseases, vaccinate herd bulls for IBR and BVD along with the cow herd.
Try always to purchase yearling (virgin) bulls from purebred breeders. This ensures predictability of the calf crop and minimizes exposure to any reproductive diseases such as trichomoniasis that old bulls may harbour. Any mature bulls with unknown history should be trich tested.
Your veterinarian can evaluate bulls for potential fertility. A BSE (breeding soundness evaluation) is a relatively small investment in comparison to the potential loss if sub fertile dominant bulls are chosen as herd sires. BSE looks at the scrotal size, semen morphology, and semen motility.
Ideally a BSE should be done on every bull before the breeding season. It is especially important to evaluate young (new), older (more than five years), and bulls, which have had a medical history such as frostbite.
Any bulls purchased from purebred breeders should be tested some time after their first birthday.
Watch a new bull to make sure he succcessfully breeds the first couple of times.
Up to 20 per cent of bulls may be sub-fertile.
When young bulls are tested, other conditions such as hair rings, penile warts and a persistent frenulum (ligamentous attachment between the prepuce and penis) can be detected and dealt with before they become a problem. The persistent frenulum causes a marked bending at erection and can result in severe damage if breeding is attempted.
The internal organs are palpated during a BSE. This can detect seminal vesiculitis, which is a gland infection. Generally bulls with this condition are culled as they produce pus in the ejaculate.
When selecting for horned versus polled in bulls remember polledness is genetically dominant to horns. Homozygous polled means all calves produced will be polled regardless of the dam’s status. Double polled means both parents are polled increasing the likelihood of the offspring being homozygous. Scurs are the result of an independent gene and is dominant in bulls yet recessive in heifers hence we see more scurred bulls.
When selecting colour keep in mind that black is dominant to red.
Semen quality and sex drive (libido) are not related. You can test for semen quality but the best way to check on the libido is observation. It is extremely important to observe your bull’s breeding ability.
Some bulls spend more time herding and guarding cows than breeding them. Does your young bull become cow smart and spread himself around several cows that are in heat?
If a young bull tries to mount a cow in heat three or four times without success chances are his problem is inherent.
A bull’s posture at breeding should be a c-shape versus a straight back.
Try to keep bulls together during the breeding season. Adding a new bull to the group will lead to disruptions until they reestablish the pecking order.
Horned bulls will dominate polled or dehorned bulls.
Minimum acceptable scrotal circumferences for yearlings
range from 29 cm for Limousin up to 33 cm for Simmental. Do not compare sizes between breeds as each breed has a different range for achieving an acceptable fertility level.
Research has shown that 38.5 cm is the maximum useful scrotal size. Above that there is no improvement in semen output.
Evaluate the shape of the scrotum when purchasing a new bull. Fat deposits in the neck are not a good thing.
Testicular degeneration it is a shrinking of the testicles and hence fertility. It can be caused by increased body temperature, infection, trauma, frostbite, and many unknown causes.
If your breeding season is extended due to the bull missing one heat cycle his calves will be 20 per cent lighter in the fall.
Never implant a breeding bull.
Put your bull on a rising plane of nutrition, like the cows, before the breeding season.
Exercise is important prior to the breeding season to get your sires in breeding condition.
Tend to the bulls feet at least a few weeks before breeding season begins. This is very important. Keeping the feet healthy can extend the breeding life of a bull by preventing abscesses, cracks, and corns from developing.
Consider using a commercial foot rot vaccine on your herd sires. A bull down with a foot problem in the middle of breeding season spells disaster.
Select bulls based on EPDs (expected progeny difference). These are good indicators of the calves he will throw in terms of birth weight, weaning weight, etc. Newer genetic tests can predict these values as well.
All of the above factors have a huge impact on your bull/ cow ratio which can vary from 1/15 for yearlings to 1/45 for mature, sound, mobile, fertile bulls.
Follow the above guidelines and have a productive breeding season.
A breeding soundness evaluation is a relatively small investment in comparison to the potential loss if sub fertile dominant bulls are chosen as herd sires