Warrants of fitness needed

01-07-2010 | Jackie Harrigan

Just as you can't judge a book by its cover, you can't tell if your bull is fertile and capable
of doing the business by looking at him.

The only way to be as confident as possible that he is going to be a breeder is by having him service and semen tested. Hunterville vet Dave Warburton recommends bulls be tested before each breeding season.

Addressing the Beef Returns Improvement Group seminar at Hunterville, Warburton said he had four simple rules about bulls.

No 1: They must eat - so get their jaw checked;

No 2: They must walk - hence the need to check their feet, leg structure (not too straight) and tracking movement;

No 3: They must breed - have each bull checked for big-toned testicles, normal penis, normal sheath and good libido;

No 4: Semen needs to be tested as normal. Warburton recommends 70+% for single-sire mating and 50+% for multiple sire mating groups.

According to Warburton, for a bull to gain a warrant of fitness it should be BVD tested and vaccinated, 7-in-1 vaccinated, service ability tested, semen motility and morphology tested, and structurally assessed and passed. Buyers need to discuss their testing programme with their bull breeder to be confident they are buying a fertile bull.

A Meat and Wool NZ project identified that only 22% of commercial farmers check the service ability of their bulls, 2.5% get a semen test done, and 5.5% get both done by their vet.

The $5000 sire which lasts only one season and sires 40 calves is costing $87.50 a calf compared with the sire that lasts three seasons, sires 120 calves and has a crude calf cost of $29 a calf.

Annual service testing for the bull team is also highly recommended by Warburton as difficult to detect problems, such as corkscrew penis, develop over time and penile injuries that prevent breeding can go unnoticed in a paddock. Lameness in the hips, hocks, spine or feet can also impact on breeding rates, and would be identified during a service test. Warburton also recommends a semen test, particularly if the bulls are in poor condition, have had an infection of any sort, or have been lame during the past 12 months.

Annual testing is a cheap insurance policy, he says. "Don't make the assumption that just because the bulls did the job last year they will be all right this year."

An annual BVD vaccination pre-mating is also important, he says. Vaccination prevents bulls becoming infected with BVD if it is circulating in the cow herd, as it commonly does. Infection would cause temporary sub-fertility in the bull.

Bulls also need to be fit before mating, with 4-6 weeks acclimatising to country similar to that the cows will be mated on. Warburton emphasises fit doesn't mean starved - they must still have good body condition to account for the loss of condition over the mating period, and mineral levels should be assessed because they can impact on sperm quality.

Semen quality is also affected by the prolonged stress of illness. Any sort of infection can reduce semen quality for up to 70 days, even with antibiotic treatment.

Outlining the pros and cons of multiple-sire mating, Warburton says the regime tries to cover the potential of bull failure with less work during a busy time of year. As well, the competition effect of more than one sire probably increases libido. It is best to use a junior and senior sire together so there is a clear hierarchy resulting in fewer fighting injuries.

The dominant bull can be a problem if sub-fertile or unsound and if it prevents the junior bull from working.

Using single-sire mating but rotating the bulls after each cycle is extra work, but carries a lower risk of injury by having just one bull in the mob at a time and bull failures are covered, although it may mean the calves are born 21 days later - but better this than not at all. There is also a probable increase in libido when the bull joins another mob of cows.

Mating ratios depend on the size and terrain of the mating paddock and whether the bull is experienced or a first-timer. Warburton generally recommends 1:25 cows for yearling bulls, 1:35 for two-year-old virgin bulls and between 1:25 and 1:55 for older bulls depending on the paddock conditions.

Bulls are a necessary evil, he says - they are expensive, can break down at any time, and their health, body condition and fitness level need to be managed carefully to get the most value from them.

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