You might know a farmer who isn’t big on machinery maintenance. Some people figure that if it worked when they parked it, it will work when they pull it out again. Some cattle producers follow that same philosophy. If a bull bred cows one season, he will breed cows the next season. It’s not always the best plan for equipment maintenance, and sometimes it can leave you with open cows.

“We’ve seen it happen several times,” says Chris Parker, Morgantown, Ind. He raises forage and has a small cow-calf herd. He’s also a retired Purdue University Extension educator, with over 30 years of experience in Morgan County. During his tenure, the Morgan County Beef Cattle Association began offering an annual bull test day each spring. It’s been ongoing for over 20 years.

“We believe there is definite value in knowing if a bull is sound,” Parker says. “You only get one shot for a calf per year.”

Several other county groups, especially in southern Indiana, offer bull testing clinics. By having producers bring bulls to one location on a specific day, they can maximize the veterinarian’s time and lower the fee per bull.

Making the grade

In Morgan County, any bulls at least 12 months old and weighing at least 1,000 pounds can be tested, Parker says. One of the first things the vet does is measure the circumference of the scrotum.

“Each breed sets a minimum size,” Parker says. “You need adequate size to produce sperm, but there is also research tying the size of the scrotum to how fertile female offspring will be.”

The vet stops the test if the scrotum doesn’t meet minimum size, Parker says. He’s seen this happen several times.

Next, the vet collects semen and immediately puts a droplet under a microscope, set up in the barn lot.

“He’s looking for motility, which means sperm that are swimming,” Parker explains. “He’s also checking to see how many sperm there are in the sample on a relative basis.”

Later, the vet adds a stain to the slide back and checks morphology to make sure there are a minimum number of deformed sperm, or sperm with double heads or broken tails. If the bull has plenty of mobile sperm with minimum defects, he earns a passing grade.

“That doesn’t guarantee he will breed lots of cows, because there is no way to judge libido,” Parker says. “You don’t know that until you observe a bull during breeding season. What the test does is confirm whether the bull is sound and has the ability to breed.”

A bull that doesn’t pass the test still may breed cows, Parker notes. However, he may only breed 50% to 60% instead of 90%. That’s the value of testing, he says.

“Things can happen over time, even to bulls that were sound the year before,” Parker says. “Perhaps he gets injured. Or maybe there is a severe cold snap during winter and his testes are damaged.”

Parker has also seen cases where a bull was marginal on the day of the bull test but was producing plenty of semen later.

“That can happen because the semen collected on test day was produced weeks before,” he explains. “One year my bull was marginal when we tested him. I took him to a different test site a month later and he was fine.”