Winter bull management affects animal health, breedback and herd geneticsWritten by Heather Smith Thomas
Ram Kasimanickam from the Department of Veterinary Clinical Sciences at Washington State University says some producers leave bulls with the cows all year long but this doesn’t give them much chance to recover.
“Also, when cows are checked for pregnancy in the fall, if results are below par, there may be a bull or bulls that need to be checked, and replaced if necessary – rather than waiting until the last minute. Producers need to make sure that the bull power for their operation is sound, before the next breeding season,” he says.
“Bulls need to maintain body condition, and any bull that has lost weight should be brought back to adequate condition. Studies have shown that a body condition score of five is adequate for a breeding bull. Yearling bulls need special attention because they are still growing,” says Kasimanickam.
Feed supplies and sources may vary, from ranch to ranch, regarding what is economical to feed as forage and/or concentrates or supplements. The main thing is to make sure young bulls have adequate nutrition to keep growing and stay in adequate body condition.
“Bulls need the proper levels of trace minerals and vitamins for good sperm production. Vitamins A and E, and selenium, copper, zinc and manganese serve as protectors and prevent damage to sperm from stress. Stress-damaged sperm will result in reduced fertility; even if fertilization occurs, the resultant embryo will fail to develop. Knowledge of soils and what they might lack will give the rancher an idea about which minerals need to be supplemented,” he says.
This will depend on the region and the individual ranch. The vitamin-mineral program should be part of the year-round management and not just seasonal. Producers don’t need to do anything special for the bulls, but just keep them on the same program as the cows, regarding mineral and vitamin supplementation.
One thing that is sometimes ignored is exercise. Bulls need exercise to stay fit.
“There are many ways to make sure they get enough exercise. Some producers put the feed and water at different ends of the pen or pasture, so bulls have to walk. They need to be fit before the next breeding season so they can cover their cows early in the season,” he says.
You don’t want bulls too soft and fat – with no endurance – after their winter “vacation.” Bulls should not be underfed or overfed; they need optimum condition to have enough stamina to cover the cows.
They do need to be fed a little extra during winter, however, to have enough extra energy to keep warm during cold weather. Weather severity will determine how much extra feed the bulls will need.
If bulls come out of the cow herd a little thin after the breeding season, some producers tend to overfeed them.
“The fat layers around the scrotum insulate the testes and can interfere with proper thermo-regulation of the testes. The sperm parameters and sperm production will be adversely affected in overfed bulls. This is why lean-to-moderate body condition is better than over-fat bulls,” he says.
It’s also important for health reasons.
“Over feeding with grain can lead to acidosis and liver abscesses, or foot problems,” he says.
Also make sure feeds don’t contain endophyte-infected fescues or other plants that act as vaso-constrictors, which interfere with circulation to the extremities. Cattle have been known to lose ears, tails and have foot problems during cold weather when eating certain feeds.
“This can also have an effect on the testicles and sperm production, affecting thermoregulation,” says Kasimanickam.
“During cold weather in winter, there can be adverse effect on the testicles if bulls can’t get out of the wind. Scrotal frostbite adhesions will hinder the bull’s ability to raise or lower the testicles for proper thermoregulation, and this can dramatically and adversely affect sperm production and parameters,” he explains.
“If it’s mild frostbite, there is good chance for recovery, but if it’s severe frostbite the bull may not recover and won’t be fertile – and will need to be replaced. Prevention is best, so producers should make sure bulls have windbreaks and bedding. Some people pile up old hay and straw for bedding. Heat from fermentation in these piles will help the bull stay warmer in cold weather. Any bull that is exposed to severe cold weather may suffer frostbite unless he has some protection,” says Kasimanickam.
“Also pay attention to vaccination programs, and control any internal parasites as well as lice and ticks. A sound health program is important. Most people have a pretty good program for the cow herd but sometimes the bulls are ignored,” he says.
Don’t wait until the last minute for vaccinations, since the animals need enough time to build immunity.
The bulls are half your herd, genetically, so you need to make sure they have adequate health care.
“They need good care during winter so they can be at their best for the next breeding season,” he says.
Any new bull brought in should come from a reputable source, and should have vaccination records.
“Usually the bulls are vaccinated before being sold, but if they haven’t been vaccinated, this should be done in a timely manner before the next breeding season,” he says.
Bulls should also be tested for trichomoniasis before breeding season and also have a breeding soundness exam.