Plan ahead for breeding

An early start can help ensure that bulls have ample body condition before breeding season begins. Industry experts encourage producers to start thinking about their bulls — evaluating overall flesh, age, and nutritional needs — 120 days before turnout. In order to better understand nutritional needs, divide a bull’s year into three seasons (see below). Then, evaluate body condition 30, 60, 90, and 120 days before breeding begins.

1. Prebreeding or conditioning: 2 months
2. Breeding season: 2-3 months
3. Post-breeding season or rest and recuperation: 4-8 months

The best thing a producer can do when conditioning bulls for breeding season is to plan ahead; the more time to prepare bulls for turnout, the less expensive it is to add condition. The goal of conditioning is to add flesh while promoting fertility and libido. Over-conditioning can cause bulls to fatigue or “melt” off body condition shortly after turnout, reducing libido and negatively affecting breeding soundness and effectiveness.

Optimally, a bull should be a body condition score (BCS) 6.0 at turnout. One unit of condition is equal to about 80-100 pounds (lb.). Therefore, figure that it takes more than 30 days at 3 lb. per day to add 1 unit of condition. Body condition — nutrition — affects semen production, especially in younger  bulls. Therefore, a body condition of 6.0 to 7.0 can help to ensure a sire achieves optimal sperm production, motility, and breeding effectiveness. Thin bulls and overly conditioned bulls are likely to have reduced reproductive efficiency.

Sperm cells take 60 days to develop and mature; therefore, a bull needs conditioned to reach and maintain a body condition score of 6.0 for a minimum of 60 days before he is used heavily. Typically, bulls lose one body condition when breeding; a 6.0 ensures they have the extra fat reserves to carry them through the entire breeding season.

The ideal diet energy level for older bulls depends on their body condition at the beginning of the conditioning period. Most mature bulls that are in good flesh can be maintained on an all-roughage diet.
A rule of thumb is to provide about 2% of their body weight in dry feed per day. If bulls are younger, they’ll have higher nutrient needs because they are still growing and developing. Yearlings should be gaining weight and maintaining moderate condition before breeding  season.The body stores of energy a yearling loses during breeding should come from energy stored as fat (condition) rather than muscle tissue.

How physically fit a bull is also plays a role in his breeding-season success. Often bulls may have to travel several miles a day to breed cows, and those that are preconditioned and fit for the range are better work candidates. Exercise is especially critical for yearlings; it strengthens their back and leg muscles and hardens up their feet.

Evaluate breeding soundness

While nutrition and exercise can prepare bulls for work, an assessment of physical and reproductive soundness and health can help ensure they are fertile. This assessment is best accomplished through a Breeding Soundness Exam (BSE).

A bull that passes his test as a yearling isn’t necessarily good for life. All bulls should be annually evaluated for breeding soundness 30 to 60 days before turnout. The breeding soundness exam is a uniform system used industry-wide to screen bulls for breeding potential. The test is passfail
and is particularly effective at identifying sub-fertile bulls. The biggest reason to conduct exams on all bulls, including new and resident, is to reduce the risk of infertility.

Manage for prevention, watch for injuries

When considering other preparations pre- and post-turnout, keep in mind bull health, biosecurity, and breeding aggressiveness. “Maintaining a good vaccination program certainly is critical to make sure the bull is not a vector for bringing disease into the herd,” advises, Dr. David Anderson, Professor and Section Head, Agricultural Practices, Kansas State University College of Veterinary Medicine, Manhattan.

Before turnout, both newly acquired bulls, as well as any carry-overs, need to be current on their herd vaccinations; consult your veterinarian for your area’s recommended health practices. Also, treat for external and internal parasites before breeding season.

Biosecurity is also of importance. Anderson says, “Certainly we talk about biosecurity with bulls to try to prevent introduction of diseases into the herd. The type of bull and where it comes from can help to determine what the risk factors are.”

He says BVD is a very easy thing to test for and can prevent the introduction of that virus into a herd, at least from the standpoint of having a persistently infected animal. Trichomoniasis, or trich, a cause of pregnancy losses in cow-calf herds, is one of the big things they’re also watching more closely.

“If you have one bull that is carrying trich, it can spread through the herd relatively easy,” Anderson says. Trich spreads through breeding activities, and can infect bulls as well as cows.

“What we have found is that a lot of people are testing young bulls at purchase, but these virgin bulls are the least likely to be infected,” he says.

“Bulls that have gone through multiple breeding seasons are more likely to be infected with trich, and are the ones we probably should be taking a closer look at.”

A weather-related factor to consider is frost bite. If bulls were exposed to extreme weather stress, frost bite could have affected the normal reproductive function of the scrotum. If it occurred in February, March, and April, poor semen quality could result in April, May, or June, given the two month time frame required for sperm development and maturation. After turnout, keep an eye out for injured animals, and be sure bulls are breeding. Injuries incurred during breeding season are often what removes bulls from the breeding herd.

Also pay attention to how bulls are grouped in breeding pastures. The effects of hierarchy and  dominance most frequently occur when older and younger bulls are turned out together. The most dominant bull is often the oldest, heaviest, and longest-standing herd bull.These older bulls – which are often decreasing in reproductive ability –may prevent younger, more potent bulls from mating. To get around this, experts recommend grouping bulls that are more alike for age, size, and breed type.

Before Breeding Season: Don’t Assume – Test Bulls for Fertility

Fertility is unquestionably one of the most important traits a bull possesses, but evaluating these animals for breeding soundness is probably one of the most neglected management practices in cow-calf operations.

“A breeding soundness exam is one of the only tools you have to predict if a bull is a successful breeder before you use him,” shares Dr. David Anderson of Kansas State University’s College of Veterinary Medicine.

An increasing number of open cows in a natural serviced herd could be the tell-tale signs of an inefficient bull caused by reduced fertility or sterility.“Many herds don’t realize that they have a bull that is under potent,” Anderson says, “because they have multiple bulls servicing those cows.”

In herds like this, other dominant bulls will assume the breeding responsibility, so cows still become pregnant. But if the most dominant bull becomes sub-fertile, there will be a significant loss in pregnancies, he explains.

“If you’re really pushing genetics, and have bulls that are sub-fertile, and instead of breeding with three bulls you’re only getting pregnancies from two, you’re losing a third of your potential genetic improvement.

“Breeding soundness examinations are critical. They can’t guarantee that a bull is fertile, but they can come pretty close to it. Basically a breeding soundness exam says that ‘on the day of examination, that bull was normal; the indices tell us that they’re likely to be a successful breeder.’”

A Breeding Soundness Exam (BSE) is administered by a veterinarian and includes a physical examination (feet, legs, eyes, teeth, flesh cover, scrotal size and shape), an internal and external examination of the reproductive tract, and semen evaluation for sperm cell motility and normality.
Veterinary professionals like Anderson recommend that bulls are evaluated for breeding soundness at 30 to 60 days before turnout. This allows time for retesting of bulls that initially fail a semen test and sufficient time to replace questionable bulls.

Mature bulls that initially fail should be retested after six weeks. Young bulls just reaching puberty that fail may later meet all minimum standards when retested 30 to 60 days later. Therefore culling decisions should be made with caution.

It is generally accepted that about 10 to 20 percent of bulls in any herd group won’t pass a BSE. There are a number of factors that can impact future fertility of any bull such as age, health, and injury. While the BSE is a useful management tool that serves to reduce the risk of potential sub-fertility in herd bulls,
one thing it doesn’t do is predict a bull’s eagerness to mate (libido). That’s why producers are urged to observe and evaluate the reproductive and physical soundness of bulls throughout the breeding season.