Good bull management is key to a successful breeding season – Jamestown Sun

It’s bull sales season and many producers are deciding which bulls will sire their next calf production. Buying the right bulls for an individual operation involves a series of critical and time-consuming decisions, but the job doesn’t end when the bull is home on the ranch. Ensuring bulls are in good physical condition and fit for the next breeding season is key to breeding success, according to North Dakota State University extension specialists ( NDSU).

Most bulls are developed by semen stock producers and development strategies vary by operation.

“While there are many different rations used to develop bulls, a type of high-concentration ration is typically used to determine the genetic growth potential of herd mates,” says NDSU Breeding Systems Specialist Janna Block. Extension based on Hettinger research. Extension Center.

“A common complaint from bull buyers is that bulls quickly lose condition when they come home. This is often the result of the inability to gradually adjust bull rations from a high energy ration to a forage-based diet,” adds Block.

Consequences of a poor bull transition can include increased stress, digestive upset, loss of body condition, and impacts on sperm quality and quantity.

Flow Considerations

In beef cattle, the rumen is the main fermentation chamber of the stomach. It contains billions of microorganisms that break down food consumed by the host animal. Different species of microbes have different functions and preferred food sources. Some digest starch and sugars, while others digest fiber. The number and proportion of each species varies according to the composition of the diet. Therefore, when an energy-dense diet is provided to the animal, the rumen microbial population consists mainly of starch-digesting bacteria. When the diet is changed abruptly, the microbial populations are out of balance with the food source.

“It can take four to six weeks for the population of fiber-digesting bacteria to build up after the concentrates are removed from the ration,” says Block. “Downgrading bulls from a high level of nutrition through gradual grain reductions combined with increased amounts of forage is necessary to stabilize the rumen microbial population and avoid digestive problems and rapid weight loss.”

Zac Carlson, NDSU Extension beef specialist, recommends bull buyers get detailed information on the previous ration and try starting with similar feeds.

“A diet of 80-90% of the previous amount of concentrate can be offered initially, then reduced by 10% every few days until the final diet formulation is reached,” says Carlson. “If previous diet information is not available, high quality grass hay and 4-6 pounds of concentrate can be provided.”

The total crude protein (CP) content of the ration should be between 10% and 11%, with energy levels (total digestible nutrients or TDN) between 60 and 70%. Producers should have feeds analyzed for nutrient content and develop a ration, advises Carlson. Since the semen production process takes approximately 60 days, it is ideal that the transition to a forage-based ration be completed at least 90 days before the breeding season.

BCS Considerations

“Body Condition Scoring (BCS) is another important component in developing an appropriate nutrition program for bulls,” says Block. “Bulls should have a BCS of 5.5 to 6.5, depending on the length of the breeding season, the cow-to-bull ratio and other factors.”

In the BCS range of 4 to 7, there is about an 8% difference in body weight between each score. A yearling bull weighing 1,200 pounds with a BCS of 6 would weigh about 100 pounds less than a BCS 5. If there are 70 days left until the start of the breeding season and the bull is to earn a score of condition, he should gain about 1.4 lbs. every day.

When bulls are in a BCS of 6, no ribs will be visible, the back will appear slightly rounded, and there will be signs of fat in the chest and tail head. If the bulls are lean, with a BCS below 5, they will need to be on an increasing nutrition plan to achieve the desired performance. In this situation, additional concentrate may be needed initially; however, bulls will still need to transition to a high forage diet prior to watering.

“Some bulls will be overweight after purchase and may need to lose fat and add muscle before breeding, but it’s important to remember that they should still gain weight,” says Block. “If the bulls are overweight after the sale, the goal is to slowly reduce their condition to avoid problems.”

Nutrition monitoring

“It’s important to closely monitor the nutritional status of growing bulls during the first few seasons of use,” says Carlson.

After their first breeding season, bulls should be managed to weigh 65% to 75% of their estimated adult weight by the time they reach 2 years of age. Bulls may need to gain significant amounts of weight to overcome the weight lost during the first breeding season and allow for continued growth.

If a bull with an adult weight of 2,000 pounds weighs 1,200 pounds at release and loses 200 pounds during the breeding season, he should gain 400 pounds between the end of the breeding season and his second birthday. (Goal weight of 1,400 pounds [70% of 2,000 lbs.] – 1,000 pounds [weight at the end of the breeding season] = 400 pounds).

“Drawing yearling bulls early or using them for a limited amount of time during the breeding season can help reduce total weight loss and provide more time to regain lost weight,” says Carlson. “Adult bulls will also need to regain lost weight during the breeding season, but their nutrient requirements are lower than those of growing bulls.”

“Feeding bulls to optimize fertility isn’t just about protein and energy,” adds Block. “Minerals and vitamins play an important role in spermatogenesis and can also impact sperm quality. In particular, copper, zinc and phosphorus have a direct role in fertility, and forages are often marginal to deficient in these minerals.

Mineral analysis of forages and other feeds will allow producers to select a mineral that best suits the feeding strategy. Producers should also supplement vitamin A when feeding harvested forages, either through a mineral supplement or injection. Vitamin A deficiency can impact spermatogenesis.

The cost of bulls and their potential genetic contribution to the cow herd indicate that they need to be managed to optimize performance. For more information on body condition scoring and bull management, refer to the NDSU Extension Ag Hub resources available at https://bit.ly/3vQRxGa. Guidance on biosecurity, animal health and general management of yearling bulls can be found in the NDSU Extension AS2011 publication, available at https://bit.ly/3MDT7Bc. Contact your county NDSU extension agent for more information.