Transitioning Newly Purchased Bulls

By Warren Rusche

By now the task of selecting new herd sires has been largely completed. Now it’s time to shift focus towards management practices to make sure that the investments made in new herd sires will last for the long-term.

One of the major components of the cost of natural service in the cattle business is the number of years of useful life of the herd sires. The more years that a bull remains productive allows the initial purchase price to be spread out over more calves. Considering the value of most yearling bulls at production sales this spring, spending some additional attention to help make sure that the transition phase proceeds smoothly would seem to be effort well spent.

In most cases yearling bulls have been developed on higher energy diets than what will be available to them during the breeding season. If these bulls are simply turned out to the breeding pastures without being adapted to lower energy diets, there is a high likelihood of excessive weight loss and potentially a reduction in fertility and libido. This would not only impact breeding success this year but could affect the useful lifespan of the bull if the weight loss were too great.

Changes in diets should be made gradually. There is a 60-day period before sperm cells are mature, so avoid any drastic changes during the two months before the start of breeding season whenever possible. The concentrate portion of the ration would be gradually reduced in a series of steps until the desired level is reached. It’s important to remember that these bulls are still growing and to not restrict nutrient intake too much. They should be gaining 1.5 to 2 pounds per day and be in a body condition score of about a 6 at the start of the breeding season. As with any class of livestock, the necessary mineral and vitamin supplementation as well as a high quality water source should be provided.

Beyond the nutritional and dietary considerations of bull development, there are other factors that need to be considered as well. Breeding bulls will have a high level of physical activity, especially early in the breeding season, seeking out and breeding cows in heat. Much like an early season “training camp,” allowing for increased opportunities for exercise will help improve the bulls’ physical condition and stamina levels, which should help insure their ability to remain functional throughout the breeding season. Additional exercise for the bulls is also a great way to help bulls come down from the higher energy rations they might have been fed while being performance tested.

Many producers will utilize more than one bull in a breeding pasture. If the bulls have not run together previously, they will very likely spend time fighting to establish a “pecking order” rather than getting cows bred. Grouping the bulls according to their assigned breeding pasture groups prior to the start of the breeding season allows those “social adjustments” to take place before breeding season starts.