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Managing New Herd Sires

April 4, 2016

New bulls need to be managed carefully between delivery and the start of breeding season to maximize the return on the investment in new genetics.

New herd sires represent a sizeable investment to a cow/calf business. One of the major components of the cost of natural service is the number of years of useful life of the herd sires. Greater lifespan 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.

Dietary Adjustments

In most cases yearling bulls have been developed on higher energy diets than what will be available to them during the breeding season. Simply turning young bulls out to the breeding pastures increases the likelihood of excessive weight loss and potentially a reduction in fertility and libido. Extreme weight loss could also impact longevity. Adapting bulls to lower energy diets prevents bulls from “crashing” and increases the odds of success.

Changes in diets should be made gradually. Sperm cells mature over a 60-day period, so avoid any drastic changes during the two months before the start of breeding season. 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.

Physical & Social Considerations
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 on pasture also serves to reduce the potential for feet and leg problems.

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.

Breeding Soundness Exam
Finally, a breeding soundness exam (BSE) should be conducted by a veterinarian approximately 30 to 60 days before the start of the breeding season. A BSE would include a physical examination of the bull, with particular emphasis on the reproductive organs, along with an evaluation of the semen and sperm cells. An earlier iGrow article written by Dr. Julie Walker addresses the key components of a BSE in greater detail.

Source: Warren Rusche, South Dakota State University