Management of Yearling BullsTuesday, March 20, 2007
By Drs. Scott P. Greiner and John B. Hall, Extension Animal Scientists, VA Tech.Winter and spring are the primary bull buying seasons in Virginia. A diligent amount of time spent studying performance information, EPDs, pedigrees and other pertinent information is warranted as sire selection is the most important tool for making genetic progress in the herd.
Of equal importance is the care and management of the newly acquired bull. Proper management and nutrition are essential for the bull to perform satisfactorily during the breeding season. With most new herd sires in the state purchased as yearling bulls- management prior to, during, and after the first breeding season is particularly important.
Management Prior to the Breeding SeasonMany newly purchased yearling bulls have recently completed a performance test, which provided a high plane of nutrition. Upon completion of this test, the energy level of the diet should gradually be reduced to prevent excessive fat deposition. The reduction in energy may be accomplished through restricting intake of high energy grain supplements, in conjunction with supplying a total diet lower in energy content (primarily forage). Young bulls should be managed to be a body condition score 6 at turn-out. This will give the bull adequate reserves of energy for use during the breeding season. Yearling bulls can be expected to lose 100 pounds or more during the course of the breeding season.
Acquiring a new yearling bull at least 60 to 90 prior to the breeding season is critical from several aspects. First, this leaves ample time for the new bull to get adjusted to the feed and environment of his new home, as well as an opportunity for several new bulls to be commingled for a period of time prior to turnout. Secondly, adequate exercise, in combination with a proper nutritional program, is essential to “harden” these bulls up prior to the breeding season. A facility for the newly acquired bull that allows for ample exercise will help create bulls that are physically fit for the breeding season. The nutrition of the bull will be dependent on body condition. Yearling bulls are still growing and developing, and should be targeted to gain 2.0 to 2.5 pounds per day from a year of age through the breeding season. Bulls weighing approximately 1200 pounds will consume 25 to 30 pounds of dry matter per day. This intake may consist of high quality pasture plus 12 lbs corn, grass legume hay plus 12 lbs corn, or 80 lbs corn silage plus 2 lbs protein supplement. Provide adequate clean water, and a complete mineral free-choice.
Prior to the breeding season, all bulls should receive breeding soundness exams (BSE) to assure fertility. All bulls that are to be used should have a BSE annually. Because a variety of factors may affect bull fertility, it may be advisable to re-test young bulls before the breeding season even if it has only been a few months since their pre-sale BSE.
Management During the Breeding SeasonThe breeding season should be kept to a maximum of 60 days for young bulls. This will prevent over-use of the bull, severe weight loss and reduced libido. Severe weight loss may impair future growth and development of the young bull, and reduce his lifetime usefulness. When practical, supplementing young bulls with grain during the breeding season will reduce excessive weight loss.
In single-sire situations, young bulls can normally be expected to breed a number of females approximately equal to their age in months. Using this rule of thumb, a newly purchased bull that is 18 months of age could be placed with 18 cows or heifers. Bulls used together in multiple-sire breeding pastures should be of similar age and size. Young bulls cannot compete with older bulls in the same breeding pasture. A common practice is to rotate bulls among different breeding pastures every 21 to 28 days. This practice decreases the breeding pressure on a single bull. Some producers use older bulls early in the breeding season, and then replace them with young bulls. The appropriate bull to female ratio will vary from one operation to the next based on bull age, condition, fertility, and libido, as well as size of the breeding pasture, available forage supply, length of the breeding season and number of bulls with a group of cows.
All bulls should be observed closely to monitor their breeding behavior and libido to ensure they are servicing and settling cows. Additionally, observe the cowherd to monitor their estrous cycles. Many females coming back into heat may be the result of an infertile or subfertile bull. All bulls should be monitored for injury or lameness that may compromise their breeding capability.
Management After the Breeding SeasonYoung bulls require a relatively high plane of nutrition following the breeding season to replenish body condition and meet demands for continued growth. Yearling bulls should be maintained in a separate lot from mature bulls, so these additional nutritional requirements can be provided. Body condition and projected mature size of the bull will determine his nutrient requirements during the 9 months following the breeding season. Bulls should be kept away from cows in an isolated facility or pasture after the breeding season. In the winter months, provide cover from extreme weather that may cause frostbite to the scrotum resulting in decreased fertility.
All herd bulls should receive breeding soundness exams (BSE) to assure fertility on an annual basis. Assess the bull battery well in advance of the breeding season, so that new herd sires can be acquired in a timely fashion.