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Yearling bulls need proper management

published: October 3rd 2008
by: Martha Hollida Garrett

Fall bull sales are here and cowmen are beginning to think about the type of bull they need and will purchase.  In most cow-calf operations, bringing a new bull into the herd is the primary way of making genetic improvement and many of these new bulls are yearlings. In recent years there has been a real move, to incorporate yearling bulls and the trend has become quite popular in certain breeds and areas of the country. Yearlings require higher levels of care and management than do mature bulls and its critical that producers recognize this fact.
    Over time, it is estimated that bulls provide 90% of the genetic change in most beef herds and an older bull requires a larger investment for the breeder because of the extended time involved in the feed and care of the bull for another year.  For the buyer, it also provides an extra calf crop if the bulls are managed correctly.
    Yearling bulls must be properly managed so genetic potential and reproductive performance will be maximized as they have a significant amount of growth and development ahead of them. They offer cowman the opportunity for greater genetic potential than older bulls as there are a greater number to select from and use of yearlings decreases generation intervals which will speed genetic progress in economically important traits, according to James B. Neel, and Neal Schrick, professors of animal science at the University of Tennessee.
    The breeding ability of bulls usually is at its peak about 36 months of age, and it declines after five or six years of age.
    Cowman should consider three phases of management of a yearling bull. Phase one is pre-breeding or conditioning which is normally about 2 months, then the actual breeding season,which is  two-three months and post-breeding season, which is about seven-eight months.
    Twig Marston, Kansas State University, extension beef specialist writes that
one of the most common complaints of yearling bull purchasers is the run down condition these bulls can exhibit after their first breeding season.  Most yearling bulls are going to lose weight during their first breeding season. 
    However, minimizing the loss of body condition will extend a bull’s usefulness and productivity.  Whether the bulls were developed on the ranch, in a commercial facility, or at a centralized bull test, they were probably fed to gain from 2.5 to 4.0 pounds per day from weaning to one year of age.  After coming off of test, and until they are turned out with females, they should continue to gain around 2.0 pounds per day.
    If yearling bulls are overly fat, they may need to tone up before the breeding season.  However, fat bulls should not be let down too quickly.  Rapid weight loss may affect libido or fertility.  Conversely, thin bulls may need to be fed hard before breeding.  Ideally, yearling bulls should be purchased several months prior to their first breeding season so there is adequate time to prepare them for the rigors of duties.  At turn out time, ideally, a yearling bull should exhibit a body condition score of 6 (the upper end of moderate on a scale of 1-9).
    Assuming all other factors are in good order (breeding soundness exam, body condition score, feet and legs, health, etc.) the newly purchased bull should be at least 13 months old and weigh a minimum of 1,100 pounds before being turned out for the first time.  The older and larger he is, better his chances are of coming through his first breeding season without problems.          Setting absolute guidelines for cow-to-bull ratio is difficult because there are several variables that have an impact on this number.  Examples are a bull’s age, size, condition, and sex drive.  Environmental factors like: size of the breeding pastures, type of terrain, climate, and length of the breeding season can also affect the correct cow-to-bull ratio.  Absolutely, a yearling bull will not be able to service as many cows as an older counterpart.  As a rough guideline, however, the working range is approximately 10 to 25 females per yearling bull during a 45 to 60 day breeding season.  Ninety days is an absolute maximum.  Regardless of management style, it is usually not advantageous to run yearling bulls with cows for long periods of time.  They will waste a considerable amount of energy chasing cows and losing body condition instead of building up reserves for the next breeding season.   
    Marston also stresses that producers need to pay attention to scrotal size as it is an indicator of how well a bull will breed.
    “Adequate size is 30-34 centimeters (cm), which can be illustrated by holding two soft drinks cans together. Even though 30 cm is published as a minimum, raising the scale to 32 cm ensures the bulls have a pretty good chance of passing their breeding soundness exam,” he explains.
    Try to observe the yearling bull closely to make certain he is detecting heat and breeding cows.  Also, keep an eye on his condition; if he is getting too thin and rundown, he needs a rest.  Thin bulls are more apt to hurt themselves, become less fertile, and have increased nutritional needs after the breeding season.  Yearling bulls should not be pasture mated to cows that are extremely large.  Physically, this height mismatch may cause injury and failure to mate properly.
    Research shows that when bulls are run together in a breeding pasture, they should be as close to the same size and age as possible.  Larger, stronger, older bulls tend to dominate smaller, younger bulls and may prevent them from performing as well.
    Yearling bulls will probably lose from 100 to 300 pounds during their first breeding season.  In addition to gaining back this weight during their first rest, they must also gain enough body mass as to achieve 75% of their mature weight by their second birthday.  A word of caution: do not try to bring a bull back too fast with too much grain because of risk of foundering him.
     Yearling bulls are some of the most valuable animals on a ranch.  Proper care and management can have a positive impact on herd fertility.  Successful bull management gets cows bred early in the breeding season, optimizes weaning weights, and increases profits.  Most yearling bulls can be used effectively, if they are critically selected, properly developed and carefully managed.
SLS