Young Bulls Care Management
Yearling bulls should be well-grown but not too fat. The energy content of a ration should
be reduced if bulls are getting too fat. Fat bulls may fatigue rapidly, contributing to fewer cows
For a yearling bull to be used successfully, he should have reached puberty 3 to 4
months before breeding time. The age of a bull at puberty depends on several interrelated factors, but size or
weight and breed are probably the controlling factors.
The production of semen by a young bull largely depends on his overall growth as well
as the development of his testicles and other reproductive organs. The size of testicles and volume of semen
produced are positively correlated.
Bulls should also follow similar nutritional diets from the approximate 60 to 120 days
from yearling age until breeding time. All bulls should be gaining weight and maintaining moderate condition during
this time. Study the Body Condition Scoring System used for cows (Oklahoma Beef Cattle Manual). The system uses "1"
for emaciated animals and "9" for very obese animals. Therefore an optimum body condition score for young bulls is
"6". Perhaps the best way to verbally describe the ideal condition is bloomy but not fat. A young bull will use
body stores of energy and lose over 100 pounds during the breeding season. This should come from energy stored as
fat (condition) rather than muscle tissue since the bull is still growing. Excessive rapid condition loss lowers
the bull's fertility and libido and should be avoided.
Highly Fitted Bulls
Research at Kansas State University has illustrated that young "gain-tested" bulls have
normal fertility and libido when allowed to return gradually to moderate fleshiness and hearty physical condition
before the breeding season. In fact, many performance-tested bulls are returned to the owner's ranch after the gain
test in order that they be allowed to be properly conditioned before the sale date. Test station sales usually
offer bulls that completed their gain test about 6 months previously.
Any rancher that purchases a young, highly fitted or conditioned bull should plan to
gradually reduce the fleshiness of the bull before the breeding season. To let these bulls down, it is a good
practice to start them on a ration that is not too dissimilar to the one they have been accustomed to but that is
60 to 70 percent of their previous intake. The amount of grain can be reduced at the rate of about 10 percent per
week until the desired level is achieved. At the same time, substitutions should be made in the form of light,
bulky feeds--such as oats or alfalfa hay. Ideally, this letdown should be completed prior to the time bulls are
turned out. Dramatic nutritional changes can have an adverse effect on semen production, so it is important that
these ration modifications be done gradually. Allow the change to take place gradually instead of allowing a rapid
condition and weight loss which could be reflected in a reduced calf crop next year.
If a young bull is coming off of a high energy diet (i.e. gain test), an example
feeding schedule would be as follows:
Continue feeding the grain mix to the young bull during the breeding season if at all possible.
OSU Cow/Calf Corner
Bulls After Breeding Season