Yearling Bulls
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 conceiving.
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:
% of
lb. for
lb. for
Week Type
Body wt.
1000 lb. bull
1500 lb. bull
--------------------------------------------------------------------------------
1st
bull test 1.5
15
23
hay
1.0
10
15
2nd bull
test 1.0
10
15
hay
1.5
15
23
3rd bull
test 1.0
10
15
hay
1.5
15
23
4th bull
test
.75
7.5
11
hay
1.75
17.5
27
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Continue feeding the grain mix to the young bull during the breeding
season if at all possible.
From:
http://www.ansi.okstate.edu/exten/cc-corner/archcareofyoungbull.htm