Probably the most common mistake made in purchasing young, weaning age bulls is failure to provide an adequate diet to continue their growth and development. Often bulls are delivered, turned out with the other bulls, and let to "rough it" until breeding time. Thus, bull development is delayed, sexual maturity is not achieved, and the resulting calf crop is less than it should have been.
The first step in providing adequate nutrition is determining the desired level of performance. Typically, young bulls have 160 days to grow from weaning to yearling age. Because of the growth potential of our current beef population, yearling bulls are heavier than 1,000 pounds. Therefore, young bulls need to have gains of 2.5 daily. Moderate energy diets (those with grain) are needed to attain these performance levels.
For young bulls not intended for gain testing, rations should include concentrates fed (as a minimum) at about 2 percent of body weight. That is, 600-pound calves can easily consume about 10-12 pounds of grain with alfalfa hay or grass hay fed free choice. This will require 18 pounds of total dry matter or about 20 pounds of air dry feed per day. This will help promote rapid growth without excessive fattening. Be certain to start the grain feeding gradually. As the bulls increase in size, the amount of grain must increase to maintain the 2 percent of body weight level unless it is obvious that they need more high-energy feed. At this age the bulls should be growing rapidly, so they need to have 12-13 percent total protein in their diet. Depending on the kind and quality of the roughage and the grain being fed, this will probably require a protein supplement be included in the grain mix. Young bulls may require 16 to 20 percent protein in the grain mix. Mature bulls require lower concentrations of protein in the diet. However, rumen function may be impaired if the diet does not contain at least 10.5 percent protein. This is the reason that supplemental protein is still desirable for mature bulls grazing low quality grasses or hays.
One way to manage the feed for young bulls is to offer a high quality grass hay free choice and a concentrate fed at a rate of about two percent of body weight. An example ration for young bulls would be: 44 percent grass hay (the hay is offered free choice)
43 percent cracked corn
11 percent soybean meal
0.9 percent limestone (calcium carbonate)
.35 percent salt
.0122 percent vitamin A-30000
The grain mix could be ground and mixed separately. It should be fed at the rate of 2 pounds per 100 pounds of bull body weight. To mix a one ton batch of the grain portion of the diet, the amounts of ingredients per ton would be as follows:
1566 lbs. corn
392 lbs soybean meal (44 percent)
29 lbs limestone
11.5 lbs salt
0.5 lbs vitamin A-30000
If smaller amounts of the grain mix are to be fed to young growing bulls, the protein and calcium content must be increased to meet the needs of these rapidly growing animals. Seek assistance from your local extension office. Remember to start the grain feeding program gradually and bring bulls up to the desired intake over at least a two-week warm-up period.
If the producer wishes to use high quality alfalfa (19 percent crude protein), then the concentrate portion of the ration only needs to be grain and can be provided as one part grain and two parts alfalfa hay on an as fed basis. These "dry lot" rations should produce at least 2.5 to 3 pounds a day gain for large frame bull calves.
High quality small grain pastures such as rye and ryegrass combination pastures are used to produce similar rates of gain. These are often the pastures used in forage-based gain tests and provide enough energy and protein to achieve average daily gains at about 2.5 pounds per day and the yearling bulls come off the test at about 1,000 pounds and in a body condition score of 6. If individual producers choose this method to grow young bulls, they should not forget to supply appropriate mineral mixes to bulls on these lush pastures. Often the critical mineral needs for cattle on small grains are calcium and magnesium such as wheat pasture stocker cattle need to avoid grass tetany.
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 three to four 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 - 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 tests about six 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 but 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 a rapid condition and weight loss which could be reflected in a reduced calf-crop next year.