Nutritional Management of Beef Bulls
By Dennis B. Herd, Ph.D., professor emeritus and
Extension beef cattle specialist-nutrition, Texas A&M University, College Station

Maximizing reproductive performance is the key to profits for beef cow-calf operations. Although much attention is given to cow health, bulls must also be managed properly to meet the herd’s reproductive goals. Proper nutrition, of course, is just as important for bulls as cows to reach fertility goals.

General nutrition
Providing proper nutrition to bulls can be troublesome. Although a relatively small group in numbers, bulls can require large amounts of space. The tendency, however, is to run all the bulls together and hope they don’t cause too much damage to facilities or each other.
But nutritional needs vary with activity, age, weight and condition, so some bulls may not get adequate nutrition while some get too much.
Use judgment when grouping bulls for feeding. Always have plenty of feed trough space for each bull. Using self-fed supplements may help when bulls, mismatched in size, are fed together.

Body condition scores for bulls
The yearly nutritional program for bulls has two periods: The breeding season and the non-breeding season.
The entire year’s nutritional program for bulls should be designed to have them at body condition score (BCS) 6.0 to 6.5 at the start of breeding season. Bulls that are too thin (BCS less than 4.0) or too fat (BCS greater than 7.0) have lower fertility.

BCS management
Bulls should be evaluated when pulled out of the breeding pasture to estimate the weight and condition that will have to be put back on before the next breeding season.
Approximately 150 pounds is needed to change BCS one unit for an average bull (about eight percent of body weight at BCS 5.0).
The bulls should then be closely evaluated three months prior to the start of breeding season to increase, maintain, or slow down BCS improvement.
Remember the quality of sperm delivered on the first day of the breeding season is influenced by the quality and quantity of nutrition fed approximately six weeks prior to turn-in.
Check BCS when bulls are turned into the breeding pasture and continue to monitor during the breeding season.

Feeding young bulls
Bulls 12 to 18 months old are still growing and need extra feeding and care, especially when losing their baby teeth.

If young bulls are fat after coming off a gain test or market conditioning program, they need to be “let down easy” and allowed to harden over 60 to 90 days.
If they are just kicked out in a pasture, especially if forage quality is low, these young bulls may fall apart and lose excessive amounts of weight.

Feeding approximately one percent of body weight (12 to 16 pounds) per bull per day should allow young bulls continued growth from purchase until breeding, or should allow condition to be put back on thinner bulls.

The feed should contain 12 to 14 percent protein and 12 to 15 percent fiber, possibly more if the source of fiber is known to be highly digestible. Lower fiber, higher energy supplements can be fed if managed carefully to avoid acidosis, bloat and possibly founder.
Using feeds with highly digestible fiber, like dehydrated alfalfa pellets, wheat midds, soybean hulls, beet pulp or rice bran to reduce the amount of corn (less than 20 percent of the total diet), will provide energy for conditioning while better preparing the bulls to use forages.

Hay or pasture should be 10 to 12 percent protein or better.
If fed at the same time every day while breeding cows, young bulls may be trained to come for feed at the corral, outside a pasture gate, etc., to avoid feeding the entire cow herd.

If this isn’t practical, pull the young bull out for a short feed-up period after 30 to 45 days of work, returning him for more work later if necessary.

After 60 to 90 days, the young bull should be pulled regardless for a feed-up period to restore body condition.

After feeding the young bulls to their pre-breeding body condition, they may be run with mature bulls. It would be best, however, if they are maintained separately from older bulls until after their second breeding season.

Supplementing mature bulls
Bulls that lose two or three BCS units during breeding will need to gain 300 to 450 pounds before the next season.

Assuming eight months is available to regain weight, this requires a daily gain of 1.5 pounds, more if the gain period is shorter.

Annual winter pastures and high quality spring or early summer pastures can produce daily gains of 1.5 pounds without protein or energy supplementation. Mid-summer and fall pastures, however, aren’t adequate and neither are most typical grass hays. Thus a period of supplementation will be needed to recondition the bulls.

Easy-keeping older bulls may do well with one to three pounds of a high protein supplement and plenty of forage, even if forage quality is slightly lacking.

Others will do better with four to eight pounds of 20 percent range cubes. Many young bulls and hard-doing older bulls may need 10 to 20 pounds per day of a 12 to 14 percent protein, 12 to 15 percent fiber bull conditioner type of feed.

Even higher levels of supplementation may be needed if trying to recondition in less than 60 days and more than 0.5 BCS units are needed.

A moderate rate of conditioning (gains of 1.5 to 2.5 pounds daily) is preferred. The higher energy diets necessary for daily gains of three to four pounds can lead to acidosis, bloat, founder, and even death without proper management.