Chart 1. Nutrient requirements of growing bulls Dry
Body Weight, lb
Average Daily Gain, lb/d
1.0
300 2.0 3.0 1.0 2.0 3.0 1.0 2.0 3.0 1.0
500 700
900 2.0 3.0
1500 2.0 2000 0.0
Matter Intake, lb/d
8.3 8.6 8.6
TDN, % of dry matter
58 65 72
12.2 58 12.6 65 12.6 72 15.6 58 16.3 65 16.3 72 18.9 58 19.6 65 19.6 72 34.5 63 37.2 46
Crude Protein, % of dry matter
11.4 16.3 21.3 9.8
12.9 16.3 9.1
11.4 13.9 8.3 9.9
11.9 6.1 5.6
Adapted from Mississippi State Extension publication 2564
may need more development back at the ranch before breeding. “Poor body condition can result in poor semen qual-
ity, and with the improved breeding selection made possible by expected progeny differences (EPDs), high energy bull-test rations are less common than they used to be. However, the breeds that are typically slower to reach puberty, such as Brahman or Hereford, can be fed more energy to accelerate the onset of puberty. “In some cases, bulls are going to have suffi cient
gains on forage, especially some cool-season forages or annuals, without a lot of supplementation,” says Holland. “But if forage quality or quantity isn’t there late in the summer or with warm-season grasses over the winter, bulls may have to be supplemented with free-choice hay plus some kind of concentrate. They can also be fed a mixed ration, which might be in the range of a 40 to 60 percent concentrate.” Test the forage to be sure it meets the growing bulls’
nutritional needs. Holland says a 700 to 900 pound bull is going to need rations with total digestible nutrients (TDN) around 75 percent and between 9 to 12 percent crude protein. Depending on their weight, bulls are going to con-
sume between 15 to 20 pounds of dry matter per day. A 900-pound bull will gain 3 pounds per day by eat- ing 22 pounds of dry matter at 75 percent TDN and 12
tscra.org
percent crude protein. If forage comes up short of that amount, the rancher
will have to consider supplementing energy, protein, or both, to meet the requirements. While they are growing, bulls will continue to con-
sume around 2.25 percent of their body weight (dry matter basis). This means a 1,500-pound bull would eat 34.5 pounds. Requirements for individual nutrients change. Limit-feeding may be used in some cases to meet requirements while managing costs. Refer to Chart 2, where NEm is net energy for maintenance, NEg is net energy for gain, and CP is crude protein.
Conditioning for the breeding season The body condition score of a bull should be moni-
tored throughout the year. At pre-breeding, Holland looks for a score of between 5.5 and 6.5, meaning fat should be palpable over the ribs and tailhead, and pres- sure should be required to feel the spinous processes (backbone). While not ideal, he says that bulls can lose up to
200 pounds of body weight through the breeding sea- son and summer; therefore, they need to be in good condition when turned out because once the bulls and cows are in the pasture, they can’t realistically be managed separately. “If bulls lose weight during breeding, we’re going to
have to put that weight back on before the next breed- ing season,” Holland says, “which in 2-year-old bulls is going to require them to gain 1.5 to 2.5 pounds per day, so they’re going to have a different requirement than the more mature bulls whose frames are not still growing.” Ranchers may have to manage the entire bull bat-
tery for the ranch in separate pens. He notes, “You have growing, developing bulls that have never been through a breeding season, bulls that have been through 1 breeding season that are still growing and regain- ing the weight they may have lost during the previous breeding season, and more mature bulls, all of which have different requirements. For example, mature bulls that have maintained adequate condition throughout breeding may be maintained on grass or hay (2 percent of body weight with 10 to 11 percent CP), but younger bulls and those who lost signifi cant body condition might need more supplementation. Because of the potential development of a hierarchy
among the bulls, it’s important to monitor body condi- tion scores, feeding behavior and injuries throughout the winter months, and in the spring before turning
February 2015 The Cattleman 77
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