YC.com:Bull Management

One of the most important, and often overlooked, areas of cow/calf herd management is the reproductive and nutritional management of bulls in the herd. Too often a bull's breeding capacity is taken for granted. However, a bull is expected to impregnate from 15 to 40 females during the breeding season in a typical cow/calf operation. That means that the fertility of a bull has a greater impact on the herd than the fertility of an individual cow.

Fertility Factors
Semen quality can play a major role in the productivity of a cow/calf operation. Factors affecting fertility include semen score, semen density, and sperm motility.

Scrotal circumference may be the best single criteria to use when determining the fertility of young bulls, according to the Beef Cattle Handbook, published by the Extension Beef Cattle Resources Committee. Desirable scrotal circumference has been linked to several good traits including early onset of sexual maturity in bulls, early onset of puberty in daughters and the early onset of pregnancy in daughters. Factors affecting scrotal circumference include heritability and breed difference.

Health Management
Health management is another important part of caring for bulls both in and out of the breeding season. Newly purchased bulls need to be vaccinated according to the herd management plan being used for the cow/calf operation.
The total cost of the vaccines is minor when compared to the cost of the diseases. Booster shots are also recommended if the bull has not been vaccinated prior to purchase.

Pasture management
The right bull to cow ratio needs to be kept in the pasture during breeding season. According to a recent USDA study, the average bull to cow ratio was 1:19 for yearling bulls and 1:29 for mature bulls.

In a Georgia study, bulls were exposed to 25 or 40 cows during a 90-day breeding season in a one bull per pasture mating scheme. The results showed no difference in pregnancy rates. A ratio of 1:25-30 for yearling bulls and 1:40 for mature bulls appear to be realistic, if the bulls have been properly evaluated prior to the breeding season, according to the research.

Nutritional Development
Conditioning prior to the breeding season is important. Both yearling and mature bulls need to be considered for a pre-breeding conditioning plan. "There is limited potential for special nutrition management for bulls during the breeding season," according to the handbook. "Thus, it is critical that the nutritional management of the bull occur prior to the breeding season."

The nutritional management of the bull after breeding season will depend on the age of the bull and how much weight it lost. If mature bulls come out of the season in fairly good condition, they can be maintained on an all-roughage diet during winter. However, young bulls need to continue gaining after the breeding season to help reach their optimum size upon maturity.

"The general goals in the development of a beef bull are to have a bull that is capable of breeding cows as a yearling, is capable of producing quality semen, is physically able to seek out cows and heifers in heat, and is physically able to breed those females," the handbook says. "A proper evaluation, including semen quality and physical soundness prior to the breeding season, should be a routine practice on all bulls.