Health

Purchasing Bulls

Bulls are usually purchased from outside sources. Genotype and phenotype are important factors in bull selection, but information about health should also be considered. The following health issues should be considered:

• Breeding Soundness Examination (BSE)
  • Only purchase bulls that have been classified as Satisfactory Potential Breeders following a complete BSE.
    • The recommended minimum requirements for scrotal circumference, sperm motility and sperm morphology as outlined by the Society for Theriogenology should be met.
• Purchase only virgin bulls to avoid introducing venereal diseases.
  • Although there are tests for venereal diseases such as Trichomoniasis, they are not 100% in determining that a bull is not a carrier (see “Bovine Trichomoniasis” at www.lsuagcenter.com).
• Test for other diseases.
  • Testing for other diseases such as Bovine Viral Diarrhea Virus, Johne’s Disease and. Anaplasmosis, etc. should be considered and discussed with the herd veterinarian.
    • Testing prior to purchase is preferred.
• Purchase bulls from local sources.
  • Heat stress has a major impact on fertility and libido in bulls.
  • Bulls from herds developed in the Southeast will be acclimated to heat and have fewer problems.
• Quarantine bulls for 4 weeks prior to introducing to native bulls or cows.
  • If bulls were not tested for diseases prior to purchase, test while in quarantine.

Health Maintenance of Bulls

Breeding Soundness Examination (BSE)

BSEs should be completed each year at least three months before breeding season. This leaves time to recheck questionable bulls and locate replacements if necessary.

A BSE is a uniform method of assessing a bull’s likelihood of accomplishing pregnancy in an appropriate number of open, healthy, cycling cows or heifers in a defined breeding season. Bulls can be classified as satisfactory or unsatisfactory potential breeders. A classification of unsatisfactory does not mean a bull is completely sterile but is considered sub-fertile. A sub-fertile bull eventually may get cows pregnant, but he will take longer than a fertile bull to settle a group of cows. The result is that sub-fertile bulls produce fewer calves as well as calves that are born late in the calving season, which are therefore younger and lighter at weaning. The net effect is fewer pounds of beef per exposed cow.

A breeding soundness evaluation does not evaluate a bull’s libido or actual mating ability, nor does it ensure that a bull will remain a satisfactory potential breeder the entire breeding season. If a bull suffers injury to its feet, legs, reproductive tract or other area, such an injury may render it incapable of breeding cows. Therefore, it is important to observe bulls closely throughout the breeding season for libido, mating ability, health and injuries.

For more information on BSEs, see “Bull Breeding Soundness Evaluations” at www.lsuagcenter.com

Disease Prevention

A preventive herd health plan should always include bulls. A comprehensive plan for bulls should be developed with the herd veterinarian and include purchasing decisions (health status of the herd of origin), vaccinations, deworming and nutrition. Vaccinations are generally the same as for the cow herd, but additional or more frequent vaccinations may be warranted based on the value of the bulls. Bulls are generally more susceptible to parasites, so attention to both internal and external parasite control is crucial.

Any disease that impacts the health of bulls can impact fertility. In the South, heat stress is a major cause of bull infertility and decreased libido. High temperatures, especially combined with high humidity and high nighttime temperatures, are especially detrimental to bull health and fertility. Bos taurus breeds, especially those from northern herds, are more susceptible.

Nutrition

A body condition score of 6 out of 9 is the ideal target prior to the start of breeding season. Body condition can be affected by length of breeding season, number of cows the bull is expected to service, grazing and supplemental feeding conditions, topography (marsh, hills, etc.) and the distance required to travel during breeding.

1) Mature bulls in good body condition

• Mature bulls can subsist on a 100% forage-based diet of moderate quality (7-10% crude protein and 50% TDN). They will consume approximately 2% of their body weight. For example, a 2,000-pound bull will need approximately 40 lbs. of dry matter.

2) Mature bulls that need to gain weight

• Mature bulls that need to gain weight will require forage plus potentially a grain supplement. Their diet will need to consist of 8-10% crude protein and 55-65% TDN. The greater the weight gain needed, the greater the energy concentration needed in the diet.

3) Young bulls (2 year olds and yearlings)

• Young bulls should be targeted to be about 75% percent of their mature weight at two years of age. Young bulls need to gain up to 2.5 pounds per day from weaning to 15 months. Growth should continue at 2.0 to 2.5 pounds per day until three years of age. Supplemental feed should be fed to young bulls during breeding season if needed.
• Young bulls after the first breeding season
  • 75% of mature weight by 2nd birthdate.
  • May lose 100-300 lbs. during breeding season.
  • Example: 1,250 lbs. at turn out – 200 lbs. lost during breeding season = 1,050 lbs. If he needs to weigh 1,500 lbs. @ 2 yrs. – 1,050 lbs. current weight = 450 lbs. gain needed
  • Full feeding hay plus grain.
  • Amounts will vary based on required gain.
  • High quality forages may be used.
  • Caution: don’t bring bulls back too fast!

Minerals – All bulls should be maintained on a good, balanced mineral program similar to the rest of the herd.