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CATTLE TODAY

MANAGE BULLS TO INSURE LONGEVITY AND FERTILITY

by: Dr. Lisa Kriese-Anderson, Dr. Diego Gimenez, Jr., and Rickey G. Hudson

Beef producers spend considerable time and effort to find the right bull for their herd, however, too often this carefully selected bull is brought home and forgotten. Bulls require proper management, the same as cows and calves. Sound breeding, health, and nutrition programs help to ensure bull fertility, longevity, and productivity.

Bulls need a reproductive checkup (also known as a BSE or breeding soundness exam) prior to the start of each breeding season. This BSE should be performed by a licensed veterinarian. The BSE includes an evaluation of the semen and several physical characteristics of bulls.

Sperm cells collected in semen samples of bulls are evaluated for morphology (shape) and motility (movement). The microscopic observation of normal, live sperm cells in adequate numbers that possess good motility is needed for bulls to pass the BSE. This ensures that bulls have the potential to successfully settle cows and heifers.

The BSE physical is an evaluation of the internal and external reproductive organs, structural soundness, and the nutritional level of bulls. Their mating ability is directly related to their body condition (for energy and stamina) and physical attributes (ability to see, smell, move, mount and breed). Physical defects of the teeth, eyes, feet, legs, sheath, prepuce, penis, testes, and internal reproductive organs greatly diminish the mating ability and fertility of bulls. Defects from dis- ease or injury to the joints, muscles, nerves, bones, or tendons cause structural unsoundness and limit bull mobility.

A comprehensive herd health program must include a health plan for bulls. The health of the cow herd is dependent on sound health management practices (biosecurity, immunization, parasite control, etc. ) for bulls.

The isolation of new bulls for a period of 4 to 6 weeks and the employment of a veterinarian to test new bulls for infectious disease and agents are needed prior to commingling or introducing bulls to the herd. Establishing a veterinarian-client-patient relationship is an important component in any health management program.

A veterinarian can ensure bulls are properly immunized to fit into a designed herd health program. Bulls need annual boosters for IBR/BVD/PI3/BRSV Leptospirosis (5-way) and Vibriosis, prior to the breeding season (6- 8 weeks).

Bulls need deworming to control internal parasites. Deworming may be timed to closely follow the first killing frost in the fall and the green up of grass in the spring. External parasite and fly control are highly dependent on specific farm conditions; explore control options with a veterinarian or Extension agent.

Nutrition is a vital component of bull management. Meeting the nutritional needs of bulls varies with respect to age, condition, and activity. Bull nutritional programs should be designed to start the breeding season with bulls in a 6.0 to 6.5 BCS (body condition score). Thin bulls (BCS < 4.0) and fat bulls (BCS > 7.0) have more fertility problems. Diet and nutrition have long term consequences for bull semen quality; as spermatogenesis (sperm production) is a 60 days process.

Young bulls (less than 36 months old) require much nutrition management. "Hardening" or slowly adjusting (60 to 90 days period) yearlings bulls (12 to 15 months old) from a high concentrate diet of a performance test or conditioning program to a lower energy, higher roughage diet is a must to avoid excessive body condition losses. Bulls from 15 to 36 months old need a diet to gain approximately 2.0 lbs. of body weight per day. This diet should contain approximately 60 to 70 percent TDN (total digestible nutrients - energy) and 10 to 11 percent CP (crude protien) to allow for their maintenance needs and continued growth. There are numerous diets to meet these needs. Example: A bull weighing 1200 lbs. is fed 6 lbs. of shelled corn with nutrient values of 88 percent dry matter, 90 percent TDN and 8.5 percent CP along with 24 lbs. of grass hay with nutrient values of 86 percent dry matter, 55 percent TDN and 11.0 percent CP plus free choice minerals to produce a diet with total approximate values of 86.4 percent dry matter, 62.0 percent TDN and 10.5 percent CP.

Mature bulls (36 months and older) need proper nutrition, too. While mature bulls usually maintain body condition on high quality pasture and good quality hay, they may need supplementation (additional energy), when consuming lower quality forages and during heavy breeding periods. Good nutrition management is needed to avoid significant losses in a bull's BCS. Bulls with a 2 to 3 BCS loss during the breeding season will need to regain 300 to 450 pounds of weight during the next seven to nine months (prior to the start of the next breeding season). Approximately, 1.5 lbs. of ADA (average daily gain) is needed to regain proper body condition. Most mid-summer to fall pastures in Alabama and typical grass hays will not support the needed 1.5 ADG without supplementation (energy and possibly protein).

In a controlled breeding season (60 to 90 days in length), the recommended number of beef females to breed per bull is 25 -40 females per mature bull and 10 -20 females per young bull. Bulls on a sound nutrition program that possess good body condition can be expected to successfully service these numbers of beef females.

Time spent to study and select the right bulls to improve the genetics of the cowherd is indeed, time well spent. However, failure to provide the proper care and management of these selected herd sires will diminish their value for herd improvement and lower the returns to investment (time and money) used in selecting them.

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