Reproduction is a key profit driver for cow–calf producers, and our goal is to get as many cows pregnant as possible in a reasonable time frame.
Reproductive efficiency is dependent upon fertility in both the male and female counterparts of the herd. Cows must cycle and be ready to breed at the start of the season, and the bull must be able to detect and breed cows with fertile semen. Many bulls have not needed to perform these duties in the last few months, and a bull's history of getting cows pregnant does not predict his future ability.
The breeding soundness examination (BSE) is a quick and economical procedure to screen bulls for fertility prior to sale or use, and a relatively cheap insurance measure to remove problem bulls prior to the breeding season. The BSE is a pass/fail exam, and a bull must pass all three categories to be deemed an acceptable breeder. The BSE, however, should not be used to compare fertility between bulls.
National reports indicate 10% to 20% of bulls will fail a comprehensive breeding exam. If a bull does not pass, the veterinarian will either deem him an unsatisfactory breeder or defer classification depending on the reason he didn't pass. The three categories:
1. Physical evaluation.
The bull must be able to travel to, effectively mount and breed cows in heat. Normal vision, feet and leg soundness are crucial. The bull should not be showing any outward signs of a systemic disease that would hamper reproductive function.
The bull is also evaluated for body condition, as bulls that are over- or underconditioned can have problems with semen quality, libido or mating ability. A good body condition score at the start of the breeding season is important because bulls tend to lose weight when they are working.
2. Reproductive evaluation.
A bull's reproductive organs are evaluated to assess potential fertility. Evaluation of the testicles is a critical part of the exam. Testicles are palpated to identify variation in size, shape and consistency. Measurement of scrotal circumference is an accurate predictor of testicular size, weight and sperm output. Bulls with larger testicular volume produce more sperm cells than bulls with a smaller scrotal circumference. It is also an accurate predictor of the onset of puberty in male and female offspring.
Rectal palpation evaluates internal accessory sex glands for infection, inflammation or adhesions. The penis and prepuce are evaluated for inflammation, hair rings, infections and signs of trauma or scarring.
3. Semen evaluation.
Semen is evaluated for motility and morphology. Motility is a measure of the productive movement the sperm cells are making. Many of the sperm cells need to exhibit progressive advancement in order for the bull to pass. This is essential, as sperm must swim to the egg to initiate fertilization.
Morphology is a measure of how many of the semen cells appear to be normal. Individual cells are evaluated to determine the number and type of defects present. In order to pass, the bull has to deliver an adequate number of normal cells in order to provide fertilization.
DAN GOEHL, DVM, and his wife own Canton Veterinary Clinic in Canton, Mo., working with stocker and cow–calf beef operations. He is also a partner in management and marketing of beef cattle. E-mail him questions and comments at email@example.com.