Are Your Bulls Ready to Work?

Published on: 11:19AM May 04, 2009

By Dan Goehl

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Reproduction is a key profit driver for cow-calf producers, and our breeding season goal is to get as many cows pregnant as possible in a reasonable time frame.

Reproductive efficiency is dependant upon fertility in both the male and female counterparts of the herd. Cows must be cycling and ready to breed at the start of the breeding season, and the bull must be able to detect and breed appropriate cows with fertile semen. Many bulls have not needed to perform these duties in the last few months, and previous history of a bull getting cows pregnant does not predict his future ability to function. 

The bull BSE is a quick and economical procedure for screening bulls for fertility prior to sale or use, and is a relatively cheap insurance measure to remove problem bulls prior to the breeding season. The BSE is a pass/fail examination based on three categories, which a bull must pass in all three to be deemed an acceptable breeder. The final result of a BSE, however, should not be used to compare fertility between bulls.

National reports indicate that 10-20% of bulls will fail a comprehensive BSE. If the bull does not pass, the veterinarian will either deem the bull an unsatisfactory breeder or defer classification depending on the reason he didn’t pass. 

Below are the three categories:

1. Physical Examination

The physical examination is a very important part of the breeding soundness examination. The bull must be able to travel to and effectively mount and breed the cows in heat. Normal vision, feet and leg soundness are important.

The bull should not be showing outward signs of a systemic disease that would hamper reproductive function. The bull is also evaluated for body condition. Over or under conditioned bulls can have problems with semen quality, libido, or mating ability. Good body condition at the start of the breeding season is important because bulls tend to loose weight when working.

2. Reproductive Examination

The reproductive organs are evaluated to assess potential fertility. Evaluation of the testicles is a critical portion of the examination. Testicles are palpated to identify variation in size, shape, and consistency. Measurement of scrotal circumference is an accurate predictor of testicular size and weight and subsequently sperm output. Bulls with larger testicular volume produce more sperm cells than bulls with small scrotal circumference. Scrotal circumference is also an accurate predictor of onset of puberty in male and female offspring.

Rectal palpation is performed to evaluate internal accessory sex glands for signs of infections, inflammations or adhesions. The penis and prepuce are evaluated for inflammation, hair rings, infections, and signs of trauma or scarring.

3. Semen Evaluation

The quality of the semen is evaluated for both motility and morphology. Motility is a measure of the amount of productive movement the sperm cells are making. Many of the sperm cells need to exhibit progressive advancement for the bull to pass. This is essential because the sperm must swim to the egg to initiate fertilization.

The morphology of the semen is the evaluation of how many of the cells appear normal. Individual cells are evaluated to determine the number and type of defects. In order to pass the bull needs to have adequate numbers of normal cells to provide fertilization.

Dan Goehl, DVM, and his wife own and operate Canton Veterinary Clinic in Canton, MO, where Dan works primarily with stocker and cow/calf beef operations. Dan is also partner in Professional Beef Services, LLC, which offers herd consultation and helps in data management and marketing of beef cattle.

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