This section is on cattle reproduction. These are all questions that have been submitted or that I have been inspired to talk about because of a question submitted. If you have any topics that you would like to have discussed please feel free to email me with the topic or question.
A gomer bull is an intact but vasectomized bull. His job is to mark via a dye pack on his chest the cows that are in heat so that they can be bred or artificially inseminated. Detecting heat in cows can be difficult since they are only in for a very short time 12-24 hours. The use of a gomer bull greatly reduces man hours needed to monitor cows.
Yes, the cow as well as the bull are also affected by Brucellosis. The organism is Brucella abortus. The effects of the disease are similar to that in canines such as abortions and infertility. Through extensive testing and culling from breeding stock any positive animal, Brucellosis in cattle in the United States has dramatically decreased in incidence. Many areas of the country are declared Brucella-free. There is significant concern over the increasing contact of cattle with buffalo since buffalo also carry the Brucella abortus organism. Transmission is like that of Brucella canis -- sexual contact, contact with aborted fetal material, etc.
The purpose of the dairy cow is to provide milk. Mastitis is an infection of the mammary glands. The milk produced from a dairy cow with mastitis is laden with the infecting agent and, thus, not safe for human consumption. Which means that for the entire course of the mastitis and for a specific period of time after it resolves (the time varies with the treatment given to clear up the infection), the milk from the mastitic cow can not be sold for human consumption. The dairyman loses money and the consumer loses milk and milk products. Mastitis does, therefore, affect the dairy economy significantly. Therefore, dairies take great precautions to prevent mastitis from ocurring.
On average, a good quality, healthy heifer (cow that hasn't had a calf) will be able to be bred for the first time around 18 months of age. This would make their first calf be born when they are approximately 27 months of age. It is the goal of breeding operations to have a calf every 13 months.
I have researched and answered these questions to the best of my ability. But I am human and make mistakes. If there is any part of my answer that you feel is incorrect, please let me know. The last thing I want is to disseminate false or incorrect information.