Breeding soundness exams necessary for sheep flock profitability
November 29, 2011
Breeding soundness exams can play an important role in profitability and efficiency in a sheep flock, was the message delivered by Wyoming State Veterinarian Dr. Jim Logan, during the Northeast Wyoming Sheep Symposium in Gillette recently.
With a ram contributing 75 percent of the genetic improvement in a flock, it is very important to make sure the ram purchased can do the job. “You need to be able to justify the expense of these rams,” Logan explained. “With the increase in the market, and some sales and breed auctions experiencing record highs this year, it is important to have a breeding soundness exam performed on rams prior to breeding. Even if you purchased a ram over the summer with a negative ELISA test, I would still recommend having him rechecked just prior to breeding,” he added.
Rams are the main carriers of Brucella Ovis (B. Ovis), which is a disease that can cause ewes to abort or become infertile. Rams can transmit the disease to one another through homosexual activity, and to the ewes during breeding. Typically, the ewes can get the bacteria, but don’t carry it long-term. However, they may abort or become infertile while carrying the disease. Once a ram contacts the disease, he can become infertile.
“Infertile rams can have the same hormone levels, libido, and sex drive as a fertile ram,” Logan explained. “He will continue to try and breed the ewes, and in some cases, I have seen infertile rams chase the fertile rams away and hoard the ewes. What happens is this will extend the lambing period, and reduce the average weight of lambs at weaning time. That is why it is so important to have your rams tested before breeding,” he stated.
A critical part of evaluating whether a ram should be used is keeping good records, Logan continued. “If the ram is two or three-years-old, you should look at the performance records of that animal, in addition to the fertility and breeding soundness exam. Poor breeding is a risk of unevaluated rams. He could look physically fine, but a lot can be told by the semen and ELISA blood tests. You also need to select a ram that is sound on its feet, has good hooves, sound bone, good teeth and good eyes.”
If a ram has an injured on infected eye, Logan said it is possible for the infection to spread to other parts of the animal’s body, including the reproductive organs. In addition, the animal may lay around and not do its job because it doesn’t feel well, he said.
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“It is important to have a veterinarian evaluate the ram for breeding,” he continued. “During the exam, he will make sure the ram can extend its penis, and see that it is free of any lesions. He will also palpate the testicles, in addition to performing an ELISA test. Sometimes the animal can look physically okay, but he still may be infertile.”
The veterinarian can also evaluate the semen of the ram using proper equipment. “If the ram is fertile, and doesn’t have other problems, he should ejaculate within a few seconds,” Logan explained. “Once the veterinarian has a sample, he can use a microscope to evaluate the viability, mobility, size and shape of the sperm. He can also determine the number of sperm cells, and make sure the sperm look normal with no broken tails.
Logan said a normal ram should have at least 90 percent active, viable sperm cells. To determine the number of sperm cells, the veterinarian will take an estimate based on the density of what shows up under the microscope. “You can determine the viability by the swirl or tornado effect on the slide,” Logan explained. “You can also increase the magnification to look at the structure of the sperm, and determine if any have broken tails or axioms.” During the process, the veterinarian will also check for the presence of white blood cells or tissue which could indicate the ram may be a non-breeder.
Logan said a veterinarian can also test the ram for B. Ovis, explaining that an animal with the disease can have swollen testicles and epididymis making the sperm not viable. However, if an animal was recently exposed or early in incubation for the disease, he may palpate normal, but the test can show the ram has the disease. “Clinically, he might be physically normal. He could have good libido, be an active breeder, and palpate normal. However, a B. Ovis test can find the positive animals and get them out of the flock before they contaminate the other animals,” Logan said.
Depending upon the amount of time since exposure and the incubation since the ram was exposed, it is also possible to get a false negative test, Logan said. “Usually, a producer can be 90 percent assured it is not in the herd after testing the animals.”
During his discussion, Logan also encouraged producers to keep reproductive records on their ewes and consider vaccinating their herds if there are too many ewes aborting or without lambs. “Ordinarily, we don’t do a lot of vaccinating in the sheep industry,” Logan explained. “Some people vaccinate for Vibrio, but I also recommend they vaccinate for Chlamydia. It shows the same clinical signs as Vibrio. However, if you have a clean lambing history, I wouldn’t recommend vaccinating for these diseases.”
Logan also cautioned producers to be more careful handling aborted fetuses, placentas and other tissues from contaminated animals. “Chlamydia and Q Fever are zoonontic diseases that can be transmitted to humans. You need to protect yourself because these diseases can impact your health,” he said.