By Jessica Crabtree and Dr. Jared Harlan
No matter the breed, the ultimate goal of any cow/calf operations is to have the highest reproductive efficiency. Much like we talked last month about bulls, cows, too, serve a vital purpose in achieving the objectives of breeding. As producers, pregnancy testing puts them in position to make the best possible decision. With high market prices and cost of feed, each cow must be a producer. If not, she is costing the producer money, especially when selling. Cows sold with a guaranteed live calf attract a higher price at market.
Producers concern themselves with pregnancy testing their cows for multiple reasons. Whether to manage their herds in specific calving periods,helping to determine sire in a artificial insemination program, adding value to cattle going to market, or to cull open cattle. In the latter case, early detection is key in a non-pregnant cow. Early detection of an open cow translates to less input without return. Reliable pregnancy testing can be initiated as early as 6 weeks from the end of a breeding season.
Another major reason is determining the age of the calf and its calving date. With that information, producers can separate early calves from those calving later. This also aids in the culling process, if necessary, to downsize the herd, especially in times of drought. Culling cows based on non-pregnancies is more efficient than basing it off age. This also alleviates stress from calving season. Producers can replace late-calving cows with heifers that conceived early.
Pregnancy testing is also a great way to detect any abnormalities in cows that may cause infertility. Those may include cystic ovaries, uterine infection, injuries from previous deliveries, or anatomical deficiencies. Pregnancy testing is also a way to control diseases that could affect the entire herd along with management problems. For example, if a herd has a low pregnancy rate, it may indicate problems in an individual bull with poor fertility. Poor fertility throughout the herd may be caused from infectious diseases or inadequate nutritional practices. In the case of Trich. Foetus, culling open cows is a major part of the control program.
Pregnancy testing on cattle is typically done by rectal palpation. Rectal palpation can identify a pregnancy as early as six weeks after conception. It is perhaps the most inexpensive and convenient method. When palpating a cow, the veterinarian feels for the calf’s body, a pulse in the artery supplying the blood to the uterus, cotyledons within the uterus, or the embryonic vessicle within the uterus. This is a convenient option due to low cost of equipment, and immediate results. However, modern technology and new techniques have advanced in the production area. An alternative to manual palpation is ultrasound assisted evaluation of the reproductive tract. Portable ultrasonic pregnancy detectors may detect a pregnancy earlier than palpation. Doppler scanners have an external probe containing both transmitting and receiving elements that project a beam of low-energy sound waves. The newest technology includes an extension arm. Essentially, it is a probe that doesn’t have to be taken in to the rectum by hand or arm, reducing fatigue on the operator. Another option and advancement in pregnancy testing in blood testing.
The trans-rectal ultrasound has become a great tool for veterinarians to visualize the embryo or fetus and give additional information beyond rectal palpations. Trans-rectal ultrasound can even determine the sex of the calf, according to Dr. Ram Kasimanickam of Washington State University in the article, Pregnancy Testing: New Technology Provides Several Options. He went on to say that the ultrasound can detect a pregnancy with high accuracy as early as 26 days following breeding.
Ultrasonography works in two ways. The traditional ultrasound is arm-in rectal probe. The new trans-rectal ultrasound extension arm probe eliminates the need for putting an arm into every cow. The technology has been around close to 12 years and was designed to makes work easier for veterinarian’s arms. A pro about the trans- rectal probe is that it is an oscillating probe so the rod doesn’t have to be rotated to view the uterus and its contents. A con to the trans-rectal probe is that veterinarians must be cautious when using it. If there is any sudden or unexpected movement, the rectum could be damaged. There is an advanced version of this called Repro-Scan invented by Dr. Andrew Bronson of Alberta, Canada, with his partner Bruce Hill. Their version uses a convex rectal probe that produces a much larger image. Even with these advancements in technology special training is needed to become accurate with these machines.
Blood testing was developed by Dr. Garth Sasser of the University of Idaho. Dr. Sasser found a protein produced by the placenta and detectable in the blood. It is called Pregnancy Specific Protein B. That evolved into his company called BioTracking and into his blood test called BioPry, (Pregnant ruminant yes/no) in 2002. Many believe that drawing a blood sample is actually less stressful for the cattle than other methods of pregnancy detection. In some studies, blood testing has been shown to be more accurate than palpation or ultrasounding, depending on experience drawing blood samples may actually be quicker as well. However turn around time on the test is often several days, which does not allow for decisions to be made while cattle are already gathered. It also requires that each cow be permanently identified. Collecting blood samples is also an easy skill to learn, eliminating the need to schedule a veterinarian. The blood test is done by taking a blood sample from a vein under the tail. Collection supplies are usually provided by the laboratory performing the testing.
Producers may not choose to pregnancy test at all based on expense. Instead they may choose to monitor oestrus (also called estrus) or returns to heat. Once a cow conceives, all but approximately five percent cease to cycle for the duration of the pregnancy. Oestrus detection after the end of the mating period can be a useful alternative to pregnancy testing, though it may come with some inaccuracy. Due to extra labor required when checking signs of heat, oestrus detection is unlikely to substantially reduce the cost of identifying non-pregnant cows over pregnancy testing. Other measures that can be done to test for pregnancy include measuring the levels of progesterone in the blood or milk. Both involve extra labor and cost.
It is important to remember that no method of determining pregnancy status is 100% accurate. Cost, convenience, accuracy, required equipment, and time investment should all be factors you consider when determining the method you choose. All three have specific cases where incorrect results can be obtained. All three can also be extremely accurate depending on the skill of the person performing each task. Discussing these options with your veterinarian can help you make decisions best suited to your program. They can also help you to decide based on their skill and preference. Dr Harlan prefers palpation over other methods for the majority of his clients. With adequate facilities and defined breeding dates an average of 100 cows per hour is easily attained. However when short bred cows are needed to be checked, he prefers to have the ultrasound available, at least for a back up to double check opens. He also believes that blood testing is a good option for smaller groups of cattle, especially when inadequate facilities are available for palpation or if all cattle cannot be gathered at the same time.
In conclusion, producers must seek out the best pregnancy testing method for their individual program based on their herd needs. Of the methods discussed, a producer can find which works to identify non-pregnant cows, fertility problems and management problems that need to be addressed to be efficient and achieve ultimate breeding objectives: happy cows and healthy calves.