Preg. test options offer pros, cons
Blood testing to detect pregnancy in cows has yet to take a strong hold over the tried and true results of palpating or ultrasounding, but it is making its way into the industry. Palpating is still the main practice of most veterinarians, in part because old habits die hard, and ultrasounding still has its place in the industry. Despite the method, early pregnancy detection in replacement heifers or cows is a tool producers continue to use to increase profit. But some producers and veterinarians alike are embracing the blood pregnancy testing. Dating back about 12 years, the blood pregnancy test has proven to be 99 percent accurate, if the animal is determined open at least 28 days postbreeding. It has proven to be 95 percent accurate when a cow is identified as pregnant, with a 5 percent difference accounted for as early embryonic death loss. But for some producers, the tried and true palpating or ultrasounding method remains to be the pregnancy test of choice.
A new article touting blood pregnancy tests was published in The Veterinary Journal by researchers at Iowa State University and Virginia Herd Management Service. This article describes the use of dried blood spot technology for diagnosis of pregnancy. According to the study, pregnancy can be detected from 28 days using pregnancyassociated glycoproteins (PAGs) in blood.
Blood testing can be more economical than traditional testing in smaller set-ups with fewer cows to be tested, or in remote areas where pregnancy testing is not currently carried out due to travel time from the local veterinary practice. Blood testing can also be useful to maximize the efficiency of artificial breeding programs where pregnancy status needs to be known in between vet visits in order to know which animals are empty and need to be treated to induce the next estrus cycle.
The TEGO does offer a fix for this problem. Applied with Allflex ear tag applicators, the device creates a bleed on the ear and absorbs the blood onto the self-contained blood card. The cards are then placed in envelopes and returned to the lab at room temperature. An alternative product, TEGO Card can also be used to collect dried blood spot samples. In this case the producer creates a bleed on the ear with a lancet or needle and simply holds the card to the ear to collect the sample.
The authors developed a laboratory process for processing the dried blood spot samples for pregnancy testing. This dried blood spot laboratory process yielded equivalent results to blood tubes for both pregnant and empty cows in a total of 68 cows of known pregnancy status, with no false positive or false negative results. The study concluded that dried blood spots can be used as an alternative for pregnancy diagnosis with the benefits of easy blood collection, shipping cost savings and convenient sample storage.
BioPRYN® offers another blood pregnancy test for producers, and according to Jeremey Howard, Director of Sales and Marketing, the test requires only 2cc of blood from the animal. The samples are then shipped to a laboratory, and results are available within 24 hours of receiving the sample.
“We were the first blood based technology, and have provided over 500 million tests,” Howard said.
While these advantages of blood testing exist, there are some challenges to collecting blood in tubes. A skilled operator is required to draw the blood sample from the vein, but it does not require a veterinarian. Blood tubes are transported cooled and need to be protected against breakage, adding to shipping costs.
The first BioPRYN® - tested cattle blood sample was run on July 30, 2002. The two millionth sample was tested on May 12, 2010, and came just 21 months after the one millionth sample mark was achieved.
While the cost is comparable to other pregnancy tests, the blood test offers options for additional data.
“You can also take that sample, archive it, and then use that same sample to get a genomic test. The costs are about the same as traditional methods of pregnancy testing, but the advantage of blood tests is they can be combined with something else such as a genomic profile,” Stewart Bauck, General Manager with GeneSeek pointed out at the recent National Cattlemen’s Beef Association meetings.
While not as common, pregnancy can be detected in cows as early as 26 to 30 days using ultrasound, and it is considered a reliable and relatively simple method. With an accuracy rating of over 99 percent, it’s definitely a test to consider.
With a proficient ultrasound reader, and proper restraint of an animal, the speed of ultrasonography can compare to palpation, and offer more information on each animal. The rate of detection of early embryonic loss is somewhat higher with ultrasound, according to research from Merck Animal Health.
While placing the ultrasound transducer on the flank of a cow is an option, this test usually requires it to be inserted into the animal by hand.
Research shows 10 to 16 percent of cows diagnosed pregnant at 28 days post AI experience early embryonic loss by 56 days post AI. Cows diagnosed pregnant at 28 days post AI using ultrasound should be scheduled for a subsequent examination around 60 days post AI, when the rate of embryonic loss per day decreases dramatically.
Two other disadvantages include cost, and the possibility of tears, according to Bruce B. Carpenter and L. R. Sprott with Texas A&M University. A trained person puts the transducer probe in the rectum of the cow. Using the same hand to manipulate the probe and the uterus, the transducer sends and receives sound waves that have been directed along the uterine horns. Since tissues and/or fluid will reflect or absorb sound waves differently, those sound waves are transduced into an electronic image. This is then viewed on a special monitor. Skill is needed to manipulate the probe and to interpret the image produced on the monitor.
This method does offer other advantages, including speed of determination, less strain on the tester, and the option to diagnose other conditions, including the thorax, umbilical area, testicles and more.
Today rectal palpation remains the easiest, fastest, cheapest method, and is arguably accurate comparatively to the other methods while still meeting producers’ goals.
For cows to be identified as pregnant with the palpation method, they need to be at least 35-50 days pregnant. Experience of the person palpating can make a significant difference on how early in this range that pregnancy can be detected.
But there are still some complications with this method. According to the University of Nebraska- Lincoln, producers should realize that stress to heifers and cows early in pregnancy can result in loss. Research has shown a pregnancy loss of 1-3.5 percent with palpation, or even ultrasound, if used for pregnancy diagnosis at 40 - 75 days of gestation. — Traci Eatherton, WLJ Editor