Success of a herd health pregnancy check is measured by the number of cows safe in calf, but in actuality, the nonpregnant ones are just as important. "In reality, you are looking for open cows,'' said Paul Fricke, a reproductive specialist with the University of Wisconsin-Madison, during his presentation at the 4-State Dairy Nutrition and Management Conference last week. "You need to identify those nonpregnant cows so that you can implement a strategy to rapidly return them to an A.I. service," he noted.
Identifying pregnancy in humans is pretty simple. Women who are pregnant have hCG (human chorionic gonadotropin) in their blood. This can be detected through urine just eight to 10 days after ovulation. Two minutes after taking a test, a female human can confirm her pregnancy by the appearance of two pink lines.
Unfortunately, cows don't have an equivalent of hCG, explained Fricke. Instead, common forms of current pregnancy detection include the evaluation tissue or fluid, either manually (rectal palpation) or with electronic instrumentation (ultrasound).
While cows do not have hCG, they do produce some pregnancy-associated glycoproteins (PAGs). In more recent years, tests have become more widely available to measure PAG levels and confirm pregnancy.
Two such options are blood serum and milk testing. Research has shown that these methods accurately diagnose pregnancy, if used at the correct time. Producers should note that state of gestation, parity, pregnancy loss and milk production all impact PAG levels and could, therefore, affect the outcome. And since neither is a cowside test at this time, there is also a waiting period between conducting the test and receiving results, which may delay breeding for open cows.
Still, for some farms, these PAG tests could be a great complement to a veterinarian's pregnancy check program. And in locations where access to veterinary services is limited, PAG tests may provide an opportunity for earlier pregnancy detection than is currently available. The best method will vary farm to farm, but options for pregnancy diagnosis and their applications in herds will continue to change and evolve.
(c) Hoard's Dairyman Intel 2015
June 15, 2015
