New possibilities for pregnancy diagnosis in ruminants: Limitations, advantages, use

Abstract

Early pregnancy diagnosis in ruminants, especially in high production herds, is one of the most important components of reproduction management. Reducing the time between insemination and the exclusion or confirmation of pregnancy is of major economic importance. That is why the traditional method of pregnancy examination by transrectal palpation is increasingly complemented by additional tests, such as ultrasonography. An alternative to these methods of pregnancy diagnosis are also simple field tests. The best known are tests for progesterone and estrone sulphate concentrations. Over the last few years, the measuring of pregnancy-associated glycoproteins (PAGs) has also been gaining popularity. In cattle, this method can be used as early as the 28th day of pregnancy, when the plasma concentration of PAGs exceeds 1ng / ml. Maximum values of pregnancy-associated glycoproteins are observed about day 240 after fertilization. After calving, their level quickly decreases. In sheep, the concentration of PAGs increases significantly in the 3rd and 4th weeks of gestation and reaches its maximum level around the 9th week. In goats, the concentration of PAGs differs between races, but its measurement can be quite a reliable indirect method of pregnancy diagnosis. The PAGs value in this species grows until about the 8th week after insemination and, depending on the breed, reaches a maximum value of 50 to 69 ng/ml. One limitation for the use of PAGs field tests may be false positives which occur after the death of the embryo. Similarly, an increased PAGs concentration can persists for up to about 70 days after calving. Moreover, the PAGs concentration is also affected by the health, age and milk production of the female. The advantages of field tests are the simplicity of performance, the ease of reading and interpreting the results and the short time needed to complete the entire procedure. Field tests based on the commonly used ELISA method are characterized by low invasiveness (blood, milk), combined with high sensitivity and specificity. Their rapid application under field conditions makes them an excellent extension of diagnostic capabilities, especially in large herds of cows, .