Non-invasive methods for diagnosing pregnancy in cows and their real value.

Proper management of cattle reproduction has a major impact on the efficiency and profitability of dairy production. Ultrasound examination and transrectal palpation or the pregnancy-associated glycoprotein (PAG) test are currently the most commonly used methods for pregnancy diagnosis. However, alternative methods to those mentioned above are constantly being sought in order to minimise stress during the examination, the cost of veterinary services and to reduce the rate of errors in pregnancy diagnosis. Non-invasive methods of pregnancy diagnosis in cows are being improved, which include the barium chloride test, sulphuric acid, seed germination test, measurement of progesterone, interferon-tau or interferon-stimulated genes (ISGs), PAG, early pregnancy factor (EPF), estrone sulphate, thermography and electrocardiography. Over the past few decades, these methods have been extensively described. Some of these tests require blood, milk or urine for the diagnosis of pregnancy, while others require prolonged contact with the animal in order to take the appropriate measurements. Despite their advantages in terms of simplicity and lower cost compared with traditional methods of pregnancy diagnosis, they are sometimes problematic because of the difficulty of collecting material for testing. They allow the determination of a pregnancy without determining its age or pathology on the part of the development of the fetus and the reproductive system. They are also generally characterised by lower accuracy, sensitivity and specificity, which can have a negative impact on reproductive management and translate into the economics of dairy production. In the context of the above information, it appears that non-invasive methods of pregnancy diagnosis need to be further improved to minimise or eliminate the disadvantages cited.