Role of early pregnancy diagnosis by means of ultrasonography in improving reproductive efficiency in a dairy herd

Transrectal ultrasonography (7.5 MHz linear-array transducer) was used in a Hungarian Holstein-Friesian dairy herd to test the accuracy of finding a corpus luteum on day 20 or 21 or a conceptus on day 29 or 30 after mating, respectively. All of the cows with non-pregnancy diagnoses and having a corpus luteum were re-examined on day 33 or 34 after AI. The final ultrasonographic examination was between days 53 to 58 after mating. 20 non-pregnant cows were recognized by the absence of a corpus luteum at the first ultrasonographic examination on day 20 or 21 after AI and these cows might be treated at this early stage if needed. The 7 false negative ultrasound diagnoses made on day 29 or 30 after AI could be corrected on the basis of repeated ultrasonographic examinations 3 to 4 days later. With the exception of one cow, every non-pregnant cow was correctly diagnosed on day 29 or 30 after AI and these cows might be treated at this stage if needed. Three to 4 ultrasound examinations might be beneficial to the achievement of optimum calving to conception interval under field conditions.