| Popis: |
SUMMARY The authors in this literature review emphasize that parallel with the successful genetic selection for higher milk production in Holstein dairy cows, a dramatic decline in their reproductive performance has occurred. The average number of days open, the number of services per conception and the number of cows culled for infertility increased substantially. At the same time, it is very impor tant to emphasize that reproductive performance of heifers was not affected. In order to decrease prolonged lactations and the number of cows culled for reproductive reasons it is very important to improve our reproductive monitor ing practices. Achievement of optimum herd reproductive performance (calving interval of 12 or 13 months with the fi rst calf born at 24 months of age) requires high-level management activities, especially during the fi rst 100 days follow ing calving. After calving, a cow overcomes a series of physiological hurdles before becoming pregnant. Several real-time diagnostic devices and methods are available to monitor specifi c events in the peripartal and service period to appropriately identify problems and their potential causes furthering their rec tifi cation. These include calving alarm vaginal thermometers, monitoring rumi nation, electronic hand-held BHBA measuring systems, metabolic profi le tests, regular measurements of milk constituents, long-term measurement of retic uloruminal pH value by indwelling and wireless data transmitting units, ultra sonography, oestrus detectors and/or detection aids and on-farm progester one tests. According to the authors the following monitoring and management activities are needed to pursue during the early postpartum period to reach the optimal calving interval: prediction the onset of calving, monitoring post par turient metabolic diseases, early diagnosis of post parturient uterine diseases, accurate oestrus detection, correct timing of insemination and accurate early pregnancy diagnosis. Despite the higher milk production acceptable fertility results even in large scale dairy farms can be achieved if the impact of the above-mentioned factors causing decreased fertility can be moderated. |
