INFLUENCE OF STAGE AND NUMBER OF LACTATION ON SUCCESS OF THE ARTIFICIAL INSEMINATION IN DAIRY COWS

The objective of this study was to analyse the influence of stage of lactation and parity(number of lactations) on success of the artificial insemination in Holstein-Fresian dairy cows. Complete lactation records were obtined from Dairy Record System of the dairy farm of Agricultural Research and Development Station (ARDS) Şimnic Romania. A total of 204 dairy cows were grouped by their number of lactation (first, second and third). All conception date distribution was recored for eight postpartum intervals (each of 21 days) form 50 to 218 days in milk. All artificial inseminations were performed by designated inseminator after estrous detection. The percentage of cows that conceive within 112 days postpartum was 49,3% in first lactation, 48,8% in second lactation and only 39,6% in third lactation. Mean for all lactation was 47,0%. After 218 days in milk the percentage of pregnant cows was 77% in first lactation, 85,1% in second lactation, and only 65,1% in third lactation. A proportion of cows in this study had better reproductive performance and the other proportion had poor reproductive performance. In herds in wich reproduction is based on estrous detection for insemination the interval to pregnancy is extended and creates more variability in when cows receive their first insemination and become pregnant