EN
This study was carried out on the records of 698 Polish Holstein-Friesian cows, residing in 2 free-stall farms. The relationship between somatic cell counts in milk (SCC) and fertility was tested using records from the first 7 test-days (≈ months) after calving. The analysed fertility traits were the number of AI services per confirmed pregnancy and calving to conception interval. The SCC pattern on consecutive test-days was different in both farms, indicating a diverse microbiological background for mastitis. No significant correlations were found between SCC from particular test-days and cow fertility, whereas SCC determined on the test-day preceding the first AI service was correlated significantly with both fertility parameters (r from 0.11 to 0.14; p ≤ 0.05). Analysis of variances showed that the lowest values of both parameters were in the cows in which SCC on test- -day preceding the first AI service was below 50,000 and between 201,000-400,000 cells/ml of milk, whereas they were highest in the cows in which SCC exceeded 1,000,000 cells. Neither significant correlations nor significant differences among SCC classes were found for data from a test-day performed following the first AI service. In conclusion, the results of this study confirm that there is a close relationship between udder health and cow fertility, and show that SCC determined on the test-day preceding the first AI service after calving can be used for the identification of cows at risk of decreased fertility. The results also indicate that a negative effect of mastitis on cow fertility depends rather on the severity of the disease than on the etiological agent.