How does extended lactation in combination with different milking frequencies affect somatic cell counts in dairy cows?

With 18 months CI, there were no significant differences between the two milking frequencies, neither when analysing the WL nor the L10 separately. Multiparous cows, irrespective of milking frequency, had higher LSCC (the logarithm of the SCC) values than primiparous cows, and during L10 the difference was significant. This study shows that the LSCC throughout the lactation does not differ as a result of an extended CI, compared to the traditional 12 months CI (P = 0.84). Furthermore, the results on extended CI in combination with different milking frequencies show that the LSCC values were not influenced by the milking frequency. Compared to the cows in the traditional system with 12 months CI and milking 2× daily, cows in 18-2 and 18-3 had no increased LSCC values, P = 0.21 and 0.45, respectively. Therefore, these results indicate that a production system with extended calving interval can be used, with milking 2 or 3 times per day, without increased risk of increased milk somatic cell counts.