The Effects on Somatic Cell Score and Milk Components by Days in Milk in Holstein Dairy Cows

The present study was carried out to investigate effects of various factors such as sire, bovine leukemia vi- rus(BLV) carrier/non-carrier, parity, calving month and lactation periods on somatic cell count(SCC) and milk components in dairy cows. The animals calved from January 2001 to March 2004. Milk samples were col- lected every 30 ± 5 days in milk(DIM), and somatic cell count and milk components were analysed by Somascope MK2/Lactoscope FTIR. Bovine Leukemia Virus(BLV) was detected by ELISA method. The lactation periods were divided into five periods; (1) 30DIM, (2) 31 to 60DIM, (3) 61 to 120DIM, (4) 121 to 180DIM, and (5) more than 180DIM. The level of SCC and milk components in all lactation periods were significantly affected by sire, parity, calving month, lactation period and BLV carrier/non-carrier. The results suggest that BLV carrier/non-carrier analysis in a herd may be necessary if milk quality is low owing to a high SCC. BLV carrier/non-carrier did not affect milk protein content for all lactation periods.