Changes in the concentrations of somatic cell counts, lingual antimicrobial peptide and lactoperoxidase activity in milk at periovulatory period in dairy cows.

The objective of the present study was to examine the changes in innate immune factors in milk during the estrous cycle in dairy cows. Milk was collected from cows with a normal ovulatory cycle and cows subjected to the OVSYNCH protocol, and somatic cell counts (SCC), lingual antimicrobial peptide (LAP) concentrations and lactoperoxidase (LPO) activity in milk were measured. In cows with a normal ovulatory cycle, there was no significant change in LAP concentrations and SCC during the ovulatory cycle. However, LPO activity at days 0 and 19 (day 0 = day of ovulation) were significantly higher than those at days 10, 12 and 15. In cows subjected to the OVSYNCH protocol, a significant increase in SCC was observed at day 9 (2 days after prostaglandin treatment) compared with that at day 11 (2 days after second administration of gonadotropin). There were no significant changes in LAP concentrations and LPO activity during the OVSYNCH protocol. These results indicate that LPO activity, an innate immune factor, was enhanced in the preovulatory period.