Crystallization and the number of neutrophils increase in the cervical mucus as parturition approaches in dairy cows

The aim of the present study was to determine changes in the crystallization and cytology of cervical mucus in late gestation in dairy cows. Eleven 7-month pregnant Holstein cows with a sound reproductive history were used in this study. Samples of cervical mucus were collected on 53±3, 38±3, 23±3, 12±2, 8±1, 5±1 and 2±1 days before parturition for cytology and examination of crystals. Coccygeal blood samples were also collected after each cervical mucus sampling for determination of plasma estrogen and progesterone concentrations. A sample of nasal secretions was also collected after each blood sampling for examination of crystals. The thin cervical smears were Giemsa stained for cytological examination and the thick smears of cervical and nasal mucus were also evaluated for crystallization. The results of the present study showed an increased (p<0.05) percentage of neutrophils and typical crystals in the cervical mucus as parturition approached. This coincided with the gradual rise of the plasma estrogen concentrations and the gradual decline of the plasma progesterone concentrations in the last 2 weeks before the onset of parturition. Further, a significant positive correlation was observed in the changes of the crystallization pattern between nasal and cervical mucus samples (p<0.05; r=+0.86). In conclusion, crystallization and increased neutrophils in the cervical mucus in late gestation could be related to impending parturition in dairy cows.