Physical properties of bovine cervical mucus during normal and induced (progesterone and/or PGF2α) estrus

Abstract

Ninety two Friesian cows were used to determine physical properties of cervical mucus collected during normal estrus and estrus induced. Estrus was induced using either progesterone (P 4) releasing intravaginal devices (PRID) and/or prostaglandin F2α (PGF2α). The animals were assigned to 4 groups (no treatment, a PRID for 12 days plus an injection of 1000 IU PMSG at the removal of the PRID, a double injection of 3 mL PGF2α 11 days apart, and a PRID for 7 days plus an injection of PGF2α 24 h before the removal of PRID). A number of cows with normal estrus exhibited three consecutive estrus cycles after calving. Cows that had not shown estrus for three months after calving had their reproductive system palpated twice at 10-day intervals, to determine their ovarian activity. Then PRID and/or PGF2α was administered to cows that were found to have a palpable corpus luteum in one of two palpations (cycling cows). The cows of the three induced estrous groups were artificially inseminated (AI) twice, while those with normal estrus received only a single AI. Cervical mucus samples were collected from all cows 5 to 30 min before the first AI. Additionally, samples of cervical mucus were collected from 20 cows at their first estrus after the induced estrus. The results are summarized as follows: 1) The physical properties of cervical mucus were similar in the first three normal consecutive estrus cycles after calving. 2) The physical properties of cervical mucus in normal estrus after calving were similar to those in the first estrus after an induced estrus. 3) The pH values for normal estrus were similar to those for induced estrus. 4) Viscosity of cervical mucus in the normal estrous group was significantly lower than that in the induced estrus. Furthermore, significant differences were noticed among the three induced estrous groups. 5) Spinnbarkeit, crystallization and receptivity of cervical mucus (penetration test) were significantly higher in the normal estrous group than in the induced estrous groups, while no difference was detected among induced estrus groups. 6) Pregnancy rates in physical properties of cervical mucus at the time of the second AI were similar to those for normal estrus but this suggestion needs further investigation. On the other hand, at the time of the first AI very few cows in the induced estrus groups produced cervical mucus similar to that of cows with normal estrus. The physical properties that differed the most were viscosity, spinnbarkeit, and the penetration test. Other authors found that cows do not exhibit estrus at the same determined time (11,26). On the basis of this finding physical properties of cervical mucus could be used as an indicator for the time of estrus manifestation, in order to increase pregnancy rates by applying AI at an optimal time. In summary, the results from the present study showed that the physical properties of cervical mucus in the first three consecutive normal estrous periods after calving are similar; that the first estrus after an induced estrus is a normal estrus; that viscosity, spinnbarkeit, crystallization and receptivity of cervical mucus (penetration test) are significantly different for normal than for induced-estrus groups at the time of first AI; and a small percentage of cows with induced estrus produce cervical mucus with parameters of viscosity, spinnbarkeit and receptivity similar to those found in normal estrus. These properties could be used as indicators for the quality of cervical mucus produced by the cows with induced estrus.