Chemical properties of bovine cervical mucus during normal estrus and estrus induced by progesterone and/or PGF2alpha.

Ninety-two Friesian cows were used to determine the chemical properties of cervical mucus during normal estrus and estrus induced by progesterone (P4)-releasing intravaginal devices (PRID) and/or prostaglandin F2alpha. The animals were assigned to 4 groups (no treatment, a PRID for 12 days plus injection of 1000 IU PMSG at the removal of PRID, a double i.m. injection of PGF2alpha 11 days apart, or PRID for 7 days plus an im injection of PGF2alpha 24 h before the removal of PRID). A number of cows with normal estrus exhibited three consecutive estrous cycles after delivery. Cows that had not shown estrus for 3 months after delivery had their ovaries palpated twice at 10-day intervals, to determine their ovarian activity. Then PRID and/or PGF2alpha was administered in cows that had a palpable corpus luteum in one of the two palpations (cyclic cows). A double artificial insemination (AI) was performed to the cows of the three induced-estrus groups, while the cows with normal estrus received only one 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 during their first estrus after the induced one. The results are summarized as follows: 1) The biochemical properties of cervical mucus in the first three estrus periods after delivery were similar. 2) These properties were similar both in normal estrus after delivery and in the first estrus after an induced one. 3) Glucose and fructose concentrations for normal estrus were similar to those for induced estrus groups. 4) Total protein and cholesterol concentrations were significantly lower (P < 0.001) in normal than in induced estrus, while no difference was found among the induced estrus groups. 5) Pregnancy rates of the cows did not differ significantly among the normal and the induced-estrus groups. 6) The percentages of cows in the induced-estrus groups that produced cervical mucus with total protein and cholesterol concentrations similar to those for the normal estrus groups was very low.