title: Characteristics and functions of a minor FSH surge near the end of an interovulatory interval in Bos taurus heifers.
abstract: The apparent function of a minor FSH surge based on temporality with follicular events was studied in 10 heifers with 2 follicular waves per interovulatory interval. Individual follicles were tracked from their emergence at 2 mm until their outcome was known, and a blood sample was collected for FSH and LH assay every 12 h from day -14 (day 0 = ovulation) to day 4. A minor FSH surge occurred in each heifer (peak, day -4.6 ± 0.2). Concentration of LH increased (P < 0.05) during the FSH increase of the minor surge but did not decrease during the FSH decrease. A minor follicular wave with 8.2 ± 2.0 follicles occurred in 6 of 10 heifers. The maximal diameter (mean, 3.4 ± 0.9 mm) of 77% of the minor-wave follicles occurred in synchrony on day -4.4 ± 0.4. Most (59%) of minor-wave follicles regressed before ovulation and 41% decreased and then increased in diameter (recovered) on day -1.9 ± 0.3 to become part of the subsequent wave 1. A mean of 3.7 ± 0.9 regressing subordinate follicles from wave 2 recovered on the day before or at the peak of the minor FSH surge. The growth rate of the preovulatory follicle decreased (P < 0.02) for 3 d before the peak of the minor FSH surge and then increased (P < 0.03). Concentration of LH increased slightly but significantly temporally with the resurgence in growth rate of the preovulatory follicle. A minor LH surge peaked (P < 0.0002) on day 3 at the expected deviation in growth rates between the future dominant and subordinate follicles. Results indicated on a temporal basis that the recovery of some regressing subordinate follicles of wave 2 was attributable to the minor FSH surge. The hypothesis was supported that some regressing follicles from the minor follicular wave recover to become part of wave 1.
authors.affiliation: Eutheria Foundation, Cross Plains, WI 53528, USA; Pathobiological Sciences Department, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, WI 53706, USA. Electronic address: oj.ginther@wisc.edu.
authors.forename: O J
authors.initials: OJ
authors.lastname: Ginther
authors.affiliation: Eutheria Foundation, Cross Plains, WI 53528, USA.
authors.forename: J M
authors.initials: JM
authors.lastname: Baldrighi
authors.affiliation: Eutheria Foundation, Cross Plains, WI 53528, USA; Pathobiological Sciences Department, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, WI 53706, USA.
authors.forename: M A R
authors.initials: MA
authors.lastname: Siddiqui
authors.affiliation: Pathobiological Sciences Department, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, WI 53706, USA; CAPES Foundation, Ministry of Education of Brazil, Brasilia, DF 70040-020.
authors.forename: C A
authors.initials: CA
authors.lastname: Wolf
mesh_terms: D000818:Animals; D002417:Cattle / Q000097:blood*; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood*; D007986:Luteinizing Hormone / Q000097:blood; D006080:Ovarian Follicle / Q000502:physiology; D010060:Ovulation / Q000502:physiology*; D013997:Time Factors
chemical_list: D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone
keywords: Follicle recovery; LH; Minor FSH surge; Minor follicular wave; Preovulatory follicle