title: Effect of insemination timing on the fertilizing capacity of frozen/thawed equine spermatozoa.
abstract: A breeding trial was conducted to evaluate the effect of insemination timing on the fertility of mares bred with frozen/thawed equine semen. One stallion and 60 reproductively sound, estrous-synchronized mares were included in the study. Mares were assigned to one of three groups (n = 20): 1) insemination with fresh semen every other day during estrus from detection of a 35-mm follicle until ovulation, 2) insemination with frozen/thawed semen every day during estrus from detection of a 35-mm follicle until ovulation or 3) insemination with frozen/thawed semen once, within 6 h after ovulation. Single-cycle 18-d pregnancy rates resulting from insemination with fresh semen (70%), preovulation insemination with frozen/thawed semen (60%) and postovulation insemination with frozen/thawed semen (55%) were not different (P > 0.05). Possibly, equivalent pregnancy rates could be achieved with frozen/thawed semen using either daily inseminations until ovulation occurs or frequent ovarian palpations with a single post-ovulation insemination. Further studies regarding the effect of insemination timing on stallion fertility are needed since the present investigation included only one stallion and a small number of mares.
authors.affiliation: Department of Large Animal Medicine and Surgery College of Veterinary Medicine Texas A&M University College Station, Texas 77843 USA.
authors.forename: L H
authors.initials: LH
authors.lastname: Kloppe
authors.forename: D D
authors.initials: DD
authors.lastname: Varner
authors.forename: R G
authors.initials: RG
authors.lastname: Elmore
authors.forename: K N
authors.initials: KN
authors.lastname: Bretzlaff
authors.forename: J W
authors.initials: JW
authors.lastname: Shull