title: Effect of time of artificial insemination on embryo sex ratio in dairy cattle.
abstract: The objective of the present study was to examine whether different intervals between insemination and ovulation have an influence on the sex of seven-day-old embryos in dairy cattle. Cows were inseminated once with semen of one of two bulls of proven fertility between 36 h before ovulation and 12 h after ovulation. Time of ovulation was assessed by ultrasound at 4-h intervals. In total, 64 embryos were determined to be male or female. Of these 64 embryos, 51.6% were female. The sex ratio in the various insemination-ovulation intervals (early: between 36 and 20 h before ovulation; intermediate: between 20 and 8 h before ovulation; late: between 8 h before and 12 h after ovulation) did not significantly differ from the expected 1:1 sex ratio (50, 50 and 55% females, respectively). Bull (Bull A and B) and Parity (primiparous and multiparous) had no influence on the expected 1:1 sex ratio either. The number of cell cycles was similar for male and female (P = 0.23) embryos when quality of the embryo (P < 0.0001) was included in the model. The results of this study indicate that, in cattle, the interval between insemination and ovulation does not influence the sex ratio of seven-day-old embryos.
authors.affiliation: Adaptation Physiology, Department of Animal Science, Wageningen University, P.O. Box 338, 6700 AH Wageningen, The Netherlands.
authors.forename: J B
authors.initials: JB
authors.lastname: Roelofs
authors.forename: E B
authors.initials: EB
authors.lastname: Bouwman
authors.forename: H G
authors.initials: HG
authors.lastname: Pedersen
authors.forename: Z Riestra
authors.initials: ZR
authors.lastname: Rasmussen
authors.forename: N M
authors.initials: NM
authors.lastname: Soede
authors.forename: P D
authors.initials: PD
authors.lastname: Thomsen
authors.forename: B
authors.initials: B
authors.lastname: Kemp
mesh_terms: D000818:Animals; D002417:Cattle / Q000196:embryology*; D004622:Embryo, Mammalian / Q000502:physiology; D005260:Female; D007315:Insemination, Artificial / Q000379:methods* / Q000662:veterinary*; D008297:Male; D010053:Ovary / Q000000981:diagnostic imaging; D010060:Ovulation; D010298:Parity; D011247:Pregnancy; D012732:Sex Determination Analysis; D012744:Sex Ratio; D013997:Time Factors; D014463:Ultrasonography