title: The effect of insemination time and sperm dose on pregnancy rate using sex-sorted ram sperm.
abstract: The objective was to determine the optimum timing of insemination and minimum effective dose rate of sex-sorted ram sperm. Semen from three Merino rams was sorted into high purity X- and Y-chromosome bearing sperm populations. Ovulation was controlled in 732 Merino ewes using PMSG at progestagen pessary removal and GnRH 36h later. Sorted (S) and non-sorted (NS) doses of 1 or 15x10(6) motile, frozen-thawed sperm were inseminated laparoscopically at 50, 54, 58, 62, and 66h after progestagen withdrawal. An additional treatment dose of 0.5x10(6) S or NS sperm was inseminated at the 58h time point (n=60). Pregnancy was diagnosed by ultrasound at 60-62 d gestation. Both 1x10(6) and 15x10(6) sperm achieved similar pregnancy rates, regardless of sperm type, at 58h (S1: 46+/-9.4%; S15: 43+/-9.3%; NS1: 41+/-9.2%; NS15: 49+/-9.4%). However, pregnancy rates were lower (P<0.05) for doses of 1 than 15x10(6) sperm inseminated at 50 (15+/-6.3% vs. 36+/-9.1%), 54 (14+/-4.4% vs. 55+/-7.3%), 62 (33+/-6.9% vs. 54+/-7.3%), and 66h (29+/-8.6% vs. 56+/-9.5%). There was no difference between S and NS sperm for inseminations with 0.5x10(6) motile sperm at 58h after PR (15+/-3.6% vs. 14+/-3.3%), nor with 15x10(6) motile sperm at all insemination times (49+/-6.3% vs. 49+/-6.3%). However, fertility was higher for S than NS sperm at the 1x10(6) dose level (37+/-6.1% and 16+/-4.0%). More than 90% of lambs born were of the predicted sex. We hypothesise that the sorting process selects a homogeneous, fertile sub-population of sperm, removing those that are dead, damaged and morphologically abnormal.
authors.affiliation: Faculty of Veterinary Science, The University of Sydney, Sydney, NSW 2006, Australia. kirib@vetsci.usyd.edu.au
authors.forename: K H
authors.initials: KH
authors.lastname: Beilby
authors.forename: C G
authors.initials: CG
authors.lastname: Grupen
authors.forename: P C
authors.initials: PC
authors.lastname: Thomson
authors.forename: W M C
authors.initials: WM
authors.lastname: Maxwell
authors.forename: G
authors.initials: G
authors.lastname: Evans
mesh_terms: D000818:Animals; D002469:Cell Separation / Q000662:veterinary*; D015925:Cryopreservation / Q000662:veterinary; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage; D006064:Gonadotropins, Equine / Q000008:administration & dosage; D007315:Insemination, Artificial / Q000379:methods / Q000662:veterinary*; D008297:Male; D011247:Pregnancy; D011256:Pregnancy Outcome / Q000662:veterinary; D012662:Semen Preservation / Q000662:veterinary; D012732:Sex Determination Analysis / Q000662:veterinary*; D012756:Sheep / Q000502:physiology*; D013076:Sperm Count; D013081:Sperm Motility; D013094:Spermatozoa / Q000166:cytology*; D013997:Time Factors
chemical_list: D006064:Gonadotropins, Equine; D007987:Gonadotropin-Releasing Hormone