title: Pregnancy rates in heifers and cows with cryopreserved sexed sperm: effects of sperm numbers per inseminate, sorting pressure and sperm storage before sorting.
abstract: Field trials were conducted to increase fertility with AI of flow-sorted, sexed bovine sperm. In the first trial, a novel competitive fertilization approach was used to compare pressures (30psi vs 50psi) for sorting sperm. Both X- and Y-sperm were sorted to approximately 95% purity at 30 and at 50psi; X-50+Y-30 (and the converse) were mixed in equal numbers for AI of heifers. Fetal sex divulged which treatment produced the pregnancy; 82% of pregnancies resulted from the 30psi treatment (P<0.05). Based on a similar approach, a new-pulsed laser did not damage sperm any more than the previous standard continuous wave laser. In a large field trial, sorting sperm at 40psi increased pregnancy rates in heifers relative to 50psi (42.3% vs 34.1%, n=367/group, P<0.05). Storing sperm for 20h before sorting at 40psi decreased pregnancy rates from 42.3% (n=367) to 36.8% (n=368; P<0.05). Breeding heifers with sexed sperm 55-56h after CIDR removal and PGF(2alpha) resulted in 34% (n=32) pregnant, compared to 49% (n=35) with fixed-time insemination 67-68h after CIDR removal (P>0.1). Lactating dairy cows pre-screened for normal reproductive tracts when OvSynch injections (GnRH, prostaglandin, GnRH) were initiated, had similar (P>0.1) pregnancy rates to timed AI, with 10x10(6) sexed sperm (43.9%, n=57), 2x10(6) sexed sperm (40.5%, n=57) and 10x10(6) unsexed control sperm (55.6%, n=58). A final field trial with unselected, lactating dairy cows resulted in similar pregnancy rates for 2x10(6) sexed sperm in 0.25mL straws (25.0%, n=708) and 0.5mL straws (24.4%, n=776), but lower (P<0.05) than unsexed control sperm (37.7%, n=713). Younger cows and those >84 days in milk had the highest pregnancy rates for both sexed and unsexed sperm. These studies improved sperm sexing procedures, and provided insight into appropriate commercial use of sexed sperm.
authors.affiliation: XY Inc., 22575 SH6 South, Navasota, TX 77868, USA.
authors.forename: J L
authors.initials: JL
authors.lastname: Schenk
authors.forename: D G
authors.initials: DG
authors.lastname: Cran
authors.forename: R W
authors.initials: RW
authors.lastname: Everett
authors.forename: G E
authors.initials: GE
authors.lastname: Seidel
mesh_terms: D000818:Animals; D001562:Benzimidazoles; D002417:Cattle / Q000502:physiology*; D002469:Cell Separation / Q000379:methods; D015925:Cryopreservation / Q000662:veterinary*; D005260:Female; D005434:Flow Cytometry / Q000662:veterinary; D005456:Fluorescent Dyes; D007315:Insemination, Artificial / Q000379:methods / Q000662:veterinary*; D007774:Lactation; D008297:Male; D011247:Pregnancy; D011312:Pressure; D012662:Semen Preservation / Q000662:veterinary*; D012730:Sex Chromosomes; D012732:Sex Determination Analysis / Q000662:veterinary*; D013076:Sperm Count / Q000662:veterinary*; D013081:Sperm Motility
chemical_list: D001562:Benzimidazoles; D005456:Fluorescent Dyes; C017807:bisbenzimide ethoxide trihydrochloride