title: Insemination of mares with low numbers of either unsexed or sexed spermatozoa.
abstract: Two experiments were conducted to determine pregnancy rates in mares inseminated 1) with 5, 25 and 500 x 10(6) progressively motile spermatozoa (pms), or 2) with 25 x 10(6) sex-sorted cells. In Experiment 1, mares were assigned to 1 of 3 treatments: Group 1 (n=20) was inseminated into the uterine body with 500 x 10(6) pms. Group 2 (n=21) and Group 3 (n=20) were inseminated into the tip of the uterine horn ipsilateral to the preovulatory follicle with 25 and 5 x 10(6) pms, respectively. Mares in all 3 groups were inseminated either 40 (n=32) or 34 h (n=29) after GnRH administration. More mares became pregnant when inseminated with 500 x 10(6) (18/20 = 90%) than with 25 x 10(6) pms (12/21 = 57%; P<0.05), but pregnancy rates were similar for mares inseminated with 25 x 10(6) vs 5 x 10(6) pms (7/20 = 35%) (P>0.1). In Experiment 2, mares were assigned to 1 of 2 treatments: Group A (n=11) was inseminated with 25 x 10(6) spermatozoa sorted into X and Y chromosome-bearing populations in a skimmilk extender. Group B (n=10) mares were inseminated similarly except that spermatozoa were sorted into the skimmilk extender + 4% egg yolk. Inseminations were performed 34 h after GnRH administration. Freshly collected semen was incubated in 224 microM Hoechst 33342 at 400 x 10(6) sperm/mL in HBGM-3 for 1 hr at 35 degrees C and then diluted to 100 x 10(6) sperm/mL for sorting. Sperm were sorted by sex using flow cytometer/cell sorters. Spermatozoa were collected at approximately 900 cells/sec into either the extender alone (Group A) or extender + 4% egg yolk (Group B), centrifuged and suspended to 25 x 10 sperm/mL and immediately inseminated. Pregnancy rates were similar (P>0.1) between the sperm treatments (extender alone = 13/10, 30% vs 4% EY + extender = 5/10, 50%). Based on ultrasonography, fetal sex at 60 to 70 d correlated perfectly with the sex of the sperm inseminated, demonstrating that foals of predetermined sex can be obtained following nonsurgical insemination with sexed spermatozoa.
authors.affiliation: Animal Reproduction and Biotechnology Laboratory, Colorado State University, Fort Collins 80523, USA.
authors.forename: B R
authors.initials: BR
authors.lastname: Buchanan
authors.forename: G E
authors.initials: GE
authors.lastname: Seidel
authors.forename: P M
authors.initials: PM
authors.lastname: McCue
authors.forename: J L
authors.initials: JL
authors.lastname: Schenk
authors.forename: L A
authors.initials: LA
authors.lastname: Herickhoff
authors.forename: E L
authors.initials: EL
authors.lastname: Squires
mesh_terms: D000818:Animals; D002469:Cell Separation; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage; D006736:Horses; D007315:Insemination, Artificial / Q000379:methods / Q000662:veterinary*; D008297:Male; D010060:Ovulation; D011247:Pregnancy; D019849:Sex Determination Processes; D013076:Sperm Count
chemical_list: D007987:Gonadotropin-Releasing Hormone