Submitted to: Theriogenology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/21/1997
Publication Date: N/A
Citation: Interpretive Summary: Gender preselection in cattle is a highly desired technology for upgrading genetic stock more efficiently. Prior to these studies, the Beltsville Sperm Sexing Technology was only applicable in conjunction with in vitro fertilization and subsequent embryo transfer. This collaborative study showed an improved application for the sexing technology with the use of deep uterine insemination. This technique allowed the use of much smaller numbers of sperm than previously thought possible (200,000 sperm) in order to obtain pregnancies. A total of 17 calves were born from inseminations of sexed semen sorted for X or Y sperm. The proportion of correct sexed offspring was 82%. These results will be used by scientists to perfect the adaptation of the sexing technology to a larger application and will likely be the basis for commercial companies offering the technology on a much wider basis.
Technical Abstract: Experiments were conducted to determine pregnancy rates of heifers inseminated with very low numbers of sperm under ideal experimental conditions, and to determine pregnancy rates with low doses of sexed semen. In Experiment 1, semen from three Holstein bulls was extended to 1 X 100,000 or 2.5 x 100,000 sperm per 0.1 ml; 2.5 x 1,000,000 total sperm per 0.21 ml was used as a control. Semen was cooled to 5 degrees C, packaged into modified 0.25 ml French straws, and used 26-57 hr after collection. Pregnancy rates were 48/118 (41%), 456/111 (50%), and 35/57 (61%) for 1 x 100,000, 2.5 x 100,000 and 2.5 x 1,000,000 sperm/inseminate (P<.05 between 1 x 100,000 and 2.5 x 1,000,000). In Experiment 2, freshly collected semen was sorted into X and Y sperm populations based on DNA difference using a flow cytometer/cell sorter over a 6-hr period. Sorting rates were about 100 sperm\sec of each sex at about 90% purity. Sorted sperm were shipped about 2600 km by air, and in most cases cooled to 5 degrees C during shipping over 6 hr in an Equitainer. Heifers were insemination with 1 to 2 x 10,000 X- or Y-sorted spermatozoa in 0.1 ml within 9 to 29 hr of the end of the sperm sorting session. Sperm were deposited: 1) deep in the uterine horn ipsilateral to the ovary with the largest follicle as determined by ultrasound at the time of insemination, or 2) half the inseminate into each uterine horn. None of 10 females became pregnant when inseminated with sexed sperm shipped at ambient temperature. Of 155 females inseminated with sexed sperm cooled to 5 degrees C, 17 (11%) calved. Fifteen of 67 females (22.4%) inseminated 9-13 hours post-sorting calved, but only 2 or 78 (2.6%) inseminated at 17-29 hours calved. Fourteen of the 17 calves born (82%) were of the selected sex.