Uterine horn insemination of heifers with very low numbers of nonfrozen and sexed spermatozoa
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Experiments were conducted to determine 1) pregnancy rates of heifers inseminated with very low numbers of spermatozoa under ideal field conditions, and 2) pregnancy rates with low doses of sexed spermatozoa. In Experiment 1, semen from 3 Holstein bulls was extended to 1 x 10 5 or 2.5 x 10 5 sperm/0.1 ml; 2.5 x 10 6 total sperm/0.21 ml were used for the control. Semen was cooled to 5C. packaged into modified 0.25-ml French straws, and used 26 to 57 h after collection. Spermatozoa were inseminated 24 h after detection of estrus into the uterine horn of Holstein heifers ipsilateral to the ovary with the largest follicle, as determined by ultrasound 12 h after estrus was detected; side of ovulation was verified by detection of a corpus luteum (CL) by ultrasound 7 to 9 d post estrus. Pregnancy was determined 40 to 45 d post estrus. The side of ovulation was determined correctly in 262 of 286 heifers (92%), and pregnancy rates were nearly identical for ipsilateral and contralateral inseminations. Pregnancy rates were 48/118 (41%), 56/111 (50%), and 35/57 (61%) for 1 x 10 5 , 2.5 x 10 5 and 2.5 x 10 6 sperm per insemination (P<.05 between 1 x 10 5 and 2.5 x 10 6 ). There were no significant differences in pregnancy rates (P>.05) among the heifers for the 3 AI technicians or the 3 bulls. In Experiment 2, freshly collected semen with transported from Lancaster, Pennsylvania to Beltsville, Maryland, and sorted into X- and Y-sperm populations based on DNA difference using a flow cytometer/cell sorter over a 6-h period. Sorting rates were about 10 100 sperm/sec of each sex at ~90% purity. Sorted spermatozoa were shipped ~2600 km by air, and in most cases cooled to 5C during shipping over 6 in an Equitainer. Heifers were inseminated with 1 to 2 x 10 5 sorted X- or Y- spermatozoa in 0.1 ml within 9 to 29 h of sorting. The inseminate was either deposited into the uterine horn ipsilateral to the ovary with the largest follicle as determined by ultrasound at the time of insemination, or half of the inseminate was deposited into each uterine horn. None of 10 heifers became pregnant when inseminated with sexed spermatozoa shipped at ambient temperature. Of the 155 heifers inseminated with sexed spermatozoa cooled to 5C, 15 of 67 females (22.4%) inseminated 9 to 13 h post sorting calved, but only 2 of 78 (2.6%) inseminated at 17 to 29 h calved. Fourteen of the 17 calves born (82%) were of the selected sex.
