Birth of offspring after artificial insemination of heifers with frozen-thawed, sex-sorted, re-frozen-thawed bull sperm.
Two field trials were conducted to determine the fertilising capacity of (i) frozen-thawed, sex-sorted re-frozen-thawed (FSF) dairy bull sperm inseminated close to the time of ovulation, (ii) FSF sperm following large dose insemination, and frozen-thawed, sex-sorted (FS) sperm inseminated within 12h after sorting. In Trial 1, 24 heifers in synchronised oestrus were observed for standing heat over a 30-min period once every 3h. Upon observation of standing heat, the size of the pre-ovulatory follicle was tracked by ultrasound every 6h until ovulation was judged to be imminent. Heifers were inseminated with 4 x 10(6) X-bearing FSF or Control sperm within 6h of ovulation. Ovaries were scanned 6h after AI to ensure ovulation had occurred. All 24 heifers displayed standing oestrus and 20 of these subsequently ovulated. The mean length of standing oestrus was 16.8+/-0.4h and ovulation occurred 27.6+/-1.1h after the onset of standing heat from a pre-ovulatory follicle with a diameter of 16.1+/-0.3mm. All 12 heifers that received FSF sperm returned to oestrus<26d after AI. Of 8 heifers that received Control sperm, 6 (75%) were confirmed pregnant by ultrasound 7 wk after AI, confirming that the method of AI and herd fertility were sound. In Trial 2 the number of sperm inseminated and the effect of eliminating the post-sort cryopreservation step were investigated. Heifers (n=21) were synchronised for oestrus, and inseminated 24h after the onset of standing oestrus with 10 x 10(6) X-bearing FSF, 4 x 10(6) X-bearing FS, or 10 x 10(6) non-sorted frozen-thawed (Control) sperm. Heifers were observed for return to oestrus from 21d, and diagnosed for pregnancy 7 wk after AI. Of the 7 heifers that received FSF sperm, one was confirmed pregnant (14.3%) and delivered a female calf. Four heifers inseminated with control sperm became pregnant and calved, but no pregnancies were obtained using FS sperm. The birth of a calf following AI with FSF sperm demonstrates the potential of sorting from frozen-thawed semen, and with further work, may be a promising technique that will give producers access to sexed sperm from a greater range of bulls.
Underwood
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SL
The University of Sydney, NSW 2006, Australia. s.underwood@usyd.edu.au
Bathgate
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R
Maxwell
W M C
WM
Evans
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D000818:Animals; D002417:Cattle; D002469:Cell Separation / Q000379:methods / Q000662:veterinary; D015925:Cryopreservation / Q000662:veterinary*; D004973:Estrus Synchronization; D005260:Female; D005298:Fertility / Q000502:physiology; D006358:Hot Temperature; D007315:Insemination, Artificial / Q000379:methods / Q000662:veterinary*; D008297:Male; D006080:Ovarian Follicle / Q000000981:diagnostic imaging; D010061:Ovulation Detection / Q000662:veterinary; D011247:Pregnancy; D012662:Semen Preservation / Q000662:veterinary*; D012732:Sex Determination Analysis / Q000662:veterinary*; D013094:Spermatozoa / Q000166:cytology / Q000502:physiology*; D014463:Ultrasonography