|We evaluated pregnancy results after AI of 306 lactating dairy cows, of which 157 were inseminated with 2 Ã 106 frozen/thawed sexed sperm and 149 with 15 Ã 106 frozen/thawed unsexed sperm.
The average pregnancy and calving rates were 21.0% and 20% for the sexed-sperm AIs and 46% and 45% for the unseparated control-sperm AIs respectively (p < 0.001).
The proportion of female calves derived from sexed-sperm AI was 82% compared with 49% for control AI (p < 0.01).
The proportion of live and healthy calves in single births was 100% for sexed-sperm AI and 97% for control AI (p > 0.05).
Our results indicate that AI with low-dose sexed sperm under field conditions in commercial dairy herds without oestrus synchronization results in significantly reduced pregnancy rates compared with normal-dose AI.
Improved insemination strategies combined with increased sperm doses are needed before the use of sexed sperm can be of any significant benefit for the dairy and beef industry.
Source: Andersson, M, Taponen, J, Kommeri, M & Dahlbom, M (2006): Pregnancy Rates in Lactating HolsteinÂFriesian Cows after Artificial Insemination with Sexed Sperm. In: Reproduction in Domestic Animals 41 (2), 95-97.
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