Factors of affecting pregnancy following AI of dairy cattle with frozen-thawed sexed semen
Controlling the sex of domestic mammalian offspring is important for an efficient animal husbandry.The technique separating living X-and Y-chromosome-bearing sperm and inseminating with semen of desired sex has been proved the most feasible and simple method for sex control.However,pregnancy rates of insemination with low does of sexed sperm have been low compared to conventional AI,and therefore,procedures involved in AI using sexed sperm remain to be optimized.Factors of affecting pregnancy following AI of dairy cattle with frozen-thawed sexed semen,such as thawing protocols,time and site for semen deposition,different technicians and heifers or cows,were observed with conventional and diluted conventional cryopreserved semen as controls.The results ob-tained are as follows.(1) Both bathing temperature and duration during thawing had marked effect on pregnancy rates,and the sexed sperm were more sensitive to bating temperature.(2) The time window for insemination with high pregnancy rates was narrower for sexed semen and diluted conventional semen than for undiluted semen.(3) Higher pregnancy rates were obtained with all the three kinds of sperm when inseminates were deposited in the basal uterine horn ipsilateral to the ovulatory follicle than when semen was inseminated into either the uterine horn near the utero-tubal junction or the uterine body.(4) Pregnancy rates in heifers (80%) were significantly higher than in cows (50%) with all the three types of semen.(5) Injection of heifers with LHRH-A_3 following insemination in-creased pregnancy rates significantly with all the three types of semen.(6) No significant difference was observed a-mong the five technicians proven skillful for embryo transfer techniques in pregnancy rates following inseminations.(7) Under different conditions examined,sexed sperm behaved similar to diluted conventional sperm,indicating pro-cedures for sperm sorting caused no special damage to sexed sperm.It is concluded that pregnancy rates as high as conventional AI can be achieved with sexed semen as long as management (nutrition,disease control,estrus detec-tion,semen handling and insemination techniques) is excellent.
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