| This study aimed to breeding young bulls and rapidly reproduce heifers to support the dairy breeding industry of China,followed by establishment of the key breeding technology system,and also developed the new technology and products of sexed frozen semen,and realized the large-scale industrial application.The breeding technology system in dairy cattle include embryo production and transplantation(ET),dairy herd improvement(DHI)and whole genome detection of young bulls,correlation analysis of sexed semen between in vitro fertilization(IVF)and artificial insemination(AI)conception rate.For development of new technology and product in dairy cattle,Those key points including increase the efficiency of sexed semen production and improve product quality.The results are as follows:1.An efficient system of in vivo and in vitro embryo production and ET was established in dairy cattle breeding.The average number of in vivo embryos produced from each donor cow reached 6.6,which was increased 32.0%compared with industry level of 5.The conception rate after ET was 45.0-58.6%and the calving rate was 38.4-55.8%,respectively,which both was higher than the industry level.2.A comparative evaluation system of young bulls were established by using the whole genome detection combined with the DHI.The key indicators of the growth and development of young bulls were statistically analyzed,both of the body weight and average circumference of testis were higher than the average level of the industry standard;154 dairy bulls with the highest genetic quality were selected,including 22.7%of 35 dairy bulls in total with GTPI(General Total Performance Index)?2600 index;The milk production from selected seed dairy cows,which were increased to 823.0 kg,1374.5 kg and 976.7 kg compared with normal production level in first,second and third parity,respectively.These results show the significant correlation between the whole genome detection evaluation and the DHI results.3.There was a high correlation between the IVF fertilization rate and the AI rate in same bull,which can be used as a new index to evaluate bull genetic quality.Following these results,we divided into three fertility grades of dairy bulls for:normal fertilization bulls(45-60%),higher fertilization bulls(61-80%),and highest fertilization bulls(>80%)for fertility evaluation of dairy bulls new index.4.The effect of sperm flow improving from goat,sheep and deer on the sexed semen fertilization in dairy cattle were compared,showed goat semen was the best.The new standard of sexed frozen semen product for dairy cattle was 1 million separated X sperm plus 1 million goat sperm,which technology increase 2 times of sexed semen production and also decrease 70%of product cost at same time compared with industry level.This product of sexed semen could keep the average56.2%of conception rate and 94.6%of the sexed accuracy rate following AI.5.The combination of antioxidant V_E,SOD and CAT can increase the motility of sexed semen,especially they can expending the survival time of sexed semen from4-6 h to 8-10 h,which generally improved the AI conception rate 5-10%following the field test and support the industrial application of sexed semen in dairy industry. |
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