| Uterine involution is a necessary temporary barrier during cow’s reproductive life. Understand the law of embryonic development and uterine involution postpartum has an important significance for the appropriate program of production and management, and develop new technologies of improve the estrus rate, conception rate and embryo survival rates.In total,109one to nine parities Chinese Holstein cows (primiparous (n=28), biparous(n=20),24calving the third time,17calving the forth time and20calving for the fifth to ninth time) included in present study. Diameter of cervical and uterine horns(gravid uterine horn and non-gravid uterine horn) ultrasonographic observations starting at7d after calving were performed every3days till resumption. A total of44pregnancies Chinese Holstein dairy cows (12primiparous,11biparous,8calving the third time,4calving the forth time and9calving for the fifty to ninth time)) were conclused. Diameter of uterine horns (gravid uterine horn and non-gravid uterine horn) and Crown rump length (CRL) ultrasonographic observations starting at about30d after pregnancies were performed every30days till gestational days96. Gestational age (GA) was used as the independent variable and to build different growth curves. The study of the change law of embryo/fetal and uterine in28-96gestational days, also statistically embryo/fetal mortality and analyze the reasons. The main results are as follows:1. Study on uterine involution of Chinese Holstein dairy cows(1)Interval (days) from calving to involution of the previous non-gravid horn was shortest, followed by gravid uterine horn, while maximum time is needed by uterine cervix.(2)Interval (days) from calving to the involution of the previous gravid uterine horn in multiparous cows (27.1±3.1days) was significantly shorter than that in biparous and primiparous cows (P<0.05) whereas, no significant difference (P>0.05) of parity was found between non-gravid horn and uterine cervix.(3) At2-4years of age, interval from calving to uterine involution was quickest; however, this interval was increased after that. At age2, uterine involution was significantly lower than at age4. Similarly, up to age3, gravid or non gravid uterine horn involution was found faster (P<0.05) than at age4. The gravid uterine horn involution interval at age3was significantly than that in age after4(P<0.05), age before3was significantly than that in age4(P<0.05).The non-gravid horn involution interval in age before3was significantly than that in age after4(P<0.05).(4) Diameter (mm) from calving to the involution of the previous uterine cervix in primiparous cows was significantly smaller than that in biparous and multiparous cows (P<0.01). Similarly diameter (mm) from calving to the involution of the previous non-gravid horn in primiparous cows was significantly smaller than that in biparous and multiparous cows (P<0.05). No significant difference of parity was found among non-gravid horn, gravid uterine horn, or uterine cervix.(5) Diameter (mm) from calving to the involution of uterus gradually increases with age. No significant difference of age was found in gravid uterine horn. At age2, diameter of the non-gravid horn involution was significant than at age4or after (P<0.01). Diameter of the uterine cervix involution at age3or before was significantly lower than that of age4or after (P<0.01)2. Study on law of embryo/fetal in Chinese Holstein dairy cows(1)Pregnancy losses in30-60days after AI of Chinese Holstein cows were25%while27.3%after60-90days.(2) For1st three months (28-96days) changes in the non-gravid horn’s diameter are relatively slow (before60days). But changes in the gravid horn’s diameter are relatively slow (before60days) and linear in1st three months (28-96days). Up to96days, this diameter difference between two uterine horns widens from32±4.2mm (gestational days28) to118±6.6mm(gestational days96).(3) Correlation and regression analysis was used to find the best-fit regression model and establish best-fit equations to obtain the predicted CRL and diameter of uterine horns in28-96gestational days using GA(gestational age) as the independent variable and the growth curves are as follows:CRL(mm)=-67.1966+2.2982x DAY for gestations of30to90days,(r=0.9664, P<0.01); Diameter of gravid horn(mm)=-35.7564+2.0600×DAY(r=0.8714, P <0.01)... |
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