| Large-scale pig farms in developed countries such as Germany have established a batch-based production management method with fixed-time artificial.insemination technology and pig production can achieve a high level of reproduction while realizing all-in and all-out manufacturing state.Application of fixed-time artificial.insemination procedures can greatly improve the production efficiency,reduce labor costs,and prevent cross-infection of individual diseases on pig farms.It has become the development direction of pig production system.However,the application of this technology in China’s pig industry system is still in its infancy,and there are practical problems such as increased embryo death during attachment,reduced uterine tolerance and low fertility rates in sows.Therefore,it is particularly important to optimize the existing timed,insemination procedure to improve the conception rate and litter size of the sow.The present study compared the reproductive efficiency among three models of natural estrus state,the timed artificial insemination procedure(only feeding methionin to regulate the estrus cycle)and the fixed-time artificial.insemination procedure(using estrus,follicular development,ovulation regulation hormones)in gilts.According to the initial ovarian states of the gilts before and after hormone treatments,the effects of fixed-time artificial insemination procedures on follicular development and ovulation were examined and a reliable optimization program were recommended.The research results are as follows:1.Effects of different insemination procedures on reproductive efficiency in giltsA total of 286 healthy gilts from 220 to 240 days old were randomly divided into natural estrus group,timed artificial insemination group and fixed-time artificial.insemination group(the number of samples is 92,95 and 99 heads,respeictively in three groups).The gilts in 1st group were subjected to three consecutive artificial inseminations(AI)during their natural estrus,while,gilts in the timed artificial insemination group and the fixed-time artificial insemination group were subjected to three consecutive AI according to the suggested procedures.The production status and delivery rate,litter size and litter size of gilts in each group was recorded.Statistical analysis showed that no significant difference in the number(P>0.05)was observed.The gilt uniformity of the gilts treated by the fixed-time artificial.insemination procedure was significantly higher than that of the timed artificial insemination group and the control group(P<0.05).2.Effects of ovarian status of the gilts on follicular development and ovulation before and after hormone treatmentAccording to the ovarian status,the healthy gilts from 200 to 240 days old were divided into the corpus luteum group,the red body group and the follicle group.Each group randomly selected 11 gilts for fixed-time artificial.insemination procedure treatment 5 gilts were randomly selected from each group and sacrified after 80 hours of PMSG injection.6 gilts of them were sacrified at the precise serotonin treatment procedure and 12 hours after the second AI.The follicle number and ovulation in each group after injection of PMSG for 80 h were observed.The results showed that no significant difference was found in the number of follicles among three groups(P>0.05).While,the number of follicles with 4 and 6 mm diameters in the corpus luteum group was significantly higher than those in the red body group and the follicle group(P<0.05).The results showed that the ovarian diameter of the gilts observed after 12 hours of AI was not related to the initial state of the ovary(P>0.05),while,the number of follicles with a diameter of 8 mm was significantly higher than that of the corpus luteum and red body(P<0.05).The number of follicles with a diameter of 4 mm was significantly higher than that of the corpus luteum group(P<0.05),and there was no significant difference between the follicular group and the red body group(P>0.05).The number of ovulations in each group according to the statistics of the number of fertilized eggs,the number of ovulation in the gilts was significantly higher than that of the corpus luteum group(P<0.05),which was also significantly higher than that of the red body group.The number of fertilized eggs in each group showed similar tenddency(P<0.05).The number of fertilized eggs recovered from the fallopian tubes and uterus was also significantly higher than that of the corpus luteum group and the red body group.The experimental results suggested that the gilts in the follicular phase were more favorable for increasing ovulation rates and early embryo nunbers when the serotonin treatment procedure was started. |
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