Abstract:

To explore the effect of fixed-time artificial insemination (FTAI) on earlier embryonic development and fertility of gilts, in experiment 1, totally 43 gilts (Jinwu pig) were randomly divided into control (n=24) and FTAI groups (n=19). The control group were natural estrus, and performed artificial insemination (AIs) after a standing reflex, and the FTAI group were performed AIs after administration of altrenogest+pregnant mare serum gonadotropin (PMSG)+gonadotropin releasing hormone (GnRH) (ALT+PMSG+GnRH). Blood samples were collected for detecting of the concentration of progesteron (P4), estradiol (E2), follicle-stimulating hormone (FSH) and luteinizing hormone (LH) at 0 h (stop feeding altrenogest), 42 h (intramuscular injection of PMSG) and 122 h (intramuscular injection of GnRH). Four gilts of each group were slaughtered at 33 h after AIs, and the fertilized eggs were recovered for in vitro culture, the remaining gilts were used to observe the fertility. The results showed that concentration of progesterone were downregulated from 0 h to 122 h, but there was no significant difference(P>0.05). Estradiol levels were dropped from 80 pmol·L^-1 to 58.3 pmol·L^-1 (P<0.05) during 0 h to 42 h, but dramatically increased to 134.07 pmol·L^-1 from 42 h to 122 h (P<0.01). FSH value showed no significant difference (P>0.05). The concentration of luteinizing hormone increased gradually from 0.09 IU·L^-1 to 0.12 IU·L^-1, and decreased to 0.09 IU·L^-1 at these three time points, showing a up and down trend, which conformed the trend of normal physiological cycle, indicating the administration was reasonable and had no side effects. The ovaries were collected from the control and FTAI groups at 33 h after AIs, the ovulation point were counted, showing that there was no significant difference (P>0.05) between FTAI group (17.5) and control group (15.25). Meanwhile, compared with the control group, the litter size and alive litter size of FTAI group did not show significant difference (P>0.05), but the litter size and alive litter size of FTAI group were all increase of 1.05 heads relatively. In experiment 2, totally 189 gilts (Yorkshire×Landrace) were randomly divided into control (n=95) and FTAI groups (n=94). The alive litter size of FTAI group was increased 0.58 heads, and the weaning survival rate increased 2.99 percentage point compared with the control group. In summary, the administration of FTAI procedure was conforming to the characteristics of gilts physiological estrous cycle, and might increase the ovulation number without adverse effects on the earlier embryos development. Meanwhile, the FTAI procedure had a positive effect on improving the utilization of gilts and increasing the alive litter size and survival rate of weaning piglets to a certain degree, which was worthy of further optimization, promotion and application.

Key words: fixed-time artificial insemination, gilt, embryo, reproduction performance