Location: Range and Livestock ResearchTitle: Circulating concentrations of pregnancy associated glycoproteins (PAGs) are associated with embryo/fetal survival but not ovulatory follicle size in suckled beef cows Author
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/1/2010
Publication Date: 9/3/2010
Citation: Pohler, K.G., Atkins, J.A., Jinks, E.M., Johnson, C.L., Smith, M.F., Green, M.F., Macneil, M.D., Geary, T.W. 2010. Circulating concentrations of pregnancy associated glycoproteins (PAGs) are associated with embryo/fetal survival but not ovulatory follicle size in suckled beef cows. 8th International Ruminant Reproduction Symposium Abstract #119. Interpretive Summary:
Technical Abstract: GnRH-induced ovulation of small dominant follicles resulted in increased late embryonic/fetal mortality around the time of embryo-uterine attachment. Pregnancy associated glycoproteins (PAGs) are secreted by binucleated trophoblast cells into the maternal circulation and have been used to monitor the presence of an embryo/fetus and placental function. The objective of this study was to examine the relationship between ovulatory follicle size, embryo/fetal survival, and circulating concentrations of PAGs. In experiment 1, postpartum beef cows (n = 69) were treated with the CO-Synch protocol (GnRH1 on d -9, PGF2a on d -2, and GnRH2 and artificial insemination [AI] 48 h later [d 0]) and classified into one of four ovulatory follicle size groups: 1) small follicle (= 12 mm; n = 9), 2) small-medium follicle (12-13 mm; n = 20), 3) medium-large follicle (14-15 mm; n = 28 ) or 4) large follicle (= 16 mm; n = 12). The first increase (P<0.0001) in serum concentration of PAGs after insemination occurred on d 24 and concentration of PAGs decreased before a decrease in progesterone in cows that lost an embryo/fetus. The PAG secretion pattern from d 24 to 60 after insemination (d 0) was affected by day (P < 0.0001), but not ovulatory follicle size or the interaction of ovulatory follicle size by day. In experiment 2, suckled beef cows (n = 1,166) were administered the CO-Synch protocol either with (donor cows; n = 810) or without (recipient cows; n = 354) AI on d 0. Single embryos (n = 394) or oocytes (n = 45) were recovered from the donor cows (d 7; ET) and all live embryos were transferred into recipients the same day. Embryos from cows that ovulated a small (< 12.5 mm) or large follicle (= 12.5 mm) were transferred into cows that ovulated either a small or large follicle to remove co-linearity of follicle sizes pre- and post- day 7 of pregnancy; small to small (S-S; n = 71), small to large (S-L; n = 111), large to small (L-S; n = 122) and large to large (L-L; n = 50). The following results only include cows that established pregnancy at d 27 (n = 195). Compared to cows that maintained pregnancy, cows that exhibited late embryonic/fetal mortality after d 27 had decreased (P < 0.05) concentrations of PAGs on d 27. Serum concentration of PAGs at d 27 was not affected by ovulatory follicle size (P = 0.85), embryo stage at ET (P = 0.75), embryo quality at ET (P = 0.64), or estradiol at GnRH2 (P = 0.62). In summary, there was no relationship between PAGs and ovulatory follicle size or serum concentrations of estradiol at GnRH2, embryo stage or quality on d 7; however, cows that lost an embryo after d 27 had lower concentrations of PAGs on d 27 compared to cows that maintained pregnancy. Supported by NRI grant 2006-35203-17284 from USDA-CSREES.