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United States Department of Agriculture

Agricultural Research Service

Research Project: Alleviating Rate Limiting Factors that Compromise Beef Production Efficiency

Location: Livestock and Range Research Laboratory (LARRL)

Title: Circulating bovine pregnancy associated glycoproteins (bPAGs) are associated with late embryonic/fetal survival but not ovulatory follicle size in suckled beef cows

Authors
item Pohler, K -
item Geary, Thomas
item Johnson, C -
item Atkins, J -
item Jinks, E -
item Busch, D -
item Green, J -
item Macneil, M -
item Smith, M -

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 2, 2013
Publication Date: September 1, 2013
Citation: Pohler, K.G., Geary, T.W., Johnson, C.L., Atkins, J.A., Jinks, E.M., Busch, D.C., Green, J.A., Macneil, M.D., Smith, M.F. 2013. Circulating bovine pregnancy associated glycoproteins (bPAGs) are associated with late embryonic/fetal survival but not ovulatory follicle size in suckled beef cows. Journal of Animal Science. 91:4158-4167.

Interpretive Summary: During early pregnancy in cattle, several pregnancy specific proteins known as bPAGs are produced. One factor that is known to result in pregnancy loss is induced ovulation of a small follicle from the ovary. The objective of this study was to examine the relationship between ovulatory follicle size, embryo survival, and blood levels of bPAGs. In experiment 1, beef cows were classified into one of two ovulatory follicle size groups at time of breeding (small or large follicle). The first increase in blood bPAG levels occurred in pregnant cows on day 24 after breeding. Blood bPAG levels decreased before a decrease in progesterone in three of four cows that lost a pregnancy. Pattern of secretion of bPAGs in blood from day 24 to 60 after breeding was not affected by ovulatory follicle size. The half-life of bPAGs in circulation was determined in experiment 2. The half-life of bPAGs following prostaglandin treatment on day 32 to 36 after breeding was 35.8 ± 21.9 h (mean ± SD; range 7.1 to 78.5 h). In experiment 3, embryo transfer was used to identify other factors that might affect blood bPAGs in beef cows were evaluated. Some cows provided embryos for this study and other cows received these embryos to evaluate pregnancy. Ovulation was induced (day 0) in all cows. Ovulatory follicle size and blood estradiol level on day 0, and embryo stage, embryo quality, and blood progesterone level on day 7 were compared to day 28 bPAG levels. Blood bPAG level on day 28 was not affected by ovulatory follicle size, embryo stage, embryo quality, blood estradiol levels or blood progesterone levels. Compared to cows that maintained pregnancy, cows that lost pregnancies after day 28 had decreased blood bPAG levels on day 28. In summary, there was no relationship between serum bPAGs and ovulatory follicle size or embryo stage/quality at embryo transfer; however, cows that lost a pregnancy after day 28 had lower blood bPAG levels on day 28 compared to cows that maintained pregnancy.

Technical Abstract: GnRH-induced ovulation of small dominant follicles resulted in increased late embryonic/fetal mortality. The objective of this study was to examine the relationship between ovulatory follicle size, embryo/fetal survival, and circulating concentrations of bPAGs (detects presence of an embryo/fetus and placental function). In experiment 1, postpartum beef cows (n = 91) were treated with the CO-Synch protocol (gonadotropin releasing hormone [GnRH] on d -9, prostaglandinF2a [PGF2a] on d -2, and GnRH and artificial insemination [AI] 48 h later [d 0]) and classified into one of two ovulatory follicle size groups: 1) small follicle (< 12.5 mm; n = 25), or 2) large follicle (=12.5 mm; n = 66). The first increase (P < 0.0001) in serum bPAGs occurred in pregnant cows on d 24 after insemination and circulating bPAGs decreased before a decrease in progesterone in three of four cows that lost an embryo/fetus. Pattern of secretion of bPAGs in serum from d 24 to 60 after insemination (d 0) was affected by day (P < 0.0001), but not ovulatory follicle size. Before examining the relationship between bPAGs and embryo/fetal survival, the half-life of bPAGs was determined in experiment 2. The half-life of bPAGs following PGF2a -induced abortion on d 32 to 36 post insemination was 35.8 ± 21.9 h (mean ± SD; range 7.1 to 78.5 h). In experiment 3, suckled beef cows (n = 1,164) 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. Cows were classified on d 0 as having a small (< 12.5 mm) or large (= 12.5 mm) ovulatory follicle and randomly chosen as donors or recipients to remove confounding effects of ovulatory follicle size on fertility. Serum concentration of bPAGs at d 28 was not affected by ovulatory follicle size (P = 0.85), embryo stage at ET (P = 0.75), embryo quality at ET (P = 0.64), estradiol at GnRH2 (P = 0.62) or serum progesterone at ET (d7; P = 0.14). Compared to cows that maintained pregnancy, cows that exhibited late embryonic/fetal mortality after d 28 had decreased (P < 0.05) concentrations of bPAGs on d 28. In summary, there was no relationship between serum bPAGs and ovulatory follicle size or embryo stage/quality at ET; however, cows that lost an embryo after d 28 had lower concentrations of bPAGs on d 28 compared to cows that maintained pregnancy.

Last Modified: 4/23/2014
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