Pregnancy rates and corpus luteum-related factors affecting pregnancy establishment in bovine recipients synchronized for fixed-time embryo transfer |
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Authors: | L.G.B. Siqueira C.A.A. Torres P.L.J. Monteiro Jr. L.S.A. Camargo J.H.M. Viana |
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Affiliation: | a Federal University of Viçosa, Av. P.H. Rolfs s/n, Viçosa, MG, 36570-000, Brazil b Embrapa Cerrados, Planaltina, DF, 73310-970, Brazil c Embrapa Dairy Cattle Research Center, Juiz de Fora, MG, 36038-330, Brazil d University of Alfenas, Alfenas, MG, 37130-000, Brazil |
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Abstract: | The objective was to investigate the influence of corpora lutea physical and functional characteristics on pregnancy rates in bovine recipients synchronized for fixed-time embryo transfer (FTET). Crossbred (Bos taurus taurus × Bos taurus indicus) nonlactating cows and heifers (n = 259) were treated with the following protocol: 2 mg estradiol benzoate (EB) plus an intravaginal progesterone device (CIDR 1.9 g progesterone; Day 0); 400 IU equine chorionic gonadotropin (eCG; Day 5); prostaglandin F2α (PGF2α) and CIDR withdrawal (Day 8); and 1 mg EB (Day 9). Ovarian ultrasonography and blood sample collections were performed on Day 17. Of the 259 cattle initially treated, 197 (76.1%) were suitable recipients; they received a single, fresh, quality grade 1 or 2 in vivo-derived (n = 90) or in vitro-produced (n = 87) embryo on Day 17. Pregnancy rates (23 d after embryo transfer) were higher for in vivo-derived embryos than for in vitro-produced embryos (58.8% vs. 31.0%, respectively; P < 0.001). Mean (±SD) plasma progesterone (P4) concentration was higher in cattle that became pregnant than that in nonpregnant cattle (5.2 ± 5.0 vs. 3.8 ± 2.4 ng/mL; P = 0.02). Mean pixel values (71.8 ± 1.3 vs. 71.2 ± 1.1) and pixel heterogeneity (14.8 ± 0.3 vs. 14.5 ± 0.5) were similar between pregnant and nonpregnant recipients (P > 0.10). No significant relationship was detected between pregnancy outcome and plasma P4, corpus luteum area, or corpus luteum echotexture. Embryo type, however, affected the odds of pregnancy. In conclusion, corpus luteum-related traits were poor predictors of pregnancy in recipients. The type of embryo, however, was a major factor affecting pregnancy outcome. |
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Keywords: | Cattle Corpus luteum Echotexture Fixed-time embryo transfer Ultrasonography |
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