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Table 1 Effect of iP4 supplementation and/or embryo transfer on the CL regression in beef cows

From: Exacerbated conceptus signaling does not favor establishment of pregnancy in beef cattle

Variable Non-iP4 iP4 P value
0-ET (n = 24) 5-ET (n = 27) 0-ET (n = 26) 5-ET (n = 27) iP4 ET iP4×ET
Number of cows having functional CL on D20a 4 (16.7%) 21 (77.8%) 2 (7.7%) 16 (59.3%) . . .
Estrus to structural luteolysis, db 17.58 ± 0.35 17.00 ± 0.63 17.92 ± 0.31 16.91 ± 0.46 0.79 0.09 0.64
Estrus to functional luteolysis, dc 17.11 ± 0.31 16.50 ± 0.56 16.96 ± 0.28 16.09 ± 0.41 0.50 0.08 0.75
Estrus to P4 < 1.0 ng/mL, dd 17.79 ± 0.35 16.83 ± 0.62 17.83 ± 0.31 16.91 ± 0.46 0.90 0.04 0.97
Number of pregnant cows on D30e . 15 (55.6%) . 10 (37.0%) 0.16 . .
Number of non-pregnant cows having functional CL on D30f . 6 (22.2%) . 5 (18.5%) 0.74 . .
  1. Beef cows detected in estrus (D0) were assigned randomly to receive a single injection of vehicle (Non-iP4) or 150 mg of long acting progesterone (iP4) on D4 and transfer of none or 5 in vitro-produced blastocysts on D7;
  2. aCows that did not present any of the characteristics described in items 2, 3 and 4, below;
  3. bStructural luteolysis was defined as the day between D11 and D21 when the maximum CL area (cm2) and the luteal blood flow decreased by 25% and 50%, respectively, from the mean of D10 and D11;
  4. cFunctional luteolysis was defined as the day when plasma P4 concentrations decreased > 2 ng/mL between samples collected from D14 to D20, and was followed by a progressive decrease in plasma P4 concentrations to < 1 ng/mL;
  5. dDay when plasma P4 concentrations first reached < 1.0 ng/mL;
  6. e,fPregnancy status for each animal was determined by detection of at least one conceptus with heartbeat using transrectal B-mode ultrasonography on D30. In non-pregnant cows, the functionality of the CL from D20 was checked according to criteria established for detection of structural luteolysis