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Table 2 Survival analysis of time to ovulation following oestrous synchronisation

From: Ovarian follicular response to oestrous synchronisation and induction of ovulation in Norwegian Red cattle

VariableLevelEstimatecSEHazard ratio (eb)
Herd1R
20.140.121.15
3− 0.050.060.95
40.040.061.04
AgeHeifers 14‒15 monthsR
Heifers 16‒18 months− 0.10a0.050.90
Heifers 19‒28 months− 0.20a0.100.82
Cows parity 1‒3− 0.020.061.02
Initial follicle sized≤ 10.0 mm0.050.041.05
> 10.0 mmR
Diameter at ovulationa,e9.0‒15.0 mmR
15.1‒17.4 mm− 0.15b0.050.86
17.5‒23.0 mm− 0.12a0.060.89
BCSLean (2.5‒2.9)0.070.071.07
Moderate (3.0‒3.4)R
Fat (3.5‒4.0)0.080.051.08
  1. Hazard ratio for time to ovulation by herd, and classes of age, initial follicle size, follicle diameter at ovulation, and body condition score (BCS) in Norwegian Red cattle; time variable: hours from GnRH analogue treatment to ovulation; R, reference value and SE, standard error
  2. aOverall association with time to ovulation or within variable difference relative to the reference value; P ≤ 0.05
  3. bWithin variable difference relative to the reference value; P < 0.001
  4. cEstimate for each parameter level
  5. dDiameter (mm) of the dominant follicle at the time of GnRH analogue treatment (T0)
  6. eDiameter (mm) of the dominant follicle at the time of ovulation