Paired T tests were used to compare blood sample results for differences in mean progesterone
concentrations between each of the three trials. Comparison of means between sample series T1
and T2 demonstrated a statistically significant increase (p = 0.0028) in serum progesterone
consistent with the exogenous source of progesterone from the intravaginal insertion of new
CIDRs. Comparison of sample series T2 and T3 indicated a statistically significant decrease (p =
0.0009) in serum progesterone when comparing samples from cows that received a new CIDR
versus the same cows receiving the reused CIDRs. Comparison of sample series T1 and T3
showed no statistically significant difference (p = 0.9494) in serum progesterone concentrations
when comparing cows with no CIDRs inserted to the same cows with reused CIDRs.