value) were analyzed using a GLM ANOVA model for repeated measures and
included the fixed factors: occurrence of estrus (yes/no), day, the interaction
between occurrence of estrus and day, the random factor cow ID, and the factor
occurrence of estrus was also nested within cow ID. Chi-Square tests were
employed to analyze the associations between estrus, prior fertility treatment,
lameness, and potential progesterone cycle when estrus was observed in the 1st,
2nd or ≥3rd cycle. The first day estrus was observed postpartum and the day
ovarian activity started postpartum [defined as the first day after calving when
progesterone concentrations were above baseline for two or more days, or Day
‘20’ if progesterone was already above baseline (n=9 cases)] in cows with a
naturally-occurring estrus (n=27) were analyzed with a GLM ANOVA that
included the fixed factor of lameness.