In our study, when maximum THI 3–1 days pre-AI
values were higher than 80, conception rate decreased
from 30.6 to 23%. The odds ratios for THI 3–1 days pre-
AI classes 72 THI units causes heat stress in
cows [27]. In our study, the negative effects of heat
stress on conception rate seem to appear from 75 THI
units, although the effects of heat stress become more
obvious from 80 units of THI. Moreover, in the second
logistic regression in which THI was excluded, the
conception rate decrease appeared from a mean
maximum temperature of 31 8C recorded from 3 days
before AI to the AI day, although it has been proposed