I'm studying the genotype by environmental (season) interaction in beef cattle. In other studies (e.g dairy cattle), THI (Temperature-Humidity index) was widely used as a criterion about the existence of heat stress. When I set random regression model, I want to apply it to beef cattle. other studies used the threshold about the THI for the specific traits (e.g milk yield, weaning weight etc), but I didn't find out the threshold in previous studies for my traits (carcass weight, backfat thickness, eye muscle area, marbling score). How will I use the THI for this traits?