DiscussionAlthough current cooling

Discussion
Although current cooling standards utilize a THI thresh hold of 72 before initiation of cooling, our research indicates that adverse affects can be shown as early as a THI of 68. During this study we found that physiological parameters and milk yields were affected at THI values well below 72. When analyzing the data it was observed that between a THI of 64 and 72 there were large reduction in milk yields therefore chose to analyze hours above a given THI between 65 and 72 to get a more precise estimate of the threshold and subsequently arrived at a threshold of 68. When researchers analyzed data of on farm studies they have also concluded that at an average THI of 68 milk production begins to decline however, based on entire analysis of the data they still summarize that a THI of ≥ 72 is when adverse affects are seen (Ravagnolo et al., 2000). Our results indicate that a daily THI equal to 68 results in a milk loss of 2.2 kg/day for each 24 hours. Another study reported milk yield decreases by 0.2 kg per day per unit of THI as THI increased above 72 (Ravagnolo et al., 2000). In the current study milk yield decreases averaging 2.2 kg were observed when animals experienced a minimum THI of 65 or greater (P