There are, however, some biological differences between cow colors and the cow's ability to cope with environmental stress from heat, humidity and solar radiation. Cow color isn't just personal taste or aesthetics as, for example, in the case of a Holstein whose individual coat color is more black or more white. Earlier research pointed out that there were physiological differences in adaptation and productivity, depending on the amount of black or white in the hair coat. The results are important because every year Florida suffers months of adverse subtropical weather that affects dairy cows and their production efficiency. This, combined with fans to force air, cools the animals so they are less affected by the heat.
Solar radiation is a significant factor since it increases body temperature directly.
A few years ago here in the University of Delaware's dairy herd, we tried temperature sensors on the teat cups of our milking machines to find differences in the temperature of milk as it leaves the udder. We theorized that this would give us early indication of mastitis. What we found was something else entirely. On 90-degree days, the warning lights on the cows' temperature sensors began to blink. This finding was contrary to most textbooks that stated a cow's body temperature doesn't vary in relation to the environment as a reptile's or amphibian's does.