The Effect of Environmental Temperature on the Percentage of Fat in Cow's Milk

Open Access
Publisher Website
Google Scholar
Abstract
The great variation in the composition of cow's milk is a matter of common observation. Studies of the causes of this variation, with regard to the fat content of milk, are numerous and have been summarized by Turner (30), who states that there are two fundamental causes of the variations. The first is the hereditary variation due to the genetic makeup of the breed and individual. The second cause appears to be due to physiological changes in the animal, caused by such factors as management, environment, lactation, reproduction and age. To the second cause Wood- ward (33) and Clothier (11) would add feed as a factor, and Eckles (12) adds the factor of condition of cow at time of calving. The effect of environment, or more specifically, environmental tem- perature, is considered in this paper. The relation between season of the year and the per cent of fat in milk is generally known. • It was shown by Eckles (13) in 1909 from a study of 240 lactation periods of cows in the Missouri and Iowa Experiment Station herds. He found that, regardless of when the lactation began, the percentage of fat when plotted followed a curve for the year, being lowest during June and July and gradually rising to the highest point in December and Janu- ary, and then declining again till midsummer. White and Judkins (32) concur in this opinion, presenting data taken on 49 cows over a period of seven and one-half years. They conclude that the milk tests lower in fat content in the