The corral confinement system used for intensive dairying in the Central Valley and southern California subjects the cow to various types of stress, particularly following parturition and during peak lactation. The effect of weather on these animals is of primary concern, especially in the hot, dry summer, when temperatures average highs of 95° F, with numerous days over 100° F, and relative humidity averaging 33 percent. Winters in the area are usually cool and mild; spring and fall are moderately warm.

The author acknowledges John Soares, staff field assistant, who helped compile data, and the following dairies: Cardoza Brothers and Sons, Tipton; Wilbur Brothers, Felipe Ribeiro and Sons, and Lone Palm Holsteins, Tulare; Edgerly Farms, Dinuba; William Van Beek and Case DeJong, Visalia; and Norman Martin, Stratford.