Variation in the Constituents of Milk Under Arizona Conditions. I. Variations of Individual Cows within Breeds by Calendar Months

Open Access
Publisher Website
Google Scholar
Abstract
A study concerned with variations in composition of milk of 1 1 Jersey, 11 Guernsey and 12 Holstein cows was conducted over a 30-month period. Maximum, minimum and average values for each constituent were presented by breed. Data are presented graphically by breeds and show the total solids, serum solids, and fat to be higher in winter and lower in summer. 13 of 406 samples were abnormally high in fat and low in serum solids; of these 13, 6 were Jersey, 5 Guernsey and 2 Ilolstein. Samples below legal min. for fat (3.25%) and serum solids (8.5%) were Jersey, 0 and 2.5%; Guernsey, 0.6 and 2.2; and Holstein 22.7 and 47.5% respectively. Increased protein content was accompanied by increased fat, total solids and serum solids and a decrease in lactose. Lower fat content of Guernsey milk is due presumably to higher environmental temps. which appear to exert a greater influence on milk and butterfat production than does advancing stage of lactation. Fat decreased 0.1% for each 10[degree]F rise in mean max. temp.'' between 65 and 105[degree]F under Arizona conditions. A Jersey cow family was found to produce milk 0.31% lower in lactose than normal for the Jersey breed.