The quantities and values of imports, ex ports, and re-exports of dairy products for the years 1910, 1912, 1914, 1916 and 1917 are as follows: The best and most profitable breed of dairy cattle has as yet never been agreed upon. Each of the dairy breeds has strong claims to high est merit and each has its enthusiastic advocates. The latter are often influenced by conditions which have no economic importance. The breeds differ markedly in such characteristics as size, color and disposition, as well as in quan tity and quality of milk. As a general rule, when a large amount of milk is given, it is low in fat-content or "richness." The data shown in the following table regarding several leading dairy breeds of cattle have been compiled from Advanced Registry records.* The figures of production and composition of milk arc aver ages based on the number of cows given.
There is a wide variation in the milk pro duction among cows of the same breed. Yields of milk above 30,000 pounds a year have been produced and the world's record of butterfat production at present is 1,205.09 pounds. These records of milk and butterfat production were all made by pure-bred cows.
The great majority of dairy cows throughout the country are "grades," that is, some of their ancestors are pure bred and some are not. As producers of milk, individual grade cows can be selected that will equal pure breds, but the latter are more satisfactory for breeding purposes. A grade Holstein cow in Michigan, in 1917, gave 9,139 pounds of milk containing 298 pounds of butterfat, equivalent to 351 pounds of butter. The total feed cost of the year was $73.39 and the total value of her products was as follows: 351 pounds of butter ® 40 cents per lb $140 40 7.736 " skim milk ® 40 cents per cwt 30.94 1.105 " buttermilk ® 25 cents per cwt 2.75Total $174.09 The income over cost of feed was $100.70, while the feed cost of one pound of butter was $0209.
The average dairy cow in the United States produces about 4,000 pounds of milk, containing about 160 pounds of butterfat, equivalent to 188 pounds of butter.
188 pounds of butter ® 40 cents per lb $75.20 3,360 " skim milk ® 40 cents per cwt 13.44 480 " buttermilk ® 25 cents per cwt 1.20Total $89.84 The cost of feed for such a cow would be about $60 and the income over cost of feed about $29.84, as compared with $100.70 for the grade cow previously mentioned.
Milk of the cow is secreted in the mammary glands known as the udder. Wing thus well describes the udder of a good cow: It should be large and well developed; it should occupy the whole space between the hind legs, extend ing well up between the thighs and well for ward upon the belly. It should be held firmly against the wall of the abdomen. It should be level or nearly so on the bottom, and the four quarters should be as nearly as possible equally developed and each furnished with a cylindrical perpendicular teat of moderate length. The whole organ should diminish rapidly in size, as the milk is withdrawn. The hair upon the udder should be fairly abundant, fine and soft, and abundantly supplied with brownish dand ruff." As milk is a product of the blood, the importance of an ample blood supply to the udder, a vigorous constitution, and a strong circulation is readily seen. It is highly import
ant to withdraw the milk from the udder regu larly, quietly and completely, if the flow is to he maintained.
Van Slyke gives the average of 5,552 Ameri can analyses of cow's milk, expressed in per centages, as follows: Total Water solids Fat Casein Albumin Sugar Ash 87.10 12.90 3.90 2.50 0.70 5.10 0.70 In addition to the constitutents named cer tain others are present in minute quantities. The average .specific gravity of milk is 1.032. The composition of milk of different cows varies between wide limits. The same may be true of the product of any individual cow from day to day. The New York Agricultural Ex periment Station is authority for the above averages of analyses of milks from cows of different breeds.
Koenig gives variations of milk constituents in about 800 samples, expressed in percentages, as follows: Maximum ' Minimum Water 90.69 80.32 Pat • 6.47 1.67 Vabittinin 4.23 1.79 1.44 .25 Sqyfr 6.03 , 2.11 1.21 .35 In Some instances Aanerican analyses have shown even wider variations. • The most variable constituent of milk is fat. By it the ((richness)) of milk is judged and the commercial value is determined. 'Milk fat , is a complex mixture containing several glycerine •compounds.• • It is present in the form of minute globules suspended in the remaining or watery portion called the serum. The globules. average about one• ten-thousandth of an inch in diameter and are plainly visible tinder a high-power microscope. About 150, 000,000 of them are contained in a single drop of milk, Some conditions affecting fat-tontent of milk have. been mentioned. A few others are important. From about the middle to the last of the period of lactation, the fat in milk increases slightly. The percentage of fat in creases gradually from the first to the last of any milking; the first milk drawn contains about 1 per cent fat and the last as high as 9 or 10 per cent. It is popularly supposed that the.feed given a cow has a decided influence on the quality of her milk. As a matter of fact, the milk of a cow in normal condition is little affected by the feed, except that certain feeds may give it a strong flavor. Feed has a much greater influence upon the quantity of milk than its quality. , Casein and albumin are protein or nitrogen constituents of milk. The former is coagulated by rennet or acid, the latter by heat. Coagu lated casein or ((curd° enters largely into the composition of cheese. Casein is said to be in a state of gpseudo-solutio0 in milk. Milk sugar or lactose is in solution in milk. When separated it resembles powdered sugar. It is less sweet than cane sugar and is used to a con siderable extent in druggists' preparations and in certain proprietary foods. The mineral mat ter in milk, called ash or salts, is the part re maining when milk is evaporated, to dryness and burned. It includes phosphorus, potassium, calcium, chlorine, magnesium, sodium, sulphur and iron. Certain gases and other constituents arc present in milk in minute quantities.