Station); 'Records of Dairy Herd for Five Years (Bulletin 73, Connecticut Experiment Station, Storrs, Conn.); The Cost of Rearing a Dairy Cow (Bulletin 164, Massachusetts Experiment Station); Care, Feed and Management of the Dairy Herd' (Circular 16, Iowa Experiment Station); The Feeding of Dairy Cows (Farmers' Bulletin 743, Washington, D. C.). RAYMOND A. PEARSON, President of Iowa State College and Assistant Secretary, United States Department of Agriculture, assisted by M. MORTENSEN, Professor of Dairy Industry, Iowa State College, and E. B. REID, Chief of Division of Publications, United States Department of Agriculture.

DAIRY PRODUCTS. The dairy industry is one of the most important branches of farming in this country, both from the standpoint of production of food for human consumption and, also, that of soil fertility. The size of this industry is indicated by the fact that, on 1 Jan. 1917, there were 22,768,000 milch cows in the United States, having a farm valuation of $1,358,435,000. The following are the States which had more than 1,000,000 cows in 1917: Wisconsin, 1,750,000; New York, 1,539,000; Iowa, 1,405,000; Minnesota, 1,302,000; Texas, 1,175,000; Illinois, 1,057,000. The amount of milk produced on farms in 1909 was 5,813,699,474* gallons, and the total value of the dairy products was reported as $596,413,463*. The following table shows the amounts and value of the different manufactured dairy products for the year 1914:

New York leads all the States in the production of milk for direct consumption. Wisconsin produced the most butter, followed by Minnesota, Iowa and California. In the production of cheese, Wisconsin leads, followed by New York, Pennsylvania and Michigan. For condensed milk, the leading States are Wisconsin, Illinois and New York.

For many years the dairy industry has increased steadily and quite rapidly. This growth is the more significant in view of the fact that, during recent years, there has been a decided decrease in the raising of cattle for beef. This general tendency toward an increase in the raising of dairy cattle at the expense of other kinds is, doubtless, due to certain fundamental economic principles: (1) A given amount of feed consumed by a dairy cow will produce a much greater amount of human food (milk, butter or cheese) than would be produced if it were used for the production of beef, mutton or pork; (2) the sale of milk, butter or cheese removes very little fertility from the farm, and the cow provides a means for converting certain farm products, such as hay, corn, stover, straw, etc., into more salable products; (3) it is easier to maintain the fertility of the soil where stable manure is available than where it is not; (4) labor on a dairy farm is more constant throughout the year than in most other lines

Exclusive of milk and cream consumed on farms where produced. If these amounts were included, both these figures would be increased materially.

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of farming. This makes it possible for the dairyman to use both man and team labor economically, and provide a nearly uniform income throughout the year, instead of having it concentrated into a few months, as in grain or fruit-growing. It is significant that the dairy industry has reached its greatest development in those sections of the country which have been farmed longest and where the types of farming have become most permanent and also that there is a marked tendency toward greater development of this industry in the newer sections. This may be interpreted as meaning that the dairy cow grows in importance with the increase of population, need for human food and the development of a permanent type of farming. During recent years, the number of dairy cows has increased in all sections except the New England and Middle Atlantic States, where the industry was already well developed. The market for our dairy products is chiefly domestic, a very small percentage going into export trade.

Milk. Milk is produced by the females of all species of mammals as food for their young. In nature the mother produces only the amount of milk needed to feed her young, but, in the case of the cow, the function of milk secretion has been developed by means of artificial breeding and selection far beyond the needs of the young calf in order that it may be available for human food. In appearance cow's milk is a yellowish white, slightly viscous, opaque fluid, having a pleasant, sweetish taste. Milk is a true secretion, the fat, casein, lactose, etc., being made by the activity of the cells in the mammary gland.

The analysis of several thousand samples of cow's milk shows the average composition to be as follows: water, 87.17 per cent; milk-fat, 3.69 per cent; casein, 3.02 per cent; albumin, 0.53 per cent; milk-sugar, 4.88 per cent; and ash, 0.71 per cent.

The constituents of milk, less the water, are usually called the milk solids or total solids, and the total solids without the fat, the solidsnot-fat. The entire milk, less the fat, is called the milk serum, or skim-milk.

Some of the constituents of milk are in true solution; some are simply held in suspension, while others are partly in solution and partly in suspension, Van Slyke states this condition as follows:

Milk constituents in true solution in milk serum (a) Sugar (b) Citric acid (c) Potassium (d) Sodium (e) Chlorine

Milk constituents partly in solution and partly in suspension or colloidal solution

(a) Albumin (1)
(b) Inorganic phos-
phates

(c) Calcium

(d) Magnesium

Milk constituents entirely in suspension or colloidal solution (a) Fat (b) Casein

Colostrum is the milk which a cow produces immediately after parturition. It is quite different in appearance and composition from normal milk, having a reddish yellow color and a viscous, almost slimy, consistency. Richmond gives its composition as follows: Water, 71.69; fat, 3.37; albuminoids: casein, 4.83, albumen, 15.85; sugar, 2.48; and ash, 1.78 per cent. Colostrum acts as a purgative to the newly-born calf, and should not be used for human food under four or five days after calving, by which time it becomes normal milk.

Until recent years, it was supposed that the composition of milk could be decidedly changed by the feed which the cow consumed, but later investigation has established the fact that the feed has but slight, if any, influence on the relative amounts of the various constituents. Certain feeds, however, may affect the quality of the milk fat; for example, linseed or gluten meal makes an oily, soft fat, while cotton seed meal and wheat bran make a hard fat. The fat exists in milk in the form of minute globules which are held in their spherical form by the surface tension of the liquid fat and the viscous nature of the milk serum. Since the value of

milk is largely proportional to its per cent of fat, it is often necessary to determine its fat content. This may be done by chemical analysis but this method involves considerable time and expense and the method generally used in commercial work in this country is that devised by Dr. S. M. Babcock, of the University of Wisconsin, and known as the "Babcock Test" for milk-fat. This test is based on the principle of liberating the fat globules by dissolving the casein with strong sulphuric acid and the separation of the fat by centrifugal force-the fat being lighter than the other elements in the milk. Briefly, the method of making the Babcock Test is as follows: (1) Secure an accurate sample of the milk to be tested; (2) measure out 17.6 cubic centimeters, and place it in the test bottle; (3) add 17.5 cubic centimeters of sulphuric acid, and mix thoroughly by rotating the test bottle; (4) place bottles in centrifuge and whirl at proper speed for five minutes; (5) add hot water to bottom of neck and whirl two minutes; (6) add hot water to bring fat up to graduated scale and whirl one minute; (7) place test bottles in water bath at 135°-140° F. for five minutes; (8) read amount of fat column, including meniscus both at top and bottom of column.

Milk is heavier than water, the average specific gravity of normal milk being 1.032, with variations between 1.029 and 1.035. The specific gravity of milk may be determined by an instrument called a "lactometer." Taken in connection with the Babcock Test, the lactometer reading makes it possible to determine both the total solids and the solids-not-fat in any given sample of milk. There are a number of formulæ which may be used for this purpose. Babcock's modified form is as follows:

in which L stands for the lactometer reading and F for the per cent of fat. The total solids may be obtained by adding the solids-not-fat to the fat reading.

Milk is a delicate substance and very susceptible to undesirable flavors and odors. These may be either of two types: (a) those which are absorbed from feed eaten by the cow or from outside sources, or (b) those resulting from the action of microorganisms, especially bacteria, in the milk itself. If it is exposed to strong odors, such as foul stable air, cabbage, gasoline, etc., they will be absorbed very quickly. If placed in an ice-chest with such foods as pineapple or strawberries, it will be quickly tainted and have a disagreeable flavor. Disagreeable as these absorbed troubles may sometimes be, they are not so serious as those resulting from the growth of bacteria. The former decrease after removal from the source of contamination, while those resulting from bacterial action continue to increase in intensity as the milk grows older. It is highly desirable that milk should reach the consumer in as nearly as possible, the condition in which it leaves the udder of the healthy cow. This means that much care must be exercised in its production and handling to prevent contamination. Bacteria gets into milk chiefly from the following sources: the interior of the cow's udder, the milk utensils, the surface of the cow's body, the atmosphere of the stable and milk house, and the hands and clothing of the milker. If

the udder is free from disease, it is not a serious source of contamination, since its germ content rarely exceeds a few hundred per cubic centimetre. If, however, the udder is diseased, it may be a very serious source of infection. To secure milk with a low bacteria content those parts of the cow's body around the udder should be as clean as possible at milking time. The stable air should be free from dust, the milker's hands should be clean, and he should wear a clean suit. In many cases the utensils are the worst source of trouble, and great care should be taken to see that these are properly constructed and thoroughly washed and well sterilized either with boiling water or steam.

As soon as produced, milk should be cooled to a temperature which will prevent the rapid development of the bacteria in it. Bacteria grow very rapidly at temperatures above 70° F., but more and more slowly as the temperature is reduced below that point; at 50° or below, growth is relatively slow, hence for best results, milk should be held at these low temperatures. During recent years, the "pasteurization" of milk for the purpose of reducing the bacteria content and destroying any disease germs which may be present has become a common practice. Pasteurization consists of heating the milk to a temperature sufficient to kill all pathogenic organisms and a large percentage of the other forms, and then immediate cooling to prevent the rapid growth of those that remain. A temperature of 145° F. maintained for 30 minutes is believed to be sufficient to destroy all disease organisms.

The average per capita consumption of milk is about one-half pint per day. Large quantities, therefore, are required to supply the needs of the large cities, New York city alone consuming about 2,000,000 quarts daily. The problem of getting this vast amount of milk to the consumer in the city is a serious one for, as the cities have increased in size, it has been necessary to go farther away for the necessary supply of milk. At present, New York city obtains part of its milk supply from farms 300 to 400 miles away, which means railroad transportation of 10 to 12 hours, after which it must be taken to the city plant, pasteurized, cooled and bottled before ready for delivery. As a result this milk is frequently 24 to 36 hours old when delivered to the consumer. Because of the great rapidity with which bacteria grow, the injection of this long period of time between production and consumption has greatly increased the problem of a satisfactory city milk supply and has changed many of the methods of production and handling on the farm, during transportation and in the city.

Grades or Classes of Milk.- The present tendency is toward the division of milk and cream into grades, primarily upon its sanitary quality. The grades established in New York city will illustrate the general divisions into which market milk is placed: (1) Grade "A" — For infants and children. Raw: Cows tuberculin tested and free from all diseases; bacteria not more than 30,000 for milk and 150,000 for cream when delivered to the consumer or at any time prior to such delivery; employees free from all communicable diseases or disease germs; delivered to consumer within 36 hours after production. Pasteurized: Cows healthy, as determined by physical examination at least

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once each year; bacteria content not to exceed 200,000 before pasteurization and not more than 30,000 for milk and 150,000 for cream when delivered to consumer or at any time after pasteurization; employees free from communicable disease or disease germs; delivered to consumer within 36 hours after pasteurization; (2) Grade "B" For adults (pasteurized). Cows in good health as determined by physical examination at least once each year; must not contain more than 1,500,000 bacteria before pasteurization and not more than 100,000 for milk and 500,000 for cream when delivered to consumer or at any time after pasteurization; employees free from communicable disease or disease germs'; milk delivered to consumer within 48 hours after pasteurization, and cream within 72 hours; (3) Grade «C»— For cooking and manufacturing purposes. Milk or cream not conforming to all the requirements of the subdivisions of Grade A or Grade B, and which has been pasteurized, according to the regulations of the Board of Health, or boiled for at least two minutes. This milk must come from healthy cows, as determined by physical examination at least once each year; bacteria content must not be excessive; milk delivered to consumers in cans only, within 48 hours and. cream within 72 hours after pasteurization. Same requirements as to health of employees as for Grades A and B. In addition to these requirements certain other regulations must be observed for each grade. In the case of each of these grades, the container must bear a distinct label, approved by the Board of Health, indicating the grade and no other statement or designating mark.

Certified milk is milk produced under the supervision and in conformity with the requirements of a medical milk commission appointed by the local county medical society. This milk must conform with very rigid regulations laid down by the commission, which insures this grade of milk being of a very high standard of composition and sanitary excellence.

Butter. Butter is the fat of milk which has been separated from most of the other constituents by the process of churning. In modern dairy practice the cream is removed from the milk by centrifugal force, by means of the cream separator, this being possible because of the fact that the fat globules are lighter than the other constituents of the milk and are thrown out as the milk passes through the rapidly revolving bowl of the separator.

Bulletin 149 of the United States Department of Agriculture gives the following composition for butter:

AVERAGE COMPOSITION OF BUTTER BY CLASSES

There are two common types of butter, known as sweet cream and sour cream butter. The sweet cream butter is made from cream in which lactic acid has not been allowed to develop. It has a mild flavor which is desired by many persons, and may be made from either raw or pasteurized cream. Sour cream butter is made from cream in which lactic acid has been allowed to develop, resulting in a product with a more highly pronounced flavor. This is the standard type of butter in America and in most countries of Europe. The production of good butter of uniform quality and high flavor requires the use of cream which has been produced and handled with care, cleanliness being a first essential in the making of good butter. After the clean, sweet cream is obtained, the next step is the development of the proper degree of acid or the "ripening" process. This is brought about by the action of certain forms of bacteria commonly known as the lactic acid bacteria (Bact. lactis acidi), which work on the milk-sugar, changing it into lactic acid. It is during this ripening process that the characteristic flavors and odors of the butter are developed, the final flavor depending upon the kinds of bacteria which take part in the ripening and the degree to which the fermentation is allowed to develop. The finest qualities of the butter may be lost by the over-ripening of the cream. Cream may be ripened by the action of the lactic acid bacteria normally occurring in it or the process may be hastened by the use of a "starter," which is a pure culture of the lactic bacteria grown in skimmilk or buttermilk. In many factories the cream is pasteurized before the starter is added, thus destroying most of the miscellaneous bacteria in the cream and making it possible to more completely control the nature of the ripening process. The purpose of churning is to remove the butter-fat from the milk serum and bring the fat globules into compact form. This is done by placing the cream in a churn of such form that when it is revolved slowly the cream is thoroughly agitated, thus bringing the minute fat globules in contact with each other and causing them to adhere as a result of the concussion. The ease with which cream will churn is influenced by many factors, but chiefly by the richness of the cream, the temperature and the speed of the churn. When a sufficient number of fat globules have coalesced to form visible granules, the butter has "come." The churning process may be controlled to give granules of any desired size. After the churning has been com

pleted, the buttermilk is drawn off and the butter washed with cold water to insure the further removal of the buttermilk and to firm or harden the butter-fat, so it can be more easily handled. The wash water is then removed, the desired amount of salt added and the butter worked enough to give an even distribution and thorough incorporation of the salt. It is now ready to be packed in tubs or made into prints, depending upon the market to which it is to be sent. The butter markets recognize certain fairly definite grades known as extras, firsts, seconds and thirds.

DEFINITION OF GRADES.- Extras shall be a standard grade of average fancy quality in the season when offered under the various classifications. Ninety per cent shall conform to the following standard; the balance shall not grade below Firsts:

Flavor: Must be sweet, fresh and clean for the season when offered if creamery, or sweet, fresh and reasonably clean if renovated or ladles. Body: Must be firm and uniform. Color: Not higher than natural grass, nor lighter than light straw, but should not be streaked or mottled. Salt: Medium salted. Package: Sound, good, uniform and clean.

Firsts shall be a grade next below Extras and must be good butter for the season when made and offered, under the various classifications. Ninety per cent shall conform to the following standard; the balance shall not grade below Seconds:

Flavor: Must be reasonably sweet, reasonably clean and fresh if creamery or renovated, and reasonably sweet if ladles. Body: Must be firm and fairly uniform. Color: Reasonably uniform, neither very high nor very light. Salt: May be reasonably high, light or medium. Package: Sound, good, uniform and clean.

Seconds shall be a grade next below Firsts. Flavor: Must be reasonably good. Body: If creamery, must be solid boring. If ladles or renovated, must be 90 per cent solid boring. Color: Fairly uniform, but may be mottled. Salt: May be high, medium or light. Package: Good and uniform.

Thirds shall be a grade below Seconds and may consist of promiscuous lots.

Flavor: May be off flavored and strong on tops and sides. Body: Not required to draw a full trier. Color: May be irregular or mottled. Salt: High, light or irregular. Package: Any kind of package mentioned at time of sale.

In grading any given lot of butter, it is scored on the basis of the following numerical values:

with milk, skimmilk, buttermilk or cream and rechurned and worked to get the desired texture and flavor. In 1916 there were 23 factories operating under Federal licenses. These plants produced 27,542,015 pounds of renovated butter during the vear, of which 635,038 pounds were exported.

Cheese Cheese is a product made from milk by the coagulation of the casein and the expulsion of a portion of the moisture. The finished cheese contains most of the milk-fat, the casein and a part of the milk-sugar and salts. In the process of making, a small per Icent of the fat, most of the albumin and milksugar and a small part of the mineral matter are washed out with the larger part of the original water, in the form of whey. The chief purpose of making cheese is to bring the nutrients of the milk into a concentrated form so they will keep longer and develop the special flavors characteristic of the different types of cheeses. A great variety of cheeses are found on the markets of this country and Europe, the variety being much greater in Europe than here, although the number is increasing here. The Department of Agriculture gives a list of more than 100 kinds of cheese, with the methods of making and chemical composition of each. Cheeses may be divided into two general groups, based on the method used for coagulating the casein, these are the "acid-curd» cheeses and the "rennet-curd" cheeses. In the first group the casein is coagulated by the formation of lactic acid in the milk. This may result from the growth of the lactic acid bacteria normal to the milk or by the addition of a "starter." The cheeses in this group are little more than fresh, sour curd and are eaten fresh without any ripening process. There are but few varieties. In the second group the coagulation is caused by the action of rennet, which is added to the milk while it is fresh and has but little acid. This group contains the varieties which are of greatest commercial value. At one end of this group are the so-called "hard," while at the other end are the "soft" varieties. Between these extremes there are many kinds which blend into each other by imperceptible degrees, the chief differences being due to the degree of moisture they contain and the nature of the micro-organisms causing the ripening processes. The most important of the cheeses is the one known as the American or Cheddar cheese. Its composition depends upon the quality of the milk and the method of making. Extended studies by the New York Experiment Station show the following composition for Cheddar cheese made from normal milk:

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It will be seen that the yield of cheese increases with the per cent of fat in the milk, the increase, however, being not directly proportional to the increase in fat because the casein does not increase as rapidly as the fat. The quality of the cheese which can be made from any given lot of milk depends very largely upon the care it has received. Clean milk is the first essential for successful cheese making, and great care should be used not to take in milk having high acidity or bad flavors or odors or showing visible dirt. Any of these conditions indicate the presence of certain types of bacteria which will injure the quality of the finished product. After milk of good quality has been obtained, the first step is to develop the proper degree of acidity. This may be done by allowing the milk to stand at a temperature favorable to the growth of the lactic acid bacteria, or the process may be hastened by using an artificial starter, as in the making of butter. As soon as the desired degree of acidity has developed, the rennet should be added. The amount to be used, as given by Publow, depends on (1) the strength of the extract; (2) the temperature of the milk; (3) the acidity of the milk; (4) the composition of the milk; (5) the kind of cheese to be made, and (6) the temperature of curing. In general, an amount sufficient to coagulate the milk fit for cutting in 25 to 35 minutes should be used; generally from 2 to 4 ounces for 1,000 pounds of milk will suffice.

When the milk is well coagulated, small wire knives designed for the purpose are used to cut it into small cubes to allow the whey to escape. It is important that the expulsion of the whey and the firming of the curd should be carefully controlled, which is done by stirring the curd and by the application of heat. When the little cubes of curd have contracted to slightly less than one-half their original size and are firm and rubber-like, the whey is drawn off from the vat. As soon as the whey is sufficiently removed the curd is piled along either side of the vat and allowed to drain thoroughly; after it is well matted it is cut into strips which may be piled to any desired depth to hasten the further removal of the whey. This cheddaring process is continued till the curd shows the desired texture and the whey coming from the curd has the required degree of acidity. The curd is now "milled" by running it through a machine which cuts it into small, even sized pieces in order to further assist in the escape of the whey and make the salting process easier. The curd is then spread over the bottom of the vat, the salt sprinkled over the surface and the curd is stirred to insure the even distribution of the salt to the surface of each piece. The