IQ4 DAIRYING 



When milk sours, the sugar is changed into lactic acid, 

 which gives to milk its sour taste. 



Other Substances in Milk. Casein is the chief protein 

 in milk. It is of value in cheese making. If rennet or 

 a weak acid be added to milk, the casein is changed into a 

 curd, from which the cheese is made. 



Albumen, another protein in milk, is much like albumin 

 in the blood. It differs from casein in that it coagulates, or 

 thickens, when heated. It is the skinlike or paperlike sub- 

 stance that appears on the surface of skim milk when it is 

 boiled. 



The ash in milk is composed mostly of phosphate of 

 lime, but there are many other minerals found in small 

 quantities. 



Colostrum The first milk that the cow gives after 

 the birth of a calf is called colostrum. It contains from 

 ten to fifteen times as much albumen as the milk does later, 

 and contains less fat and sugar. Colostrum is sometimes 

 called " calves' milk." It should not be used for at least 

 three days after the birth of the calf. It is safer to wait 

 one week before using the milk. 



Yield : Quantity and Quality. The average cow pro- 

 duces about 4,000 pounds of milk per year. Some herds 

 will yield an average of 6,000 pounds for each cow. In 

 one exceptional case, the yield for a single cow reached 

 30,000 pounds. In general, the cow should yield at least 

 six times her live weight to be a profitable member of a 

 dairy herd. 



The profitableness of a dairy cow depends as much on 

 the quality of the milk as it does on the quantity. Milk 

 rich in fat and of large quantity should be the aim of all 



