48 CLEAN MILK 



Rhode Island, and solids amounting to twelve per cent., in most 

 states, and as high as thirteen per cent, in some. 



The legal requirements for fat and total solids are often too 

 high and unfair to owners of cows yielding milk below these 

 standards or to those shipping milk which has not been thoroughly 

 mixed. The Massachusetts standard requires that in the fall and 

 winter months milk shall contain not less than 3.7 per cent, fat, 

 nor less than 13 per cent, of total solids. 



This works harm to owners of Holstein-Friesians, especially, 

 as these cows often yield milk below the legal standard and yet it 

 is milk best suited for infants.* 



The composition of milk varies according to the period of 



milking, the milk growing richer in fat and the fat globules larger 



as milking advances, the last of the milking or " strippings " being 



very rich. 



Per Cent. 

 Fat. 



tFore Milk - 3-8 



Middle Milk 6.74 



Strippings 8.12 



The reason for this is said to be that the fat globules are retarded 

 by friction on the sides of the milk ducts in the udder and are 

 forced out in abundance towards the last of milking. The per- 

 centage of the other solids remains practically unchanged at differ- 

 ent periods of milking. 



It is a curious fact that when the calf sucks the cow, the last 

 of the milk appears to be much poorer in fat than the first part. 



If cows are milked at frequent intervals the yield of milk is. 

 greater and the percentage of fat larger. The milk is formed in 

 the cells of the udder and is conducted through numerous fine tubes 

 of increasing size until it empties into a reservoir (holding about 

 one-half pint on an average) connected with the upper end of the. 



* The standard for fat content must not, however, be removed or made too low 

 so as to encourage production of low grade milk. Holstein milk may be much- 

 improved by breeding, see p. 68. 



t Dr. Charles Harrington's analysis. 



