112 MILK 



The proteins varied less than 0.2 per cent., but the sugar 

 not infrequently varied 0.5 per cent, from the average, although 

 about 90 per cent, of the analyses showed a variation of less than 

 0.2 per cent. 



Morning and evening milk differ chiefly in the greater fat 

 content of the former. This, however, depends largely upon the 

 period elapsing between milkings. When cows are milked twice 

 daily, exactly twelve hours apart, the difference in fat content is 

 slight. Eckles and Shaw state that there is no appreciable dif- 

 ference in the protein and melting-point of the fat and in the size 

 of the fat globules. The Reichert-Meissl and the saponification 

 numbers are lower in evening milk and the iodin number higher 

 than in the morning milk. There is no noticeable variation in 

 the amount of sugar. 



There is then, on the whole, no great variation in the plasma 

 solids between milkings when the intervals are of the same length, 

 but the fat is slightly higher in morning milk than in evening milk. 



Composition of Fore-milk, Middle Milk, and Strippings. It is 

 a well-known fact that the strippings contain more fat than either 

 the middle milk or fore-milk. The reason for this phenomenon 

 has been stated before. A few illustrations are given here: 



DIFFERENCE IN FAT CONTENT OF DIFFERENT PORTIONS OF MILK (VAN SLYKE) 



Percentage of fat in milk of 

 Cow 1. Cow 2. Cow 3. 



First portion drawn 0.90 1.60 1.60 



Second portion drawn 2.60 3.20 3.25 



Third portion drawn 5.35 4.10 5.00 



Fourth portion drawn (strippings) 9.80 8.10 8.30 



Leach gives figures comparing fore-milk and strippings as fol- 

 lows: 



DIFFERENCE OF COMPOSITION OF FORE-MILK AND STRIPPINGS 



Water. Solids. Fat. 



v , /88.17 11.83 1.32 



Fore - nulk 188.73 11.27 1.07 



Q* ;: /80.32 19.18 9.63 



trippings {gogj 1Q.W> 10.36 



Richmond gives the following two tables, one showing the 

 composition of morning and evening milk, the other the results 

 of partial milking by analysis of six portions: 



COMPOSITION OF MORNING AND EVENING MILK 



Specific Total 



gravity. solids. solids. Fat. 



Morning 1.0323 12.47 8.91 3.56 



Evening 1.0319 12.83 8.90 3.93 



These are averages for seventeen years throughout the year. 



PARTIAL MILKING 

 Portion. 123456 



Total solids 10.47 10.75 10.85 11.23 11.63 12.67 



Fat 1.70 1.76 2.10 2.54 3.14 4.08 



Plasma solids '. 8.77 8.99 8.75 8.69 8.49 8.59 



