XV. MILK AND MILK PEODUCTS 325 



Crowther and Euston l obtained results in general agreement with 

 those just quoted, their figures being, 9-17, 8-96, 8-88, 8-86, 8-89, 8-77 

 and 8-67, while for the eighth, ninth and tenth months they found 

 8 - 60, 8*66 and 8*67 per cent. The proportions of ash and of milk 

 sugar appear to undergo but little change with advancing lactation. 



The changes in composition of milk with advance of lactation differ 

 considerably in individual cows, but on the average, milk is richest in 

 fat, total solids and albuminoids in the earliest and latest stages of 

 lactation and is most watery about the second or third month. The 

 fat not only alters in amount but also in constitution, for it seems 

 clearly proved that with cows far advanced in lactation, the proportion 

 of volatile fatty acids in the fat becomes distinctly smaller and some- 

 times gives rise to the suspicion that butter made from it has been 

 sophisticated. 



Influence of food. The character of the food of a cow has an in- 

 fluence on the quantity and quality of the milk only between narrow 

 limits, unless incipient starvation be induced. Eich, palatable, con- 

 centrated food is conducive to an increase both in the quality and 

 quantity of the milk, but only up to a certain point. It is usually 

 asserted that the use of succulent or sloppy food to stall-fed cows in- 

 creases the quantity but reduces the quality of the milk ; but according 

 to Danish and American experiments this is not true. At Copen- 

 hagen (20th Eeport, 1890), for example, experiments conducted with 

 636 cows for three years showed that the addition of 40 Ib. of mangels 

 or 50 Ib. of turnips per day increased the daily milk yield by over 

 2 Ib., while the animals increased in weight and consumed 3*08 Ib. 

 less straw daily ; but no appreciable alteration in the composition of 

 the milk could be detected. The writer found that the addition of 40 Ib. 

 of brewers' grains to the food of cows at pasture had certainly no 

 effect in increasing the amount of water in their milk. Tangl and 

 Zaitschik 2 also failed to find any change in the composition of milk 

 when the food of the cows was changed from a dry to a very watery 

 one. 



Many investigations as to the influence of food upon milk produc- 

 tion have been made in America. 3 The majority of these have been 

 directed to contrasting the effects of rations with wide and with narrow 

 albuminoid ratios, and the results show that a distinct improvement 

 both in the quality and quantity of the milk can clearly be detected 

 when the food of the cows is changed to a more nitrogenous ration. 

 Thus in tests including some 150 animals the mean results on the next 

 page were obtained. 



It is very doubtful whether these changes, clear and distinct though 

 they are, are of more than a temporary character. 



In 1901, 4 the writer carried out investigations upon the effects of 



1 Trans. High, and Agric. Soc. Scotland, 1911. 

 2 Landw. Versuchs-Stat., 1911, 74, 183. 



3 Vide Keports of the Storrs Agric. Expt. Station, 1894-7. 



4 Trans. High, and Agric. Soc. Scotland, 1902, 284. 



