528 NUTRITION OF FARM ANIMALS 



the milk, while others, more conservative, have contented them- 

 selves with pointing out the conflicting nature of the evidence. 



624. Influence on percentage of fat in milk. Since fat is 

 the specially valuable ingredient of milk, the discussion has 

 centered around this substance. An increase in the percentage 

 of fat in the milk may result from an increase in the percentage 

 of total solids, i.e., a decrease in the water content, as well as 

 from a specific increase in the fat. The conservative view on 

 this point was thus summed up by Jordan in igoS. 1 



" This question has been much discussed and much investi- 

 gated from the work of Klihn in 1868 down to the present day. 

 Many experiments have been conducted for long periods and 

 short periods in which very moderate rations have been com- 

 pared with very large ones, highly nitrogenous foods with those 

 of a low protein content, dry with green or succulent materials, 

 and grains of the same class with one another, and, in a great 

 majority of cases, the verdict has been that ' no consistent 

 relation appears to exist between the quantity or character of 

 the ration and the composition of the milk.' The writer has 

 examined the results of nearly all the important experiments 

 of this character of which he could find a record, and in but few 

 cases could he discover that there was a material increase or 

 decrease in the proportion of milk solids which bore a logical 

 relation to variations in the ration. In some cases a temporary 

 change appeared in the milk immediately after a violent change 

 in the ration, but in most instances of this kind there was very 

 soon a return to the animal's normal product. In a small 

 proportion of experiments, the milk appeared to sustain a per- 

 manent though not extensive modification. The weight of 

 testimony bears out the statement that the quality of milk 

 cannot be changed at will by the farmer, but is largely deter- 

 mined by causes not under his control, such as breed and indi- 

 viduality, although feeding and treatment, especially the latter, 

 have more or less influence upon the character of the milk 

 secreted." 



Much of the alleged effect of feeding stuffs upon the com- 

 position of milk is associated with the question of the so-called 

 " specific " effects of feeding stuffs (618). As was pointed out 



1 The Feeding of Animals, 5th Edition, The Macmillan Co., New York, 1908, 

 PP- 317-318. 



