468 NUTRITION OF FARM ANIMALS 



hand, while the ordinary feed of herbivora contains carbohy- 

 drates yielding galactose, the latter is apparently transformed 

 into glycogen quite promptly and at any rate has not been 

 found in the blood, while animals receiving feed containing no 

 galactose (carnivora, e.g.) produce lactose in their milk. The 

 probability seems to be that the galactose half of the lactose 

 is manufactured in the milk gland from the dextrose of the 

 blood. 



555. Sources of ash. The ash ingredients of the milk, 

 including its sulphur and phosphorus, are, of course, derived 

 ultimately from the corresponding ingredients of the feed. In 

 liberal milk production on ordinary winter rations containing 

 a sufficiency of organic nutrients, however, it appears from in- 

 vestigations by Forbes 1 that considerable amounts of calcium, 

 magnesium and phosphorus may be drawn from the relatively 

 large store contained in the body, presumably to be replaced 

 in later stages of lactation. 



556. Character of milk production. While the statement 

 that milk production is a form of tissue growth is probably 

 incorrect anatomically, it is essentially true so far as the chemical 

 composition of the product and the demands which it makes 

 on the feed supply are concerned. This is clearly shown by 

 comparing the ratio of protein to fat in the organic matter of 

 milk and in that of the increase in weight of growing animals. 

 In the solids of milk, it is evident that in order to make a fair 

 comparison its milk sugar should be reduced to the equivalent 

 amount of fat. Taking Babcock's figures (547) as representing 

 the average composition of milk, the 4.88 per cent of sugar di- 

 vided by 2.25 is equivalent to 2.17 per cent of fat, which added 

 to the 3.69 per cent of fat present as such makes a total fat 

 equivalent of 5.86 per cent, while if milk sugar were thus re- 

 placed by fat the total organic matter would amount to 9.41 

 per cent. On this basis, 100 parts of organic matter would 

 contain 37.73 per cent of protein and 62.27 per cent of fat. 

 Comparing these figures with those given in Chapter XI (458) 

 for the composition of the increase in growth, it appears that 

 the proportion of protein to fat is greater than that computed 

 for young animals except in the earliest stages of growth. 



The computed energy content of average milk solids is 2620 



1 Ohio Expt. Sta., Bui. 295 (1916). 



