645 



Effect of the large quantity of water. — The large water content of the 

 diffusion residue forces the animals to coiisunie abnormal quantities of 

 water. This may be disadvantageous in several ways. As the effect 

 of water upon milk and meat production is of general interest and the 

 discussion includes references to other inquiries, the considerations 

 may be cited here. 



In the first place the water in the cold diffusion residue must be 

 raised to the temperature of the body of the auinuil. Tlie heat for this 

 must come from the combustion of the food. The juithors estimate, for 

 instance, that in the experiments with sheep in series S (see page 051), the 

 excess of consumption of water daily with the wet food over that with 

 the diy food amounted to l.S kg. per head, and that the wet diffusion 

 residue had a temperature of from 5° to 10° C, so that this excess of 

 water must be warmed 32.5° to 27.5° in the body, for which the potential 

 energy of from 14.8 to 12.5 gr, of starch would be required. Though this 

 amount is not large, it is worthy of consideration. 



Again, with increase of water consumption there is increase of evap- 

 oration from the skin and lungs. For changing this excess of water 

 to the form of vapor, still more heat is required. How much of the 

 excess of water consumed would be excreted in the form of water through 

 the kidneys and intestines and how much as vajior from the lungs and 

 skin, it is impossible to say. From earlier experiments by Henneberg, 

 Maercker had assumed that 40 per cent of the excess of water would 

 be excreted in the latter manner, but exj)eriments lately pubKshed by 

 Vogel * imply that it is much less. The amount of water evaporated 

 from the lungs and skin must be considerable and must increase with 

 the amount consumed by the animal. In the average of Vogel's experi- 

 ments with sheep, 23.57 per cent of the total water consumed was evap- 

 orated through the lungs and skin. In the experiments of series S and 

 T the extra quantities of water with the wet diffusion residue were 

 1.4 and 1.8 kg. per head per day respectively. Assuming that 23.57 

 per cent of the whole water consumed in each case was evaporated 

 from the lungs and skin, the extra amount evaporated would be in 

 the one case 0.33 and in the other 0,42 kg. The amounts of heat 

 required for evaporating this water are estimated to be those correspond- 

 ing to the potential energy of 49 and 62 gr. of starch, respectively. Or, 

 to make the statement in a form more easily understood by practical 

 feeders, the increase of water consumption with the wet residue would 

 involve an increased evaporation, for which as much starch would have 

 to be burned in the body as would be contained in 103 gr. of wheat 

 bran in the one case and 130 in the other. In other words, it would by 

 this estimate require the carbohydrates of from 4 to 5 ounces of bran per 

 day to provide for the extra water evaporation by each sheep eating 

 diffusion residue. 



*.Touru. f. Laudw., 39 (1891), p. 39. 



