110 ANIMAL EXCRETA LITTER. 



that the amount of plant food, say nitrogen, in the solid excrement, 

 will be greater, the less digestible the food consumed. 



The composition of the excreta of animals depends greatly upon 

 that of their food. This is well known, and as will be discussed in a 

 later chapter, is the basis upon which manurial residues of foods are 

 based. In a paper on " The distribution of manure values of foods 

 between dung and urine," l Crowther emphasises the very high propor- 

 tion of the total manurial value which is contained in the urine of 

 farm animals. After considering, in detail, the cases of fattening oxen, 

 horses, milch cows and young growing animals, he arrives at the con- 

 clusion that the total liquid excreta, as they leave the animals, possess 

 from three to four times the manurial value of the total solid excre- 

 ments, so far as these manurial values are determined by the chemical 

 composition of the fresh excreta. Owing, however, to the ready de- 

 composition of the nitrogenous constituents of urine, the ratio tends to 

 diminish rapidly when the excreta are kept, unless special precautions 

 against loss of nitrogen are' taken. He considers that 40 per cent of 

 the nitrogen of the urine is probably the average loss, during storage, of 

 farm-yard manure. Even after suffering this loss, the manurial value 

 of the urine produced by an animal greatly exceeds that of the solid 

 excrement. 



In the estimation of the money values employed in the calculations, 

 the following values were ascribed to the manurial ingredients : 



d. s. d. 



Digestible nitrogen (that in urine) . . 6 per Ib. = 12 1 per unit. 

 Indigestible nitrogen (that in dung) . 2 ,, = 42 ,, 

 Phosphorus pentoxide . . . . l| ,, = 2 9J ,, 

 Potash 2 ,, = 3 9 



The urine is assumed to contain all the nitrogen in the digestible 

 protein of the food, except that retained by the animal in the form of 

 increase of weight, or in milk production, and 85 per cent of the total 

 potash, while the dung is assumed to contain all the nitrogen in the 

 indigestible protein, all the phosphoric acid of the food, except that in 

 the increase or milk, and 15 per cent of the total potash of the food. 



The litter and waste food. Litter serves several useful purposes. 

 Besides the obvious advantages attending its use from the point of 

 view of cleanliness and comfort for the animal, it also fulfils several 

 other functions. It greatly increases the bulk of the manure, render- 

 ing it more porous and therefore better able to retain the valuable 

 liquid portion of the excreta, it provides a large amount of carbon- 

 aceous matter which will eventually be converted into humus, and it 

 adds its quota of plant food, small though it be. It has a considerable 

 effect upon the various fermentative changes which the excreta of 

 animals so readily undergo, both by its influence on the porosity and 

 consequent admission of air and also by the micro-organisms with 

 which it is said to be often abundantly supplied. 



Various substances are used as litter in different districts. The 

 following are the chief : 



1 Trans. High, and Agric. Soc. Scotland, 1910, 125. 



