46 A Study of yitriHjeii Metabolisni in the Dairy Cow 



minations were made daily on independent hay samples, since this factor 

 was found to be sul)ject to consitleiable variation. 



Analysis of milk. Cow J) was milked twice daily during its period of 

 lactation and half-weekly com])osites were made up. The sam])les were 

 preserved by the addition of one or two drops of formalin. The deter- 

 mination of the nitrogen in the milk samples was carried out in duplicate 

 by the Kjeldahl method. 



The experiments were carried out at the Manor Farm, (iarfortii, 

 (Experimental Farm of the University of Leeds and the Yorkshire 

 Council for Agricultural Education). The care of the animals was in the 

 experienced hands of Mr H. J. Hargraves, N.D.A., to whom we are 

 greatly indebted for the skill and accuracy with which this important 

 side of the work was carried out. 



Table II. Analysis of seeds hay and linseed cake composile. 

 (Calculated on dry matter.) 

 Seeds hay 



It will he noted that the composition of the hay, and in particular, its 

 content of protein, were subject to considerable variation during the 

 course of tlie trial. This rendered neces.sary, in the later stages of the 

 experiment, a slight increase in the amount of hay fed per day, in order 

 to maintain the amount of protein consumed per day at its initial level. 

 Another factor disturbing to some extent and difficult to regulate was 

 the great variation to which the moLsture-content of the hay was subject 

 from day to day. For these reasons it was impossible to avoid an ap- 

 preciable variation in the nitrogen-.supply without recourse to methods 

 which the resources at our disposal did not permit. It will be seen from 

 the second column of Table III what the extent of this variation was. 



Comments on Tabic III (First Main Period of Experiment). 



We cannot attempt to tabulate here in detail the whole of the data 

 accumulated day by day during the trial. The figures given in Table 1 1 1 

 therefore represent daily averages for the difFerent periods, the nitrogen- 

 balance columns giving the average daily gain or loss of nitrogen by the 



