242 REPORT OX NUTRITIVE VALUE Or CERTAIN AUSTRALIAN (iRASSES, 



Certain interesting modifications of these methods, however, are of con- 

 siderable vakie, and these 1 hope to make the subject of a further communica- 

 tion in the future. Dr. Petrie (1908), discussing those used for the precipita- 

 tion of the proteins, gives an account of some preliminary experiments which 

 he carried out with the seeds of Acacia pycnantha, copper hydroxide, (Stut- 

 zer's Reagent), tannin salt solution and alcohol being severally used as preeipi- 

 tants. He found that, apparently, alcohol and tannin salt solution gave dis- 

 tinctly more reliable results than copper hydroxide which is the reagent used 

 in the ofheiid American methods. These reagents might also be used to ad- 

 vantage in the precipitation of the proteins in grasses. Similarly acetone has 

 been suggested as a precipitant for the proteins (Weyl, 1910). 



No attempt has been made so far in this work to examine the non-protein 

 nitrogen in the grasses. Although Van Slyke's method (1911-12) appears at 

 tirst sight to be suitable for the purpose (Grindley and Eckstein. 191G; Grindley. 

 etc., 1915), other writers (Dowell and Menaul, 1919; Gcirtner, 1918; Gortner 

 and Holm, 1917; Hart and Sure, 191()) show that furfurol and dextrose tend 

 to react on the amino acids and protein hydrolysates (Dowell and Menaul, 1919. 

 p. 131), and that consequently an unusually large percentage of nitrogen is 

 found in the humin. This weakness in the method has also been noted by 

 Grindley, Joseph and Slater (1915). From a consideration of their own re- 

 sults, confirmed as they were by Gortner (1918), Hart and Sure conclude that 

 the method of direct hydrolysis for the estimation of amino acids in feeding 

 stuffs by the Van Slyke method is inapplicable, and tliat the results so secured 

 will be open to question. It is further suggested by them that, in the present 

 unsatisfactory status of the methods for estimating the amino acids in the 

 complex protein-carbohydrate mixture of feeding stuffs, the only reliable pro- 

 cedure for obtaining an insight into the nuti'itive worth of the proteins in 

 such a mixture is the biological one. 



All the writers mentioned above, however, ius well as Nollau (1915), Kellner 

 (1910), and Brunnich and Smith (1907), stress the great importance of the 

 non-protein nitrogenous compounds of feeding stuffs, and especially of the 

 amino acids. In the actual determination of proteins in the grasses, I have 

 followed the Kjeldahl Gunning Arnold method recouunended by the Associa- 

 tion of OHicial Agricultural Chemists of America (1920), and have found it to 

 work satisfactorily. Slight modifications in the olficial metiiods of estimating 

 proteins have been suggested from time to time (Brill and Ascavili, 1917; 

 Phelps and Daudt, 1920), the last named writers suggesting that the use of rubber 

 stoppers in the apparatus, as in the official method, may contribute small amounts 

 of ammonia-reacting substances, and recommending that cork stoppers, entirely 

 covered with tin foil, be used instead. In the determination of true protein. 

 or albuminoid nitrogen, Stutzer's Reagent has been employed as a precipitant 

 for the proteins (Assocn. Offic. Agric. Chemists. 1920). 



Crude Fibre. — The acid-alkali method has been used in estimating the crude 

 fibre in the grasses (Assocn. Offic. Agric. Chemists, 1920). Although the method 

 may have many drawbacks (Bidwell and Walton, 191(); Francis, 1916), it is 

 usually considered su])erior to other methods. 



Bidwell and Walton (1916) point out that crude (ihre is not the name of 

 a definite substance, but oidy a convenient and scimewhal descriptive term used 

 to denote the result obtained by treating a feed by the olficial method. "Inas- 

 much," tiiey say, "as crude fibre designates simf)ly a lunnerical value obtained 

 by following the official nietlmd which is strictly an cinpirica) one. any dcvin- 



