BY MARGARET H. O'dWVER. 241 



iii. The Value of Digestibility Experiments. 

 In ;i jnihlication entitled "The Relathe Value of Feeding Stuffs — Experi- 

 ments with the Respiration Calorimeter in Co-operation witli the Bureau of 

 Animal ludustr'" CArmsby, 1907), the writer states tl-at the only safe ba-:is for 

 a comparison of the natriti\e value of ftcding stuffs is the actual experiment 

 upon the animal, in \vhich tlie real gain or loss of flesh and fat is accurately 

 determined. In other words, that the only way to ascertain the nutritive effect 

 is to actually determine it. Kellner (1909) found that, in the case of coarse 

 fodders, the actual results were much lower than the computed ones. The dif- 

 ference was found by him to be very closely proportional to the amount of 

 crude fibre present, amounting to 617 calories for each lb. of the total crude 

 fibre. When this deduction was made, tlie computed results agreed very closelj' 

 with those found. 



Pammel, etc. (1901) give the following digestion coefficients for pasture 

 grass : — 



Digestion Digestible 



Coefficients. Ingredients. 



Dry matter 69 . . 13.8% 



Organic matter 70 . . 12.6% 



Crude protein 66 . . 2.3% 



Crude fibre 74 . . 3.0% 



N free extract 73 . . 7.1% 



Ether extract 55 . . 0.4% 



The digestion coefficient is tlie percentage of the particular nutrient which 

 is digested during the passage of food through the animal. 



The percentage of digestible ingredients is found by multiplying the per- 

 centage of each ingredient in the substance by its digestion coefficient. 



Hence if the percentage of protein in a feeding stuff' is 7.4, and the 

 digestion coefficient is .59, the percentage of digestible ingredients in the pro- 

 tein content of the feeding stuff' will be (7.4 X. 59) =4.4 (pammel, 1901). 



The figures given in the table may serve to indicate roughly, at any rate, 

 the digestibility of similar feeding stuff's in Australia, but it is to be hoped that 

 before long, digestibility experiments may be carried out in this State, for, 

 without these, no completely accurate basis of the nutritive value of feeding 

 stuffs can be arrived at. 



iv. Discussion of Methods. 



Up to the present the official methods of the Association of American 

 Agricultural tUiemists, a.s revised up to the end of the year 1919, have, in the 

 main, been followed. (Assocn. of Official Agricultural Chemists, 1920.). 



The principal reasons for adopting the American methods in this early 

 stage of the work are: — 



(a). A large amount of investigation into suggested modifications in 

 methods has been carried out by the American Agricultural Colleges, Bureaux of 

 Chemistry, etc. (Francis, 1916;' Bidwell and Walton, 1916; Bidwell, 1916; Francis, 

 1919; Clarke. 1920; Phelps and Daudt. 1919). and the methods have apparently 

 been subjected to very close scrutiny lief ore being classed as official (Assocn. 

 Official Agricultural Chemists, 1920, Introduction). 



(fe). Only by practically adopting the same methods, is it possible to make 

 any comparisons between the analyses of our native grasses and those of the 

 United States. 



