Agricultural Chemistry. — Pig Feeding. 



521 



in the Report of his elaborate investigation, on the Composition 

 of Turnips, grown under different circumstances, and in different 

 localities, has taken their per-centage of Nitrogen as the measure 

 of their comparative feeding values. 



It has been found, however, that the indications of Tables of 

 the comparative values of foods, founded upon their per-centages 

 ■of nitrogenous compounds, were frequently discrepant w ith those 

 which common usage, or direct experiments on feeding, seem to 

 give. These discrepancies have not escaped the attention of some 

 of the authors of the theoretical Tables ; but they have attributed 

 them, rather to erroneous interpretations of common practice or 

 experiment, than to any defect in the theoretical method of 

 estimation. It has been admitted on all hands, however, that 

 further direct experiment bearing upon this important question 

 was much needed; and it was the acknowledgment of this 

 necessity, and the fact that the further we proceeded with our own 

 investigations, the more we became convinced that the current 

 views on the subject required some modification — that led us to 

 give a paper, " On the Composition of Food in relation to 

 Respiration and the Feeding of Animals," at the meeting of the 

 British Association held last year at Belfast. That paper is now 

 in print, as a " Report " in the annual volume of the Association. 

 But, as in that medium it will probably come under the notice of 

 few but scientific readers, we have been induced, in compliance 

 with a wish expressed by Mr. Pusey, as the editor of this 

 Journal, to embody in this article, so far as these experiments on 

 Pigs illustrate them, som.e of the vievrs of that paper, W"hich may- 

 be of interest more particularly in their agricultural bearings. 



Recumng to the question of the adopted views on the subject 

 of the Chemistry of Food, to which we have called attention, we 

 may observe, that in our paper on Sheep Feeding, in vol. 10, 

 part 1, of this Journal, we ourselves had, to a certain extent, 

 adopted the current opinion that the increase in weight in the 

 fattening animal will bear a pretty direct relationship to the 

 supply in the food of the nitrogenous or plastic elements of 

 nutrition. At that time, however, w-e observed in our results, 

 some marked exceptions to this rule ; and we pointed out, that it 

 seemed to apply only so long as the nitrogenous supplies in the 

 food did not exceed a somewhat narrow limit, frequently reached 

 in our current fattening food-stuffs — and beyond w^hich, the pro- 

 portion of increase obtained from a given amount of nitrogenous 

 substance consumed seemed to be considerablv diminished. In 

 that paper, we also showed, that the amount of food consmned to 

 a given weight of animal, within a given time, bore in the experi- 

 ments then brought forward, a much closer relationship to the 

 amounts in the food of the available non-nitrogenous constituents^ 



