670 



SCIENCE PROGRESS 



fully-grown animals — might perhaps be determined by reversing the fattening 

 process — i.e. by gradually reducing the rations of a fat animal so as to cause it to 

 lose weight. It is to be expected that the loss would be, at first, confined to the 

 fat, but that a point would ultimately be reached at which loss of protein would 

 begin. As this would result in increased excretion of nitrogen consequent upon 

 a reduction in the amount of food consumed, the critical point could probably be 

 detected. If this should prove to be the case the whole question could be 

 investigated experimentally. 



If the whole of the fat be treated as true fattening increase, and only non- 

 fatty matter as growth, the results would be as follows : 



Original weight .... 



Fat in same 



Net weight of " lean " animal 

 Growth increase (non-fatty matter) 

 Weight of grown " lean " animal . 

 Total fat in fat animal . 

 Final weight of fat animal . 



Growth per 100 lean weight 



Same compared with ox 



Fattening increase per 100 grown weight 



Same compared with ox 



Fat 

 sheep. 



lb. 



95*55 

 24-67 



70-88 



3*28 



74-16 



45*22 



119-38 



4-62 



3*7° 

 6o'9 



1*3 



Extra-fat 

 sheep. 



lb. 



95*55 



24*67 



70*88 

 52*85 



123*73 

 115*64 



239*37 



74*56 

 59*64 



93*5 



2'0 



Whichever point of view is adopted it is clear that in the ox the increase was 

 due almost entirely to fattening, whereas in the pig and extra-fat sheep it was 

 largely due to growth. Fattening increase consists of pure fat. Growth increase 

 consists mainly, if not entirely, of non-fatty matter of which about three-fourths 

 is water. Growth increase is, therefore, less valuable and less food is required to 

 produce it. 



The importance of these facts with reference to the question of comparative 

 efficiency of animals as meat-producers is obvious, but even now it is not always 

 fully appreciated. Thus, many farmers hold that cattle should be fattened while 

 still young "because they put on weight more rapidly." This conclusion may be 

 sound, but the argument is false, for it ignores the fact that the additional gain of 

 weight is largely due to growth and that the composition of the increase is not the 

 same. It has not been established that young animals fatten more rapidly than 

 those which are fully grown. That question remains open. 



Again, 1 Warington has declared that " the pig is the most economical meat- 

 making machine at the farmer's disposal." This may be true, but the experi- 

 mental evidence on which it is based seems too slender to support the inference. 

 In order to justify the statement it would be necessary to show either (1) that pigs 

 require less food for maintenance, or (2) that they produce equal amounts of 

 growth or of fattening increase from less food or in less time than in other animals 

 under similar conditions. 



According to the surface law pigs and calves of the same weight should 

 require about the same amount of food for maintenance, but ten pigs, each of 

 100 lb., should require about twice as much as one ox of 1,000 lb. live weight. 

 These inferences are consistent with the results obtained in Sanborn's experi- 



1 Chemistry of the Farm. 



