GROWTH 409 



daily gain of from six to nine pounds of protein per thousand 

 live weight during the first sixteen days after birth. Plainly, 

 young pigs need a relatively large supply of protein in their feed, 

 but unfortunately no attempts have thus far been reported to 

 determine the minimum of feed protein necessary at different 

 ages and especially by older pigs, simply to ensure normal 

 growth. There are on record, however, a considerable number 

 of experiments in which rations supplying varying amounts of 

 protein have been fed to fattening pigs and the effects upon the 

 make-up of the carcass and upon the rate of increase in live weight 

 observed. These experiments have served to demonstrate in a 

 striking manner the practical advantages of a liberal protein 

 supply and while in many instances the minimum protein re- 

 quirement may have been considerably exceeded, nevertheless, 

 the results as a whole are perhaps no less useful as a guide in 

 practice. 



It is impossible to include here even an enumeration of the large 

 number of experiments of this sort. For a summary of earlier inves- 

 tigations the student may be referred to the summary published by 

 Wolff in 1876. 1 A considerable number of earlier experiments in the 

 United States as compiled by the writer gave results of the same 

 general nature. 



The later experiments upon this subject may be divided into those 

 directed more specifically to the determination of the influence upon 

 quality and chemical composition of the carcass and those in which 

 the increase in live weight was the principal criterion. 



489. Effect of insufficient protein upon the carcass of pigs. 



Striking results as to the make-up of the carcass in young pigs 

 have been reported by several investigators in experiments in 

 which exclusive maize feeding was compared with the use of 

 mixed rations supplying much more protein and ash. The 

 trials have been popularly spoken of as " Feeding for fat and 

 for lean." In reality they are a study of the effect of inade- 

 quate protein (and ash?) supply in limiting growth. The 

 subject was first taken up by Sanborn 2 and soon after by 

 Henry. 3 In general it was found that in the pigs receiving the 



1 Ernahrung der landwirtschaftlichen Nutztiere, pp. 465-496. 



2 Mo. Agr'l College, Bui. 10, 14 and 19. 



3 Wis. Expt. Sta., Rpts 4, 5, 6, 17, 18, 19 and 21. 



