GROWTH AND FATTENING 81 



per ct. of the animal proteins. With wheat proteins as the sole source of 

 amino acids for growth, obviously a considerable part will be wasted. 

 There are certain proteins which entirely lack some of the essential amino 

 acids and so will produce no growth. However, when the missing amino 

 acids are fed to supplement such a deficient or imperfect protein, the 

 animal will then be able to continue growth. 



The various incomplete proteins do not all lack the same amino acids. 

 Hence, when two incomplete proteins are combined, one may supplement 

 the deficiencies of the other and better growth be made than on either 

 alone. To study this problem, young growing pigs were fed by 

 McCollum and by Hart and Steenbock at the Wisconsin Station 12 on 

 many rations in which the protein was supplied by a single feed or by 

 two or more feeds. When fed only corn, wheat, or oats, the pigs retained 

 in their bodies for growth only 23 to 28 per ct. of the protein in their 

 feed. The protein of linseed meal was of even poorer quality, only 17 

 per ct. being stored. However, with skim milk 66 per ct. of the protein 

 was stored in the body. Milk casein was nearly as efficient, 51 per ct. 

 being retained. A mixture of one-third each of corn, wheat, and oats 

 was only a trifle better than any one of the cereals alone. On the other 

 hand, when a mixture of three-fourths corn and one-fourth linseed meal 

 was fed, 37 per ct. of the protein was stored, considerably better than 

 with either feed alone. Of the feeds tested, skim milk was the most 

 efficient supplement to the cereals. Pigs fed 1.3 Ibs. of skim milk with 

 each pound of corn, stored about 62 per ct. of the protein in their feed. 

 On corn and tankage or on barley and tankage about 40 per ct. of the 

 protein was stored, but on corn and alfalfa hay only 32 per ct. On 

 corn, gluten feed, and alfalfa hay only 28 per ct. was retained, while 39 

 per ct. was retained on corn, alfalfa hay, and whey, and 41 per ct. on 

 corn, alfalfa hay, and skim milk. 



These results show that the proteins from the cereals are deficient in 

 the same amino acids and do not supplement each other, while the milk 

 proteins supplement the cereal proteins most excellently. Tankage is 

 a considerably more efficient supplement to the cereals than alfalfa hay 

 or linseed meal. 



In feeding trials with pigs Morrison and Bohstedt have secured simi- 

 lar results at the Wisconsin Station. 13 Pigs weighing 129 Ibs. made 

 average daily gains of 2.10 Ibs. on barley and skim milk, and 1.95 Ibs. 

 on barley and tankage, while on barley and linseed meal the daily gain 

 was only 1.22 Ibs., and on barley and middlings only 1.27 Ibs. Tho whey 

 contains but 0.8 Ib. protein per 100 Ibs., this small amount was found 

 to be surprisingly efficient in supplementing barley, pigs fed only barley 

 and whey gaining 2.53 Ibs. per head daily. 



In another trial pigs averaging 147 Ibs. at the start gained only 1.48 

 Ibs. per head daily on barley and middlings, while a lot fed barley and 



12 Jour. Biol. Chem., 19, 1914, p. 323; 38, 1919, p. 267; unpublished data. 



"Wis. Buls. 319, pp. 70-71; 323, pp. 8-10. 



