Apr. IS. 191S Organic Constittients of Kelps 53 



ECONOMIC CONSIDERATIONS 

 FEEDING VALUE 



The extensive use in Japan and Hawaii of certain seaweeds as articles 

 of food has given rise to the suggestion that the giant kelp might be 

 utilized for feeding man or animals. This question was discussed in a 

 general way some years ago by Alsberg (4, p. 263-270), but he pointed 

 out that practically no data regarding the composition of the kelps were 

 available at that time. The chemical studies reported in the present 

 paper make it evident that from the standpoint of nutrition the principal 

 varieties of the California kelps could have but slight value. The carbo- 

 hydrates are undoubtedly of a very resistant type, hydrolized with great 

 difficulty, and their percentage utilization would necessarily be low. 

 Saiki (20) has investigated this question for the carbohydrates of Irish 

 moss (Chondrus crispus), several varieties of Japanese edible seaweeds, 

 and agar-agar. Digestions were made with ptyalin, pancreatic amylase, 

 and intestinal extract. In none of the cases was there any evidence of 

 hydrolysis by the enzyms present. Feeding experiments on a human 

 subject and on a dog gave very low coefficients of digestibility. This 

 has been the import of many other experiments (16) in which pentosans, 

 galactans, and similar carbohydrates have been investigated with refer- 

 ence to their nutritive value. It has never been shown that they are 

 directly hydrolyzable by any of the enzyms of the digestive tract. Some 

 value they unquestionably have because of bacterial decomposition, 

 especially for animals of the ruminant type, but these resistant carbo- 

 hydrates are at the best of low rank among feeding materials. 



Analyses of the Pacific coast kelps show in some cases very appre- 

 ciable percentages of nitrogen. If this were all in the form of utilizable 

 proteins, it would make a very important addition to the feeding value, 

 but it is doubtful whether such is the case. It has been shown earlier 

 in this paper that a considerable portion of the nitrogen exists in the 

 nonprotein form. Although the percentage of acid amid nitrogen is 

 apparently very small, it would still be necessary to prove that the 

 remainder of the soluble nitrogen was present in the form of suitably 

 proportioned amino acids, before a high nutritive value could be assigned 

 to the material. Furthermore, the nitrogenous compounds would 

 undoubtedly be rendered less available because of the admixture of 

 large percentages- of highly resistant polysaccharids. 



In order to recover the potash, it would be necessary to leach the kelp. 

 Only the residue would ordinarily be considered for feeding purposes. 

 Since much of the organic matter is soluble in water, the value of the 

 residue would be still further decreased. Moreover, it is not believed that 

 the kelp would produce a very palatable ration. Mr. F. W. Woll, of the 

 University of California Division of Animal Industry, reports that cows 



