[Agr. Biol. Chem., Vol. 34, No. 9, p. 1314•`1319, 1970]

Availability of Energy in Ester and Ether Derivatives of Glycols by Growing Chicks

By Minoru YOSHIDA, Hiroshi MORIMOTO,* Masanao MATSUI** and Ryohei ODA***

National Institute of Animal Industry *Japan Scientific Feeds Association **Faculty of Agriculture, University of Tokyo ***Faculty of Technology, Kyoto University Received March 4, 1970

Biological availability of 33 esters, 17 ethers and 2 acetals of ethanediol, 1,2-propanediol, 1,3-butanediol and 1,4-butanediol was compared by mini-test with chicks. Chicks can utilize esters of ethanediol, 1,2-propanediol and 1,3-butanediol with acetic acid and fatty acids of carbon chain length from 5 to 12 with more improved palatability than that of free acids, while availability of esters of these glycols with propionic and butyric acids was low. Esters of 1,4-butanediol and ether derivatives of these glycols was not available, except ethyl ether of di-ethanediol which was partially available. Acetacetal of ethanediol was partially available but n-butyracetal was not.

This is the third paper of the studies on fore, it is suspected that chicks have enough the possibility of various chemicals as energy enzyme system or systems to utilize energy sources of poultry feed. In the previous in these acids readily. papers,1,2) biological availability of 54 aliphatic While Ozaki reported about 40 years ago4) mono-, di- and tri-carboxylic acids, 23 alcohols, that rats on acetic, butyric, capric acids died 16 aldehydes and 2 ketones was compared by within 40 days of experimental period, bioassay procedure, mini-test, developed speci Ashida's recent works5) revealed that growth fically for this purpose.3) rate of rats on acetic, propionic and valeric It was observed in the first paper of this acids was satisfactory but none of them series of studies that chicks can not utilize exceeded that of the control rats. energy in volatile fatty acids of carbon chain Since in these previous works volatile fatty less than 6, when the acids were mixed in acids were mixed in the diet and fed to the diet and fed to chicks. These findings chicks and rats, some physiological activities were unexpected, since these acids were of free fatty acids, such as influence on pH known as energy source for ruminants, being in digestive canal, may possibly depress the produced by the fermentation in rumen, and utilization of the acids. To avoid any such at the same time, various metabolic pathways detrimental physiological influence of free of these acids were published already. There acids, it was planned to study the availability of these volatile acids, in the form of ester 1) M. Yoshida, H. Morimoto and R. Oda , Agr. with four diols, i.e. ethanediol, 1,2-propanediol, Biol. Chem., 34, 1301 (1970). 2) M. Yoshida, H. Morimoto, M. Matsui and R. Oda, ibid., 34, 1308 (1970). 4) J. Ozaki, Nippon Nogeikagaku Kaishi , 8, 1286 3) M. Yoshida and H. Morimoto, ibid., 34, 684 (1932). (1970). 5) K. Ashida, private communication (1969). Availability of Energy in Ester and Ether Derivatives of Glycols by Growing Chicks 1315

1,3-butanediol and 1,4-butanediol. As for the EXPERIMENTAL moiety of the esters, initial three diols were Test material. Ethanediol di-laurate, ethanediol found available by chicks when mixed in the acetal and n-butyracetal, 3-ethoxy-, 3-propoxy- and diet at a level of 5%, but the last one, 1,4- 3-n-butoxy-1,2-propanediols were synthesized in Oda's butanediol, was observed unavailable by Laboratory, Kyoto University. Eleven esters of 1,2- chicks.6) Therefore, in the experiments propanediol, 13 esters of 1,3-butanediol and 7 esters planned, it was also attempted to confirm of 1,4-butanediol were synthesized in Matsui's Labora whether chicks can utilize 1,4-butanediol tory, University of Tokyo. when fed as esters of fatty acids. Cellosolve (ethanediol mono-ethyl-ether) and its 6 It was also found in the previous papers1) derivatives, carbitol (di-ethanediol mono-eth)-lether) that availability of free fatty acids with carbon and its 6 derivatives were all purchased as reagent, chain longer than 14 was low, mainly because of which grade were given in Note in Table I. Ethanediol mono-methyl ether, methyl cellosolve, was of low digestibility of these acids. Therefore, a highly special reagent to be used for amino acids esters of these higher fatty acids with various autoanalyzer. diols were included in these experiments to Gross energy of the test materials was determined find whether these higher fatty acids are by automatic bomb calorimeter, CA-1, manufactured available when fed in the form of ester. by Shimadzu Seisakusho. Gelatin capsule, of which Natural fat is an ester of these fatty acids caloric value was 4,371 cal/g with standard deviation with glycerol. Therefore, esters of these fatty of 197 cal, was used in the determination of volatile acids with diols, analogous to natural fat in materials. chemical construction, might be utilized by chicks better than the free fatty acids. Bioassay. Details of the procedure of bioassay was On the other hand, various ethers of exactly the same as those reported in the previous two papers.'.') All of the test materials were mixed ethanediol or its dimer, known as cellosolve in the diet at the level of 5%. Special care was and carbitol, respectively, and their derivatives taken to feed the diet containing cellosolve derivatives are readily available as solvents, so that to chicks in the smallest amount as possible at a. nutritive values of these solvents were also time, to avoid loss by evaporation. Standard dose studied by the procedure of mini-test. response curve was prepared so that available energy In the previous paper,2) it was revealed of the test material was estimated directly on the that acetal, which is a compound of acetal curve. dehyde with two molecules of ethyl alcohol, Procedure of the determination of digestibility was looked like partially available by chicks. also the same as that reported in the previous paper.1) Therefore, the analogous compounds of acetal dehyde or n-butylaldehyde with one molecule RESULTS AND DISCUSSION of ethanediol were prepared and tested for their availability by chicks. The data on ester and ether derivatives of The derivatives of 1,2-propanediol, having ethanediol were presented in Table I. ethoxy, propoxy, or n-butoxy groups at 3 Chicks could utilize energy in ethanediol position by ether bond, were also prepared di-laurate efficiently, but they could not utilize and tested. none of ether derivatives of ethanediol and In this paper, results of these mini-tests on of di-ethanediol, except ethyl ethers of di- esters and ethers of various diols were ethanediol. Methyl ethers of ethanediol summarized. were all toxic, and those of di-ethanediol retarded growth of chicks and palatability of 6) M. Yoshida, H. Hoshii and H. Morimoto, all of these ethers was low. Three ethyl Japan. Poultry Sci., 6, 73 (1969). ethers of ethanediol retarded growth of chicks 1316 M. YOSHIDA, H. MoRIMOTO, M. MATSUI and R. ODA

TABLE I. GROSS ENERGY, AVAILABILITY AND PALATABILITY OF DERIVATIVES OF ETHANEDIOL

a) See text. b) Special: special grade reagent; Fi c) D rst: first grade reagent; Reagent: reagent grade . ead/total. d) Can not be estimated because chicks died .

but the corresponding ethers of di-ethanediol already reported6) that chicks can utilize part could be partially utilized by chicks , although of energy in dimer of ethanediol . Data on available energy of these ethers was not more ethyl ether of di-ethanediol agrees with the than one-third of their gross energy . Three previous observation. butyl ethers tested were all toxic , either A derivative of ethanediol with acetaldehyde retarding growth rate or killing the chicks . seemed to be utilized partially as shown by These findings suggested that ethyl moiety possitive available energy. Since only 5 g of of the ethers can be utilized partially by the sample was obtained and was fed to one chicks, but methyl and butyl moieties of the chick, no determination was carried out on ethers were rather detrimental . caloric value of the sample . It is supposed As discussed in the previous paper ,6) low to be about 5.8 kcal/g , which is the caloric availability of ethers of ethanediol suggested value of n-butyric acid having the same that chicks apparently lack the ability to molecular formula as that of ethanediol cleave the ether bond of these compounds , acetacetal. Therefore , the availability of the since moieties of these ethers after the cleav sample was expected to be about 200o . An age, i.e. methyl or ethyl alcohols and ethane other derivative of ethanediol with n-butyral diol, were known to be partially available dehyde was unavailable by chicks . These by chicks.2,6) On the other hand , it was two derivatives are acetal in nature showing Availability of Energy in Ester and Ether Derivatives of Glycols by Growing Chicks 1317

TABLE II. GROSS ENERGY, AVAILABILITY AND PALATABILITY OF DERIVATIVES OF PROPANEDIOL

a) See footnotes of Table I,

masked carbonyl function, and no detrimental clearly by carbon skeleton of the ester, the change in the diet was observed due to free data with this ester suggested very low carbonyl function, as discussed in the previous availability of propionic acid. paper.2) However, here again were obtained The data with derivatives of 1,3- and 1,4- the data indicating that ethyl moiety of the butanediols were summarized in Table III. compound can be partially available by chicks Again, chicks could utilize energy in esters but butyl moiety can not as in the case of of 1,3-butanediol with acetic acid and fatty ethers mentioned above. acids of carbon chain from 5 to 12. The The data with ester and ether derivatives findings were quite agreeable with those in of 1,2-propanediol were presented in Table II. esters of 1,2-propanediol mentioned above, Chicks could efficiently utilize energy in and were not unexpected, since moieties of esters of 1,2-propanediol with acetic acid and these esters, 1,3-butandiol and fatty acids fatty acids of carbon chain longer than 5. were known to be available by chicks.1,6) The findings were not unexpected, since Availability of esters of 1,3-butanediol with moieties of these esters, 1,2-propanediol and propionic, n- and isobutyric acids was again fatty acids were known to be available by negative, suggesting very low availability or chicks."' However, the esters of 1,2-pro rather detrimental effect of these volatile panediol with n- and isobutyric acids had fatty acids as in the case of esters of 1,2- detrimental effect to chicks as shown by propanediol. negative available energy in Table II. Availa Availability of 1,3-butanediol dimyristate bility of energy in the ester of 1,2-propanediol was lower than those of esters of 1,3-butane with propionic acid was only 30%. Since diol with fatty acids with carbon chain about one-third of energy in this ester come shorter than 12. This was apparently due to from readily available propanediol as indicated low digestibility of the ester, being 42% as 1318 M. YOSHIDA, H. MORIMOTO, M. MATSUI and R. ODA

TABLE III. GROSS ENERGY, AVAILABILITY, PALATABILITY AND DIGESTIBILITY OF DERIVATIVES OF BUTANEDIOLS

a) See footnotes of Table I . shown in Table II. The findings were just be determined due to poor appetite.6) comparable with those observed on free Since caloric contribution of fatty acid myristic acid reported previously," whose moiety, which is readily available , was larger digestibility was 37%. than that of 1,4-butanediol moiety in these As shown in Table III, 1,4-butanediol di-n- esters, low availability of gross energy in butyrate was detrimental, and 2 chicks out these esters suggested that most of these of 8 on this ester died within 6 days of ex esters passed through digestive cannal without perimental period. any cleavage of ester linkage by lipase . Much Availability of ester of 1,4-butanediol with lower digestibility of esters of 1,4-butanediol caproic acid was also negative and those with with lauric and myristic acids than that of caprylic, nonanoic and lauric acids were corresponding esters of 1,3-butanediol may much lower than those of corresponding support this assumption . esters of 1,3-butanediol. One chick out of 8 Excellent availability of 1,4-butanediol di- on 1,4-butanediol dicaprylate died . These caprate was exceptional to above discussion. data revealed that the availability of 1 ,4-b Since the availability of this ester was un utanediol was much lower than that of 1,3- expectedly high in the first mini-test with butanediol. Free 1,4-butanediol was hated the ester, the test with 8 chicks was repeated by chicks, and energy availability could not and the similar availability was again ob- Availability of Energy in Ester and Ether Derivatives of Glycols by Growing Chicks 1319

tained. In Table III, average of the data in bility of the esters of 1,2-propanediol and these 2 trials were given. The reason why 1,3-butanediol with fatty acids of carbon chain only this ester, 1,4-butanediol dicaprate, was length between 6 to 12, it should be pointed available by chicks, while all of the other out that palatability of fatty acids is greatly esters with l,4-butanediol tested were low in improved in these esters. Average palata availability, is unknown. bility index of 5 esters of 1,2-propanediol Summarizing all of the data, it is clear shown in Table II and of 6 esters of 1,3- that acetic acid was available by chicks, butanediol shown in Table III, is 91 and 92, when fed as esters with 1,2-propanediol and respectively, while that of corresponding free 1,3-butanediol. Detrimental effect of free fatty acids" is 68 and 70, respectively. Even acetic acid observed in the previous paper'' the palatability of esters of 1,4-butanediol, of is certainly due to the physiological effect of which availability by chicks is low, is ex free acid infused directly into crop as aqueous cellent as shown in Table III. The improve- solution of rather high concentration of 10%. ment of palatability is certainly much favora Contrary to the findings with acetic acid, ble and important in the use of these deriva it is confirmed that not only chicks fail to tives of fatty acid as dietary energy source. utilize propionic and butyric acids efficiently, Besides the practical merit of improved but also these acids have some detrimental palatability of esters of fatty acids with diols, influence on chicks, although the data on another economically significant merit should 1,2-propanediol dipropionate indicate partial be pointed out. That is the tendency of availability of energy in this ester. The data increase in the caloric value of esters in on 4 esters of valeric acids with 1,2-propane- comparison with that of the corresponding diol and 1,3-butanediol as a whole reveals free fatty acids. Especially, caloric value of that availability of valeric acid by chicks is acetates of the diols is nearly twice as high lower than that of higher fatty acids, although as that of free acetic acid. Unpublished the data on 1,2-propanediol di-iso-valerate evaluation of caloric value in this Laboratory, was excellent. It should be kept in mind, estimated by procedure of linear programming as mentioned in the previous papers1•`3) re using an electronic computor, TOSBAC 3400

peatedly, that the reliability of the data of of the Computing Centre for Research in each mini-test is not high enough, therefore, Agriculture, Forestry and Fishery, revealed the discussion should be based on all the data that 1,000 kcal of biologically available energy with related compounds. The findings with of the chemical products can be evaluated the esters of these volatile fatty acids are roughly to be 9 yen. Therefore, the increase

quite agreeable with the findings on availa in caloric value of chemical products is bility of free fatty acids reported in the pre favorable from economical point of view, if it vious paper.1) It will be worth-while to study is available to domestic animals and poultry. further the reason why availability of volatile Esterification of acetic acid with diols may fatty acids with carbon chain length between be one of the possible ways to utilize rela 3 to 5 is low by chicks. tively cheap acetic acid as feedstuffs in the With regard to satisfactorily high availa future.