TEXAS AGRICULTURAL EXPERIMENT STATION C. H. McDOWELL, ACTING DIRECTOR, College Station, Texas BULLETIN NO. 675 NOVEMBER 1945 DIGESTIBILITY OF HUMAN FOODS AND ANIMAL FEEDS AS MEASURED BY DIGESTION EXPERIMENTS WITH RATS G. S. FRAPS Division 0f Chemistry L! RY e A, & M. CuLLbeki. Of TEXAS AGRICULTURAL AND MECHANICAL COLLEGE OF TEXAS GIBB GILCHRIST, President D22-1245-6M-L180 '* / [Blank Page in Original Bulletin] As part of the comprehensive investigation of the energy values of animal feeds and human foods, digestion experiments were made with white rats. Results of 508 tests of the digestibility of foods and feeds by rats are summarized. The rats digested slightly less protein than chickens from the animal feeds but slightly more than the chickens from the human foods. The rats digested less fat but more crude fiber and more nitrogen-free extract than chickens. Digestibility of protein and of nitrogen-free extract averaged prac- tically the same for both rats and humans, but the digestibility of fats averaged a little lower by rats than by humans. Digestion ex- periments of foods with rats can give a good idea of digestibility with humans. CONTENTS Introduction . . . . . . . . . . . . . . . . Previous Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..'\' Methods...... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. Coefficients of Digestibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 Variations as Shown by Standard Deviations . . . . . . . . .‘ . . . . . . . . . . . . . . . .e.- ' Variations in Digestibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I Comparative Digestibility by Rats and Chickens . . . . . . . . . . . . . . . . . . . . . Comparative Digestibility by Rats and Humans . . . . . . . . . . . . . . . . . . . . . Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . x References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V BULLETIN NO. 675 NOVEMBER, 1945 DIGESTIBILITY OF HUMAN FOODS AND ANIMAL FEEDS AS MEASURED BY EXPERIMENTS WITH RATS G. S. Fraps Collaborating Chemist, Division of Chemistry This publication is part 0f a comprehensive investigation of the energy values of animal feeds and human foods. Previous work has shown that the differences in energy values of food and feeds as measured by experiments with chickens are due to a large extent to differences in digestibility and to a much less extent to differences in the energy values of the digested nutri- ents (3). It was thought that digestion experiments with white rats would add to the information as to the energy values of animal feeds and human foods. For this reason, digestion experiments with rats were conducted in conjunction with the other work on the productive energy of feeds and foods (3, 4). White rats are used extensively for experimental work on metabolism, vitamins, and for other types of work relative to nutrition. The digestibilities of various foods and feeds, secured by means of rats, were compared with those for chickens and for humans. Rats may have nearly the same digestive powers as humans; therefore the data secured by digestion experiments with rats may be applied to human foods. Previous Work Data from some of the previous work on the digestibility of proteins, fats and oils by rats are tabulated in Table 1. Experiments with rats in which the digestibility of the protein, fat, crude fiber and nitrogen-free extract is reported, such as have been made with chickens, sheep and other animals, have not been found in the literature. The work tabulated gives the apparent digestibility of protein, in which corrections were not made for metabolized products. Experiments in which rats were used to ascertain the biological value of proteins are not included, because in these experiments the digestibility of the protein was corrected for the metabolized protein in the excrement. Methods Digestion experiments were made on simple mixtures containing 18% pro- tein, or on more complicated rations used in the productive energy work with chickens (3, 6) and with rats (4). When simple mixtures were used, they were made to contain as much as possible of the feed to be tested, with the ddition“ of 1% salt, 1% dicalcium phosphate, 0.2% fortified cod liver oil, and casein if the food was low in protein, or starch if it was high in protein. f the rats would not eat sufiicient quantities of any mixture, another mixture 6 BULLETIN NO. 675, TEXAS AGRICULTURAL EXPERIMENT STATION Table 1. Digestibility of protein and fat by rats (compiled) _ Protein 3 Food used 1n ration apparent Fat Reference digestibility Number ;j‘ Beef protein (10% protein ration) . . . . . . . . . . . . . . . 88 . . . . . . . . . . . . 10 Butter, Standard, lo_w protein ration . . . . . . . . . . . . . . . . . . . . . . . . . 89 1 Butter, Standard, high protein ration . . . . . . . . . . . . . . . . . . . . . . . . 96 1 Butter spread, special, low protein ration . . . . . . . . . . . . . . . . . . . . . 92 1 Butter spread, special. high protein ration . . . . . . . . . . . . . . . . . . . . 96 1 Casein (15% protein ration) . . . . . . . . . . . . . . . . . . . . 83 . . . . . . . . . . . . 10 Corn (107 protein ration) . . . . . . . . . . . . . . . . . . . . . . 81 . . . . . . . . . . . . 10 Cottonseed meal (high protein ration) . . .. . . . . . . . . 72 . . . . . . . . . . . . 7 Cottonseed meal, autoclave . . . . . . . . . . . . . . . . . . . . 64 . . . . . . . . . . . . 7 Cottonseed meal, extracted . . . . . . . . . . . . . . . . . . . . . 81 . . . . . . . . . . . . 7 Cottonseed oil, 15% . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 9 Cottonseed oil, hydrogenated, 5% . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 9 Lard, leaf (5% in ration) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . _ . . . . . 93 9 Lard, refined (5% in ration) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 9 Lard, hydrogenated (5%) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 9 Lard, neutral, 5% . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 9 Lard, steam, low protein ration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 1 Lard, steam, high protein ration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 1 Lard special, low protein ration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 1 Lard special, high protein ration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 1 Milk (10% protein ration) . . . . . . . . . . . . . . . . . . . . . . 83 . . . . . . . . . . . . 10 Milk, fresh whole . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 99 11 h/Iilk, powdered whole . . . . . . . . . . . . . . . . . . . . . . . . . . 8'7 99 11 Milk, evaporated . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 91 11 , Oleo oil, 5% . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 9 Peanut oil, 5% . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 9 Potato (10% protein ration) . . . . . . . . . . . . . . . . . . . . 79 . . . . . . . . . . . . 10 Soybean protein (15% protein ration) . . . . . . . . . . . . 77 . . . . . . . . . . . . 10 Soybeans, raw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 . . . . . . . . . . . . 8 Soybeans, heated . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 . . . . . . . . . . . . 8 Wheat protein (10% protein ration) . . . . . . . . . . . . . 79 . . . . . . . . . . . . l0 Yeast_(10% protein ration) . . . . . . . . . . . . . . . . . . . . . 79 . . . . . . . . . . . . 10 was fed containing a smaller quantity of the test feed. The more complicated rations usually contained 50% of the feed to be tested, except in case of oils, and feeds very high in protein (3, 4, 6). Details for the digestion experiments were as follows: Select rats which do not shed much hair. Mix up enough of the ration to be tested for the experiment and for analysis. Place six rats in the rectangular cage made for the purpose with 3 /8-inch mesh bottom. Place a wire-screen platform at an angle of about 45°, directly beneath the metabolism cage. The size mesh of this inclined platform should be small enough—about 1/4-inch mesh,—to prevent feces from passing through. It should permit passage of wasted feed and urine. A tray covered with clean smooth absorbing paper should be placed beneath the platform to collect urine and waste feed. The inclined platform should be hung with wire and its lower edge should be about two inches from the bottom tray. A wire screen should be placed in front of the cage,—resting on the tray,—in order to prevent loss of feces. Put the feed in a McCullum feed cup with a piece of 1/4-inch hardware cloth cut slightly smaller than the diameter of the cup and resting on the feed. This prevents the rats from scratching out the feed. The feed cup is put in a flat 8-inch evaporating dish held in place by a piece of 1/4-in mesh hardware cloth with a hole cut in the center to allow the feed cup to project. The hard- ware cloth is turned down the sides of the dish so as to hold it firmly in place. Feed s0 as to leave little or no residue. DIGESTIBILITY EXPERIMENTS WITH RATS 7 If the rats eat only 75 grams of a particular feed, only 75 grams should be fed the next time. Feed three days for a preliminary period. Then Weigh the feed to 0.1 gm., put it in a weighed jar and feed the rats 7 days if sufficient feces is obtained, if not, feed longer. Enough feed should be fed and the feeding period should be long enough to give feces weighing 30 gms. or more. Collect the feces daily (except Sunday) for 7 days, putting in clean paper frequently. The feces should be freed of all feed residues and hair by careful brushing. Dry the feces daily in an electric drying oven for about two hours, g but do not over-dry. Save all feed residues, dry if necessary, and Weigh. Weigh the dried feces at the end of the experiment. Also weigh residual feed and the jar as a check to eliminate errors in weighing. In calculating the digestibility o? the feeds tested from the digestibility of the mixture and rations, the coefficients of digestibility given in Table 2 were used. These iwere derived from some preliminary experiments. Table 2. Digestion coefficients of feeds for rats used in calculations Ether Nitrogen-free Name of feed Protein extract Crude fiber extract. % % % % Alfalfa leaf meal . . . . . . . . . . . . . . . . . . . 60.0 46.2 30.0 74.7 Casein . . . . . . . . . . . . . . . . . . . . . . . . . . . 94.0 89.0 0 98.7 Corn meal . . . . . . . . . . . . . . . . . . . . . . .. 84.5 89.2 51.6 96.0 Cottonseed oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96. 7 . . . . . . . . . . . . . . . . . . . . . . . . Skim milk, dried . . . . . . . . . . . . . . . . . . 88.6 99.2 0 98.4 Starch . . . . . . . . . . . . . . . . . . . . . . . . . . . 80.0 90.0 O 99.0 Cod liver oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96. 7 . . . . . . . . . . . . . . . . . . . . . . . . Wheat gray shorts . . . . . . . . . . . . . . . . . 77.2 75.6 23.4 76.2 Yeast... . . . . . . . . . . . . . . . . . . . . . .. 813 45.9 93.1 89.7 Coefficients of Digestibility On account of the large number of experiments, the results are not reported individually. The average compositions of the feeds tested are given in Table 3. The average digestion coefficients for 508 tests are given in Table 4. Where there were 4 or more tests, the standard deviations are given. The standard. deviations are discussed below. Digestibility of the protein was over 90 percent only in wheat flour, casein, macaroni and powdered whole milk. Meat (muscle tissues) was not included in the tests. Digestibility of the protein was 80 to 90 percent in asparagus, corn gluten meal, cottonseed flour, fish by-products, graham flour, grain sor- ghum seeds, white bread, buckwheat flour, ground careless weed seeds, kafir, linseed oil meal, millet seeds, oatmeal, peanuts, green peas, rice, rye, dried skim milk, soy bean oil meal, and yeast. The protein in beans was much more highly digestible when cooked than when raw, but there was little difference between the cooked and raw black-eye peas. Careless weed seed are very small. Some of them probably escape digestion unless ground, as is seen by comparing the digestibility of the ground and the unground seed. Ether extract (fat) was digested more than 90% in bone meal, White bread , cocoanut oil meal, cod liver oil, cottonseed cake or meal, cottonseed flour, W“... 90 “.3 0.0. a.» 9S. . ...n.08,. up,» fin n6 / w“? E3 m. a.» ......._.=.:_ w§flswww “w. P0 oh 0.8 w.N Nmh 0.5 1.1.000: "0300300 w... . . . . . . . ....................................0050.5 N . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . no no: E0 m. I Z <5 w: Z Z ....................................... ..@..»....sr 5w M S wiw ad mNh wiN NQ m6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13E? .500 N T o4; w.w 0.3. mww N.m N.mN . . . ‘ . . . . . . . . . . . ‘ 4 , . . . . . . . . . . . . . . . . . . . . . . 102.5 dwfimzoU N N c6 m8 odw mdw wiw owN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130E =0 00000910 N E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..@Q@.~mu .Q_w.-Q mnwhd@u mm M w aw 7v wNm m.ow win wAwN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Imflsvm fiuwuwiwhazU m m . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..@Q@kwv ->%hQ@QU § E oé Nd ma" N. w. mNw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Z5300 mw P aw. mfv mic N6 mw 9w . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18in dwobmU v X O.® w.®fi WQQA N.®m . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 600w UQOBmmQ-Quwmw w E @ @.Q @.% . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ....@UT~@ nnwmfl§gwu ¢ L 5N mdw 0.30 w.N 5m w.ww . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Olllllkfioq wwfifivxusmw w A mqv wiow mdw oh n5. wd .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .003 E00 5000M w R oNw 9m adv wbw N.N mwN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Iuviw fiouoohmw w U wN wb awn w. wé wéw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .......31.w3 £53m m T @w.m_ $.Aha . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..@@QQ% Hmflwcwwsv ifikm % L $.00 who 9m m. mN mdN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213E 000m N U . . . . . . . . . . . . . . . . . . . . _ . . ... . . . . ...........@Qwh@ Xwwa-QAQUQ @ w N mm . . . . . . . . . . . . . . . . . . . . . axvU>OsQk EUMM .@Q god .m-OQ.w £09m V R .m mNw wBm wN w.w wNN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...3m@..3E .550 G AL¢.@ w . . . . . . . . . . . . . . . . . . . . . . . . . . . .@U@H@ fink“ tUXQQU ->>N= QMQNQW w A §.#w m.§ x.w~ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..>>N: ~wiflfim fi S ¢.@ . . . . . . . . . . . . . . . . .........-...@U@H@ @QN @QVwQ°nv PNE@@ ‘mnmawm x m Nw.N @.% . . . . . . . . . . . . . ...... . . . . . ... . . . . . . . ......3@N?NE@@ ‘Mflnwfim fi . .@@ N».% . . . . . . . . . . . . . . . . . . . . .......@QT~@ @:N tUXOQU w mwcflQ E 3 Z is 3 T fa .................. ............ émiwwuzu=wmv_.w=wom M T .@.% x.$ mwzm . . . . . . . . . . . . . . . . . . . . . . . . . .... . . . . . . . ..@U@H@ uwmwTm-ww ~WQWUQ x p0: . . . . . . . ... . . . . . . . .....~...... . . . . . ... . . . . ..U~Ow~2w.~nmv—.wflm N 7 .. . . . . . . . . . . . . . . . . . ..-..................@DT~@ .mwwwfihflfim< @ 6 . , . . . . . . . . . . ... . . . . . . . . ............~v0@.wwv.m.w0Qw.-a UXOSQSL< m O. 9N Nbm mtww 5m w. w.w . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Iwvoiw. dow00< w N . . . . . . . . . JNQE M $ C W é x x.§ ...... . . . . . . . . . . . . ... . . . . - . ..... . . . . . . .@NQE%NQ% @ N n x N x 0. s x E 009508 his womwwxo @3050» L i4 .5335 v00 o s» .5 w E300 m om .00 00 0 0 w U am . Am v 0 q m 0 W |cowobwZ hQJEwwZ mEoEw-oano 0030030 E wvom: an 100w a0 noflwmi-Eou @0965. 5 03am. 8 NF-‘N? nflémwmwm~wmmmmmwwvowwmhwwwmbwoddbémmwmwwood2$d6€jb ~QN&AmmhdA'~ P101 P400 N 1-1? 1-1 "jgw~w~mmwc 5 lv-n ' Q; "d m~wmN N~ w . v-< '-¢'-1<1~.-<-<<1~o1cq v-w m~wmmNN N®®hNm¢wOwmm~wmb©m®©6hmwN©NO~NwNwwhN 'm m~w~@~o~mmmmv€Nmmm F‘ &£~N— nn mwh~mmh~wmmmN~m~mwSA~AJd v-u-n N4'&m5'AéS>mm~n+w~h5mhmmmmhvmm F1 ¢ DIGESTIBILITY EXPERIMENTS WITH RATS P1 MOO N IQ??? Vfi QOFCDQWO P CY‘.<‘CO¢Ol\<1"NLOQDQQmNEMLQQLOFOOQOOOPfiNLOF bmmflfiOOv-u 0CvCk-‘i7.51551NNQWONd"OLONN?‘BOHOLQMLOLOOCQDCOOGFQQMfififiv-lfilfilfiQCqfiFmNflfi N N QPN O>l\v—4 N" -1-<¢~1 v-ir-l -1 N w! $75K!-I=Ol\¢D\0OOOMMOOQfiOv-(OQNO¢DFMO5QG5OO$Mfiv-lv-ltfifiwv-lbtflblfibOwFwwNfi --£53?}IDNQFOGHOOOUIv-MDOv-MOOOOONBNv-ltfif-DOOfbtbv-lrflflw-ltfimv-nblflfiwfitfiwmflflflwvqQ NOOV-O5ECDLQQMOOQC1LQG>N=OOOOOUDCOOOLGBOEO10iO1v-lfil\<.Ol\M¢OO5U7UiO%@0OMQ‘0OfiCQOO5Q'l\w-lm §\:§—4 --$-—r-v-@QWJQUEZQAMNQ %°@ u-nnoao-oauunuuq-uv-uummwhmgawgwIwoowumcwaoiwgina .... . . . . ............................UNE5M-@QQWE=H—@.MO@ ......................................... ..—QUEQETMA~@ . . . . nvrvnnnIIQQI-lIIlOnnnlIn-Qonlpuo | | u - n unno-onncgwi%oauuim nH“Huipfiwifi.....................m=._figm ......................H~NHQ02m ........................................-...-.aflk.QU@m ........ . . . . . . . . . . . . . . .............wv0@htvnmflwvflxOQO-Qnvwm .......-.. . . . . . . . . . . . . . ..................@Q@kwv‘nzxnmefim Quin-ovavlI-cnuanuonnnnnnoolcnnnoiIcncaikflQaoogmlouwu°m ....-....-...-.....-.......-.-...-.-%vmw@kt.§M@H%qofififiam . . .....wuQT~wvQQQQHQ.MHQQQQH% ................-....-.................@Q@Hwu.§UUhm-fl@Qm ......................................BNHQm.NOQaQO~MNQH% ....................................-BNH.Q>%Q¥ON—Q\flNQfi% ...............-..........@O@h%v@:NtQ3o°U.Q%QV@Q.NT£-M“Qm ........ . . . . . .... . . . . . . . . . . . . . ..............@NQEQZQNQH% ............................................3NHQWMUQNUA% ~ - n ¢ - | unnu---I-noc-n-n-pIlanu.vn-o-vuu-nqeikanhuimhqm . . . . . . . . . . . .....................@vOT:u.UQQWmuiflmwvmvnmflhxo .. . . . . . . . ‘ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..<fl0EwNfiv . _ . . . . 4 . . . . . . . . . . . . . . . . . . . . . ............wvC-JQ.~W.w=ag.wflo - - » - - . - . - . . . . ~ . - . . . . - » » ~ . . . . ¢ - ~ - - - - 4 . . . . . . . . . . . . . . . . . . ‘ . . . . . . . ...............@UT~@.0Cd®_ww@2 HHHUHHHHHUHHHHAHHHHHUUHUNHHHHHHHHHUr@a@=@>~h~a@.¢=<4 . 1.80m $52 ¢ - - - » ¢ - - . . - ¢ - - ¢ ~ ¢ ~ | . ¢ ¢u»¢-~¢--nuqwhovaoamvéosahxikz ..- . . . . ........... . . . . . . . . . . . . . . . . . . ....@U@h%v¢-.PE3M¢V¢@T2 . . . . . . . . . . . . . . . . . . . . . . . . - . . . . . . . - . . @QTM@ »V=@E.~QQPEQ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .mQN.~Ow e602 ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..—N®E QCOQ wuifi dflQz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..@CQMGUNE . . . . . . . . . ‘ . . . . . . . . . . . . . . . . . . . . . ..............—NQEkQ>@J . . . . . . . . . . . . . . . . . . . . . . . ..................~GUE=OUOQMH:J . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . wunxhwv .QO:.~.M01_ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..OmQQQN1~ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..h€flm - - - ~ ~ . - . . ~ - - ~ . . . - ~ . ~ ~ . . - - - - - . ~ ¢ - - Q Q - - \ - . n Q ¢ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . _ . . . . . . . . . Iww-UQQQ nhgoxm ..4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...~QU~Q Qhinvwh - ~ - . ~ - ~ . - ~ - . ~ . . - . - . - ~ . ~ v 4 - ~ ¢ - 1 . . o - ¢ - . - I n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . _ . . . . . . . Eflzflh Rmfl-Oéh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .._fl0=n ma“ . . . . . . . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . TQT»: ?::.-@ QCNQQ fifiQN-‘TCNQMHNv-INNv-INVNNNv-Nfilfii‘?v-INVMQNFHQMSOONNVfiCONMNflMMN¢DN 10 BULLETIN NO. 675, TEXAS AGRICULTURAL EXPERIMENT STATION ........ .. . . . . . . . . ... ¢ . . . . . . . . . . . . . . . . . . ............aflk-o&figg-finmflfim fi fl.%w~. &..%m @.§ . . . . . ... . . . _ . . ... . . . . . . . . -.@Q3°°U \\%>“= qflnnwvm Q §..? . . . . . . - . - . . - - . . . - - . . - . . ' . . ..-.awpm n . . . . ... N . . . . . . . . . . . . . . . . . . . .. 5cm mév ado "flow . . . . . . . . . . . . . . . . . . . . . . . . Iééimi: mcwum m . ... . . . . . . . _ . . . . . . . |.. . . . . ... . . . . . . . . . . . . . . . . . . . . . . . . .@0XOOU $fl0imvmum Qmflflflm m nu ‘o 1-. . - . - . . . » . . . . . - . - . . .. . . - . . . ¢ . . . . . _ - . . . . . - . . . . . - .-3“|% N .¢- ~ . - . - . . . . . . . . - - . . . . .. . . - . . - . . . . . . . . . . . . - . . . . . ¢ ' - N -. . - . - . . . . . < . . . . - - - ¢ . . .. . . . . . . . . . . . . . . . - . . . - ..> . . . . . . . . N .-.--- . . . . . . . . . . . . - . . . . - -. .. . . . . . . . . . . ~ . . . . . . . . . . . . . . . N . . . . . . . . . . . . mdw wém o Thw .. . . . . . . . . . . . . . . . . . . . . . . . . . . Iwfini oxonomvi ~ u. - - . - . - . - . . .. . .. o - - . . . . . . . - - . . . . . - . - . . . . ...-.-.-wwrhrv .F “AN mdm v.2 wdw wém 5mm Wvm .. . . . . . . . ....................._wwE F2 wad?» w“ as m“. “m. g auwflxv 3x55 RE .85 H cfibobm Qumbxw ~25 Qowbxo 3mg. LSWOHZZ ooh QEZU Hwnww cmfiobm wand .6 wooh “o |cowobmZ QQQESZ wcoiat/vw wbwwcfim wuiQET-QQNQ wnhzldnc$um>ow whuwa-Sm avid QQGOMQEOQD nomwmvuomfi 1n. Qiflflk. magm- @.@ . ... .... .....-............._.wh0a0hfi—wvUTmmv-QWNQ? 5 q-fi c-w m-m - - - - - - ‘n. t:lIcaaInnlitlnIlilnnlloUwqlimuhonm%flhuaaong €.£ &~.@ x-m . . -.-.....-.--..-.-..mx=@=nw@¢~nvm .7 m6 “v.2 mdm m6 ogv m4: . . . . . . . . . . . . . . . . . . . . . . . . . . . ......cw.~n £355 m wé m6 ado “an w; 9: . . . . . . . . . . . . . . . . . . ...................M....Ifiwonk/ m M.du BZQ ... . . . . . . ...........................UQ@.~U w¢i0®hw nzihivm. N o-a o-fi 0-? .- a -¢--. -.-.-..-- . v . - - N @.@ mw.@ .. ... ...............................@OT~@»wOQ\~.NEQP m. M.NN fi.© @.fi . .. . ............................ . . . . . . ....QWNM5N'P m a. fix. Q. Q. x s 3.268 3am uumbxo 338$ $4 .1355 oak e350 hifim cmrohm wvoo.“ no cosh mo LBmoSMZ uwnfizZ woznflaculmfiuofimhuano zeumowmw E com: m: 233 we uomzmoaficu 329$. 5. 2.1a DIGESTIBILITY EXPERIMENTS WITH RATS r' fijOOFObOOfiwQwOlfiOwtYfi m O0 91l\l\@\-D€‘OO1l\C1QDON<-D0’Jfil\@ t0 G5 M w coao~l~oohooo~o 0C 1D 1-1 ommmSw>mNwnwmowwNmN~hNw @m®@¢©ww®whwbOwwmw®@m®h <' "Q?v-WOOltOOfiwwudéfififlfiUifibmflOioOfiflfiNditOtO N QfiQOOOOOOOOLOFQ>PNQ fifinvg . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . ..-.@—HOH.NONE ...Z.~won-o>£ afiwim - - . - ~ ~ - - - . . -.....-....~..-.-..¢--5qqég . . . . . . . . . . ..wa~m:@wo~ >= hfinmmn .zo voomco¢~oU ...........uv~wcwmo~w n ~=:muo¢~.zo @oom:o-oU ....... . . . . . . . . . . . ... . . . . . . . .._wo:~ woow:o¢~oU ...... . . . . . . . . . . . . . . . . . . ......m::n woowaoufiou .... . . . . . . . . . . . . . . . . . . . . . . . . ..»:c¢ uuowco-oU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..=o wuomnogdou ...... . . . . . . . . . . . . . . . . . . . . . . ..oxwo woomcoggou . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ......_mvE F80 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112:0 :30 . - . . . . . . . . . . . . . . . . . . . . . . ‘ . . - . . . . - . . . . . . . . . . . - . . . . . . . . . . - .-@Unw% . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..:m~Q =»oU . . . . . . . . . . . . . . . . . . . . ...............:~oU . . . . . . . . . . . . . . . . . . . . . . . . . .............m©~w=oU IX . . . . . . . . . . . . . . . . . . . . . .........zo._o>=woU .. . . . . . . . . . . . . . . . . . . ....._mo:~ 10 uscwocu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .....Q—5Q wH-HZU . u . u . . ‘ - - - . - - . . . . - . - - ~ . - . - . . - . . - . . . . . . . . . - . . . . . . . . - - . - . . . .-..-.-EQiQU IEommU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... ..m~o~hanv . . . . . . . . . . . . . . . . . . . ..%v==o.mw ~tmvww @QQ3 wwQiQhflu . . . . . . . . . . . . . . . . icsohw “o: fioww new? wmBPEU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..@U@H%v .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ixziuofinm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I~:o¢¢wunBxo:m . . . . . . . . . . . . . . Zlioowcuoofioohm .. zouoohm . - . ¢ . - - - . - . - - - - - . . . - ~ - . . ¢ . - . . . . - . . . . . . Cwmsm wanna wificoov woo“ Zfixwvkn 53m . . . . . . . . . . . . . . . .... ..I..........4mon~o:om . . . . . . . . . . . . . ..............-...._...Q@=QQUQQ .... . . . . . ... . . . . . . . . . . . . . . . . .......w¢oo~.m~uvMw H NCONtOCOMmNGOv-lnfiv-ufltbmmcofl N ‘O N WI-OEOLGQQNNFWv-tv-IfimN¢OOONII5NNC>QIOM©COWDNNN 12 BULLETIN NO. 675, TEXAS AGRICULTURAL EXPERIMENT STATION Q.w~ . ..... . a ..........................MHU>VUkA~@O@k rwmflflw 5w wAZ ma 90w 9mm max» m6“. . . . . . . . . . . _ . . . . . . . . . .522» >3 .2355 5 .. mfl. 3w" 5m Wow 5mm v.3 mAK . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...-aha aaonk/ 2 . . . . . . . . . . . . . . . . . . . . . . . . . .. 5mm 50m 75 5R m -¢.-¢- - . - - . . - . - ~ . ..>--.-< - - - - - . . - - . - - - . . . .¢.-@:o®Qm N . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. Qww mAK Ndm mém ......_....T....................;Bmo~@255. fl . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. mdw min" 3mm 5mm mooHwEoH ~ m-v.@x . ...........R.. Z...................... . . . . . ..QQQU»NMUF @ . . . . . . . . . . . . . . . . . . . . . . . . . . . .. wfim 9mm mSm 7w.» .. T. . .463 kuaocasm n 1 . - . - . . - . . - . . - - - . . . . .. ... . . . . . . . . . . - ... - - . - -- -i-‘i...u~flm.wgaw N m; . . . . . . . . .. . . . . . . .. 9mm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F5» 553m m; . . . . . . .. . . . . . . .. 5m.» oéw adm wéh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Inuwciw m afi Q3 9w qmw 93 9?. m8 . . . . . . . . . . . . . émoocha fiEZom .165 E. .5218 a - - ¢ . - . . . .- .-.-...- ...-...... o c o ......-...-.....-n¢.-.-...-.->-ir° ? .. . . . . . . . . . . . . . . . . . . . . . . . . .. Nnww 5mm Qmw whw . . . . . . . . . . . . . . . .....ow:.€.m vvvw Es: 5m m . 06w ma“ 06m o wAm oSw .....xaEE§m m . m..m . . . . . . . . . . . . . . .... . . . . . . . . . . . . . . . . . .. ..~NQE MUDmvOMQQWQ fi n 00 -¢ - - . - - . - - ¢ » . - - . . . .- #16 - - - . . . - . - ' . . . . . . - » . . ' - . - - . - - - - . - .|..Q:°q H ---.-.|- . - - ' - . - . - . - ¢ . . . - -. ~ . . . . - . - ~ . . . . ~ . .- - - - - - . . . - - . - -~.-..--o>m m - - - - ~ . - - - - . . . . - - - . - - . . . . .- ¢..-..-.».-..i . . . - ... - . - - - ' . m . . . . . . . . . . . . . . . . . . . . .. 9am 9m wan o . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 21E 3E m mfifl o6. wa: ohm 5mm flaw min . . . . . . . . cmfifvfim w . . . . . . . .. . . . . . . . . . .. 9mm wat. 9o“. wéw . . . . . . . . . . . . . . . . . .. . . . . . . . . . uvxooo 3E m . . . . . . . . . . . . . . . . . . . . . .. mdm mbw mAK o4? .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .;.58 dog m u» ~ - . . - . . ~ - | . - . - - - . . . .. - - - . v » . - - . . - . . » - . . .-v.>i - - - ¢ . m 3m 06m R3 mfla mdw haw Ngwm . . . . . . . . ZfiEBm 633m on o6. Qmm. 9:2 5mm 95 mtw" Rum . . . . ..Emm.5.ofi3om m u <.-.~> . - . - ¢ . . - . - - ~ . . - . . . . - . ~ - - . . . . . ~ . - - . . - . - - . m IIUQ - . < - . - . - . . v . . . . - . . - . . - . - - - . - . . - . . . . . . . . ..~ - . . . . . . . . . fi .. . . . . . ... . . . . . . . . ..........>rflh 0~m®¥Ofl~Q £60m flu 00- R... - -¢.i... . - ' . . . - ... ... - . . ' v - - . - - - - -..-.f--uqwxoog m w m w w 9m méw 9cm mam v.3 . . . . . . . . . . . . . . . . . . . ....._@oEfiEmvm w .. . . . . . . . . . . . . . . . . . . .. o o odw o . . . . . . . . . . . . . . . . .........:o,§ca@m w . .. ... .. . . . . wbh 93. Rwm wéw . . . . . . . ..............B§.$::wom m v- tannin - - - - v ~ ... ¢ . - n. N-g -<-.»¢u- - - - . - . - . - -- - . . . nllfillflvilkw i #.Q ...... . . . . ... .....- . . . . ..i>.........awvQm.k%vw “Ego ¢ - mm an fig fine mdm wow . . . . . ....._woE~wO N. m6“ ném N2: “mom m4: wBm 5: . . . . . . . . . . . . . .............m=:_:mO w -<-<¢¢-. -- ¢ . - ~ a. - - ¢ - - . . - - - - - .-¢ ~ - - . - . - ..~ -¢--.--@g@®km N .. ... 7S “i3 o ma! .. . . . . . . . . . . . . . . . . . ..vo~vimm§ w & fi Q. x aoflsxo Qowbxo out Hofim Evfizm @2238 hone uomuaxo n33 -5w¢EZ o3“ 2:50 35H cmfiohm v2; .5 doom we éomobmZ 3:252 wcofiwtéw vhmucfiw A1o::w-:ouv|u~:e~=muonuo aaulmsoflam>ou Ewan-Sn us: DQHOMUEQQO GOmuQQMmQ .V 03am. DIGESTIBILITY EXPERIMENTS WITH RATS 13 cottonseed oil, medium hydrogenated cottonseed oil, low-grade flour, liver meal, meat and bone meal, powdered whole milk, millet seed, oatmeal, pea- nuts, rice polishings, rye flour, sunflower seed and turnip roots. N itrogen-free extract was digested over 90% in beans, both raw and cooked, beets, white bread, buckwheat flour, clear flour, patent flour, kafir, lactose, macaroni, powdered whole milk, milo, oatmeal, green peas, potatoes Irish or sweet, pumpkin, rice, rice polishings, rye, rye flour, skim milk, starch, wheat and yeast. Variations as Shown by Standard Deviations Standard deviations are given in Table 4. The standard deviation is rec- ognized as a measure of variation. The standard deviation was calculated in the usual way by adding the squares of the differences from the average, dividing the sum by the number of tests less one, and extracting the square root. A deviation greater than the standard deviation occurs about once in 3 trials, while twice the standard deviation is exceeded about once in 22 trials (2). Variations in Digestibility Variations in the digestibility of feeds as shown by the standard deviations are due partly to differences in the digestive process, partly to differences between different samples of the same feed, and partly to errors of manipula- tion and analysis in the experimental work. Experimental errors, while small when the entire ration is considered, may be large when all the errors are assigned to any one ingre dient of the ration, as shown below. Table 5 contains a comparison of the variations in coefficients of digestibility of corn meal rations and of the corn meal in the rations calculated from the results of the tests with the same rations. The standard deviations of the coefficients of digestibility for the entire ration were quite low for protein, ether extract and nitrogen-free extract, although higher for the crude fiber. Crude fiber is present only to a small extent and comparatively slight errors in the analysis of the excrement or the feed could cause large differences in the coefficients of its digestibility. The standard deviations were much larger for the corn meal contained in the ration than for the entire ration, ranging from 1.5 to 14 times as much. The differences increased with the extent to which casein was present as shown by the percentage of protein in the rations. The standard deviations for the nitrogen-free extract were quite low: This nutrient comprised about 70% of the corn meal. Those for the protein, the ether extract, and especially the crude fiber, were much higher; these nutrients are present in much smaller percentages than the nitrogen-free extract. It would be reasonable to think that the actual digestibility of the corn meal does not vary any more than that of the ration in which it is fed. When all the experimental and analytical errors are assigned to a portion of the ration such as the corn meal, the variations appear larger than they really are/ When high standard deviations occur a small number of experiments are not sufficient for an accurate average. When the feed tested is fed as part of a 14 BULLETIN NO. 675, TEXAS AGRICULTURAL EXPERIMENT STATION w; hé v.0 NA m5 v.0 fix. Quwbxo cob éwmfiz: Z Qwm mSN 92 N? 0.0m hvv w? 2 .........Ev~o._a §..om=o:~m 9M: o5 v.2 Ndm Nam :5 9E. w .........E£8@ &¢.§=2§m Qww 92 ma ~23 w? fig v.2 v .........Eo~o~Q $52 cofiwfl “mcofiwk 26mm Eoh wogmizzwu 13E F50 Mo zfimnfimwmmfl m4; wd v; w. 3 52.. v.3 2% 2 . . . . 1530.5 $9M doing 13E F50 o4! w; w; >3 mgm 2% Nbw w ......E~5o~Q $8 503mg 13E E00 mm» 9mm v§ mg» mwv www “ma v . . . dfizohn AREAS 622E 13E EoU 55c 333$ #2955 Sea Qumbxo QYZU “$3M 533m 3C 3:10 hvfim 533m |cwmobmZ wemwhwi». ~53 .5 cofiwfi dZ mccfimt/vw whmucfim zfiznmfivwmw Mo BcBQEvQU 925a.- ofi u: .::3:m§:. o5 59G uovai-Bau 13E :2:- uc via mafifii 73E F-eu we fimznflmwwiv E mcoflaia.» we GOmT-QQEOU .m “JAN-H DIGESTIBILITY EXPERIMENTS WITH RATS 15 ration, high standard deviations do not necessarily mean that the digestibility of constituents of the feeds are as highly variable as the standard deviations would lead one to suppose. These differences are partly mathematical, rather than actual. ' Comparative Digestibility by Rats and Chickens Comparisons of the average digestion coeflicients secured with rats with those for corresponding feeds with chickens (5) are given in Table 6. On an average of all the comparisons of the feeds, the rats digested slightly less pro- tein, a little less fat, and appreciably more crude fiber and nitrogen-free extract than the chickens. The rats digested a little more protein from the human foods than the chickens, and more nitrogen-free extract, but less fat. Differ- ences between the digestive powers of chickens and that of rats occur chiefly with feeds low in the constituents being studied. When the feed is high in protein, in fat or in nitrogen-free extract, the differences are usually small. On the average rats have slightly higher digestive powers than chickens. Comparative Digestibility by Rats and Humans Average digestion coefficients of feeds by humans, a compiled by us from the literature, compared with these for rats fed corresponding foods, are given in Table 7. The average of the coefficients compared is 70.0 for protein by rats and 71.3 by humans; 72.6 for fat by rats, and 82.4 for humans, and 91.5 for nitrogen-free extract by rats and 91.7 for humans. Except for fat, the average digestibility was practically the same by rats and humans. The human diges- tion experiments listed in which crude fiber was determined were so few (five) that a comparison is not justified. It would seem that for foods on which reliable digestion experiments with humans are not available, results of digestion experiments with rats could be used with no great error. This is the case especially with vegetables. Many human digestion experiments have been carried out with complicated diets, in which the food to be studied was only a small portion of the entire ration. When fed in this way, as pointed out in this publication and in a previous publication (57), the coefficients of digestibility of the ingredients are subject to greater error than that of the entire ration. Digestion experiments with rats may in such cases give more accurate data than the experiments with human beings. 16 BULLETIN NO. 675, TEXAS AGRICULTURAL EXPERIMENT STATION “w . Q p; . . . . ,. 2 3 9995???? ?@I@9I§€1§@I#°3I5?§9°II"”¢"99@“” x p omwmowmw wo- ~mwmmw~w w-woman--.m ow v 3 mhwwwwmb wh;§§:mmmwm-m m-mmwam-~gw§Ewwg€§ Q U _ . . .. - G) i- 3-1 , . g . . . . Q . . . . .. § 3 @?9?3§?9 @§Z2TI@§@”°'"@@I@*”“°"°°”°”°@"“ H “ wwm momm mm-om-owwdfiidmv-Nhd¢d::@dd@~"-' E 2 www$mmw> mm-hm-wmwwh-m w-~mmmm-~mowmgg§§g . . . . .. _ 2 :3 : : : : g QQ§QQqQo o:;q§:§Qwmw-mmv w2ww¢ Q-~fiO~NN© E 3 o2mNwhmw --mm-m~wmo-mac-m¢mw2 N-@>m-25¢ 3 Q v—oo - mw-fifl _ U W . 2 w 0 l1 "o . II . f 6 3 w¢mn2mh~ o -No-wmwhn-2a2 2mom2--2-mmw-wm2 E E w2Nww->wm~Nmmm~--w-2mm-m~v Q Nmvvwmwm N mw~mv~mw-w N wwmnn--w-mm -nm2 In . o . fin 9 m . U c _ § g @MwNh@~h ¢¢Nm—hmmNm~mmmhw>h@mmmma-~~vomNm * S 3 wmmwm~vm vmwoNm¢ammmnw~wmmwmww2ma-wmohwvm 5 2 S mh@b©hmh hm¢>awwwwwmwwmmww@mm@mwh~hw@n@wh --1 U " a ‘>1 Q u o 2 In U g 5 3 ho~~@mo2 ¢wNhoov>>moomwwww¢wcwhmm ~o~ch~2 E 2 “ mmwhmv v hommommwwhmmwwmmmmmwnmhm~mmN~nwo 2 Nwwwmm w wwNmommhwm2wwmmmwwmwwmvn-wwamahm 3 2 ID *3 Q . In U) - u c: " Q g mwmomwmo w22m¢ w2m>m moo-wmmnw m mwwamam 3 p wmvv~m>h mmmww-mwm~o~m o-wvwmm m mhcvoho " mmmnwmmm www2m-wwmww-h n-hhwww B ®b©hhwN 5 =5 II! "4 U U IE *6 o u - 3 Q 3 ~mowwmow >mw2>-mhNon~wow~oommm n-owbowoo = “ wm~mwmom mhm~m~ww>~w-~ m-mhmwm N omwhowm 3 2 mmwwwm w whc Q-hhmbw-W h-wwmmm w~wmwwmh2 6 . . . . I11 o H) 2 - Q . . . t,’ 22222 I2 222 2 22 122 222222222 2 2 2 1 ' a I w 5"‘ 'II'III.'IIIIlIIIIIIIIIIIIIIIIIIIIIIIII IIIIIIII I IIIIIIIIIIIIIIIII.I;;IIII;IYII """""::3':::::"'"'::::::':<¢Q:"‘:<“:::: ,6 ...-.. . .... .9“ ..Q g’, .IIIIIIIIIIIIIIIIIIIIIIIIIIf;7_-_¢;_-IIIIEIIII m .§IIIIII’r-TI.IIIIIIIIIIIIIIIIIII°°IIII°IIII ....... ................ ...- 0.... .... O ...-....=................;....8v....Q.... w - .w... .... . .- . .. .wW.... .... o _-._... . ... _.(§ .c: vo o _.__U.-U.PU-U:.....-.-...:__.q).:.°o....=:... ___. .M3°.u-1,.Uh...-¢.-.-,om.‘_m,_,_‘_,.o..QQ--__;-....Q . ,_,q,>,__g -_ ..Q.D‘__:.. E.2o__,$gé_..E....ME.§EE6u§E:aEE..E.€@_.. .,..,. _.‘-—u..- . .. - .. -.~<°=“§‘§Ifi'8-*x "E15 -_;~E,5--c:-<:-o-c:3-=°°§5'5§-"~IE§-c" §jEEmmQ@~§:j:°hZw§~~I$$$$QE32§“=I'5E-20I$ -".Z:c5'EEgJ:E.Q";g,ggs-23:wmwm>,m29D-&&qflqQgfig-= q>,----Q_ Q p; _ QUJMO2222_Q_,,.Qo.mQp _ :2 '—'-‘_°£€€E’E’.=é"-E3‘$3g'=§n:===3333 EE5S-'5£53%3Gx§o'= ‘Qhwgqgqggm UnJilzbOlu=hinhui-1Hfiw-lG-o-Ii°o°°>‘>?U=;qQ:=Z'i-’ _moovoou ::m2ooooocooocoo2___2 -qmzzzgzw < . . . . . AI $.08 cwfisfi konisz ...........HH . . . . . ..c3omfiu>< . . . . . _ . AZNVLLQEE5Z . . . . . . . . . . . . . . . . . . . . . . . . . . Zine? . . . . . . . . . . . . . . . Zmfioaw 52w “was? . . . . . . . . . . . . . . . . . . . . . Iss5 .235’? . . . . . . . . . . . . . . .. ....t8=3 . . . . . . . . . . . . . . . . . ...$ws_=§ .........:fl..w..e8w $2222.” . . . . . . . . . . . . . . . . Inohfiw ..._muE~=o caonzow . . . . . . . . Izo cue how . . . . .. omgnw Juoom E52 pow . . . . . . . . . . . . . iwwoEnnEisw . . . . . . . . . . . . . . . . Ziiocwzfl . . . . . . . . . . . . . . ...............omfl . . . . . ...............Ihmzoaoomm . . . . . . . . . . . . Imzssoamfl xxx:mwm...........=whpoowm . . . . . . . . . . . . . 13F“ ....Joo>$ ifiwgom 0x33 woxoou imam ......_mvE animal ascaom .................~aaE.~aO ...............0% N O w“ “.8 9S 9w“. m? fiww 9Q mAh . 5o» . . . . . . . Iuwwpw>< A § § m a mm mm mm mm F533 .2634 m w fim ........ .. Tm ma mw Mum H»HiHNHHH....w.azazeprawwmmwfl.% d . m . . . . . . . . .. . . , W 00H 9mm . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Isuhfim E -.-.» . . . . . - . - - . . . . . - . . . . . . . . . . . - - ¢ - . . - . .. ...............-............><-.>>@>%>>>@@>@>z}>>>>za@@fvzfluz>ow M 8 #8 . . . . . . . . .. Q 2 .22: fi 93. Hxvqmzx . . . . . . . . . . . . . . . . . . ;..=.e<..>m m S Q2: www 8 f3 fi m3 . . . . . . . . . . . . . . . . . . . . . . .. . lwsm E :..%.... ..~.....§... min? mm mm» ..:§ . . . . . zmk... . . . . . . . . . . . . . . . . . . . ..Q.>.Q.M_.O.G.E..@WHNQN=NMWM m 2.. 9Q E #5 3 m5 E fifi mmHxnmmmmmxflnnnnwn .... ....@.=..:....s°@ E 2 WS . . . . . . 9i 5 wBh E a 3 =25 wwfi L MM MHWM “HRH mm“ ..:&..: mww Mm MHNM HHHHH......................HH....HHHinmmfimwacwuw m . . . . . . . . _ . . . . . . . . . .. U aw 0.0m . . . . . . . . . . . . . . . . . . .. hm wSm mm 50m . . . . . . . . . . . . . . . Iiwin? 5S2 T nm mic . . . . . . . . .. mdm mm obw ww 9mm . . . . . . . . . . . . . . . . . . .. Mcobwomz L ....... . . . . . . ... . . . . . . . . . . . . . . . . .. . . _ . . ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . UQOwGOQQOO wuQMNCQWOkU.WE U . . . . . . . . .. a . . . . . . . . . . . . . . ... . . . . . . . . . . ..Q@NR@ >/°@ Tmfiwoéh w . . . . . . . . .. hfinim R . . . . . . . . . . . . . . . . . . . . . . . . . . .. . mm 7mm . . . . . . . . . . . . . . . . . . . . . . ImovoowcofioU m . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . ..~N0E wvQQwCOHHWU . . . . . . . . .. wm ofiw s Mm www ........ .. way‘ WM mfi. a mum“ .AM.HENRInimwufinnmwwcnwmw A . . . . . . .. . .. . . . . . . x Q N5 R $3 3 95 fi QB Hm...w.. . . . . . . . . . . . Qmwzfi E Ma m? mm v2 i Q5 5 9% . . . . . . . . . . . . . . . . . . . . . . . . . . .......Q.Ea v.85 T 8 W8 é m? 2: 9% Q. m»? . . . . . . . . . . . . . . . . . . . nee. s5 s. 2w <8 QB ....8.:. is R m? . . . . . . . . . . . . . . . . . ...w@..~.¢....@. 2.3m m MM .Q@@....m@. .12“... w.“ .......m~...:. MW . . . . . . . . ......................8=awwmmw o0 l -.--- . - - - . - . » .- . - . . . . . . -. -.---- o ----.-..-¢-. | | - . v-a-up-.v.waiuflwn@a_égg< N N wcaism 3am wcwism 3mm wcaism 3mm mama-am mfiwfl I dam.“ .5 wooh M aoabxo oofifaomobmz ponc 0250 “$2.36 $5M cmwuoum L L % min-EZ- 3 una mun.- .3 mwocu uo mafimnflmoumv 0>madudfiEOU 4. Bash 8 1 \ DIGESTIBILITY EXPERIMENTS WITH RATS 19 SUMMARY p Results of 508 tests of the digestibility of foods and feeds by rats are sum- » I arized. The rats digested slightly less protein than did the chickens from ll the feeds, but digested a little more protein than did the chickens from uman foods. The rats digested less fat but more crude fiber and more nitro- V en-free extract than the chickens. The digestibility of protein and of nitrogen- “ ree'extract by rats and humans averaged practically the same. Rats digested ~ maller percentages of fats than the humans on an average. ACKNOWLEDGMENT p Acknowledgment is due to E. C. Carlyle, T. L. Ogier, Raymond Reiser, nd other members of the stafi for assistance. REFERENCES Barnes, R. H., Primrose, M. T., and Burr, G. O. 1944. The influence of the protein content of the diet upon fat digestibility. Jour. Nut. 27: 179. Fisher, R. A. Statistical methods for research workers. Fraps, G. S. and Carlyle, E. C. 1942. Productive energy of some feeds as measured by gains of energy of growing chickens. Tex. Agr. Exp. Sta. Bul. 625. Fraps, G. S. 1943. Productive energy of certain feeds as measured by the production of fat and flesh by growing rats. Tex. Agr. Exp. Sta. Bul. 632. Fraps, G. S. 1944. Digestibility of feeds and human foods by chickens. Tex. Agr. Exp. Sta. Bul. 663. Fra s, G. S. 1944. Maintenance requirements of chickens and productive energy of fee s as related to age. Tex. Agr. Exp. Sta. Bul. 6 5. Gallup, W. D. 1928. The digestibility of the proteins of some cottonseed products. J . Biol. Chem. 76: 43. Hayward, J . W., Steenbock, H., and Bohstedt, G. 1936. The effect of heat as used in illifi ZXIfgIaCtlOD of soy bean oil upon the nutritive value of the soy bean oil meal. J . Nutr. Hoagland, Ralph, and Snider, G. G. 1940. Nutritive properties of certain animal and vegetable fats. Tech, Bul. 725, U. S. Dept. Agr. Mitchell, H. H. 1923. A method for determining the biological value of protein. J. Biol. Chem. 58: 873. Nevers, W. B., and Shaw, D. B. 1933. The apparent digestibility of fresh whole milk and powdered whole milk. J . Nutr. 6: 139.