Using a purified diet deficient in choline and containing 18% casein, it has been found that in the duckling: (a) betaine and aminoethanol have little or no lipotropic activity, are poor growth factors, and cannot prevent perosis; (b) monomethylaminoethanol and dimethylaminoethanol, on the other hand, have well marked lipotropic activity. Both substances stimulate growth and are antiperotic, dimethylaminoethanol being the most active of the two in these respects; (c) ducklings, like chicks, appear unable to methylate aminoethanol to any extent; (d) a level of 28% casein is more satisfactory than one of 18% in the prevention of fatty infiltration of the liver in ducklings.Betaine and methionine have a definite lipotropic activity, when fed to ducklings along with a semipurified diet containing peanut meal as the only natural ingredient. The substitution of yellow corn meal to sucrose in the above semipurified diet inhibits the lipotropic activity of methionine, without affecting that of betaine.The availability of a protein low in sulphur amino acids has resulted in the preparation of a more hypolipotropic diet. On this diet, ducklings presented livers containing, on the average, 24% of lipids. Methionine added to this diet is strongly lipotropic, but is without effect on growth. Methionine will promote growth only in presence of choline.Ducklings like chicks and poults appear to be able to convert methionine to cystine. In presence of 0.4% cystine, approximately 0.5% methionine is required for normal growth.
A purified diet suitable for the study of the qualitative amino acids requirements of the larvae of the Coleoptera Tribolium confusum is presented. The composition of the diet is as follows: amino acid mixture 20%, cornstarch 75.5%, cholesterol 1%, wheat germ oil 1.5%, salt mixture No. 2 U.S.P. XII 2%, yeast 0.5%, vitamin mixture M.V.–II. In presence of amino acids, glucose cannot be used as a source of hydrocarbon. The mixture is very hygroscopic, develops a brown color, and is apparently toxic to the larvae. The importance of choline as a growth factor is demonstrated. Wilson's Liver Fraction L or Liver Concentrate 1: 20 cannot replace this vitamin. Yeast appears to contain unknown factors for it improves growth when added to a diet already supplemented with vitamins known to be essential for the larvae. A mixture of 19 crystalline amino acids known to occur in casein satisfies the nitrogen requirements of the larvae of T. confusum equally as well as purified casein.
The quantitative req~~irements of the larvae of Triholit~iia c o t z f i~s~~n r are studied. For optimal growth, the larvae require 1% to 8% of salt n l i x t~~r e No. 2 U.S.P. XIII. For the imaginal metamorphosis, we must add a t least 2% of the salt Mixture. The req~~irernents of the male and female are absolutely identical.Nous savons tl-6s peu de chose sur les besoins des insectes en sels minkraux, e t cela est particuli&rement vrai pour les larves de Triboliz~ln colzfz~sum. Nous ne connaissons en effet qu'un seul travail sur la nutrition d e ce Col6opti.re en sels inorganiques: Nelson e t Palmer (11) ont d6montrC que, chez T. confz~sum, la duree du stade larvaire est en relation directe avec la teneur en phosphore du regime.Les pourcentages de m6lange salin couramlnent ~~t i l i s e s dans les travaux sur la nutrition des larves de ce T6116brionicle varient entre 1% et 5yo. Frobrich (7) ajoute A ses rCgimes 5% du m6lange salin d'osborne e t 31endel;Barton-IVright (1) utilise 4% du n16ine melange; Ofihaus (12) n'en ajoute clue 3+%; e t enfin Chiu e t 1,IcCay (2), 37,. Rosenthal e t Reichstein (13) compl&tent leurs r6gimes avec 57; du in6lange salin de TvIcCollurn, tandis que Fraen1;el e t Blewett (5) n'en rnettent que 2% ou I%, seloil qu'ils utiliseilt ou no11 la levure comme source de vitamines. Le~nonde e t Bernard (8) ajoutent A leurs r6gimes 27, clu mClange salin no 2 U.S.P. S I I . Xucun de ces auteurs n'a cependent dCtermin6 la teneul-optimum d u in6lange salin dans ~1 1 1 rkgime. Dans cette premi&re partie de notre travail, nous avons rechei-chi. le pourcentage optimum du m6lange no 2 U.S.P. XI11 nCccssaire & la croissance larvaire e t A la m6tamorphose de T. conjz~sz~nz. M6thodes exp6rimentales ilde'thodes d'e'levageKos mCthodes d161evage sont partiellemerlt inspir6es de celles d6jA decrites ailleurs (3, 4, 8). Xous n'en donnerolls doilc ici qu'un bref apersu.Voici comment nous proc6dons pour vCrifier i'2ge des larvules mises en expkrience. Au moyen de sas appropribs, nous r6coltons les ceufs dans des cultures 2gCes de 15 jours. Nous d6posons ces ceufs dans un bocal qui ne 'Manuscrit reql le 8 avril 1957.
The quantitative requirements of the Tribolium confusum larvae for magnesium, calcium, sodium, and potassium are reported. Magnesium and potassium are definitely essential for larval growth. Without these elements, the larvae do not survive long. Calcium appears essential for imaginal metamorphosis. In its absence, rapid dehydration of the pupae occurs and emergence of the adult is practically suppressed. The importance of sodium could not be demonstrated because the minute quantities already present in the basal diet appear sufficient to meet the requirements of this insect. The requirements of both sexes for these cations are of the same order of magnitude. Additions of these cations in excess of the optimum values are well tolerated.
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