FOR years eggs have been studied as a

Vitamin A Content of Eggs as Related to Rate of Production* MYRA C. KOENIG, M. M. KRAMER AND L. F. PAYNE Kansas Agricultural Experiment Station, Manhattan FOR years eggs have been studied as a source of vitamin A and are among the animal products now receiving increased attention concerning variations in this vitamin due to ration, breed, season and rate of production. Bethke, Kennard, and Sassaman (1927) reported that the ration of the hen has a marked influence on the vitamin A content of the egg yolk, bluegrass range or cod liver oil in the mash being particularly effective. Sherwood and Fraps (192) showed that laying hens require large amounts of vitamin A, often lacking unless there is access to green feed. Low egg production, low vitamin content of the egg, undernourishment, and eventual death of the hen may result from this shortage. Fraps and Treichler (19) found that normal eggs, produced by hens receiving a complete diet plus green feed, contained 20 to 0 Sherman units of vitamin A per gram of yolk. "When the pullets were kept on a ration where the sole source of vitamin A was yellow corn there was a gradual decrease in the vitamin A content of the egg yolk from 20 units per gram to 7 units per gram over a period of approximately five months." Ellis, Miller, Titus, and Beyerly (19) fed cod liver oil to hens and obtained eggs with yolks of good vitamin A content although deficient in the pigments usually associated with vitamin A. Carotene (intensely yellow) has been * Contribution No. 9, Department of Home Economics and Contribution No. 8, Department of Poultry Husbandry. (Received for Publication June, 194) [178] found to be a precursor of vitamin A (almost colorless) in the animal body. Egg yolk is recognized as a good source of vitamin A, if the ration of the hen contains vitamin A or its precursor carotene. The amount of yellow pigment, xanthophyll, in the yolk is not necessarily an indication of the vitamin A content. Recent work includes that of Bethke, Kennard, and Sassaman (1927) who reported an approximate five fold increase in the vitamin A content of egg yolk after adding cod liver oil to the ration, although this did not add to the pigment in the yolk. Ellis (19) stated, "Hens on diets nearly devoid of yellow pigments but with cod liver oil supplement produced nearly colorless eggs which were equal to or possibly richer in vitamin A than highly pigmented eggs produced on normal diet containing yellow corn, alfalfa leaf meal and cod liver oil." For the purpose of distinguishing good layers from poor layers, poultrymen have made detailed studies of effects of heavy egg production upon the pigmentation of the hen. Jull (190) stated that "The yellow pigment in the beak and shanks of breeds that normally have yellow skin color tends to disappear as egg production continues.... Yellow corn and green feed contain xanthophyll but if rations are fed that do not contain this pigment, the beaks and shanks may be relatively pale though the hens may have laid but few eggs." According to Palmer and Kempster (1919) when normally yellow-skin breeds are given

MAY, 19. VOL. XIV, No. 179 feeds rich in yellow pigment the commencement of laying diverts the pigment received in the feed to the yolks. After continuous production over a period the pigment contained in the beak and shanks becomes depleted, first demonstrated by Blakeslee and Warner (191). PROCEDURE The present investigation is concerned with the vitamin A content of the yolks of eggs with reference to differences between eggs laid by high and low producing pullets, some beginning and some completing the first year of production. All eggs used were from White Leghorns and were supplied by the Department of Poultry Husbandry. With one exception, a group with pale yolks, the eggs were produced by flocks receiving the regular college poultry farm ration, as follows: Ground yellow corn Ground wheat Ground oats Meat and bone scraps Dried buttermilk Alfalfa leaf meal Salt Cod liver oil lbs. lbs. lbs. SO lbs. 2 lbs. 2 lbs. This mash mixture was before the birds continuously. In addition to this the hens had access to shelled yellow corn in one hopper and wheat in another. The eggs with pale yolks were produced by hens receiving the following ration: White corn Dried buttermilk Wood pulp fiber Brewers' yeast Cod liver oil Salt (NaCl) 70 lbs. 20 lbs. lbs. 2 lbs. 1 lb. The hens producing eggs with pale yolks received 2 percent cod liver oil while the regular poultry farm ration contained about 1 percent of cod liver oil, in the mash only. The eggs were prepared for storage by dipping in hot mineral oil mixture, thus partially sealing the pores of the shell. This process largely prevents the loss of moisture and materially slows the rate of loss of carbon dioxide. The eggs were then packed in labeled cartons and the several cartons placed in a waxed paper container ready for storage at to 4 F. until needed. Before use, each egg was cooked for 20 minutes in a double boiler. The hard cooked yolk when not used immediately was stored in the freezing unit of an electric refrigerator. Eggs of kinds were used in the fall series. Their description follows: 1. F-l eggs laid by low-producing hens in the fall. This group included eggs from individuals whose actual production for the first or pullet year did not exceed eggs (average 9). 2. F-2 eggs laid by high-producing hens in the fall. These hens produced 200 eggs or more (average 21) during their pullet year. The eggs in both group F-l and group F-2 were produced by birds near the close of their first year of production.. F- eggs (eggs with pale yolks) were produced by hens on the special pigmentpoor ration containing cod liver oil as a source of vitamin A. The winter series included the following: 1. W-l eggs laid by low-producing pullets about the fourth month of their first year. Records of the pullets showed a production of eggs or fewer (average 6) for the period October 1 to March 1, 19-4. 2. W-2 eggs laid by high-producing pullets about the fourth month of their first year. Any hen producing 60 eggs for the period October 1 to March 1, may be considered a high producer. This group included eggs from no individual that produced less than 8 eggs (average 9) for the same period.

180 POULTRY SCIENCE» TABLE 1. Summary of experimental data Source of egg used Quantity fed 6 days weekly grams Rats used No. Av. wt. at end of depletion period, grams Av. gain in wt. for experimental period Av. survival days Estimated quantity to give 24 grams gain in 8 weeks, grams Units (Sherman) per gram Fall Series F-1 F-2 F-2 F- F- W-1 W-1 W-2 W-2 0 0 0 Negativ e controls Positive controls 0 0 Negativ e controls Positive controls 1 1 8 1 8 4 79 76 8 8 7 82 79 97 96 96 9 97 The rat-growth method of Sherman and Munsell (192) was used for the vitamin- A determinations. Vitamin D was provided in the vitamin A-free diet by adding viosterol in amount equivalent to percent of cod liver oil, having a vitamin D value of units per gram. The experiment was conducted in the usual way, using a foreperiod for depletion of vitamin A storage in the body of the rat. An effort was made to determine the weight of egg yolk necessary to provide one unit of vitamin A. The unit as recommended by Sherman and Munsell (192) for numerical expression of results is that amount of vitamin A which when fed daily induces an average gain of grams per week in a standard test animal under the conditions described. About equal numbers of males and females were used for each group of experimental rats. Positive and negative control groups provided satisfactory checks for the experiment. 2 4 1 18 2-18 6 Winter Series 4 7 27 44-26 1 2 40 48 46 1 6 2 4 2 6 19 6 0 More than Less than Less than About 20 2 More than 2 About 2 DISCUSSION Data obtained from the records were used to compile composite curves, the summary of which appears in Table 1. A vitamin A content of about units per gram is indicated for the F-1 egg yolk as daily feedings of 0 gram contained approximately 1 unit of vitamin A. Some animals died before the end of the 8-week period. Experience indicates that it is difficult to keep an entire group of depleted animals alive for 8 weeks at this low nutritive level. The same amount of F-2 eggs did not approach the Sherman unit, so a group of rats receiving gram of the egg yolk was started. These animals made distinctly better gains during the first 4 weeks but after this period lost weight and some died. At the end of the 8 weeks only 4 percent of the original group survived. These results show that gram of the F-2 egg yolk furnishes much less than 1 unit of vitamin A. Therefore, 1 gram would con-

MAY, 19. VOL. XIV, No. 181 tain distinctly less than 2 units of the vitamin. It is estimated that the vitamin A content is not over 20 units per gram. The 0 gram amount of the pale yolk (F-) also proved to be too small, but the larger amount, gram, approached the unit. Eggs of the winter series, W-l and W-2, were richer in vitamin A than the F-2 eggs. The W-2 egg yolk contained at least 2 units of vitamin A per gram. Considering the growth and survival of all groups of rats, the W-l egg yolk is shown to be similar to the W-2 egg yolk in vitamin A content. Egg production makes pronounced nutritive demands upon the hen. The recognized demand for vitamin A is more pronounced the greater the number of eggs produced and the longer the laying period. The birds producing eggs F-l, F-2, W-l, and W-2 all received the same ration. The young pullets of the W-l and W-2 groups, near the close of the first 4 months of production, laid eggs with yolks of similar vitamin A content, at least 2 units per gram. This period of production was apparently too short to have brought about marked differences between the vitamin A content of the yolk of eggs of high producers and low producers. On the other hand, distinct differences were found in the eggs of the older birds, completing the first year of production. The low producers, consuming the desirable ration and laying infrequently, gave yolks of higher vitamin A content, units per gram. The egg yolks of the high producers were distinctly less potent in this regard, about 20 units per gram. The yolk of pale eggs (F-) produced on a ration devoid of carotene and xanthophyll but supplying vitamin A in the form of cod liver oil contained 2 units of vitamin A per gram, thus being superior to the F-2 eggs. This is in agreement with the work of Palmer and Kempster (1919) who fed a carotinoid-free ration and obtained fertile eggs from which second generation chickens were eventually produced. SUMMARY Eggs were studied for the vitamin A content of the yolk. The investigation included eggs laid by high producers, low producers,' and hens receiving a pigment poor ration. The biological method of Sherman and Munsell was used for all determinations. The modified vitamin A-free diet contained viosterol to supply vitamin D. Young rats of suitable age and size were fed this vitamin A-free diet during the customary depletion period, after which they were placed on experiment. During the experimental period they received weighed supplementary portions of the yolks of eggs to be tested, at the rate of 0,, and 0 gram fed 6 days per week. Composite tables were prepared from data concerning the various groups of animals. These data were studied and results evaluated according to Sherman and Munsell. Findings are as follows: Both high and low producing young pullets, nearing the end of the first 4 months of production, laid eggs with yolks of similar vitamin A content, at least 2 units per gram. This period of production was apparently too short to have brought about marked differences between the vitamin A content of the yolk of eggs of the two groups. Pullets of high and of low production records laid eggs with dissimilar vitamin A content near the close of the first year of egg production. Eggs from low producers at that time showed units of vitamin A per gram of yolk as compared with about 20 units in the high producing group, high producers having decreased and low producers increased the vitamin A content as

182 POULTRY SCIENCE compared to the content of similar eggs produced at the end of only 4 months of laying. The pale eggs produced on a ration devoid of carotene and xanthophyll but supplying vitamin A in the form of cod liver oil contained 2 units of vitamin A per gram. REFERENCES Bethke, R. N., D. C. Kennard, and H. L. Sassaman. 1927. The fat-soluble vitamin content of hen's egg yolk as affected by the ration and management of the layers. J. Biol. Chem. 72: 69-706. Blakeslee, A. F., and D. E. Warner. 191. Correlation between egg laying and yellow pigment in the domestic fowl. Am. Nat. 49:60-68. Ellis, H. R. 19. The relation of egg yolk color to some nutritive properties of eggs. The U. S. Egg and Poul. Mag. 9:47-48. Ellis, H. R., David Miller, H. W. Titus, and T. C. Byerly. 19. Effect of diet on egg composition, J. of Nutr. 6:24-262. Fraps, G. S., and Ray Treichler, 19. Vitamin A content of foods and feed. Texas Agr. Exp. Sta. Bui. 477. Jull, Morley A. Poultry Husbandry, 19 Mc Graw-Hill Book Company, Inc., New York. 69p. Palmer, L. S., and H. L. Kempster. 1919. Relation of plant carotenoids to growth, fecundity, and reproduction of fowls. J. Biol. Chem. 9:299-. Sherman, H. C, and H. E. Munsell. 192. The quantitative determinations of vitamin A. J. of Am. Chem. Soc. 47:1,69-46. Sherwood, R. M., and G. S. Fraps. 192. The quantities of vitamin A required by pullets for maintenance and for egg production. Texas Agr. Exp. Sta. Bui. 468. Effects of Common Feed Ingredients on the Iodine Content of Hen's Eggs EXPERIMENTS on the iodine content of hen's eggs and the effects of iodine on reproduction have usually involved the use of an iodine concentrate. The literature on these subjects has been adequately reviewed by Johnson, Pilkey and Edson (19), and by Wilder, Bethke and Record (19). It is the purpose of this paper to place on record results obtained during 19 on the influence of iodine in common feed ingredients on the iodine content of hen's eggs and on several egg characteristics of interest. The essential data are given in Table 1. TABLE 1. Composition of rations and iodine content of eggs produced on these rations Group II III IV VI Hens per group, S.C. White Leghorns.. Composition of ration Corn, yellow Wheat Alfalfa, dried ' Skim milk, dried Salt... ; Sardine oil Meat scrap Sardine meal Limestone Oyster shell, eastern Oyster shell, western Abalone shell 0 4 1.2 2 0 4 1.2 2 6 4 1 4 1 4 1 4 1 Total Iodine as gammas* per grams of feed Average iodine content of eggs as gammas per eggf 0 20 42 00 60 41 184 0 2 1 * 1 gamma is equivalent to one millionth of a gram. t Average of several composite samples of approximately eggs each taken after weeks of feeding. (Continued on page 190)