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On the Supposed Effect of Iodocasein Upon Egg Production
Gn the Supposed Effect of Iodocasein Upon Egg Production F . B . HtTTT AND R . S. GOWE Department of Poultry Husbandry, Cornell University, Ithaca, N. Y. (Received for publication October 22, 1947)
HREE recent papers in this journal by Turner et al. (1945, 1945a. 1946) and a review by Reineke (1946) report experiments which led these writers to conclude that iodinated casein, a substance having the properties of thyroxine, has a marked stimulatory effect upon the production of eggs by domestic fowls. In most of the experiments this effect was believed to be exerted chiefly during the months of late spring and early summer, when production normally declines, but in one test (Turner et al., 1946, Lot IV) the treated birds laid better throughout the year. Since any such effect would have considerable economic value, it seemed desirable to repeat the experiments. THE E X P E R I M E N T
Birds.—Single Comb White Leghorn pullets of the C and K strains resistant to lymphomatosis (Hutt and Cole, 1947) were utilized. The total number enrolled at the start of these trials was 401, these being divided in four pens as follows: „ . s
j L o t I: 102 birds given iodocasein [Lot I I : 98 controls
s
/Lot I I I : 101 birds given iodocasein \Lot IV: 100 controls
„ .
All pullets in Lots I and II were of about the same age, being approximately nine months old when feeding of iodocasein was begun on January 22, 1946. Those in the other two lots were slightly
younger. That the controls and the treated birds were fully comparable in age, in development, in capacity for egg production, and in environmental conditions is shown by the fact that within each series the two lots had almost identical egg production up to January 31 (Table 1). In addition to these birds, each pen contained from 16 to 22 Leghorns of a strain susceptible to lymphomatosis. They were omitted from consideration because the egg production of such birds is usually subnormal. Dosage.—The iodinated casein used in these tests is called protamone by the Cerophyl Laboratories, Inc., of Kansas City, Missouri, which produce it. Our supply was kindly provided by Dr. W. R. Graham, Jr., of that company, who informed us that in content of thyroxine it was almost identical with the protamone used by Turner and his associates. According to chemical assays of Cerophyl Laboratories, the material contained 2.31 percent thyroxine, and biological assays showed that "0.235 percent of thyroxine is absorbed by the chick." It was fed at the level winch Turner and his associates considered optimum, viz,. 10 gms. protamone per 100 lbs. of feed consumed. However, since the Cornell birds ate both scratch grain and laying mash, and these in approximately equal quantities, it was necessary to feed the supplement at the rate of 20 gms. per 100 lbs. of mash. By determining weekly the amounts of
286
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IODOCASEIN IN EGG PRODUCTION
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Control birds received 10 gms. of ordinary untreated casein per 100 lbs. of feed eaten, 'fhanks to Dr. Graham, who provided it, this supplement for the controls came from the same original stock as the iodinated material. Environment.—The four lots of birds were kept in four adjoining pens, each 20 ft.X20 ft. in one laying house. They were confined until May, after which they were allowed to run in yards outdoors. Feeding space at mash hoppers, facilities for drinking, the number of nests, roosting space, and other conditions of the environment were identical in all four pens. The laying mash, which was prepared by a commercial firm, varied slightly during the year, but was always uniform in all four of the pens. Duration.—Feeding of the supplements was begun on January 22, 1946, and continued until August 31 of that year.
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grain and of mash eaten, it was possible to regulate the supply of both and thus to maintain the intake of the supplement at approximately the level desired. During the 31 weeks of feeding, the average weekly dosage proved to be 9.75 gms. of iodocasein per 100 lbs. of feed eaten. In February, when egg production of the experimental birds dropped significantly below that of controls, it was difficult to maintain consumption of mash at 50 percent of the total feed eaten, and, as a result, the intake of iodocasein dropped in one week as low as 7.5 gms. per 100 lbs. of feed in one pen. This was perhaps just as well, since the higher level at which feeding of the supplement was begun had precipitated a decline in the production of the experimental birds. During the late spring and summer, when the maximum effect of the treatment was to be expected, the dosage was easily maintained at approximately the tengram level.
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FIG. 1. Egg production of hens fed iodocasein and of controls. Details are given in the context; numbers Q of birds at the beginning and end of the experiment are given in Table 1. EFFECTS ON EGG PRODUCTION
The egg production of the four Jots, measured weekly, in percentage of the maximum possible for the mean number of birds alive each week is shown in Figure 1. In both Series I and Series II, a slight decline in productivity was under way when feeding of iodocasein was begun. In both series this decline was accelerated in the lots getting iodocasein and recovery from it was retarded in these same lots. The uniformity and consistency of results in the two series shows that the feeding of iodocasein significantly lowered egg production for a period of about eight weeks. Thereafter there was no significant difference. Production of the birds getting iodocasein in Series II was consistently lower than that of their controls right from February 1 onward, but, since a similar difference did not persist in the other series, it should not be considered as significant.
Contrary to the results of Turner et al, there is not the slightest indication that the feeding of iodocasein retards the normal decline in production after May 1. Comparisons between experimental and control birds for different periods are given in Table 1. These show that in both Series I and Series II, the egg production of the two component lots up to January 31, i.e., to about a week after the experiment began, was practically identical. Obviously, the experimental and control birds were evenly matched in both series. During February, March, and April, the controls laid more eggs than the birds getting iodocasein, the difference being statistically significant in Series I, but not in Series II. When data for the two series for this period were combined, the mean numbers of eggs were as follows: For 186 control birds: For 191 getting iodocasein:
55.84+1.04 51.56+1.27
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IODOCASEIN IN EGG PRODUCTION
EFFECTS ON THICKNESS OF EGG SHELL
According to Gutteridge and Pratt (1946) and Gutteridge and Novikoff (1947) the egg-shells of hens fed iodinated
ends. For each test there were used approximately fifty eggs selected at random from the experimental birds and the same number from controls. For each of the three tests, every egg came from a different hen, all being gathered in one day. The results (Table 2) do not show any significant or consistent effect of iodocasein upon thickness of shells that could be measured by these tests. In both groups, the shells were somewhat weaker in July than in June, but such a decline in summer is normal. It is true that the mean breaking strength for the controls was 0.S2 Kg. lower in July than in May, while the corresponding reduction for eggs of hens getting iodinated casein was only 0.04
TABLE 2.—Breaking strength of eggs from hens fed iodinated casein and from controls (1) Iodocasein Date of test Eggs
May 22 June 20 July 20
Number 50
so 48
(2) Controls
Mean breaking strength
Mean breaking strength
Difference
Eggs
Kgm. 3.90±.128 4.04±.119 3.86±.1S8
Number 52 48 54
Kgm. 4.26±.135 4.41±.143 3.74±.156*
Kgm. -0.36 -0.37 +0.12
(D-(2)
t.
1.94 2.0* 0.59
* P .05 in this instance.
casein were significantly stronger as measured by the specific gravity of the egg during the summer months tban those of controls. It had been found earlier by Asmundson and Pinsky (193S) that hens given desiccated thyroid gland produce significantly heavier shells than do the same hens when not receiving desiccated thyroid. In this experiment, strength of the shells was measured on May 22, June 20, and July 20, using the apparatus devised for this purpose by Romanoff (1929). I t measures the weight required to break the shell when pressure is applied at both
Kg. One might argue from this that strength of shell had been better maintained by the supplement, but that would not explain why the mean breaking strength for the controls was 0.36 and 0.37 Kg. higher in May and June, respectively, than in the other group, the differences being almost statistically significant. Before the eggs were tested for breaking strength in July, their specific gravity was measured by the method of Olsson (1934), whose procedure had also been followed by the Ottawa workers. The results showed no difference:
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The difference between these—-4.28 + 1.64—is statistically significant, as would be anticipated from inspection of Figure 1. After May 1, production of the controls was slightly higher in both series, but not significantly so. Considering the whole period, February 1 to August 31, the controls laid five eggs per bird more than those getting iodocasein, but the difference was not significant in either series, nor was it when both series were combined.
289
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F. B. HUTT AND R. S. Go WE
Hens on iodocasein: Controls:
Eggs, Mean specific prising because Crew and Huxley (1923) Number gravity and Cole and Hutt (1927) had found it 51 1.07662 impossible to raise egg production by 57 1.07663
OTHER CONSIDERATIONS
As the data in Table 3 show, the birds gettign iodocasein did not differ significantly from their controls in size of egg, in body weight (both recorded in March), or in viability.
feeding desiccated thyroid. It was first thought that the results of the Missouri workers might be similar to those of Larionov (1936), who lowered egg production by feeding large single doses of thyroid with the natural result that the thyroid-fed birds did
Group
Birds
Mortality Feb.1Aug. 31
Birds
Mean body weight in March
Birds
Mean egg weight in March
Number
Percent
Number
Grams
Number
Grams
Series I Iodocasein Controls
102 98
18.6 14.3
98 92
2,003 2,052
87 88
59.8 60.1
Series II Iodocasein Controls
101 100
14.8 19.0
95 97
1,985 1,986
93 95
59.1 59.0
Any possible effect on body weight was more likely to have been evident in February, soon after feeding of protamone was started, than in mid-March when the experimental birds were increasing in production. However, calculation of the dosage showed it to be approximately 0.4 mgm. of thyroid iodine daily per 2,000 grams of body weight. As this is less than half the dosage earlier found necessary to induce a loss in weight (Hutt, 1930), none was to be expected. DISCUSSION
(a) Of egg production It is clear that in this experiment the feeding of iodinated casein—at the level considered by the Missouri workers to give the maximum stimulus to egg production-^had no effect except to decrease the number of eggs laid during the first eight weeks of feeding. This is not sur-
excel the controls after the former had recovered from the treatment. It seems more likely, however, that the illusory effects in the Missouri experiments are attributable to the fact that the numbers of birds used in their experiments, while ample for some types of experiment, were not adequate for dealing with anything as variable as egg production. In their first test (Turner, 1945) among the 10 surviving controls, one had laid only 6 eggs, another 35, and the highest only 143, with an average for the 10 birds of only 90.1 eggs. This is inordinately low for the second year of laying, and it is not surprising that other groups of 10 or 11 should have done much better whether they got iodocasein or not. In another experiment (Turner et al., (1945a—Lots I and II), more birds were used, but it is difficult to believe that the difference of 7 eggs per bird between the 18 experimental hens and 21 controls
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TABLE 3.—Showing lack of effect of iodocasein upon some other items
IODOCASEIN IN EGG PRODUCTION
Since completion of the tests at Cornell, Temperton and Dudley (1947) have reported experiments in which control hens laid slightly better than three lots of birds getting different levels of iodocasein. The differences were not significant, and production in all four groups was unusually low. Gutteridge and Novikoff (1947) were unable to raise egg production by feeding iodinated casein. On the other hand, De Man and Bos (1946) claim that it increased production by 20 percent, but their data hardly justify that conclusion. (b) Of thyroid physiology Turner and his associates considered the normal decline in egg production in late spring and summer to result from a decrease in secretion of the thyroid gland. The continuance of laying at that time by birds getting iodocasein was attributed to maintenance thereby of the level of thyroid hormone. This required some modification for the one group on iodo-
casein that excelled its controls right throughout their second laying year (turner et al. 1946, Lots II and III). (Since, as can be computed from their Table 2, the mean first-year egg production of these controls was only 187, against 220 for the experimental birds, the most logical explanation in that case is that the latter were genetically better layers). This interpretation of the" supposed effect of iodocasein rests on the opinion held by Turner et al. (1945) that: "Thyroid secretion is markedly increased in the winter at a time when the chickens' thyroids are enlarged (Galpin, 1938) and is decreased in the summer months when the temperatures are high."
The available evidence suggests that the true situation is exactly the reverse. Galpin did find the thyroids to be larger in winter and to decrease in size up to midsummer, but she herself suggested that the functional activity is inversely related to the mass, so that the smaller glands of spring and summer would be more active than the large ones of winter. The fowl's thyroid contains more thyroxine in winter than in spring and summer (Cruickshank, 1929) but this does not mean that the amount secreted is any greater. On the contrary, Podhradsky's (1935) histological studies showed that in October and January the fowl's thyroid contains much colloid and looks like a storage organ, while in May it is more active and in July most active. Similarly, Riddle (1925) showed that in the pigeon the thyroid is small in the season of frequent ovulation and larger when ovulation is restricted. In some cases, animals given supplementary hormone treatment, show an initial response but later become refractory. Thus, Cole and Hutt (1927) found that after receiving thyroid for six weeks males failed to respond (as they
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that survived could be attributed to the treatment. Even though a statistical test of the records from May to September (when the experimental birds did excel the controls) showed "less than one chance in twenty that the difference is due to chance variation," that difference could result from the presence in one group of a few persistent layers just as well as from the iodocasein. In another test, Rhode Island Red pullets getting iodocasein laid better than the controls, and the difference was attributed to the treatment by Turner et al. (1945a—• Figure 2) and by Reineke (1946—Figure 10). The validity of this claim will seem doubtful to experienced poultrymen because at the time of maximum difference between the lots there were only 10 survivors in the controls and 11 in the other lot.
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F. B. HUTT'AND R. S. GOWE
had earlier) by growing feathers of female type. In the present experiment, it is obvious (Figure 1) that there was a slight initial adverse effect of iodocasein, but that it disappeared in eight weeks or less. It is difficult to believe that iodinated casein at a level causing no initial effect when first given in October (as in the Missouri experiments) could have a significant influence 7 to 11 months later.
On the other hand, just such a persistent effect is apparent in the data of Gutteridge and Novikoff (1947) showing eggs of hens fed iodocasein to be slightly higher in specific gravity than eggs of control hens six months after feeding began. Unfortunately, actual tests or measures of shell thickness were not made. While, as Olsson (1934) showed, the specific gravity is very highly correlated with the proportion of shell (0.94 to +.98) it is not necessarily related equally closely to the strength of shell or its thickness. In the present authors' studies, the correlation between specific gravity and breaking-strength was only + . 6 1 . In several instances eggs of the same specific gravity varied as much as 3 Kg. in breaking strength. Presumably this last may be affected by the porosity of the shell, by the shape of the egg, by localized areas of thinner shell, and other factors that could have less direct effect upon specific gravity. Furthermore, if strength of shell is to be measured by specific gravity, it would seem desirable to demonstrate that the latter is not influenced (in tests with iodinated casein) by the disproportionate reduction of the yolk induced by feeding thyroid substance (Asmundson and Pinsky, 1935). In any case, although statistical tests by Gutteridge and Novikoff were said to show "the
SUMMARY In two series of tests, White Leghorn females given iodinated casein at a level of approximately 10 gms. per 100 lbs. of feed consumed were compared for over seven months with controls. The total numbers started in the test were 203 experimental birds and 198 controls. In each series the treatment (begun on January 22) reduced egg production about 4 eggs per bird during the first three months, but had no significant or consistent effect thereafter. Iodinated casein had no measurable effect upon body weight or egg weight (in March), upon viability, or upon strength of egg shells in May, June, and July. The experiments of Turner and his associates which were believed to show that iodinated casein permits birds to maintain production during late spring and summer are considered and reasons given for the illusory nature of the data. Evidence is cited in support of the opinion that the fowl's thyroid gland is more active in late spring and summer than in the fall and winter, and that its functional activity is inversely related to its mass. This is the antithesis of the view elaborated by Turner and his associates to account for the supposed beneficial effect of iodinated casein in their experiments. REFERENCES
Asmundson, V. S., and P. Pinsky, 1935. The effect of the thyroid on the formation of the hen's egg. Poultry Sci. 14: 99-104.
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(c) Of egg sheik
shell strength of the group fed thyroprotein to be significantly superior to that of the control," their graphs reveal that this supplement prevented only 11 to 20 percent of the normal summer decline in shell strength as measured by specific gravity.
IODOCASKIN IN EGG PRODUCTION
leistung beim Huhn. Zeitschr. f. Zuchtg.: B. Tierzuchtg u. Zuchtgsbiol. 36:377-385. Olsson, N., 1934. Studies on the specific gravity of hen's eggs. Pp. 1-16. Otto Harrassowitz, Leipzig. Podhradsky, J., 1935. Die Veranderungen der inkretorischen Drttsen und einiger innerer Organe bei der Legeleistung. Zeitschr. f. Zuchtg.: B. Tierziichtg. u. Zuchtgsbiol. 33: 76-103. Reineke, E. P., 1946. Thyroactive iodinated proteins. Vitamins and Hormones 4:207-252. Riddle, O., 1925. Studies on the physiology of reproduction in birds. X X Reciprocal size changes of gonads and thyroids in relation to season and ovulation rate in pigeons. Amer. J. Physiol. 73: 5-16. Romanoff, A. L., 1929. Study of the physical properties of the hen's egg shell in relation to the function of shell-secretory glands. Biol. Bull. 56: 351-356. Temperton, H., and F . J. Dudley, 1947. The effects of feeding iodinated casein to laying hens. Harper Adams Util. Poultry Journ. 32:20-25. Turner, C. W., M. R. Irwin, and E. P. Reineke, 1945. Effect of the thyroid hormone on egg production of White Leghorn hens. Poultry Sci. 24: 171-180. Turner, C. W., H. L. Kempster, N. M. Hall, and E. P. Reineke, 1945a. The effect of thyroprotein on egg production. Poultry Sci. 24:522-533. Turner, C. W., H. L. Kempster, and N. M. Hall, 1946. Effect of continued thyroprotein feeding on egg production. Poultry Sci. 25:562-569.
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Cole, L. J., and F. B. Hutt, 1927. Further experiments in feeding thyroid to fowls, Poultry Sci. 7:60-66. Crew, F. A. E., and J. S. Huxley, 1923. The relation of internal secretion to reproduction and growth in the domestic fowl. I. Effect of thyroid feeding on growth rate, feathering, and egg production. Vet. Journ. 79:343-348. Cruickshank, E. M., 1929. Observations on the iodine content of the thyroid and ovary of the fowl during the growth, laying, and moulting periods. Biochem. Journ. 23:1044-1049. De Man, Th. J., and K. Bos, 1946. Over de beinvloeding van den leg bij kippen door gejodeerd caseine. Tijd. f. Diergeneeskunde 71: 755-764. Galpin, N., 1938. Factors affecting the hatching weight of Brown Leghorn chickens. Proc. Roy. Soc. Edin. 58, I I : 98-113. Gutteridge, H. S., and J. M. Pratt, 1946. The effect of vitamins D 2 and D 3 in fish oils and of iodocasein on shell quality. Poultry Sci. 25: 89-91. Gutteridge, H. S., and M. Novikoff, 1947. The effect of natural and synthetic vitamins D2 and of thyroprotein on egg shell quality. Poultry Sci. 26: 210-212. Hutt, F. B., 1930. A note on the effects of different doses of thyroid on the fowl. J. Exper. Biol. 7:1-6. Hutt, F. B., and R. K. Cole, 1947. Genetic control of lymphomatosis in the fowl. Science 106: 379384. Larionov, W..T. 1936. Experimentelle Analyse der Wechselbeziehung zwischen Mauser und Lege-
293
HREE recent papers in this journal by Turner et al. (1945, 1945a. 1946) and a review by Reineke (1946) report experiments which led these writers to conclude that iodinated casein, a substance having the properties of thyroxine, has a marked stimulatory effect upon the production of eggs by domestic fowls. In most of the experiments this effect was believed to be exerted chiefly during the months of late spring and early summer, when production normally declines, but in one test (Turner et al., 1946, Lot IV) the treated birds laid better throughout the year. Since any such effect would have considerable economic value, it seemed desirable to repeat the experiments. THE E X P E R I M E N T
Birds.—Single Comb White Leghorn pullets of the C and K strains resistant to lymphomatosis (Hutt and Cole, 1947) were utilized. The total number enrolled at the start of these trials was 401, these being divided in four pens as follows: „ . s
j L o t I: 102 birds given iodocasein [Lot I I : 98 controls
s
/Lot I I I : 101 birds given iodocasein \Lot IV: 100 controls
„ .
All pullets in Lots I and II were of about the same age, being approximately nine months old when feeding of iodocasein was begun on January 22, 1946. Those in the other two lots were slightly
younger. That the controls and the treated birds were fully comparable in age, in development, in capacity for egg production, and in environmental conditions is shown by the fact that within each series the two lots had almost identical egg production up to January 31 (Table 1). In addition to these birds, each pen contained from 16 to 22 Leghorns of a strain susceptible to lymphomatosis. They were omitted from consideration because the egg production of such birds is usually subnormal. Dosage.—The iodinated casein used in these tests is called protamone by the Cerophyl Laboratories, Inc., of Kansas City, Missouri, which produce it. Our supply was kindly provided by Dr. W. R. Graham, Jr., of that company, who informed us that in content of thyroxine it was almost identical with the protamone used by Turner and his associates. According to chemical assays of Cerophyl Laboratories, the material contained 2.31 percent thyroxine, and biological assays showed that "0.235 percent of thyroxine is absorbed by the chick." It was fed at the level winch Turner and his associates considered optimum, viz,. 10 gms. protamone per 100 lbs. of feed consumed. However, since the Cornell birds ate both scratch grain and laying mash, and these in approximately equal quantities, it was necessary to feed the supplement at the rate of 20 gms. per 100 lbs. of mash. By determining weekly the amounts of
286
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IODOCASEIN IN EGG PRODUCTION
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Control birds received 10 gms. of ordinary untreated casein per 100 lbs. of feed eaten, 'fhanks to Dr. Graham, who provided it, this supplement for the controls came from the same original stock as the iodinated material. Environment.—The four lots of birds were kept in four adjoining pens, each 20 ft.X20 ft. in one laying house. They were confined until May, after which they were allowed to run in yards outdoors. Feeding space at mash hoppers, facilities for drinking, the number of nests, roosting space, and other conditions of the environment were identical in all four pens. The laying mash, which was prepared by a commercial firm, varied slightly during the year, but was always uniform in all four of the pens. Duration.—Feeding of the supplements was begun on January 22, 1946, and continued until August 31 of that year.
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grain and of mash eaten, it was possible to regulate the supply of both and thus to maintain the intake of the supplement at approximately the level desired. During the 31 weeks of feeding, the average weekly dosage proved to be 9.75 gms. of iodocasein per 100 lbs. of feed eaten. In February, when egg production of the experimental birds dropped significantly below that of controls, it was difficult to maintain consumption of mash at 50 percent of the total feed eaten, and, as a result, the intake of iodocasein dropped in one week as low as 7.5 gms. per 100 lbs. of feed in one pen. This was perhaps just as well, since the higher level at which feeding of the supplement was begun had precipitated a decline in the production of the experimental birds. During the late spring and summer, when the maximum effect of the treatment was to be expected, the dosage was easily maintained at approximately the tengram level.
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AUG:
FIG. 1. Egg production of hens fed iodocasein and of controls. Details are given in the context; numbers Q of birds at the beginning and end of the experiment are given in Table 1. EFFECTS ON EGG PRODUCTION
The egg production of the four Jots, measured weekly, in percentage of the maximum possible for the mean number of birds alive each week is shown in Figure 1. In both Series I and Series II, a slight decline in productivity was under way when feeding of iodocasein was begun. In both series this decline was accelerated in the lots getting iodocasein and recovery from it was retarded in these same lots. The uniformity and consistency of results in the two series shows that the feeding of iodocasein significantly lowered egg production for a period of about eight weeks. Thereafter there was no significant difference. Production of the birds getting iodocasein in Series II was consistently lower than that of their controls right from February 1 onward, but, since a similar difference did not persist in the other series, it should not be considered as significant.
Contrary to the results of Turner et al, there is not the slightest indication that the feeding of iodocasein retards the normal decline in production after May 1. Comparisons between experimental and control birds for different periods are given in Table 1. These show that in both Series I and Series II, the egg production of the two component lots up to January 31, i.e., to about a week after the experiment began, was practically identical. Obviously, the experimental and control birds were evenly matched in both series. During February, March, and April, the controls laid more eggs than the birds getting iodocasein, the difference being statistically significant in Series I, but not in Series II. When data for the two series for this period were combined, the mean numbers of eggs were as follows: For 186 control birds: For 191 getting iodocasein:
55.84+1.04 51.56+1.27
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z g
IODOCASEIN IN EGG PRODUCTION
EFFECTS ON THICKNESS OF EGG SHELL
According to Gutteridge and Pratt (1946) and Gutteridge and Novikoff (1947) the egg-shells of hens fed iodinated
ends. For each test there were used approximately fifty eggs selected at random from the experimental birds and the same number from controls. For each of the three tests, every egg came from a different hen, all being gathered in one day. The results (Table 2) do not show any significant or consistent effect of iodocasein upon thickness of shells that could be measured by these tests. In both groups, the shells were somewhat weaker in July than in June, but such a decline in summer is normal. It is true that the mean breaking strength for the controls was 0.S2 Kg. lower in July than in May, while the corresponding reduction for eggs of hens getting iodinated casein was only 0.04
TABLE 2.—Breaking strength of eggs from hens fed iodinated casein and from controls (1) Iodocasein Date of test Eggs
May 22 June 20 July 20
Number 50
so 48
(2) Controls
Mean breaking strength
Mean breaking strength
Difference
Eggs
Kgm. 3.90±.128 4.04±.119 3.86±.1S8
Number 52 48 54
Kgm. 4.26±.135 4.41±.143 3.74±.156*
Kgm. -0.36 -0.37 +0.12
(D-(2)
t.
1.94 2.0* 0.59
* P .05 in this instance.
casein were significantly stronger as measured by the specific gravity of the egg during the summer months tban those of controls. It had been found earlier by Asmundson and Pinsky (193S) that hens given desiccated thyroid gland produce significantly heavier shells than do the same hens when not receiving desiccated thyroid. In this experiment, strength of the shells was measured on May 22, June 20, and July 20, using the apparatus devised for this purpose by Romanoff (1929). I t measures the weight required to break the shell when pressure is applied at both
Kg. One might argue from this that strength of shell had been better maintained by the supplement, but that would not explain why the mean breaking strength for the controls was 0.36 and 0.37 Kg. higher in May and June, respectively, than in the other group, the differences being almost statistically significant. Before the eggs were tested for breaking strength in July, their specific gravity was measured by the method of Olsson (1934), whose procedure had also been followed by the Ottawa workers. The results showed no difference:
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The difference between these—-4.28 + 1.64—is statistically significant, as would be anticipated from inspection of Figure 1. After May 1, production of the controls was slightly higher in both series, but not significantly so. Considering the whole period, February 1 to August 31, the controls laid five eggs per bird more than those getting iodocasein, but the difference was not significant in either series, nor was it when both series were combined.
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290
F. B. HUTT AND R. S. Go WE
Hens on iodocasein: Controls:
Eggs, Mean specific prising because Crew and Huxley (1923) Number gravity and Cole and Hutt (1927) had found it 51 1.07662 impossible to raise egg production by 57 1.07663
OTHER CONSIDERATIONS
As the data in Table 3 show, the birds gettign iodocasein did not differ significantly from their controls in size of egg, in body weight (both recorded in March), or in viability.
feeding desiccated thyroid. It was first thought that the results of the Missouri workers might be similar to those of Larionov (1936), who lowered egg production by feeding large single doses of thyroid with the natural result that the thyroid-fed birds did
Group
Birds
Mortality Feb.1Aug. 31
Birds
Mean body weight in March
Birds
Mean egg weight in March
Number
Percent
Number
Grams
Number
Grams
Series I Iodocasein Controls
102 98
18.6 14.3
98 92
2,003 2,052
87 88
59.8 60.1
Series II Iodocasein Controls
101 100
14.8 19.0
95 97
1,985 1,986
93 95
59.1 59.0
Any possible effect on body weight was more likely to have been evident in February, soon after feeding of protamone was started, than in mid-March when the experimental birds were increasing in production. However, calculation of the dosage showed it to be approximately 0.4 mgm. of thyroid iodine daily per 2,000 grams of body weight. As this is less than half the dosage earlier found necessary to induce a loss in weight (Hutt, 1930), none was to be expected. DISCUSSION
(a) Of egg production It is clear that in this experiment the feeding of iodinated casein—at the level considered by the Missouri workers to give the maximum stimulus to egg production-^had no effect except to decrease the number of eggs laid during the first eight weeks of feeding. This is not sur-
excel the controls after the former had recovered from the treatment. It seems more likely, however, that the illusory effects in the Missouri experiments are attributable to the fact that the numbers of birds used in their experiments, while ample for some types of experiment, were not adequate for dealing with anything as variable as egg production. In their first test (Turner, 1945) among the 10 surviving controls, one had laid only 6 eggs, another 35, and the highest only 143, with an average for the 10 birds of only 90.1 eggs. This is inordinately low for the second year of laying, and it is not surprising that other groups of 10 or 11 should have done much better whether they got iodocasein or not. In another experiment (Turner et al., (1945a—Lots I and II), more birds were used, but it is difficult to believe that the difference of 7 eggs per bird between the 18 experimental hens and 21 controls
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TABLE 3.—Showing lack of effect of iodocasein upon some other items
IODOCASEIN IN EGG PRODUCTION
Since completion of the tests at Cornell, Temperton and Dudley (1947) have reported experiments in which control hens laid slightly better than three lots of birds getting different levels of iodocasein. The differences were not significant, and production in all four groups was unusually low. Gutteridge and Novikoff (1947) were unable to raise egg production by feeding iodinated casein. On the other hand, De Man and Bos (1946) claim that it increased production by 20 percent, but their data hardly justify that conclusion. (b) Of thyroid physiology Turner and his associates considered the normal decline in egg production in late spring and summer to result from a decrease in secretion of the thyroid gland. The continuance of laying at that time by birds getting iodocasein was attributed to maintenance thereby of the level of thyroid hormone. This required some modification for the one group on iodo-
casein that excelled its controls right throughout their second laying year (turner et al. 1946, Lots II and III). (Since, as can be computed from their Table 2, the mean first-year egg production of these controls was only 187, against 220 for the experimental birds, the most logical explanation in that case is that the latter were genetically better layers). This interpretation of the" supposed effect of iodocasein rests on the opinion held by Turner et al. (1945) that: "Thyroid secretion is markedly increased in the winter at a time when the chickens' thyroids are enlarged (Galpin, 1938) and is decreased in the summer months when the temperatures are high."
The available evidence suggests that the true situation is exactly the reverse. Galpin did find the thyroids to be larger in winter and to decrease in size up to midsummer, but she herself suggested that the functional activity is inversely related to the mass, so that the smaller glands of spring and summer would be more active than the large ones of winter. The fowl's thyroid contains more thyroxine in winter than in spring and summer (Cruickshank, 1929) but this does not mean that the amount secreted is any greater. On the contrary, Podhradsky's (1935) histological studies showed that in October and January the fowl's thyroid contains much colloid and looks like a storage organ, while in May it is more active and in July most active. Similarly, Riddle (1925) showed that in the pigeon the thyroid is small in the season of frequent ovulation and larger when ovulation is restricted. In some cases, animals given supplementary hormone treatment, show an initial response but later become refractory. Thus, Cole and Hutt (1927) found that after receiving thyroid for six weeks males failed to respond (as they
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that survived could be attributed to the treatment. Even though a statistical test of the records from May to September (when the experimental birds did excel the controls) showed "less than one chance in twenty that the difference is due to chance variation," that difference could result from the presence in one group of a few persistent layers just as well as from the iodocasein. In another test, Rhode Island Red pullets getting iodocasein laid better than the controls, and the difference was attributed to the treatment by Turner et al. (1945a—• Figure 2) and by Reineke (1946—Figure 10). The validity of this claim will seem doubtful to experienced poultrymen because at the time of maximum difference between the lots there were only 10 survivors in the controls and 11 in the other lot.
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F. B. HUTT'AND R. S. GOWE
had earlier) by growing feathers of female type. In the present experiment, it is obvious (Figure 1) that there was a slight initial adverse effect of iodocasein, but that it disappeared in eight weeks or less. It is difficult to believe that iodinated casein at a level causing no initial effect when first given in October (as in the Missouri experiments) could have a significant influence 7 to 11 months later.
On the other hand, just such a persistent effect is apparent in the data of Gutteridge and Novikoff (1947) showing eggs of hens fed iodocasein to be slightly higher in specific gravity than eggs of control hens six months after feeding began. Unfortunately, actual tests or measures of shell thickness were not made. While, as Olsson (1934) showed, the specific gravity is very highly correlated with the proportion of shell (0.94 to +.98) it is not necessarily related equally closely to the strength of shell or its thickness. In the present authors' studies, the correlation between specific gravity and breaking-strength was only + . 6 1 . In several instances eggs of the same specific gravity varied as much as 3 Kg. in breaking strength. Presumably this last may be affected by the porosity of the shell, by the shape of the egg, by localized areas of thinner shell, and other factors that could have less direct effect upon specific gravity. Furthermore, if strength of shell is to be measured by specific gravity, it would seem desirable to demonstrate that the latter is not influenced (in tests with iodinated casein) by the disproportionate reduction of the yolk induced by feeding thyroid substance (Asmundson and Pinsky, 1935). In any case, although statistical tests by Gutteridge and Novikoff were said to show "the
SUMMARY In two series of tests, White Leghorn females given iodinated casein at a level of approximately 10 gms. per 100 lbs. of feed consumed were compared for over seven months with controls. The total numbers started in the test were 203 experimental birds and 198 controls. In each series the treatment (begun on January 22) reduced egg production about 4 eggs per bird during the first three months, but had no significant or consistent effect thereafter. Iodinated casein had no measurable effect upon body weight or egg weight (in March), upon viability, or upon strength of egg shells in May, June, and July. The experiments of Turner and his associates which were believed to show that iodinated casein permits birds to maintain production during late spring and summer are considered and reasons given for the illusory nature of the data. Evidence is cited in support of the opinion that the fowl's thyroid gland is more active in late spring and summer than in the fall and winter, and that its functional activity is inversely related to its mass. This is the antithesis of the view elaborated by Turner and his associates to account for the supposed beneficial effect of iodinated casein in their experiments. REFERENCES
Asmundson, V. S., and P. Pinsky, 1935. The effect of the thyroid on the formation of the hen's egg. Poultry Sci. 14: 99-104.
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(c) Of egg sheik
shell strength of the group fed thyroprotein to be significantly superior to that of the control," their graphs reveal that this supplement prevented only 11 to 20 percent of the normal summer decline in shell strength as measured by specific gravity.
IODOCASKIN IN EGG PRODUCTION
leistung beim Huhn. Zeitschr. f. Zuchtg.: B. Tierzuchtg u. Zuchtgsbiol. 36:377-385. Olsson, N., 1934. Studies on the specific gravity of hen's eggs. Pp. 1-16. Otto Harrassowitz, Leipzig. Podhradsky, J., 1935. Die Veranderungen der inkretorischen Drttsen und einiger innerer Organe bei der Legeleistung. Zeitschr. f. Zuchtg.: B. Tierziichtg. u. Zuchtgsbiol. 33: 76-103. Reineke, E. P., 1946. Thyroactive iodinated proteins. Vitamins and Hormones 4:207-252. Riddle, O., 1925. Studies on the physiology of reproduction in birds. X X Reciprocal size changes of gonads and thyroids in relation to season and ovulation rate in pigeons. Amer. J. Physiol. 73: 5-16. Romanoff, A. L., 1929. Study of the physical properties of the hen's egg shell in relation to the function of shell-secretory glands. Biol. Bull. 56: 351-356. Temperton, H., and F . J. Dudley, 1947. The effects of feeding iodinated casein to laying hens. Harper Adams Util. Poultry Journ. 32:20-25. Turner, C. W., M. R. Irwin, and E. P. Reineke, 1945. Effect of the thyroid hormone on egg production of White Leghorn hens. Poultry Sci. 24: 171-180. Turner, C. W., H. L. Kempster, N. M. Hall, and E. P. Reineke, 1945a. The effect of thyroprotein on egg production. Poultry Sci. 24:522-533. Turner, C. W., H. L. Kempster, and N. M. Hall, 1946. Effect of continued thyroprotein feeding on egg production. Poultry Sci. 25:562-569.
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Cole, L. J., and F. B. Hutt, 1927. Further experiments in feeding thyroid to fowls, Poultry Sci. 7:60-66. Crew, F. A. E., and J. S. Huxley, 1923. The relation of internal secretion to reproduction and growth in the domestic fowl. I. Effect of thyroid feeding on growth rate, feathering, and egg production. Vet. Journ. 79:343-348. Cruickshank, E. M., 1929. Observations on the iodine content of the thyroid and ovary of the fowl during the growth, laying, and moulting periods. Biochem. Journ. 23:1044-1049. De Man, Th. J., and K. Bos, 1946. Over de beinvloeding van den leg bij kippen door gejodeerd caseine. Tijd. f. Diergeneeskunde 71: 755-764. Galpin, N., 1938. Factors affecting the hatching weight of Brown Leghorn chickens. Proc. Roy. Soc. Edin. 58, I I : 98-113. Gutteridge, H. S., and J. M. Pratt, 1946. The effect of vitamins D 2 and D 3 in fish oils and of iodocasein on shell quality. Poultry Sci. 25: 89-91. Gutteridge, H. S., and M. Novikoff, 1947. The effect of natural and synthetic vitamins D2 and of thyroprotein on egg shell quality. Poultry Sci. 26: 210-212. Hutt, F. B., 1930. A note on the effects of different doses of thyroid on the fowl. J. Exper. Biol. 7:1-6. Hutt, F. B., and R. K. Cole, 1947. Genetic control of lymphomatosis in the fowl. Science 106: 379384. Larionov, W..T. 1936. Experimentelle Analyse der Wechselbeziehung zwischen Mauser und Lege-
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