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Seasonal Variations in Egg Quality
Seasonal Variations in Egg Quality F . W . LORENZ AND H . J . AlMQUIST Division of Poultry Husbandry, College of Agriculture, Berkeley (Received for Publication, November 6, 1934)
F
quist (1931) described by Lorenz and Almquist (1934). The temperatures used were obtained from "Climatological Data, California Section, U. S. Weather Bureau" particularly referring to the vicinity of the experiments. Data on eggs from these birds were collected for two years. Meanwhile, Flock 2, a group of 95 birds, hatched in 1932 from the eggquality breeding stock (Lorenz, Taylor, and Almquist 1934) were started on the same experiment. Data are presented for the first year's production of Flock 2. In summarizing the data, the mean value of each measurement for each bird was calculated for the period of the experiment. Deviations from this mean were then calculated for each measurement, and these deviations were averaged algebraically for the flock each day. The obtained values of the "mean deviation from the birds' means" were used in the correlations. During the first laying year of Flock 1 the coefficient of correlation between the average deviations in the mean percentage of firm white and the maximum temperature during the day the eggs were laid was found to be —.430 ± .079. The correlation coefficient for the second year, however, was only —.128 ± -118, a value which, although of the same sign, is not statistically significant. This small value may have been due to the high variation in this measurement and to the small size of the flock, which had decreased to only 17 birds, resulting in an inadequate sample. With the larger Flock 2 during the first year of production, a higher coefficient of correlation, —.730 ± .043 was obtained.
[14]
Downloaded from http://ps.oxfordjournals.org/ at Carleton University on May 9, 2015
EW reports have appeared in the literature regarding the effect of the season or of the climate of the locality on the quality of fresh eggs, although it has generally been the experience of candlers and egg graders that summer eggs were poorer in quality than spring and winter eggs. Bennion and Warren (1933), reported that air temperatures over 85°F. during formation of the egg had a tendency to decrease egg size, but they made no reference to the effect of temperature on the internal quality of the egg. Hunter, VanWagenen, and Hall (1934) reported that eggs of the highest internal quality are produced between November and March, and eggs of lowest quality in the spring and summer. No mention was made, however, of a possible effect of temperature. The present study was undertaken, partly in an attempt to determine if there is a real deterioration of eggs produced in the summer at or prior to the time they were laid or if the deterioration occurs because such eggs are exposed to high temperatures after they are laid, and partly in an attempt to discover if differences in season should be considered when interpreting the results of egg quality studies, more particularly with reference to measurements of percentage of firm white, egg weight and shell weight. Eggs from a group of 34 trapnested pullets (Flock 1) hatched in 1931 were collected one day each week, and the egg weight, shell weight and percentage of firm white were determined when the eggs were approximately 24 hours old. The percentage of firm white was determined by the modification of the method of Hoist and Alm-
JANUARY,
1936.
VOL.
XV,
No.
The data for Flock 2 were analyzed in order to determine when temperature affects egg quality. The maximum temperature of the day occurs about 3:00 p.m. which is after nearly all of that day's eggs have TABLE 1.—Coefficients of correlation between percentage of firm white of eggs less than 15 minutes old and the temperature of the cages No. Eggs
H1056 H1057 H1062 H1064 H1066 H1067
15 32 37 22 19 23
Er
r + .336 -.148 -.216 -.254 -.122 -.084
+ .155 ±.166 + .105 + .133 + .152 ±.139
r/Er 2.17 0.89 2.06 1.92 0.80 0.60
been laid. Consequently, if (as has often been suggested) the summer slump in egg quality is due to the effect of heat on the birds, the maximum temperature of the preceding day should have the greater effect. The coefficient of correlation between the average deviations in the mean percentage of firm white and the maximum temperature of the preceding day was found to be —.627 ± .056. The coefficient of correlation between the maximum temperature of the two succeeding days was +.840 ± .027. From these values the partial coefficients of correlation were calculated: —.482 ± .071 7 V * i = —.035 -+- .092
IS
(/ = the mean deviation of the mean percentage of firm white, tt = maximum temperature of the day the eggs were laid, and t2 = the maximum temperature of the preceding day.) The coefficient rft1-t2 is, of course, highly significant, while rft2-t1, is even less than the probable error, indicating that the simple correlation rjt2 is spurious. These results suggest, therefore, that the temperature during the time the eggs are being formed has no noticeable effect on the percentage of firm white, while the temperature immediately after the eggs are laid exerts a distinct effect.1 An attempt has been made to test this temperature effect more exactly. A small group of birds was kept in electrically heated cages, in which the temperature was varied at will between 60° and 85°F. Eggs were collected within 15 minutes after they were laid and the percentage of firm white determined immediately. In no case was there a significant correlation between the percentage of firm white and the temperature of the cage. Data for the birds from which sufficient eggs were obtained are sum*The regression equation of the deviations of percentage of firm white from the mean on temperature is: f = 16.1 — 0.257 t, Thus the mean percentage of firm white occurs, in this experiment, at the temperature of 62.7° F. An increase in temperature of 10° F. will cause a drop of 2.57 percent in the percentage of firm white.
TABLE 2.—Eject of storage temperature during the first 24 hours after being laid on the percentage of firm while of eggs. Fresh eggs Bird
H1056 H1057 H1059 HI 104 Average
Eggs stored 24hrs.40°F.
Eggs stored 24 hrs. 86° F.
Differences in % Firm White
Fresh— Stored40°F. Average % FreshAverage % Average % No. Firm white No. Firm white No. Firm white Stored 40° F Stored 86° F. Stored 86°F. 15 11 12 11
68.3 61.7 61.5 63.0
4 5 5 4
65.4 67.7 58.2 64.3
4 4 4 4
49.9 47.6 42.6 54.3
2.9 -6.0 3.3 -1.3
18.4 14.1 18.9 8.7
15.5 20.1 15.6 10.0
-0.3
15.0
15.3
Downloaded from http://ps.oxfordjournals.org/ at Carleton University on May 9, 2015
Bird
1
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POULTRY
marized in Table 1. For the second part of the experiment the cages were permitted to remain at room temperature, which was fairly constant at 60°-65°F. The eggs were collected within 15 minutes after being laid, as before, and were stored for 24 hours, some at 40° and some at 86°F. For this experiment eggs were obtained from only 4 birds. The data for these eggs are summarized in Table 2. Values from the fresh
Flock I r fh= - .430+ .079 (1st year production) r fh = - . 198+ . 118 (2nd year production) r wh= — .584+ .067 (2nd year production) Flock II (all first year production) r fh = - . 7 3 0 +.043 fh = - . 6 2 7 ±.056 'hh =4-.840+.027
eggs tabulated are taken from the previous part of the experiment. The first column under "Differences" gives the decrease in percentage of firm white during 24 hours storage at 40° F. It is obvious that the percentage of firm white did not decrease appreciably. On the other hand, when eggs were stored at 86°F. there was a decided decrease in the percentage of firm white. The last column in Table 1 shows that eggs held at 86°F. for 24 hours deteriorated much more than eggs held for the same length of time at 40°F. The average value of 1S.0 in the second
difference column is higher than might be expected. Previous work showed an average drop of about 2.3 percent per day in eggs stored at 86°F. during their second and subsequent days. Thus it seems likely that the temperature at which an egg is held during the first 24 hours after it is laid is of utmost importance. Further work is in progress in an attempt to determine the exact time during which the maximum liquefaction occurs. When egg weight variations were considered, it was found that a complicating factor, the natural increase of egg size during the first laying year, made the correlations between egg weight and temperature non-linear. However, the variation of egg weight in the second year's production of Flock 1 was very small. The coefficient of correlation between the mean egg weight deviations of the second year and the maximum temperature of the day before the eggs were laid (the time during which the eggs were being formed) was found to be —.584 ± -067, a significant negative correlation which was found to be linear. This indicates a decrease in egg weight proportional to the increase in temperature, at least between 40° and 90° F. In this respect, our results differ from those of Bennion and Warren (1933) in that they found no effect of temperature on egg weight below 85°F.2 It was thought desirable to determine whether or not there was any relation between the percentage of firm white and egg weight, since it had been noticed that small 2
The regression equation of the deviations of egg weight from the mean on temperature is: w =
5.34 — .0789 t,
In this case the mean egg weight occurs at 67.7°F, and an increase of 10°F will cause a corresponding decrease of 0.789 grams per egg which is equivalent to a loss of 1.002 ounces per dozen eggs for a rise in temperature of 30°F.
Downloaded from http://ps.oxfordjournals.org/ at Carleton University on May 9, 2015
TABLE 3—Summary of correlation coefficients described in the text
SCIENCE
JANUARY,
1936.
VOL.
XV,
No.
of firm white increases relatively little. This statement however, is not substantiated by the findings in the preceding paragraph. The increase in weight of liquid white of later eggs from the same bird is probably due merely to the seasonal increase in temperature resulting in greater liquefaction of the firm white after the eggs are laid. The coefficient of correlation of shell weight deviations in Flock 2 with the maximum temperature of the day before the eggs were laid was + .056 ± .092, indicating that temperature has no effect on shell weight. The coefficient of correlation between the shell weight deviations and egg weight deviations was +.447 ± .074, a significant positive correlation, as would be expected since larger eggs usually have a greater weight of shell. A positive coefficient, + .328 ± .083, was obtained between the shell weight deviations and the time from the start of the experiment, but the partial correlation (independent of egg weight) was —.226 ± .088 which shows the former value to be entirely spurious. Although this partial correlation is not a significant value, the sign reversal suggests that the birds might have a tendency to decrease their shell weight with age during the first year. This tendency is nullified by the tendency of the shell weight to increase with increasing egg weight. SUMMARY Egg weight is decreased by increased air temperature during the formation of the egg, but percentage of firm white and shell weight are not affected by air temperature during this time. The percentage of firm white is lowered by higher air temperature during the hours immediately after the egg is laid, resulting in an apparent seasonal variation in internal egg quality. The percentage of firm white does not depend in any way on the size of the egg.
Downloaded from http://ps.oxfordjournals.org/ at Carleton University on May 9, 2015
eggs frequently had very high percentages of firm white. Measuring one egg from each of 183 Single Comb White Leghorns and 155 Rhode Island Reds, Knox and Godfrey (1934) found coefficients of correlation between egg weight and percentage of firm white to be +.05 and —.13, suggesting that no such relation exists, at least in eggs from different hens. However, the possibility that individual hens might have a tendency to decrease the percentage of firm white as they increased the size of their eggs was not ruled out by their work. Actually, the correlation between mean percentage of firm white deviations and egg weight for Flock 2 was —.374 ± .079. This •correlation, however, might have been spurious, due to the fact that the birds were younger and hence their eggs were smaller during the majority of the cold periods studied. A positive correlation coefficient of + .889 ± .022 was obtained between egg weight and time from the start of the experiment, and a negative coefficient —.422 ± .076 was obtained between percentage of firm white and time. This latter coefficient, of course, has no real meaning since the significant value is merely due to the high correlation between percentage of firm white and temperature. However, the value is statistically linear, and thus a partial coefficient of correlation between percentage of firm white and egg weight independent of time could be calculated. The value + .002 ± .093 shows that the simple correlation is entirely spurious and that no relation exists between percentage of firm white and egg weight in series of eggs from the same group of birds as well as in eggs taken at random. Jull and Byerly (1934) stated that a pullet's first eggs have somewhat higher percentages of firm white than the eggs she lays later. This they suggest is due to the fact that her eggs increase in weight of yolk and liquid white, whereas the weight
17
1
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POULTRY REFERENCES
Bennion, N. L. and D. C. Warren, 1933. Temperature and its effect on egg size in the domestic fowl. Poultry Science 12:69-82. Climatological Data, California Section, 1931-34. U. S. Weather Bureau, San Francisco. Hoist, W. F . and H. J. Almquist, 1931. Measurement of deterioration in the stored hen's egg. Hilgardia 6:49-60. Hunter, J. A., A. VanWagenen, and G. O. Hall, 1934. Studies in interior egg quality. Proc. Poultry Sci. Assoc. Poultry Science 13:314-315.
SCIENCE
Tun, M. A. and T. C. Byerly, 1934. Yearbook of Agriculture 195-197. Knox, C. W. and A. B. Godfrey, 1934. Variability of thick albumen in fresh laid eggs. Poultry Science 13 :18-22. Lorenz, F. W. and H. J. Almquist, 1934. Determination of the percentage of firm white. U. S. Egg and Poultry Magazine, 40:30-33. Lorenz, F. W., L. W. Taylor, and H. J. Almquist, 1934. Firmness of albumen as an inherited characteristic. Poultry Science 13:14-17.
T ^ H E problem of the relationship existing between the nutrition of the hen, composition of the eggs, and the growth of the embryo is now commanding the attention of the biologist. Gerber and Carr (1931), Titus, Byerly, and Ellis (1933), McFarlane, Douglas, Lehman, and Jukes (1930), and Dove (1931) call attention to the numerous nutritional factors affecting the growth and death of embryos and their importance in the improvement of artificial incubation. The investigation reported in this paper was initiated to determine whether any relationship existed between the amount of protein fed the hen and the growth of the embryo. Growth of embryos from two lots of hens fed at different protein levels were compared under the same conditions. All hens were fed their respective rations from time of hatching until eggs were collected for study. The eggs were collected for ten days and placed in the incubator on March 19, 1933, during the second year of production of the hens. Lot 1 received an all-mash ration with a protein content 15.03 percent and Lot 2 was fed a similar ration with the protein increased to 23.47 percent. The protein consisted of equal parts of cottonseed meal, meat scraps, and dried milk. All birds and eggs had similar environmental conditions. All eggs used were selected on a basis of weight and shape, and incubated in a modern commercial cabinet type incubator. A temperature of 9954°F. with a wet bulb reading of 85 was maintained throughout the incubation period. The mean weight of the eggs in Lot 1 was 59.75±49 grams and 59.17±.SO grams for Lot 2. Rate of growth was determined by extracting triplicate samples of the embryos from each lot daily, beginning on the fourth day of incubation and continuing until the nineteenth day. In ex-
tracting the embryos for weighing the method of Henderson (1930) was followed. Three measures of growth were used, wet weight, dry weight, and total nitrogen. OBSERVATIONS The eggs from the low protein fed hens (Lot 1) lost more moisture, as shown by weight, from day to day than the eggs from the high protein fed hens (Lot 2) with exception of the sixth, eleventh, fifteenth, and seventeenth days. An analysis of variance, however, reveals this loss in weight to be insignificant. No apparent difference in the shell texture of the two lots of eggs was detected. The embryos from the high protein fed hens were heavier from day to day, as shown by wet weight, than the embryos from the low protein fed hens with exception of the fifth, sixth, seventh, and nineteenth days. Using dry weight as a measure of growth the high protein fed hens produced embryos that weighed more than the embryos from the low protein fed hens on the fourth, eighth, ninth, tenth, twelfth, thirteenth, fourteenth, fifteenth, sixteenth, and seventeenth days. It is interesting to note that the embryos from the high protein lot were heavier than those from the low protein lot, between the seventh and the seventeenth days. This is shown by both wet and dry weights. Needham (1927) suggested that the chick embryo uses protein as a source of energy during this period of development. He has presented evidence that protein is utilized between the seventh to approximately the sixteenth day. As a measure of growth, the total nitrogen of the embryos is the least variable, but no significant difference is revealed by the data. (Continued on page 66)
Downloaded from http://ps.oxfordjournals.org/ at Carleton University on May 9, 2015
Growth of Chick Embryos from Hens Fed Different Protein Levels
F
quist (1931) described by Lorenz and Almquist (1934). The temperatures used were obtained from "Climatological Data, California Section, U. S. Weather Bureau" particularly referring to the vicinity of the experiments. Data on eggs from these birds were collected for two years. Meanwhile, Flock 2, a group of 95 birds, hatched in 1932 from the eggquality breeding stock (Lorenz, Taylor, and Almquist 1934) were started on the same experiment. Data are presented for the first year's production of Flock 2. In summarizing the data, the mean value of each measurement for each bird was calculated for the period of the experiment. Deviations from this mean were then calculated for each measurement, and these deviations were averaged algebraically for the flock each day. The obtained values of the "mean deviation from the birds' means" were used in the correlations. During the first laying year of Flock 1 the coefficient of correlation between the average deviations in the mean percentage of firm white and the maximum temperature during the day the eggs were laid was found to be —.430 ± .079. The correlation coefficient for the second year, however, was only —.128 ± -118, a value which, although of the same sign, is not statistically significant. This small value may have been due to the high variation in this measurement and to the small size of the flock, which had decreased to only 17 birds, resulting in an inadequate sample. With the larger Flock 2 during the first year of production, a higher coefficient of correlation, —.730 ± .043 was obtained.
[14]
Downloaded from http://ps.oxfordjournals.org/ at Carleton University on May 9, 2015
EW reports have appeared in the literature regarding the effect of the season or of the climate of the locality on the quality of fresh eggs, although it has generally been the experience of candlers and egg graders that summer eggs were poorer in quality than spring and winter eggs. Bennion and Warren (1933), reported that air temperatures over 85°F. during formation of the egg had a tendency to decrease egg size, but they made no reference to the effect of temperature on the internal quality of the egg. Hunter, VanWagenen, and Hall (1934) reported that eggs of the highest internal quality are produced between November and March, and eggs of lowest quality in the spring and summer. No mention was made, however, of a possible effect of temperature. The present study was undertaken, partly in an attempt to determine if there is a real deterioration of eggs produced in the summer at or prior to the time they were laid or if the deterioration occurs because such eggs are exposed to high temperatures after they are laid, and partly in an attempt to discover if differences in season should be considered when interpreting the results of egg quality studies, more particularly with reference to measurements of percentage of firm white, egg weight and shell weight. Eggs from a group of 34 trapnested pullets (Flock 1) hatched in 1931 were collected one day each week, and the egg weight, shell weight and percentage of firm white were determined when the eggs were approximately 24 hours old. The percentage of firm white was determined by the modification of the method of Hoist and Alm-
JANUARY,
1936.
VOL.
XV,
No.
The data for Flock 2 were analyzed in order to determine when temperature affects egg quality. The maximum temperature of the day occurs about 3:00 p.m. which is after nearly all of that day's eggs have TABLE 1.—Coefficients of correlation between percentage of firm white of eggs less than 15 minutes old and the temperature of the cages No. Eggs
H1056 H1057 H1062 H1064 H1066 H1067
15 32 37 22 19 23
Er
r + .336 -.148 -.216 -.254 -.122 -.084
+ .155 ±.166 + .105 + .133 + .152 ±.139
r/Er 2.17 0.89 2.06 1.92 0.80 0.60
been laid. Consequently, if (as has often been suggested) the summer slump in egg quality is due to the effect of heat on the birds, the maximum temperature of the preceding day should have the greater effect. The coefficient of correlation between the average deviations in the mean percentage of firm white and the maximum temperature of the preceding day was found to be —.627 ± .056. The coefficient of correlation between the maximum temperature of the two succeeding days was +.840 ± .027. From these values the partial coefficients of correlation were calculated: —.482 ± .071 7 V * i = —.035 -+- .092
IS
(/ = the mean deviation of the mean percentage of firm white, tt = maximum temperature of the day the eggs were laid, and t2 = the maximum temperature of the preceding day.) The coefficient rft1-t2 is, of course, highly significant, while rft2-t1, is even less than the probable error, indicating that the simple correlation rjt2 is spurious. These results suggest, therefore, that the temperature during the time the eggs are being formed has no noticeable effect on the percentage of firm white, while the temperature immediately after the eggs are laid exerts a distinct effect.1 An attempt has been made to test this temperature effect more exactly. A small group of birds was kept in electrically heated cages, in which the temperature was varied at will between 60° and 85°F. Eggs were collected within 15 minutes after they were laid and the percentage of firm white determined immediately. In no case was there a significant correlation between the percentage of firm white and the temperature of the cage. Data for the birds from which sufficient eggs were obtained are sum*The regression equation of the deviations of percentage of firm white from the mean on temperature is: f = 16.1 — 0.257 t, Thus the mean percentage of firm white occurs, in this experiment, at the temperature of 62.7° F. An increase in temperature of 10° F. will cause a drop of 2.57 percent in the percentage of firm white.
TABLE 2.—Eject of storage temperature during the first 24 hours after being laid on the percentage of firm while of eggs. Fresh eggs Bird
H1056 H1057 H1059 HI 104 Average
Eggs stored 24hrs.40°F.
Eggs stored 24 hrs. 86° F.
Differences in % Firm White
Fresh— Stored40°F. Average % FreshAverage % Average % No. Firm white No. Firm white No. Firm white Stored 40° F Stored 86° F. Stored 86°F. 15 11 12 11
68.3 61.7 61.5 63.0
4 5 5 4
65.4 67.7 58.2 64.3
4 4 4 4
49.9 47.6 42.6 54.3
2.9 -6.0 3.3 -1.3
18.4 14.1 18.9 8.7
15.5 20.1 15.6 10.0
-0.3
15.0
15.3
Downloaded from http://ps.oxfordjournals.org/ at Carleton University on May 9, 2015
Bird
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POULTRY
marized in Table 1. For the second part of the experiment the cages were permitted to remain at room temperature, which was fairly constant at 60°-65°F. The eggs were collected within 15 minutes after being laid, as before, and were stored for 24 hours, some at 40° and some at 86°F. For this experiment eggs were obtained from only 4 birds. The data for these eggs are summarized in Table 2. Values from the fresh
Flock I r fh= - .430+ .079 (1st year production) r fh = - . 198+ . 118 (2nd year production) r wh= — .584+ .067 (2nd year production) Flock II (all first year production) r fh = - . 7 3 0 +.043 fh = - . 6 2 7 ±.056 'hh =4-.840+.027
eggs tabulated are taken from the previous part of the experiment. The first column under "Differences" gives the decrease in percentage of firm white during 24 hours storage at 40° F. It is obvious that the percentage of firm white did not decrease appreciably. On the other hand, when eggs were stored at 86°F. there was a decided decrease in the percentage of firm white. The last column in Table 1 shows that eggs held at 86°F. for 24 hours deteriorated much more than eggs held for the same length of time at 40°F. The average value of 1S.0 in the second
difference column is higher than might be expected. Previous work showed an average drop of about 2.3 percent per day in eggs stored at 86°F. during their second and subsequent days. Thus it seems likely that the temperature at which an egg is held during the first 24 hours after it is laid is of utmost importance. Further work is in progress in an attempt to determine the exact time during which the maximum liquefaction occurs. When egg weight variations were considered, it was found that a complicating factor, the natural increase of egg size during the first laying year, made the correlations between egg weight and temperature non-linear. However, the variation of egg weight in the second year's production of Flock 1 was very small. The coefficient of correlation between the mean egg weight deviations of the second year and the maximum temperature of the day before the eggs were laid (the time during which the eggs were being formed) was found to be —.584 ± -067, a significant negative correlation which was found to be linear. This indicates a decrease in egg weight proportional to the increase in temperature, at least between 40° and 90° F. In this respect, our results differ from those of Bennion and Warren (1933) in that they found no effect of temperature on egg weight below 85°F.2 It was thought desirable to determine whether or not there was any relation between the percentage of firm white and egg weight, since it had been noticed that small 2
The regression equation of the deviations of egg weight from the mean on temperature is: w =
5.34 — .0789 t,
In this case the mean egg weight occurs at 67.7°F, and an increase of 10°F will cause a corresponding decrease of 0.789 grams per egg which is equivalent to a loss of 1.002 ounces per dozen eggs for a rise in temperature of 30°F.
Downloaded from http://ps.oxfordjournals.org/ at Carleton University on May 9, 2015
TABLE 3—Summary of correlation coefficients described in the text
SCIENCE
JANUARY,
1936.
VOL.
XV,
No.
of firm white increases relatively little. This statement however, is not substantiated by the findings in the preceding paragraph. The increase in weight of liquid white of later eggs from the same bird is probably due merely to the seasonal increase in temperature resulting in greater liquefaction of the firm white after the eggs are laid. The coefficient of correlation of shell weight deviations in Flock 2 with the maximum temperature of the day before the eggs were laid was + .056 ± .092, indicating that temperature has no effect on shell weight. The coefficient of correlation between the shell weight deviations and egg weight deviations was +.447 ± .074, a significant positive correlation, as would be expected since larger eggs usually have a greater weight of shell. A positive coefficient, + .328 ± .083, was obtained between the shell weight deviations and the time from the start of the experiment, but the partial correlation (independent of egg weight) was —.226 ± .088 which shows the former value to be entirely spurious. Although this partial correlation is not a significant value, the sign reversal suggests that the birds might have a tendency to decrease their shell weight with age during the first year. This tendency is nullified by the tendency of the shell weight to increase with increasing egg weight. SUMMARY Egg weight is decreased by increased air temperature during the formation of the egg, but percentage of firm white and shell weight are not affected by air temperature during this time. The percentage of firm white is lowered by higher air temperature during the hours immediately after the egg is laid, resulting in an apparent seasonal variation in internal egg quality. The percentage of firm white does not depend in any way on the size of the egg.
Downloaded from http://ps.oxfordjournals.org/ at Carleton University on May 9, 2015
eggs frequently had very high percentages of firm white. Measuring one egg from each of 183 Single Comb White Leghorns and 155 Rhode Island Reds, Knox and Godfrey (1934) found coefficients of correlation between egg weight and percentage of firm white to be +.05 and —.13, suggesting that no such relation exists, at least in eggs from different hens. However, the possibility that individual hens might have a tendency to decrease the percentage of firm white as they increased the size of their eggs was not ruled out by their work. Actually, the correlation between mean percentage of firm white deviations and egg weight for Flock 2 was —.374 ± .079. This •correlation, however, might have been spurious, due to the fact that the birds were younger and hence their eggs were smaller during the majority of the cold periods studied. A positive correlation coefficient of + .889 ± .022 was obtained between egg weight and time from the start of the experiment, and a negative coefficient —.422 ± .076 was obtained between percentage of firm white and time. This latter coefficient, of course, has no real meaning since the significant value is merely due to the high correlation between percentage of firm white and temperature. However, the value is statistically linear, and thus a partial coefficient of correlation between percentage of firm white and egg weight independent of time could be calculated. The value + .002 ± .093 shows that the simple correlation is entirely spurious and that no relation exists between percentage of firm white and egg weight in series of eggs from the same group of birds as well as in eggs taken at random. Jull and Byerly (1934) stated that a pullet's first eggs have somewhat higher percentages of firm white than the eggs she lays later. This they suggest is due to the fact that her eggs increase in weight of yolk and liquid white, whereas the weight
17
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POULTRY REFERENCES
Bennion, N. L. and D. C. Warren, 1933. Temperature and its effect on egg size in the domestic fowl. Poultry Science 12:69-82. Climatological Data, California Section, 1931-34. U. S. Weather Bureau, San Francisco. Hoist, W. F . and H. J. Almquist, 1931. Measurement of deterioration in the stored hen's egg. Hilgardia 6:49-60. Hunter, J. A., A. VanWagenen, and G. O. Hall, 1934. Studies in interior egg quality. Proc. Poultry Sci. Assoc. Poultry Science 13:314-315.
SCIENCE
Tun, M. A. and T. C. Byerly, 1934. Yearbook of Agriculture 195-197. Knox, C. W. and A. B. Godfrey, 1934. Variability of thick albumen in fresh laid eggs. Poultry Science 13 :18-22. Lorenz, F. W. and H. J. Almquist, 1934. Determination of the percentage of firm white. U. S. Egg and Poultry Magazine, 40:30-33. Lorenz, F. W., L. W. Taylor, and H. J. Almquist, 1934. Firmness of albumen as an inherited characteristic. Poultry Science 13:14-17.
T ^ H E problem of the relationship existing between the nutrition of the hen, composition of the eggs, and the growth of the embryo is now commanding the attention of the biologist. Gerber and Carr (1931), Titus, Byerly, and Ellis (1933), McFarlane, Douglas, Lehman, and Jukes (1930), and Dove (1931) call attention to the numerous nutritional factors affecting the growth and death of embryos and their importance in the improvement of artificial incubation. The investigation reported in this paper was initiated to determine whether any relationship existed between the amount of protein fed the hen and the growth of the embryo. Growth of embryos from two lots of hens fed at different protein levels were compared under the same conditions. All hens were fed their respective rations from time of hatching until eggs were collected for study. The eggs were collected for ten days and placed in the incubator on March 19, 1933, during the second year of production of the hens. Lot 1 received an all-mash ration with a protein content 15.03 percent and Lot 2 was fed a similar ration with the protein increased to 23.47 percent. The protein consisted of equal parts of cottonseed meal, meat scraps, and dried milk. All birds and eggs had similar environmental conditions. All eggs used were selected on a basis of weight and shape, and incubated in a modern commercial cabinet type incubator. A temperature of 9954°F. with a wet bulb reading of 85 was maintained throughout the incubation period. The mean weight of the eggs in Lot 1 was 59.75±49 grams and 59.17±.SO grams for Lot 2. Rate of growth was determined by extracting triplicate samples of the embryos from each lot daily, beginning on the fourth day of incubation and continuing until the nineteenth day. In ex-
tracting the embryos for weighing the method of Henderson (1930) was followed. Three measures of growth were used, wet weight, dry weight, and total nitrogen. OBSERVATIONS The eggs from the low protein fed hens (Lot 1) lost more moisture, as shown by weight, from day to day than the eggs from the high protein fed hens (Lot 2) with exception of the sixth, eleventh, fifteenth, and seventeenth days. An analysis of variance, however, reveals this loss in weight to be insignificant. No apparent difference in the shell texture of the two lots of eggs was detected. The embryos from the high protein fed hens were heavier from day to day, as shown by wet weight, than the embryos from the low protein fed hens with exception of the fifth, sixth, seventh, and nineteenth days. Using dry weight as a measure of growth the high protein fed hens produced embryos that weighed more than the embryos from the low protein fed hens on the fourth, eighth, ninth, tenth, twelfth, thirteenth, fourteenth, fifteenth, sixteenth, and seventeenth days. It is interesting to note that the embryos from the high protein lot were heavier than those from the low protein lot, between the seventh and the seventeenth days. This is shown by both wet and dry weights. Needham (1927) suggested that the chick embryo uses protein as a source of energy during this period of development. He has presented evidence that protein is utilized between the seventh to approximately the sixteenth day. As a measure of growth, the total nitrogen of the embryos is the least variable, but no significant difference is revealed by the data. (Continued on page 66)
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Growth of Chick Embryos from Hens Fed Different Protein Levels