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Duration of Egg Formation in Chickens during Heat Stress1
Duration of Egg Formation in Chickens during Heat Stress1 J O N O . NORDSTROM
Department of Poultry Science, University of Arizona, Tucson, Arizona 85721 (Received for publication March 20, 1972)
POULTRY SCIENCE 52: 1687-1690, 1973 INTRODUCTION
HE weight of each component of the egg, i.e., the yolk, the albumen, and the shell, is decreased when laying hens are subjected to high environmental temperatures (Bennion and Warren, 1933). Under these conditions, the heat produced by the egg-forming process undoubtedly increases the amount of heat the animal must lose to prevent a rise in body temperature. Therefore, it would seem to be physiologically advantageous for the hen to move the developing egg through the oviduct as quickly as possible. If this does occur, rapid transit through the oviduct and premature expulsion of the egg from the shell gland could account for the decreased secretion of albumen and shell in hens subjected to heat stress. The purpose of this study was to determine the duration of egg formation in chickens during heat stress. The results indicate that the developing egg actually spends a slightly
T
1. Arizona Agricultural Experiment Station Journal Article No. 1908
longer period of time in the oviduct of hens subjected to high environmental temperatures than in hens exposed to moderate temperatures. METHODS
Eighteen-month old S.C. White Leghorn laying hens were used. They had been held at a constant temperature of 21 ± 1° C. for 6 months prior to the initiation of the experiment. Egg weight data and the time interval between the laying of several successive eggs were obtained for individual hens at 21° C. Then, the temperature was increased in 3° C. daily increments until a temperature of 32° C. was reached. The hens were held at this temperature (± 1° C.) for 3 weeks before the measurements were repeated. At both temperatures, the hens were exposed to a 16L:8D lighting schedule (lights on at 0400 hours) and were fed the University of Arizona laying hen ration (3.57% Ca). To determine the time of laying, the cage bottoms were checked daily for eggs at 15 minute intervals from 0800 to 1400 hours.
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ABSTRACT An accelerated transit time of the developing egg through the oviduct could account for the decreased quantities of albumen and shell secreted by laying hens exposed to high environmental temperatures. To examine this possibility, the time interval (± 15 minutes) between successive eggs in a clutch was measured in 25 S.C.W.L. hens held at a constant temperature of 21 ± 1° C. The temperature was then increased to a constant 32 ± 1° C , and after 3 weeks exposure, the time interval between successive eggs was measured again in the same hens. The mean time interval between successive eggs was significantly greater (P < 0.01) at 32° C. (27.7 hours) than at 21° C. (25.6 hours). Egg weight, shell weight (% of egg weight), and laying rate were all decreased at the higher temperature. Sacrifice data (obtained 1, 4, and 6-1/2 hours following oviposition on days when ovulation was quite certain to occur) showed no apparent differences between the two temperatures in ovulation time following oviposition or in the transit time through the oviduct to the shell gland. Thus, the developing egg appears to spend a slightly longer period of time (about 2 hours) in the shell gland at 32° C. than at 21° C. The results indicate that high environmental temperature (32° C.) does not accelerate the rate of movement of the developing egg through the hen's oviduct, and other factors must be responsible for the decreased secretion of albumen and deposition of shell under these conditions.
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RESULTS AND DISCUSSION
For the conclusions of this study to be valid, the heat treatment used must be detrimental to the egg-forming process. This is the case, as seen in Table 1. In hens exposed to both 21° C. and 32° C , egg weight and shell weight, expressed as percent of total egg weight, were both considerably decreased at the higher temperature. To determine the duration of the egg-forming process, the time interval between suc-
TABLE 1.—Effect of environmental temperature upon egg weight and shell weight (% egg weight) Environmental temperature Egg wt. (gms.) Shell wt. (% egg wt.) 'Number of hens. Mean ± S.E. P<0.10 **P< 0.01
2 3
n1
21° C.
32° C.
25 25
64.3 ± 0.72 8.05 + 0.19
60.7 + 0.8** 7.50 ± 0.263
TABLE 2.—Effect of time of lay and environmental temperature upon time interval between successive eggs Time interval (hours) between successive eggs Hour 2nd 32° C. 21° C. egg laid 0900' 26.0(1) 24.5(5)2 26.1(4) 24.6(21) 1000 27.4(2) 25.1(34) 1100 27.4(5) 25.3(21) 1200 28.3(14) 26.9(20) 1300 27.6(10) 27.5(7) 1400 28.4(6) 28.1(2) 1500 ' Second egg laid between 0846 and 0945. 2
Number of observations.
cessive eggs was first measured. The results for the two environmental temperatures are summarized in Table 2. The time interval between successive eggs when the second egg was laid between 0900 and 1300 hours appears to be greater at 32° C. than at 21° C. When the second egg was laid at 1400 hours or later, however, there does not appear to be any temperature effect on the time interval between successive eggs. The mean (± S.E.) of all observations of the time interval between successive eggs at 21° C. was 25.6 ± 0.1 hours; at 32° C , 27.7 ± 0.2 hours. The mean difference of 2.1 hours is significant at the 1% level. Laying rate is known to be decreased during exposure to high environmental temperature (Bennion and Warren, 1933). This is the case for the hens used in this study, with 59% production at 32° C. compared to 74% production at 21° C. It is also known that as laying rate (and hence clutch size) decreases, the time interval between successive eggs increases (Berg, 1945). Thus, the greater time interval between successive eggs seen in the morning hours at 32° C. probably is due to the decreased clutch size in these hens rather than to a delay in ovulation or to a defect in the egg propulsion mechanism through the oviduct. Evidence presented below supports this conclusion. Furthermore, since the last egg of a clutch would be expected to be laid
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At 32° C, however, due to the decreased clutch size, egg laying eventually had to be recorded from 0600 to 1500 hours. The eggs were weighed immediately and then stored at 13° C. Within a week, the eggs were broken out and the shells were washed (shell membranes left intact). The shells were dried at 105° C. for at least 24 hours and then weighed. A minimum of 3 eggs were broken out for each hen at each temperature. At the two temperatures, a total of 41 hens were sacrificed (intravenous overdose of sodium pentobarbital) at 1, 4, or 6-1/2 hours following oviposition on days when ovulation was expected to occur from examination of the egg records. With one exception, at least 6 hens were sacrificed at each time period at each temperature. The location of the yolk or egg in the oviduct was determined by autopsy. Differences between mean values were statistically analyzed using the "Student's" t-distribution (Snedecor, 1956).
EGG FORMATION AND HEAT STRESS
TABLE 3.—Location of developing egg within the oviduct at 1 hour following oviposition in hens exposed to 21° C. and 32° C. 21° C.
n' 2 2 2
Location in Oviduct Yolk just entering the magnum from the infundibulum. Yolk had just completely entered magnum. Yolk about a third of the way through the magnum.
32° C.
n 1
Location in Oviduct Yolk in posterior portion of infundibulum near junction with the magnum. 1 Yolk just entering magnum from the infundibulum. 4 Yolk had just completely entered magnum. 4 Yolk about a third of the way through the magnum. 1 No yolk in oviduct. 'Number of hens.
TABLE 4.—Location of developing egg within the oviduct at 4 hours following oviposition in hens exposed to 21° C. and 32° C. 21° C.
n1 2 2 2 1
Location in Oviduct Egg in posterior portion of the magnum near junction with the isthmus. Egg had just completely entered isthmus. Egg midway through the isthmus. No egg in oviduct.
32° C. Location in Oviduct Egg just entering isthmus from the magnum. Egg had just completely entered 1 isthmus. No egg in oviduct. 1 'Number of hens. n 2
TABLE 5.—Location of developing egg within the oviduct at 6-1/2 hours following oviposition in hens exposed to 21° C. and 32° C. 21° C. n' 6
Location in Oviduct Soft-shell egg in shell gland, not plumped, with a very small amount of calcification visible on both ends of the egg, particularly on the blunt end.
32° C.
Location in Oviduct Soft-shell egg in shell gland, not plumped, with a very small amount of calcification visible on both ends of the egg. No egg in oviduct. 1 ' Number of hens.
presumably less albumen was secreted during passage through the magnum in the hens exposed to the higher temperature (Bennion and Warren, 1933). Of perhaps even greater interest is evidence that the developing egg spends a longer period of time in the shell gland of the hens exposed to 32° C. As indicated previously, the time interval between successive eggs was greater at 32° C. (27.7 hours) than at 21° C, (25.6 hours), but the time interval between oviposition and subsequent ovulation appears to be the same at both temperatures (Table 3). This indicates that the developing egg spends 2
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in the early afternoon, and since the time interval between the last two eggs of a clutch is greater than the time interval between any of the preceding eggs (Berg, 1945), we might expect the absence of a temperature effect on the time interval between successive eggs during the afternoon hours. To determine the transit time of the developing egg through the oviduct, several animals were sacrificed at certain time intervals following oviposition (and subsequent ovulation), and the location and stage of development of the egg in the oviduct were determined. The data for hens sacrificed at 1, 4 and 6-1/2 hours following oviposition are presented in Tables 3, 4, and 5, respectively. There does not appear to be any difference between the two environments in the time the yolk enters the magnum, or in the time the developing egg enters the isthmus or the shell gland. Therefore, the time interval between oviposition and subsequent ovulation does not appear to be affected by the higher temperature. Similarly, the transit time of the developing egg through the infundibulum, magnum, and isthmus appears to be the same at both temperatures. But despite this fact,
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Why shell quality is diminished in hens exposed to high environmental temperature is a complex problem with many aspects yet to be resolved (Petersen, 1965;Mongin, 1968). It is clear, however, at least under the conditions of this study, that premature expulsion of the developing egg from the shell gland is not responsible for the decreased deposition of shell.
REFERENCES
Bennion, N. L., and D. C. Warren, 1933. Temperature and its effect on egg size in the domestic fowl. Poultry Sci. 12: 69-82. Berg, L. R., 1945. The relationship of clutch position and time interval between eggs to eggshell quality. Poultry Sci. 24: 555-563. Mongin, P., 1968. Role of acid-base balance in the physiology of egg shell formation. World's Poultry Sci. J. 24: 200-230. Petersen, C. F., 1965. Factors influencing egg shell quality—-A review. World's Poultry Sci. J. 21: 110138. Snedecor, G. W., 1956. Statistical Methods Applied to Experiments in Agriculture and Biology. 5th ed. Iowa State Univ. Press, Ames. Warren, D. C , and H. M. Scott, 1935. Physiological factors influencing the rate of egg formation in the domestic hen. J. Agr. Res. 51: 565-572.
NEWS AND NOTES PAPERS—WORLD'S POULTRY CONGRESS The U.S.A. Branch of the World's Poultry Science Association, organizers of the XVth World's Poultry Congress, invite members of the W.P.S.A. and other interested persons to submit papers at the Congress to be held in New Orleans, Louisiana, August 11-16, 1974. The Congress program will include symposia, special lectures and contributed papers. Symposia speakers and lecturers will be invited by the Congress organizers. Sections of the Congress program are: Economics of Production and Marketing—supply and demand economics of sale, prices, efficiency, distribution, international and domestic trade.
Genetics—breeds, breeding systems, population genetics, inheritance modes, immunogenetics, cytogenetics and chromosome studies. Management—control of bioclimatic factors, environmental housing, husbandry, waste disposal, space allotment, incubation, behavior and rhythmic phenomena. Nutrition—feeds, nutritive requirements, feeding systems and metabolic pathways. Pathology—diseases, disease agents, intoxications, parasites, control measures, drugs and residues. Physiology—functional anatomy, respiratory mechanisms (e.g. thermal), reproduction, response to stress, endocrinology, embryology and teratology.
(Continued on page 1693)
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hours longer somewhere in the oviduct of the hen at 32° C. But the transit time of the developing egg through the oviduct and its time of arrival at the shell gland appear to be similar at 21° C. and 32° C. (Tables 4 and 5). Therefore, the data suggest that the developing egg spends the extra 2 hours in hens exposed to 32° C. in the shell gland portion of the oviduct. At moderate temperatures, the variation in time interval between successive eggs has been shown by Warren and Scott (1935) to be due primarily to variations in the time the developing egg spends in the shell gland. This probably accounts for the data of Berg (1945), in which he found an increase or decrease in the time interval between eggs within a clutch to be accompanied by a corresponding increase or decrease in shell thickness. Under the conditions of this study, at least, and possibly for hens in general exposed to high environmental temperatures, it is fortunate that the developing egg spends a slightly longer period of time in the shell gland during heat stress for the deposition of additional shell. But despite this fact, the total amount of shell deposited is clearly less than that deposited by hens exposed to moderate temperatures.
Department of Poultry Science, University of Arizona, Tucson, Arizona 85721 (Received for publication March 20, 1972)
POULTRY SCIENCE 52: 1687-1690, 1973 INTRODUCTION
HE weight of each component of the egg, i.e., the yolk, the albumen, and the shell, is decreased when laying hens are subjected to high environmental temperatures (Bennion and Warren, 1933). Under these conditions, the heat produced by the egg-forming process undoubtedly increases the amount of heat the animal must lose to prevent a rise in body temperature. Therefore, it would seem to be physiologically advantageous for the hen to move the developing egg through the oviduct as quickly as possible. If this does occur, rapid transit through the oviduct and premature expulsion of the egg from the shell gland could account for the decreased secretion of albumen and shell in hens subjected to heat stress. The purpose of this study was to determine the duration of egg formation in chickens during heat stress. The results indicate that the developing egg actually spends a slightly
T
1. Arizona Agricultural Experiment Station Journal Article No. 1908
longer period of time in the oviduct of hens subjected to high environmental temperatures than in hens exposed to moderate temperatures. METHODS
Eighteen-month old S.C. White Leghorn laying hens were used. They had been held at a constant temperature of 21 ± 1° C. for 6 months prior to the initiation of the experiment. Egg weight data and the time interval between the laying of several successive eggs were obtained for individual hens at 21° C. Then, the temperature was increased in 3° C. daily increments until a temperature of 32° C. was reached. The hens were held at this temperature (± 1° C.) for 3 weeks before the measurements were repeated. At both temperatures, the hens were exposed to a 16L:8D lighting schedule (lights on at 0400 hours) and were fed the University of Arizona laying hen ration (3.57% Ca). To determine the time of laying, the cage bottoms were checked daily for eggs at 15 minute intervals from 0800 to 1400 hours.
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ABSTRACT An accelerated transit time of the developing egg through the oviduct could account for the decreased quantities of albumen and shell secreted by laying hens exposed to high environmental temperatures. To examine this possibility, the time interval (± 15 minutes) between successive eggs in a clutch was measured in 25 S.C.W.L. hens held at a constant temperature of 21 ± 1° C. The temperature was then increased to a constant 32 ± 1° C , and after 3 weeks exposure, the time interval between successive eggs was measured again in the same hens. The mean time interval between successive eggs was significantly greater (P < 0.01) at 32° C. (27.7 hours) than at 21° C. (25.6 hours). Egg weight, shell weight (% of egg weight), and laying rate were all decreased at the higher temperature. Sacrifice data (obtained 1, 4, and 6-1/2 hours following oviposition on days when ovulation was quite certain to occur) showed no apparent differences between the two temperatures in ovulation time following oviposition or in the transit time through the oviduct to the shell gland. Thus, the developing egg appears to spend a slightly longer period of time (about 2 hours) in the shell gland at 32° C. than at 21° C. The results indicate that high environmental temperature (32° C.) does not accelerate the rate of movement of the developing egg through the hen's oviduct, and other factors must be responsible for the decreased secretion of albumen and deposition of shell under these conditions.
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J. O. NORDSTROM
RESULTS AND DISCUSSION
For the conclusions of this study to be valid, the heat treatment used must be detrimental to the egg-forming process. This is the case, as seen in Table 1. In hens exposed to both 21° C. and 32° C , egg weight and shell weight, expressed as percent of total egg weight, were both considerably decreased at the higher temperature. To determine the duration of the egg-forming process, the time interval between suc-
TABLE 1.—Effect of environmental temperature upon egg weight and shell weight (% egg weight) Environmental temperature Egg wt. (gms.) Shell wt. (% egg wt.) 'Number of hens. Mean ± S.E. P<0.10 **P< 0.01
2 3
n1
21° C.
32° C.
25 25
64.3 ± 0.72 8.05 + 0.19
60.7 + 0.8** 7.50 ± 0.263
TABLE 2.—Effect of time of lay and environmental temperature upon time interval between successive eggs Time interval (hours) between successive eggs Hour 2nd 32° C. 21° C. egg laid 0900' 26.0(1) 24.5(5)2 26.1(4) 24.6(21) 1000 27.4(2) 25.1(34) 1100 27.4(5) 25.3(21) 1200 28.3(14) 26.9(20) 1300 27.6(10) 27.5(7) 1400 28.4(6) 28.1(2) 1500 ' Second egg laid between 0846 and 0945. 2
Number of observations.
cessive eggs was first measured. The results for the two environmental temperatures are summarized in Table 2. The time interval between successive eggs when the second egg was laid between 0900 and 1300 hours appears to be greater at 32° C. than at 21° C. When the second egg was laid at 1400 hours or later, however, there does not appear to be any temperature effect on the time interval between successive eggs. The mean (± S.E.) of all observations of the time interval between successive eggs at 21° C. was 25.6 ± 0.1 hours; at 32° C , 27.7 ± 0.2 hours. The mean difference of 2.1 hours is significant at the 1% level. Laying rate is known to be decreased during exposure to high environmental temperature (Bennion and Warren, 1933). This is the case for the hens used in this study, with 59% production at 32° C. compared to 74% production at 21° C. It is also known that as laying rate (and hence clutch size) decreases, the time interval between successive eggs increases (Berg, 1945). Thus, the greater time interval between successive eggs seen in the morning hours at 32° C. probably is due to the decreased clutch size in these hens rather than to a delay in ovulation or to a defect in the egg propulsion mechanism through the oviduct. Evidence presented below supports this conclusion. Furthermore, since the last egg of a clutch would be expected to be laid
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At 32° C, however, due to the decreased clutch size, egg laying eventually had to be recorded from 0600 to 1500 hours. The eggs were weighed immediately and then stored at 13° C. Within a week, the eggs were broken out and the shells were washed (shell membranes left intact). The shells were dried at 105° C. for at least 24 hours and then weighed. A minimum of 3 eggs were broken out for each hen at each temperature. At the two temperatures, a total of 41 hens were sacrificed (intravenous overdose of sodium pentobarbital) at 1, 4, or 6-1/2 hours following oviposition on days when ovulation was expected to occur from examination of the egg records. With one exception, at least 6 hens were sacrificed at each time period at each temperature. The location of the yolk or egg in the oviduct was determined by autopsy. Differences between mean values were statistically analyzed using the "Student's" t-distribution (Snedecor, 1956).
EGG FORMATION AND HEAT STRESS
TABLE 3.—Location of developing egg within the oviduct at 1 hour following oviposition in hens exposed to 21° C. and 32° C. 21° C.
n' 2 2 2
Location in Oviduct Yolk just entering the magnum from the infundibulum. Yolk had just completely entered magnum. Yolk about a third of the way through the magnum.
32° C.
n 1
Location in Oviduct Yolk in posterior portion of infundibulum near junction with the magnum. 1 Yolk just entering magnum from the infundibulum. 4 Yolk had just completely entered magnum. 4 Yolk about a third of the way through the magnum. 1 No yolk in oviduct. 'Number of hens.
TABLE 4.—Location of developing egg within the oviduct at 4 hours following oviposition in hens exposed to 21° C. and 32° C. 21° C.
n1 2 2 2 1
Location in Oviduct Egg in posterior portion of the magnum near junction with the isthmus. Egg had just completely entered isthmus. Egg midway through the isthmus. No egg in oviduct.
32° C. Location in Oviduct Egg just entering isthmus from the magnum. Egg had just completely entered 1 isthmus. No egg in oviduct. 1 'Number of hens. n 2
TABLE 5.—Location of developing egg within the oviduct at 6-1/2 hours following oviposition in hens exposed to 21° C. and 32° C. 21° C. n' 6
Location in Oviduct Soft-shell egg in shell gland, not plumped, with a very small amount of calcification visible on both ends of the egg, particularly on the blunt end.
32° C.
Location in Oviduct Soft-shell egg in shell gland, not plumped, with a very small amount of calcification visible on both ends of the egg. No egg in oviduct. 1 ' Number of hens.
presumably less albumen was secreted during passage through the magnum in the hens exposed to the higher temperature (Bennion and Warren, 1933). Of perhaps even greater interest is evidence that the developing egg spends a longer period of time in the shell gland of the hens exposed to 32° C. As indicated previously, the time interval between successive eggs was greater at 32° C. (27.7 hours) than at 21° C, (25.6 hours), but the time interval between oviposition and subsequent ovulation appears to be the same at both temperatures (Table 3). This indicates that the developing egg spends 2
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in the early afternoon, and since the time interval between the last two eggs of a clutch is greater than the time interval between any of the preceding eggs (Berg, 1945), we might expect the absence of a temperature effect on the time interval between successive eggs during the afternoon hours. To determine the transit time of the developing egg through the oviduct, several animals were sacrificed at certain time intervals following oviposition (and subsequent ovulation), and the location and stage of development of the egg in the oviduct were determined. The data for hens sacrificed at 1, 4 and 6-1/2 hours following oviposition are presented in Tables 3, 4, and 5, respectively. There does not appear to be any difference between the two environments in the time the yolk enters the magnum, or in the time the developing egg enters the isthmus or the shell gland. Therefore, the time interval between oviposition and subsequent ovulation does not appear to be affected by the higher temperature. Similarly, the transit time of the developing egg through the infundibulum, magnum, and isthmus appears to be the same at both temperatures. But despite this fact,
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J. O . NORDSTROM
Why shell quality is diminished in hens exposed to high environmental temperature is a complex problem with many aspects yet to be resolved (Petersen, 1965;Mongin, 1968). It is clear, however, at least under the conditions of this study, that premature expulsion of the developing egg from the shell gland is not responsible for the decreased deposition of shell.
REFERENCES
Bennion, N. L., and D. C. Warren, 1933. Temperature and its effect on egg size in the domestic fowl. Poultry Sci. 12: 69-82. Berg, L. R., 1945. The relationship of clutch position and time interval between eggs to eggshell quality. Poultry Sci. 24: 555-563. Mongin, P., 1968. Role of acid-base balance in the physiology of egg shell formation. World's Poultry Sci. J. 24: 200-230. Petersen, C. F., 1965. Factors influencing egg shell quality—-A review. World's Poultry Sci. J. 21: 110138. Snedecor, G. W., 1956. Statistical Methods Applied to Experiments in Agriculture and Biology. 5th ed. Iowa State Univ. Press, Ames. Warren, D. C , and H. M. Scott, 1935. Physiological factors influencing the rate of egg formation in the domestic hen. J. Agr. Res. 51: 565-572.
NEWS AND NOTES PAPERS—WORLD'S POULTRY CONGRESS The U.S.A. Branch of the World's Poultry Science Association, organizers of the XVth World's Poultry Congress, invite members of the W.P.S.A. and other interested persons to submit papers at the Congress to be held in New Orleans, Louisiana, August 11-16, 1974. The Congress program will include symposia, special lectures and contributed papers. Symposia speakers and lecturers will be invited by the Congress organizers. Sections of the Congress program are: Economics of Production and Marketing—supply and demand economics of sale, prices, efficiency, distribution, international and domestic trade.
Genetics—breeds, breeding systems, population genetics, inheritance modes, immunogenetics, cytogenetics and chromosome studies. Management—control of bioclimatic factors, environmental housing, husbandry, waste disposal, space allotment, incubation, behavior and rhythmic phenomena. Nutrition—feeds, nutritive requirements, feeding systems and metabolic pathways. Pathology—diseases, disease agents, intoxications, parasites, control measures, drugs and residues. Physiology—functional anatomy, respiratory mechanisms (e.g. thermal), reproduction, response to stress, endocrinology, embryology and teratology.
(Continued on page 1693)
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hours longer somewhere in the oviduct of the hen at 32° C. But the transit time of the developing egg through the oviduct and its time of arrival at the shell gland appear to be similar at 21° C. and 32° C. (Tables 4 and 5). Therefore, the data suggest that the developing egg spends the extra 2 hours in hens exposed to 32° C. in the shell gland portion of the oviduct. At moderate temperatures, the variation in time interval between successive eggs has been shown by Warren and Scott (1935) to be due primarily to variations in the time the developing egg spends in the shell gland. This probably accounts for the data of Berg (1945), in which he found an increase or decrease in the time interval between eggs within a clutch to be accompanied by a corresponding increase or decrease in shell thickness. Under the conditions of this study, at least, and possibly for hens in general exposed to high environmental temperatures, it is fortunate that the developing egg spends a slightly longer period of time in the shell gland during heat stress for the deposition of additional shell. But despite this fact, the total amount of shell deposited is clearly less than that deposited by hens exposed to moderate temperatures.