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Variability of Body Temperature in the Normal Chick
Variability of Body Temperature in the Normal Chick W. F. LAMOREUX AND F. B. HUTT
Department of Poultry Husbandry, Cornell University, Ithaca, New York (Received for publication May 31, 1938)
I
N CONNECTION with other studies involving variations in the temperatures of chicks during the first two weeks of life, it was necessary to determine first the normal variations and environmental conditions affecting them during that period. So far as could be ascertained the only data on this subject obtained with adequate numbers of chicks under normal conditions of brooding and diet are the unpublished figures of Fronda (1922) which indicate that at one and two weeks of age the temperature is about 3°F. higher than at hatching. Card's (1921) unwatered chicks, kept to five days, showed considerable diurnal variation in temperature. The present writers sought to find (1) possible sources of error in determination of temperature, (2) an adequate technic for temperature determination in baby chicks, (3) normal temperature variations in relation to age, weight, sex, and breed of the chick from hatching until it approaches the normal temperature of the adult. Such information is considered essential for many kinds of physiological experiments with chicks. METHODS
The data reported were obtained by the senior author at Cornell University and by the junior author at the Minnesota Agricultural Experiment Station. Readings of temperatures obtained to establish normal curves were taken at the same time each day to avoid error from diurnal fluctuations. Brooding equipment for all chicks included a heated compartment and one at
room temperature, the two together providing a range of temperature adequate to permit the chick to select its own environmental temperature as is customary in ordinary brooding practice. Thermometers: Clinical rectal thermometers were used for determining the body temperatures. In taking the temperature, the bulb of the thermometer, after being dipped in non-irritant oil to facilitate insertion into the cloaca and rectum, was held in the chick from one to one and one-fourth minutes. The depth of insertion usually varied according to the age of the chick; that is, the older the chick the greater the actual depth of insertion, but an effort was made to insert the thermometer to an approximately uniform depth for any given age and lot of chicks. In certain specified lots the thermometer was banded with several turns of adhesive tape, so placed as to limit the insertion of the thermometer to approximately the desired depth. The increased accuracy obtained with this procedure and its convenience make it desirable for any investigation involving temperature determination of chicks. In the course of this study a rapid and accurate method of reading the thermometers was devised in which the thermometer rests against a rubber pad on the inclined stage of a microscope. The observer makes the reading through the empty tube of the instrument, thus avoiding error that might otherwise result from refraction of light by the glass if the thermometer were viewed at an acute angle.
[70]
VARIABILITY OF BODY TEMPERATURE IN THE NORMAL CHICK
Thermocouples mounted in glass tubing and paraffin were compared with mercury thermometers by taking alternate readings with the two instruments upon individual chicks. However, such a thermocouple mounting had sufficient mass to delay recording of constant temperature to a time comparable to that required by the mercury thermometer. Therefore, the instrument was not used extensively and none of the data obtained are reported here. Satisfactory use of the thermocouple will require refinement of the thermocouple mounting, and perhaps insertion into another part of the body. Such technics have been described by Baldwin and Kendeigh (1932) as used with the House Wren, and by Huggins, Blocksom, and Noonan (1936) as used with rats. However, unless the thermocouple can be shown to be significantly more accurate than mercury thermometers under the conditions of such a study, its extensive use is handicapped by two disadvantages, relatively high cost and inconvenience. RESULTS OF EXPERIMENTS
A post-hatching rise in the body temperature of chicks is shown by data obtained from studies involving 398 chicks. That such a rise might occur is perhaps obvious from the fact that the temperature of the adult fowl (105-109°F.) is much higher than the incubation temperature of around 100°F. at which the chick hatches. Our data (figs. 1 and 2) show that this rise is most rapid during the first four days. This accounts for the differences between Fronda's (1922) mean temperatures for chicks at one day and at seven days. Breed differences in body temperature were determined by taking the rectal temperatures of 189 White Leghorns and 162 Rhode Island Reds brooded together in six different lots during six consecutive twoweek periods. The same brooder was used
71
for all lots. Temperatures were taken at 1:30 to 4:00 p.m. The differences in temperature between these breeds were at 7 days of age 0.904 ± 0.073°F. and at 10 days of age 0.989 ± 0.079°F., the Leghorns being the higher at both ages (fig. 2). Both these differences are statistically significant when considered in relation to their standard errors. The extensive data of Simpson (1911-12) show no difference between the temperatures of adult Rhode Island Reds and those of five other breeds. Thus, the age at which the differences in body temperature between White Leghorns and Rhode Island Reds cease to be significant has not been established except that it must lie between 10 days of age and maturity. Sex. The mean temperature of 25 adult females was reported by Loer (1909) to be 0.52°F. higher than that of 25 males. However, Fronda (1922) found "no consistent difference in the body temperatures" between sexes at various ages from "day-old" to 24 weeks. Card (1921) found no evidence that sex could be determined with practical accuracy by taking the temperatures of day-old chicks. A comparison between the male and female chicks in six lots of White Leghorns (totalling 189) and eight lots of Rhode Island Reds (302 chicks in all) showed that at 1, 2, 4, 5, 6, 7, and 10 days of age, 12 of 16 differences between the sexes were statistically insignificant. Sex differences, therefore, must contribute little or nothing to total variability in temperature. The data for the Rhode Island Reds (Table 1) show that such differences as were found were not consistent. At 1 and 2 days of age the temperature of the males exceeded that of the females, whereas at 7 and 10 days of age the females had the higher temperature. Differences between lots brooded in the same brooder during consecutive two-week
72
W. F. LAMOREUX AND F. B. HUTT
intervals and cared for by the same attendants were determined by subjecting the data to analysis of variance. For the ages 1, 2, and 4 days two variables were considered, "breeds" and "lots." For the seventh and ninth days "sex" was included. These analyses showed that for each age considered there were significant differences between lots, thus indicating that the mean temperature of one lot of more than 25 chicks may not represent the mean of another group of chicks brooded under comparable conditions. For example, at four TABLE 1.—Differences
the fourth and the fifth days of age in the 176 chicks mentioned above. The correlation coefficients of 0.304 ± 0.009 and 0.005 ± 0.100 obtained indicate that at this age the temperature of individual chicks is not consistent from day to day. Diurnal variation. To establish a normal curve of the temperature of White Leghorn chicks, without any error that might result from diurnal variation (that is, within a 24-hour day), two groups of 25 and 22 chicks were subjected to temperature determinations at a fixed hour each day. Lot
between the mean temperatures of Rhode Island Red males and females at various ages*
Mean temperature
Chicks number
Age in days
9 9
162 162 302 140 162 162
1 2 4 5 7 10
103.407+0.087 104.250+0.077 105.776+0.190 106.058+0.099 105.778 + 0.079 106.063 + 0.060
103.168 + 0.118 104.019 + 0.107 105.626 + 0.187 106.001+0.112 106.006 + 0.087 106.232 + 0.106
Difference cfcf-9 9 0.239 + 0.147 0.231+0.132 0.150±0.267 0.057±0.149 -0.228 + 0.117 -0.169 + 0.122
* Sfandard errors are used throughout this paper.
days of age the mean temperatures of six lots of Rhode Island Reds varied from 104.79 ± 0.22°F. to 106.41 ± 0.10°F. The difference between these extremes is statistically significant. This occurred in spite of there being 27 chicks in one lot and 29 in the other, and in spite of efforts to ensure identical environment for all lots. Particular caution is therefore essential in comparing the work of different investigators or the results of different experiments. Body weight in two lots of Rhode Island Reds and Barred Plymouth Rocks (176 chicks) bore no relationship to body temperature at four days of age as indicated by the insignificant coefficients of correlation, 0.118 ± 0.108 and 0.025 ± 0.099. Stability of body temperature in individual chicks was studied by determining the correlation between the temperatures on
9 was recorded from 8 to 9 p.m. and lot 10 from 9 to 10 p.m. at intervals from hatching to 13 days of age (fig. 1). At 14 days of age their temperatures were taken from 1:50 to 3:30 p.m. with lot 9 taken first as before. Throughout these experiments the thermometer was taped to obtain uniform depth of insertion. It is noteworthy that during the first 13 days the mean temperature of lot 9, recorded from 8 to 9 p.m., consistently exceeded that of the other lot, taken one hour later. This indicates that the temperature of the chicks was consistently declining from 8 to 10 p.m. However, at 1:50 to 3:30 p.m. on the fourteenth day, the mean temperatures in lots 9 and 10 were higher by 0.6 and 0.8°F., respectively, than at 8 to 10 p.m. on the previous evening. The relatively high afternoon temperature and
VARIABILITY OF BODY TEMPERATURE IN THE NORMAL CHICK
normal diurnal variation, which would cause the former to be at the high point for the day, and in part from the depth of insertion of the thermometer being restricted when the readings shown in Figure 1 were taken but not for those in Figure 2.
declining evening temperature show that in these young chicks diurnal fluctuation of temperature is much; the same as that found in adult fowls by Simpson (1911), Hilden and Stenback (1916), and Fronda (1921). The graphs in Figure 1 demonstrate that comparatively small changes, such as those ACE 2
4
3
3
IN
6
7
DAYS 8
73
9
10
II
12
13
14
FIG. 1 1 : 5 0 - 3 : 3 0 P.M.—> /
106*
LOT
) : i . ) P . M . ^
105°
m u U 104* fl£ O
/ ,
hj
O
/
/ / / / / /
//
bJ 0.
/
L O T 1 0 : 9 - I 0 C M.
Id EC 3 103* • t-
^
J
S
of X
^
1 1 1 1
/WHITE
LEGHORNS
/ 107"
FIG.3 RHODE
ISLAND
REDS
\ \ .<•• \" -^ .. \ 2 5 MM N. " ' ' - ^ \ 106° • \ N.' -:-^-...^L X -
\ 3 7 MM.-^'"'-^ \
FIG 2
_
^
12 M M . - ? I0S« 1ST
.
2ND REAOINOS OF
_ " ~ —J
^
"—
__^
" "
3RD 4TH TEMPERATURE
Fig. 1. Difference in temperature resulting solely from a difference of one hour in time. Fig. 2. Difference between the post-hatching temperatures of White Leghorn and Rhode Island Red chicks. Fig. 3. Influence of depth of insertion of the thermometer upon the reading of body temperature.
resulting from a difference of one hour in the time of taking temperatures, may be detected and measured consistently when conditions are adequately controlled. The fact that the temperature of White Leghorns at seven days is shown in Figure 2 (afternoon) to be somewhat higher than in Figure 1 (8-10 p.m.) results in part from
Differences between attendants. Attempts to eliminate errors from diurnal variation by having several persons record temperatures at one time may not be successful, since differences between attendants may also be important sources of error. A comparison of mean temperatures of chicks from the same lots, taken by two different
74
W. F. LAMOREUX AND F. B. HUTT
persons (without tape on their thermom- temperature recorded depends upon the eters), showed that in two of three com- depth of insertion of the thermometer and parisons there were statistically significant that failure to control this source of error differences between the means of the may seriously affect the accuracy of the temperatures taken by the two observers. readings. To ensure uniformity, therefore, one inWhile insertion of the thermometer to dividual should, where possible, take all 25 mm. results in higher readings than at readings of temperature. If large numbers 12 mm., it does not follow that insertion of chicks must be handled, it is desirable to 37 mm. would give readings any higher to divide them into lots which can be han- or any more accurate. Actually, insertions dled within an hour, thereby facilitating to 37 mm., after previous readings at 25 correction for diurnal variation. mm., resulted in somewhat lower temperaTemperature gradient becomes a rela- tures being recorded (fig. 3). This fact, as tively more important source of error with well as the gradual decline in temperature decreasing size of an animal, that is the with successive readings at each of the three change from internal to external tempera- depths of insertion, is attributed to the cooltures involves a shorter distance in the small ing of adjacent tissue by repeated inseranimal. Some difficulty is encountered in tion of the thermometers, which were cooled the introduction of recording instruments to between readings to room temperature of the depth of constant temperature in ani- 75 to 80°F. It is obvious that the mass of mals as small as a newly-hatched chick. cool glass introduced is greatest at the The temperature gradient is steepest with deepest level of insertion. low environmental temperature (Bazett, Elimination of error that might arise 1927). However, since chicks are usually from the temperature gradient may thus brooded in an environmental temperature involve (1) insertion of the thermometer to of 90 to 95°F., the difference between inter- an adequate and constant depth, (2) thernal and external body temperature is com- mostatically controlled preheating of the paratively small. thermometer in oil to reduce to a minimum To determine the influence of tempera- the cooling of tissues by the thermometer, ture gradient upon the recorded tempera- and (3) since the temperature gradient is tures of chicks, readings were obtained with steepest with low environmental temperathe thermometer inserted into the chicks ture, error from this source may in some to approximate depths of 12, 25, and 37 cases be reduced by maintaining as high a mm. as controlled by several turns of adhe- brooding and room temperature as is feasisive tape around the stem of the thermom- ble. SUMMARY eter. Three tested thermometers were inIn studies involving 580 chicks several serted consecutively for one minute in the same chick to depths of 12, 25, and 37 mm., factors contributing to the variability of after which the thermometers were read. temperatures in normal chicks were investiThis procedure was carried out four times, gated. giving 12 readings, from each of six chicks. There is a pronounced rise in the body The means for six chicks of the comparable temperature of the chick during the first readings at each depth showed that in every week after hatching, particularly during the case the least depth of insertion gave the first four days. There is a significant diflowest mean temperature (fig. 3). The con- ference between the mean temperatures of sistency of this difference proves that the White Leghorn and Rhode Island Red
VARIABILITY OF BODY TEMPERATURE IN THE NORMAL CHICK
chicks at 7 and 10 days of age. No consistent relationships were found between body temperature and sex, between temperature and body weight, or between temperatures at four and five days of age. It has been shown that diurnal variation and temperature gradient may be consistent and important sources of error. Differences found between attendants in their ability to record temperatures accurately and between lots of comparable chicks, brooded under comparable conditions but at different times, indicate the necessity of carefully standardized technic and of caution in comparing results of different experiments. REFERENCES
Baldwin, S. P., and S. C. Kendeigh, 1932. Physiology of the temperature of birds. Sci. Pub. Cleveland Mus. Nat. Hist. 3:1-196. Bazett, H. C , 1927. Physiological responses to heat. Physiol. Reviews. 7:531-599. Card, L. E., 1921. Body temperature of newly hatched chicks. Poul. Sci. 1:9-15.
75
Fronda, F. M., 1921. A comparative study of the body temperature of the different species and some representative breeds of poultry—a preliminary report. Poul. Sci. 1:16-22. , 1922. Temperature studies in poultry. Ph.D. Thesis, Cornell University, Ithaca, N.Y. Hilden, A., and K. S. Stenback, 1916. Zur Kenntniss der Tagesschwankungen der Korpertemperature bei den Vogeln. Skand. Arch. f. Physiol. 34:382-415. Huggins, C , B. H. Blocksom, Jr., and W. J. Noonan, 1936. Temperature conditions in the bone marrow of rabbit, pigeon, and albino rat. Amer. Jour. Physiol. 115:395-401. Loer, F., 1909. Vergleichend physiologische Untersuchungen iiber die normale Rektal te'mperatur, Atem- und Pulsfrequenz der Vogel, unter besonder Beriicksichtigung unseres Hausgefliigels. Inaug. Dissertation, Univ. Bern. R. Schoetz, Berlin. Simpson, S., 1911. Observations on the body temperature of the domestic fowl (Gallus gallus) during incubation. Trans. Roy. Soc. Edinburgh. 47:605-617. , 1911-12. An investigation into the effects of seasonal changes on body temperature. Proc. Roy. Soc. Edinburgh 32 :110-135.
Department of Poultry Husbandry, Cornell University, Ithaca, New York (Received for publication May 31, 1938)
I
N CONNECTION with other studies involving variations in the temperatures of chicks during the first two weeks of life, it was necessary to determine first the normal variations and environmental conditions affecting them during that period. So far as could be ascertained the only data on this subject obtained with adequate numbers of chicks under normal conditions of brooding and diet are the unpublished figures of Fronda (1922) which indicate that at one and two weeks of age the temperature is about 3°F. higher than at hatching. Card's (1921) unwatered chicks, kept to five days, showed considerable diurnal variation in temperature. The present writers sought to find (1) possible sources of error in determination of temperature, (2) an adequate technic for temperature determination in baby chicks, (3) normal temperature variations in relation to age, weight, sex, and breed of the chick from hatching until it approaches the normal temperature of the adult. Such information is considered essential for many kinds of physiological experiments with chicks. METHODS
The data reported were obtained by the senior author at Cornell University and by the junior author at the Minnesota Agricultural Experiment Station. Readings of temperatures obtained to establish normal curves were taken at the same time each day to avoid error from diurnal fluctuations. Brooding equipment for all chicks included a heated compartment and one at
room temperature, the two together providing a range of temperature adequate to permit the chick to select its own environmental temperature as is customary in ordinary brooding practice. Thermometers: Clinical rectal thermometers were used for determining the body temperatures. In taking the temperature, the bulb of the thermometer, after being dipped in non-irritant oil to facilitate insertion into the cloaca and rectum, was held in the chick from one to one and one-fourth minutes. The depth of insertion usually varied according to the age of the chick; that is, the older the chick the greater the actual depth of insertion, but an effort was made to insert the thermometer to an approximately uniform depth for any given age and lot of chicks. In certain specified lots the thermometer was banded with several turns of adhesive tape, so placed as to limit the insertion of the thermometer to approximately the desired depth. The increased accuracy obtained with this procedure and its convenience make it desirable for any investigation involving temperature determination of chicks. In the course of this study a rapid and accurate method of reading the thermometers was devised in which the thermometer rests against a rubber pad on the inclined stage of a microscope. The observer makes the reading through the empty tube of the instrument, thus avoiding error that might otherwise result from refraction of light by the glass if the thermometer were viewed at an acute angle.
[70]
VARIABILITY OF BODY TEMPERATURE IN THE NORMAL CHICK
Thermocouples mounted in glass tubing and paraffin were compared with mercury thermometers by taking alternate readings with the two instruments upon individual chicks. However, such a thermocouple mounting had sufficient mass to delay recording of constant temperature to a time comparable to that required by the mercury thermometer. Therefore, the instrument was not used extensively and none of the data obtained are reported here. Satisfactory use of the thermocouple will require refinement of the thermocouple mounting, and perhaps insertion into another part of the body. Such technics have been described by Baldwin and Kendeigh (1932) as used with the House Wren, and by Huggins, Blocksom, and Noonan (1936) as used with rats. However, unless the thermocouple can be shown to be significantly more accurate than mercury thermometers under the conditions of such a study, its extensive use is handicapped by two disadvantages, relatively high cost and inconvenience. RESULTS OF EXPERIMENTS
A post-hatching rise in the body temperature of chicks is shown by data obtained from studies involving 398 chicks. That such a rise might occur is perhaps obvious from the fact that the temperature of the adult fowl (105-109°F.) is much higher than the incubation temperature of around 100°F. at which the chick hatches. Our data (figs. 1 and 2) show that this rise is most rapid during the first four days. This accounts for the differences between Fronda's (1922) mean temperatures for chicks at one day and at seven days. Breed differences in body temperature were determined by taking the rectal temperatures of 189 White Leghorns and 162 Rhode Island Reds brooded together in six different lots during six consecutive twoweek periods. The same brooder was used
71
for all lots. Temperatures were taken at 1:30 to 4:00 p.m. The differences in temperature between these breeds were at 7 days of age 0.904 ± 0.073°F. and at 10 days of age 0.989 ± 0.079°F., the Leghorns being the higher at both ages (fig. 2). Both these differences are statistically significant when considered in relation to their standard errors. The extensive data of Simpson (1911-12) show no difference between the temperatures of adult Rhode Island Reds and those of five other breeds. Thus, the age at which the differences in body temperature between White Leghorns and Rhode Island Reds cease to be significant has not been established except that it must lie between 10 days of age and maturity. Sex. The mean temperature of 25 adult females was reported by Loer (1909) to be 0.52°F. higher than that of 25 males. However, Fronda (1922) found "no consistent difference in the body temperatures" between sexes at various ages from "day-old" to 24 weeks. Card (1921) found no evidence that sex could be determined with practical accuracy by taking the temperatures of day-old chicks. A comparison between the male and female chicks in six lots of White Leghorns (totalling 189) and eight lots of Rhode Island Reds (302 chicks in all) showed that at 1, 2, 4, 5, 6, 7, and 10 days of age, 12 of 16 differences between the sexes were statistically insignificant. Sex differences, therefore, must contribute little or nothing to total variability in temperature. The data for the Rhode Island Reds (Table 1) show that such differences as were found were not consistent. At 1 and 2 days of age the temperature of the males exceeded that of the females, whereas at 7 and 10 days of age the females had the higher temperature. Differences between lots brooded in the same brooder during consecutive two-week
72
W. F. LAMOREUX AND F. B. HUTT
intervals and cared for by the same attendants were determined by subjecting the data to analysis of variance. For the ages 1, 2, and 4 days two variables were considered, "breeds" and "lots." For the seventh and ninth days "sex" was included. These analyses showed that for each age considered there were significant differences between lots, thus indicating that the mean temperature of one lot of more than 25 chicks may not represent the mean of another group of chicks brooded under comparable conditions. For example, at four TABLE 1.—Differences
the fourth and the fifth days of age in the 176 chicks mentioned above. The correlation coefficients of 0.304 ± 0.009 and 0.005 ± 0.100 obtained indicate that at this age the temperature of individual chicks is not consistent from day to day. Diurnal variation. To establish a normal curve of the temperature of White Leghorn chicks, without any error that might result from diurnal variation (that is, within a 24-hour day), two groups of 25 and 22 chicks were subjected to temperature determinations at a fixed hour each day. Lot
between the mean temperatures of Rhode Island Red males and females at various ages*
Mean temperature
Chicks number
Age in days
9 9
162 162 302 140 162 162
1 2 4 5 7 10
103.407+0.087 104.250+0.077 105.776+0.190 106.058+0.099 105.778 + 0.079 106.063 + 0.060
103.168 + 0.118 104.019 + 0.107 105.626 + 0.187 106.001+0.112 106.006 + 0.087 106.232 + 0.106
Difference cfcf-9 9 0.239 + 0.147 0.231+0.132 0.150±0.267 0.057±0.149 -0.228 + 0.117 -0.169 + 0.122
* Sfandard errors are used throughout this paper.
days of age the mean temperatures of six lots of Rhode Island Reds varied from 104.79 ± 0.22°F. to 106.41 ± 0.10°F. The difference between these extremes is statistically significant. This occurred in spite of there being 27 chicks in one lot and 29 in the other, and in spite of efforts to ensure identical environment for all lots. Particular caution is therefore essential in comparing the work of different investigators or the results of different experiments. Body weight in two lots of Rhode Island Reds and Barred Plymouth Rocks (176 chicks) bore no relationship to body temperature at four days of age as indicated by the insignificant coefficients of correlation, 0.118 ± 0.108 and 0.025 ± 0.099. Stability of body temperature in individual chicks was studied by determining the correlation between the temperatures on
9 was recorded from 8 to 9 p.m. and lot 10 from 9 to 10 p.m. at intervals from hatching to 13 days of age (fig. 1). At 14 days of age their temperatures were taken from 1:50 to 3:30 p.m. with lot 9 taken first as before. Throughout these experiments the thermometer was taped to obtain uniform depth of insertion. It is noteworthy that during the first 13 days the mean temperature of lot 9, recorded from 8 to 9 p.m., consistently exceeded that of the other lot, taken one hour later. This indicates that the temperature of the chicks was consistently declining from 8 to 10 p.m. However, at 1:50 to 3:30 p.m. on the fourteenth day, the mean temperatures in lots 9 and 10 were higher by 0.6 and 0.8°F., respectively, than at 8 to 10 p.m. on the previous evening. The relatively high afternoon temperature and
VARIABILITY OF BODY TEMPERATURE IN THE NORMAL CHICK
normal diurnal variation, which would cause the former to be at the high point for the day, and in part from the depth of insertion of the thermometer being restricted when the readings shown in Figure 1 were taken but not for those in Figure 2.
declining evening temperature show that in these young chicks diurnal fluctuation of temperature is much; the same as that found in adult fowls by Simpson (1911), Hilden and Stenback (1916), and Fronda (1921). The graphs in Figure 1 demonstrate that comparatively small changes, such as those ACE 2
4
3
3
IN
6
7
DAYS 8
73
9
10
II
12
13
14
FIG. 1 1 : 5 0 - 3 : 3 0 P.M.—> /
106*
LOT
) : i . ) P . M . ^
105°
m u U 104* fl£ O
/ ,
hj
O
/
/ / / / / /
//
bJ 0.
/
L O T 1 0 : 9 - I 0 C M.
Id EC 3 103* • t-
^
J
S
of X
^
1 1 1 1
/WHITE
LEGHORNS
/ 107"
FIG.3 RHODE
ISLAND
REDS
\ \ .<•• \" -^ .. \ 2 5 MM N. " ' ' - ^ \ 106° • \ N.' -:-^-...^L X -
\ 3 7 MM.-^'"'-^ \
FIG 2
_
^
12 M M . - ? I0S« 1ST
.
2ND REAOINOS OF
_ " ~ —J
^
"—
__^
" "
3RD 4TH TEMPERATURE
Fig. 1. Difference in temperature resulting solely from a difference of one hour in time. Fig. 2. Difference between the post-hatching temperatures of White Leghorn and Rhode Island Red chicks. Fig. 3. Influence of depth of insertion of the thermometer upon the reading of body temperature.
resulting from a difference of one hour in the time of taking temperatures, may be detected and measured consistently when conditions are adequately controlled. The fact that the temperature of White Leghorns at seven days is shown in Figure 2 (afternoon) to be somewhat higher than in Figure 1 (8-10 p.m.) results in part from
Differences between attendants. Attempts to eliminate errors from diurnal variation by having several persons record temperatures at one time may not be successful, since differences between attendants may also be important sources of error. A comparison of mean temperatures of chicks from the same lots, taken by two different
74
W. F. LAMOREUX AND F. B. HUTT
persons (without tape on their thermom- temperature recorded depends upon the eters), showed that in two of three com- depth of insertion of the thermometer and parisons there were statistically significant that failure to control this source of error differences between the means of the may seriously affect the accuracy of the temperatures taken by the two observers. readings. To ensure uniformity, therefore, one inWhile insertion of the thermometer to dividual should, where possible, take all 25 mm. results in higher readings than at readings of temperature. If large numbers 12 mm., it does not follow that insertion of chicks must be handled, it is desirable to 37 mm. would give readings any higher to divide them into lots which can be han- or any more accurate. Actually, insertions dled within an hour, thereby facilitating to 37 mm., after previous readings at 25 correction for diurnal variation. mm., resulted in somewhat lower temperaTemperature gradient becomes a rela- tures being recorded (fig. 3). This fact, as tively more important source of error with well as the gradual decline in temperature decreasing size of an animal, that is the with successive readings at each of the three change from internal to external tempera- depths of insertion, is attributed to the cooltures involves a shorter distance in the small ing of adjacent tissue by repeated inseranimal. Some difficulty is encountered in tion of the thermometers, which were cooled the introduction of recording instruments to between readings to room temperature of the depth of constant temperature in ani- 75 to 80°F. It is obvious that the mass of mals as small as a newly-hatched chick. cool glass introduced is greatest at the The temperature gradient is steepest with deepest level of insertion. low environmental temperature (Bazett, Elimination of error that might arise 1927). However, since chicks are usually from the temperature gradient may thus brooded in an environmental temperature involve (1) insertion of the thermometer to of 90 to 95°F., the difference between inter- an adequate and constant depth, (2) thernal and external body temperature is com- mostatically controlled preheating of the paratively small. thermometer in oil to reduce to a minimum To determine the influence of tempera- the cooling of tissues by the thermometer, ture gradient upon the recorded tempera- and (3) since the temperature gradient is tures of chicks, readings were obtained with steepest with low environmental temperathe thermometer inserted into the chicks ture, error from this source may in some to approximate depths of 12, 25, and 37 cases be reduced by maintaining as high a mm. as controlled by several turns of adhe- brooding and room temperature as is feasisive tape around the stem of the thermom- ble. SUMMARY eter. Three tested thermometers were inIn studies involving 580 chicks several serted consecutively for one minute in the same chick to depths of 12, 25, and 37 mm., factors contributing to the variability of after which the thermometers were read. temperatures in normal chicks were investiThis procedure was carried out four times, gated. giving 12 readings, from each of six chicks. There is a pronounced rise in the body The means for six chicks of the comparable temperature of the chick during the first readings at each depth showed that in every week after hatching, particularly during the case the least depth of insertion gave the first four days. There is a significant diflowest mean temperature (fig. 3). The con- ference between the mean temperatures of sistency of this difference proves that the White Leghorn and Rhode Island Red
VARIABILITY OF BODY TEMPERATURE IN THE NORMAL CHICK
chicks at 7 and 10 days of age. No consistent relationships were found between body temperature and sex, between temperature and body weight, or between temperatures at four and five days of age. It has been shown that diurnal variation and temperature gradient may be consistent and important sources of error. Differences found between attendants in their ability to record temperatures accurately and between lots of comparable chicks, brooded under comparable conditions but at different times, indicate the necessity of carefully standardized technic and of caution in comparing results of different experiments. REFERENCES
Baldwin, S. P., and S. C. Kendeigh, 1932. Physiology of the temperature of birds. Sci. Pub. Cleveland Mus. Nat. Hist. 3:1-196. Bazett, H. C , 1927. Physiological responses to heat. Physiol. Reviews. 7:531-599. Card, L. E., 1921. Body temperature of newly hatched chicks. Poul. Sci. 1:9-15.
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