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Some Effects of Increasing Environmental Temperatures on Pullets
Some Effects of Increasing Environmental Temperatures on Pullets W I L B O R O.
WILSON
Division of Poultry Husbandry, University of California, Davis (Received for publication May 29,1948)
ity are attributed by poultrymen to be due to environmental effects. Hence, the role of environment on the performance of chickens has long been recognized. Birds have highly variable body temperatures according to Baldwin and Kendeigh (1932). They found that muscular activity was the most important factor causing variations in body temperature. Normal body temperatures in eight spe^ cies of passeriform birds were found to vary as much as 10°F., ranging from the lowest normal body temperature of 102.0°F. to the highest which was 112.3°F. The normal body temperature of chickens varies from 104.6 to 109.4°F. according to Fronda (1931). This agrees with the normal temperatures during the spring of 106.1 + .09 and 105.4±.03°F. reported by Lee et al., (1945) for Leghorns and Australorps respectively. Heywang (1938) found that body temperature of hens was affected by environmental temperature. Lamoreux and Hutt (1939) found variability in the temperature of chicks to be affected to some extent by depth of insertion of the thermometer, age, breed, diurnal variation and attendants. Yeates et al,, (1941) have reported extensive studies on the effect of air temperatures on the domestic fowl in hot atmospheres. They studied different environmental temperatures and humidities on White Leghorns and Australorps and found the latter to be the more susceptible
to heat. At 9Q°F. the rectal temperature of the birds increased while pulse rate showed no consistent change upon exposure to heat. In most instances room temperatures over 90°F. produced a higher respiratory rate. It is the purpose of the present paper to report on one phase of our inquiry into the effect of environment on birds, namely variation from 70° to 105°F. ambient temperatures on pullets. MATERIALS
The stock used in this study consisted of White Leghorn pullets about one year old. They were confined in cages of a commercial hen battery inside a room which was equipped with thermostats that would allow the temperature to be controlled to ±1.0°F. The pullets were kept in the room constantly and were accustomed to their cages. All the birds were laying. The thermostat was set at a given temperature and observations were made on the birds during a period of about seven hours. The birds were kept inside the room while the temperature was increased to the desired level. A preliminary analysis of variance was calculated to determine the effect of the position of the cage on the body temperature. The results showed that the difference between individuals was greater than the difference between positions of the cages. The relative humidity was measured but not controlled. As a result the relative humidity was higher at the lower temperatures.
813
Downloaded from http://ps.oxfordjournals.org/ at Florida International University on June 9, 2015
of the seasonal variations in egg SOME production, fertility and hatchabil-
814
WILBOR O. WILSON
At no time did the relative humidity exceed 50 percent. The birds were kept continuously under artificial lights, with a minimum intensity of about 3 foot candles. The air movement was approximately 2 cubic feet per minute as measured by a Kata-thermometer. The air temperature studies ranged from 70° to 105°F. Body temperature was taken with a clinical thermometer which was inserted into the cloaca to a depth of 3f cm and was read after a minimum insertion time of 1 | minutes. The readings were made in the early afternoon' after the birds had been exposed to the environment approximately 4 hours. The heart rate was determined by an electrocardiotachometer, similar to the one used by McNally (1941). Respiration rate was measured by visual observation and also
by counting the respirations with a stethoscope. Feed and water consumption during the time of exposure was recorded. Since the exposure time was not always the same the data are expressed as consumption per bird per hour. RESULTS
TABLE 1.-—Average and standard deviation of body temperature, feed and water consumption, heart rate and respiration of hens at various room temperatures. Room temp. °F.
Body temp. °F.
60.8 70 70 70.7 70.7 71 73 75.2 80 80.6 80.6 84.2 86.0 86.0 88 89.6 91.4 91.5 91.5 93 95 96.5 100.4 100.4 100.8 103.6 104.9 105.1
106.4± .38 106.5± .48 106.2 + .38 105.8± .79 105.8± .51 106.2 + .44 106.2± .48 106.3 + .45 106.3 + .51 106.6 + .46 107.2 + .61 107.2 + .80 106.5 + .50 106.6 + .63 106.5 + .67 106.4± .84 107.0+ .55 107.1 + .65 106.7 + .56 107.4+ .58 107.3 + .49 107.4± .55 109.0 + .62 108.4 + .66 107.9± .47 1C9.6 + .60 109.5 + 1 .33 109.8± .78
Hourly consumption Feed grams Water cc.
Heart rate beats per minute
Respiration per minute
4.7 + 1.5 7.5 + 1.7
13 + 6.9 14 + 3.5
312 + 30.
16.9±2.8
5.9±2.2
15 ± 2.1
7.3 + 7.4 + 7.0 + 5.5 +
17 + 27 + 21 + 22 +
1.4 3.2 2.4 1.6
4.8 4.3 6.2 9.8
24.1 ± 1 . 4 301 + 26. 291 ± 3 2 . 264+34.
25.7 + 5.0
255 + 27.
26.1+7.0 38.7 + 8.8 29.8 + 8.6
m
6.0 + 3.1 6.8±3.2
32 + 8.2 33 + 8.5
268 + 30. 265 + 33.
-3.9 + 2.0 1.4+1.5 5.3 + 3.1 4.8 + 3.0 2.1 + 1.6
34 ± 9.6 31 + 10.2 34+14.4 36 + 13.0 40 + 8.6
252 + 20. 278 + 25. 138.2 + 23.5
Downloaded from http://ps.oxfordjournals.org/ at Florida International University on June 9, 2015
•The results are given in Table 1. Each average is based on twelve or more observations. It was observed that the body temperature of the birds rose whenever the environmental temperature exceeded 80°F., which is somewhat lower than that reported by Heywang (1938) and Yeates et al., (1941). Body temperature rose sharply with increase in air temperature to 105°F. In air temperature of 105°F. it was impossible to keep all the birds alive
EFFECT OF ENVIRONMENTAL TEMPERATURE ON PULLETS
The standard deviation of the means shows that the variation in body temperature was greater at higher air temperatures. This would indicate that the response to heat was characteristic of the individual hen. The results show that feed consumption /bird/hour generally decreased as the air temperature increased. However, the results are not consistent. There was con-
siderable variation between birds. It is possible that the short feeding period does not permit the real differences to become apparent. The hen's eating habits may be an important source of error. Some birds did not eat during the seven hour experimental period. Other tests extending over a longer period of time are in progress to check this point further. Water consumption/bird/hour increased progressively from 70°F. The increase in water consumption is nearly a straight line as the ambient temperature increased from 70° to 105°F. Water consumption doubled with an increase in room temperature from 70°F. to 95°F. On the other hand, body temperature rose markedly above 90°F. ambient temperature. (See Figure 1.) The data for heart rate are incomplete but suggest that high temperatures depress heart rate in chickens. This is inverse to the condition found in man. The difference may be attributed to the fact that chickens do not sweat and the heart does not have an increased load of blood to carry near the surface of the body.
//
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50
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body femperafare
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75
1
Downloaded from http://ps.oxfordjournals.org/ at Florida International University on June 9, 2015
for more than six hours. The body temperature in one individual reached 114°F. before she collapsed. Several other birds showed a body temperature of 113°F. before they were removed. Observations made would bear out the results of Lee et al., (1945) that a rectal temperature of 113°F. is the uppermost limit of safety for hens. The body temperature of the hen soon returns to normal after the air temperature is cooled. In one group of twelve hens where the mean body temperature had reached 110.1° + 1.6°F., the mean body temperature fell to 105.8° + 0.4°F. within 90 minutes. During this time the ambient temperature had decreased to 68°F.
815
816
WILBOR 0 . WILSON
perature exceeds 80°F. The data confirmed this point. The variation in the response of the different birds is considerable as may be seen from the magnitude of the standard deviations. In order to determine the diurnal variation in body temperature of hens kept under a constant environmental temperature, readings were made on a group of twelve birds over a period of 24 hours. The temperature was kept at 70°F. during the entire period. The diurnal variation was much less (Fig. 2) than the 1.6 to 4.8°F. previously reported by Fronda (1921). Heywang (1938) found a difference of 1.5°F. between the high and the low readings during a 24 hour period. He suggested that air temperature may influence body temperature. The variation of body temperature in the present study was 0.3°F. This difference between these results and those of other workers may have been due to the relative inactivity of these confined birds. However, it is more
/08
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~/8 /6 /06 -
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8:00 AM
/2:00 M.
_L
_L
_L
4:00 PM.
8-00 PM.
/2:00 At.
FIG. 2. Diurnal variation in temperature at 70° F. ambient.
4:00 AM.
Downloaded from http://ps.oxfordjournals.org/ at Florida International University on June 9, 2015
Cooling of the hen's body is accomplished by an increased rate of respiration rather than by sweating and evaporation of moisture from the skin. Lee et al. (1945) did not observe any effect of high environmental temperature on heart rate. The rate of respiration was low at low temperatures but increased gradually as the air temperature rose to 90 degrees. There was a considerable amount of variation in the panting threshold of the various birds. Panting is not a continuous process at border line environmental temperatures of about 80°F. Approximately half the birds were observed to be panting at that temperature. At 90°F. the respiration rate was increased on all birds and panting occurred at a moderate rate. This agrees with the findings of Lee et al., (1945). Randall and Hiestand (1939) found panting to be associated with a rise of 0.1° to 0.4°C. in body temperature. Accordingly, one would expect the body temperature to increase when the air tem-
NEWS AND NOTES
probable that the low variability in body temperature resulted from the constant air temperature and thus merely reflected the influence of environmental temperatures on body temperature. SUMMARY
REFERENCES
Baldwin, S. Prentiss and S. Charles Kendeigh, 1932. Physiology of the temperature of birds.
Scientific publication Cleveland Museum of Natural History, Vol. 3, p. 196. Fronda, Francisco M., 1921. A comparative study of body temperatures of different species and some representative breeds of poultry. Poultry Sci. 1: 16-22. Heywang, B. W., 1938. Effect of some factors on body temperature of hens. Poultry Sci. 17: 317323. Lamcreux, W. F. and F. B. Hutt, 1939. Variability of body temperature in the normal chick. Poultry Sci. 18: 70-75. Lee, Douglas H. K., Kathleen W. Robinson, Neil T. M. Yeates and Margret I. R. Scott, 1945 Poultry husbandry in hot climates. Experimental enquiries. Poultry Sci. 24:195-207. McNally, E. H., 1941. Heart rate of the domestic fowl. Poultry Sci. 20: 266-271. Randall, W. C. and W. A. Hiestand, 1939. Panting and temperature regulation in the chicken. Amer. Jour. Physiol. 127: 761-767. Yeates, N. T. M., D. H. K. Lee and H. J. G. Hines, 1941. Reaction of domestic fowls to hot atmospheres. Proc. Roy. Soc. Queensland 53: 105-128.
News and Notes (Continued from page 801)
University) joined the Poultry Depart- & M., 1938; M.S., Oklahoma A. & M., ment of the University of Maryland- 1948) has been appointed Assistant in September 1, 1948. Dr. Combs will be in Poultry Breeding. W. D. Blackwell and charge of poultry nutrition research. William Stewart are Graduate Research Assistants and Carl Williams is Graduate Dr. Charles W. Upp is now Head of the Assistant-Teaching in the Poultry IndusPoultry Industry Department which was try Department of Louisiana State Uniestablished as a separate department at versity. Louisiana State University July 1, 1948. Previously the poultry teaching activities Dr. A. R. Robblee (B.S., M.S., Univerhad been affiliated with the Animal In- sity of Alberta; Ph.D., University of Wisdustry Department. Mr. A. B. Watts consin) has been appointed Assistant Pro(B.S., S.L.I., 1939; M.S., L.S.U., 1941) fessor in Poultry Husbandry at the is on leave to pursue work toward the doc- University of Alberta, Edmonton. His torate in nutrition. Mr. H. E. Hathaway duties will include teaching and research (B.S., Oklahoma A. & M., 1940; M.S., work in poultry nutrition. Michigan State College, 1942) has been appointed Assistant Poultry HusbandryGeorge T. Davis, formerly of the Deman and Instructor in Poultry Industry. partment of Poultry Husbandry, OklaMr. J. C. Gilbreath (B.S., Oklahoma A. homa A. & M. College, has recently been {Continued on page 821)
Downloaded from http://ps.oxfordjournals.org/ at Florida International University on June 9, 2015
Body temperature was affected severely when the air temperature rose above 90°F. Feed consumption was reduced at high air temperature, but the results were not consistent. Water consumption at 95°F. was.double that at 70°F. The heart rate was lower at the higher environmental temperatures. Respiration increased when the air temperature reached 80°F., and at 105°F. was very high.
817
WILSON
Division of Poultry Husbandry, University of California, Davis (Received for publication May 29,1948)
ity are attributed by poultrymen to be due to environmental effects. Hence, the role of environment on the performance of chickens has long been recognized. Birds have highly variable body temperatures according to Baldwin and Kendeigh (1932). They found that muscular activity was the most important factor causing variations in body temperature. Normal body temperatures in eight spe^ cies of passeriform birds were found to vary as much as 10°F., ranging from the lowest normal body temperature of 102.0°F. to the highest which was 112.3°F. The normal body temperature of chickens varies from 104.6 to 109.4°F. according to Fronda (1931). This agrees with the normal temperatures during the spring of 106.1 + .09 and 105.4±.03°F. reported by Lee et al., (1945) for Leghorns and Australorps respectively. Heywang (1938) found that body temperature of hens was affected by environmental temperature. Lamoreux and Hutt (1939) found variability in the temperature of chicks to be affected to some extent by depth of insertion of the thermometer, age, breed, diurnal variation and attendants. Yeates et al,, (1941) have reported extensive studies on the effect of air temperatures on the domestic fowl in hot atmospheres. They studied different environmental temperatures and humidities on White Leghorns and Australorps and found the latter to be the more susceptible
to heat. At 9Q°F. the rectal temperature of the birds increased while pulse rate showed no consistent change upon exposure to heat. In most instances room temperatures over 90°F. produced a higher respiratory rate. It is the purpose of the present paper to report on one phase of our inquiry into the effect of environment on birds, namely variation from 70° to 105°F. ambient temperatures on pullets. MATERIALS
The stock used in this study consisted of White Leghorn pullets about one year old. They were confined in cages of a commercial hen battery inside a room which was equipped with thermostats that would allow the temperature to be controlled to ±1.0°F. The pullets were kept in the room constantly and were accustomed to their cages. All the birds were laying. The thermostat was set at a given temperature and observations were made on the birds during a period of about seven hours. The birds were kept inside the room while the temperature was increased to the desired level. A preliminary analysis of variance was calculated to determine the effect of the position of the cage on the body temperature. The results showed that the difference between individuals was greater than the difference between positions of the cages. The relative humidity was measured but not controlled. As a result the relative humidity was higher at the lower temperatures.
813
Downloaded from http://ps.oxfordjournals.org/ at Florida International University on June 9, 2015
of the seasonal variations in egg SOME production, fertility and hatchabil-
814
WILBOR O. WILSON
At no time did the relative humidity exceed 50 percent. The birds were kept continuously under artificial lights, with a minimum intensity of about 3 foot candles. The air movement was approximately 2 cubic feet per minute as measured by a Kata-thermometer. The air temperature studies ranged from 70° to 105°F. Body temperature was taken with a clinical thermometer which was inserted into the cloaca to a depth of 3f cm and was read after a minimum insertion time of 1 | minutes. The readings were made in the early afternoon' after the birds had been exposed to the environment approximately 4 hours. The heart rate was determined by an electrocardiotachometer, similar to the one used by McNally (1941). Respiration rate was measured by visual observation and also
by counting the respirations with a stethoscope. Feed and water consumption during the time of exposure was recorded. Since the exposure time was not always the same the data are expressed as consumption per bird per hour. RESULTS
TABLE 1.-—Average and standard deviation of body temperature, feed and water consumption, heart rate and respiration of hens at various room temperatures. Room temp. °F.
Body temp. °F.
60.8 70 70 70.7 70.7 71 73 75.2 80 80.6 80.6 84.2 86.0 86.0 88 89.6 91.4 91.5 91.5 93 95 96.5 100.4 100.4 100.8 103.6 104.9 105.1
106.4± .38 106.5± .48 106.2 + .38 105.8± .79 105.8± .51 106.2 + .44 106.2± .48 106.3 + .45 106.3 + .51 106.6 + .46 107.2 + .61 107.2 + .80 106.5 + .50 106.6 + .63 106.5 + .67 106.4± .84 107.0+ .55 107.1 + .65 106.7 + .56 107.4+ .58 107.3 + .49 107.4± .55 109.0 + .62 108.4 + .66 107.9± .47 1C9.6 + .60 109.5 + 1 .33 109.8± .78
Hourly consumption Feed grams Water cc.
Heart rate beats per minute
Respiration per minute
4.7 + 1.5 7.5 + 1.7
13 + 6.9 14 + 3.5
312 + 30.
16.9±2.8
5.9±2.2
15 ± 2.1
7.3 + 7.4 + 7.0 + 5.5 +
17 + 27 + 21 + 22 +
1.4 3.2 2.4 1.6
4.8 4.3 6.2 9.8
24.1 ± 1 . 4 301 + 26. 291 ± 3 2 . 264+34.
25.7 + 5.0
255 + 27.
26.1+7.0 38.7 + 8.8 29.8 + 8.6
m
6.0 + 3.1 6.8±3.2
32 + 8.2 33 + 8.5
268 + 30. 265 + 33.
-3.9 + 2.0 1.4+1.5 5.3 + 3.1 4.8 + 3.0 2.1 + 1.6
34 ± 9.6 31 + 10.2 34+14.4 36 + 13.0 40 + 8.6
252 + 20. 278 + 25. 138.2 + 23.5
Downloaded from http://ps.oxfordjournals.org/ at Florida International University on June 9, 2015
•The results are given in Table 1. Each average is based on twelve or more observations. It was observed that the body temperature of the birds rose whenever the environmental temperature exceeded 80°F., which is somewhat lower than that reported by Heywang (1938) and Yeates et al., (1941). Body temperature rose sharply with increase in air temperature to 105°F. In air temperature of 105°F. it was impossible to keep all the birds alive
EFFECT OF ENVIRONMENTAL TEMPERATURE ON PULLETS
The standard deviation of the means shows that the variation in body temperature was greater at higher air temperatures. This would indicate that the response to heat was characteristic of the individual hen. The results show that feed consumption /bird/hour generally decreased as the air temperature increased. However, the results are not consistent. There was con-
siderable variation between birds. It is possible that the short feeding period does not permit the real differences to become apparent. The hen's eating habits may be an important source of error. Some birds did not eat during the seven hour experimental period. Other tests extending over a longer period of time are in progress to check this point further. Water consumption/bird/hour increased progressively from 70°F. The increase in water consumption is nearly a straight line as the ambient temperature increased from 70° to 105°F. Water consumption doubled with an increase in room temperature from 70°F. to 95°F. On the other hand, body temperature rose markedly above 90°F. ambient temperature. (See Figure 1.) The data for heart rate are incomplete but suggest that high temperatures depress heart rate in chickens. This is inverse to the condition found in man. The difference may be attributed to the fact that chickens do not sweat and the heart does not have an increased load of blood to carry near the surface of the body.
//
/09
50
-
40
0^
I
-30
/OS
wafer consc/mpf/on
X
body femperafare
- 20
%,I07
I
IO
°Q /Oil— 65
/OO /05 /IO 95 eo es /4/7?6/'enf Temperature, FahrenheiT FIG. 1. Body temperature and water consumption at different ambient temperatures. 70
75
1
Downloaded from http://ps.oxfordjournals.org/ at Florida International University on June 9, 2015
for more than six hours. The body temperature in one individual reached 114°F. before she collapsed. Several other birds showed a body temperature of 113°F. before they were removed. Observations made would bear out the results of Lee et al., (1945) that a rectal temperature of 113°F. is the uppermost limit of safety for hens. The body temperature of the hen soon returns to normal after the air temperature is cooled. In one group of twelve hens where the mean body temperature had reached 110.1° + 1.6°F., the mean body temperature fell to 105.8° + 0.4°F. within 90 minutes. During this time the ambient temperature had decreased to 68°F.
815
816
WILBOR 0 . WILSON
perature exceeds 80°F. The data confirmed this point. The variation in the response of the different birds is considerable as may be seen from the magnitude of the standard deviations. In order to determine the diurnal variation in body temperature of hens kept under a constant environmental temperature, readings were made on a group of twelve birds over a period of 24 hours. The temperature was kept at 70°F. during the entire period. The diurnal variation was much less (Fig. 2) than the 1.6 to 4.8°F. previously reported by Fronda (1921). Heywang (1938) found a difference of 1.5°F. between the high and the low readings during a 24 hour period. He suggested that air temperature may influence body temperature. The variation of body temperature in the present study was 0.3°F. This difference between these results and those of other workers may have been due to the relative inactivity of these confined birds. However, it is more
/08
is /or
-20
resp/raffon
~/8 /6 /06 -
I
dod
-/2 -/O
/OS
& % !
§ /04
8:00 AM
/2:00 M.
_L
_L
_L
4:00 PM.
8-00 PM.
/2:00 At.
FIG. 2. Diurnal variation in temperature at 70° F. ambient.
4:00 AM.
Downloaded from http://ps.oxfordjournals.org/ at Florida International University on June 9, 2015
Cooling of the hen's body is accomplished by an increased rate of respiration rather than by sweating and evaporation of moisture from the skin. Lee et al. (1945) did not observe any effect of high environmental temperature on heart rate. The rate of respiration was low at low temperatures but increased gradually as the air temperature rose to 90 degrees. There was a considerable amount of variation in the panting threshold of the various birds. Panting is not a continuous process at border line environmental temperatures of about 80°F. Approximately half the birds were observed to be panting at that temperature. At 90°F. the respiration rate was increased on all birds and panting occurred at a moderate rate. This agrees with the findings of Lee et al., (1945). Randall and Hiestand (1939) found panting to be associated with a rise of 0.1° to 0.4°C. in body temperature. Accordingly, one would expect the body temperature to increase when the air tem-
NEWS AND NOTES
probable that the low variability in body temperature resulted from the constant air temperature and thus merely reflected the influence of environmental temperatures on body temperature. SUMMARY
REFERENCES
Baldwin, S. Prentiss and S. Charles Kendeigh, 1932. Physiology of the temperature of birds.
Scientific publication Cleveland Museum of Natural History, Vol. 3, p. 196. Fronda, Francisco M., 1921. A comparative study of body temperatures of different species and some representative breeds of poultry. Poultry Sci. 1: 16-22. Heywang, B. W., 1938. Effect of some factors on body temperature of hens. Poultry Sci. 17: 317323. Lamcreux, W. F. and F. B. Hutt, 1939. Variability of body temperature in the normal chick. Poultry Sci. 18: 70-75. Lee, Douglas H. K., Kathleen W. Robinson, Neil T. M. Yeates and Margret I. R. Scott, 1945 Poultry husbandry in hot climates. Experimental enquiries. Poultry Sci. 24:195-207. McNally, E. H., 1941. Heart rate of the domestic fowl. Poultry Sci. 20: 266-271. Randall, W. C. and W. A. Hiestand, 1939. Panting and temperature regulation in the chicken. Amer. Jour. Physiol. 127: 761-767. Yeates, N. T. M., D. H. K. Lee and H. J. G. Hines, 1941. Reaction of domestic fowls to hot atmospheres. Proc. Roy. Soc. Queensland 53: 105-128.
News and Notes (Continued from page 801)
University) joined the Poultry Depart- & M., 1938; M.S., Oklahoma A. & M., ment of the University of Maryland- 1948) has been appointed Assistant in September 1, 1948. Dr. Combs will be in Poultry Breeding. W. D. Blackwell and charge of poultry nutrition research. William Stewart are Graduate Research Assistants and Carl Williams is Graduate Dr. Charles W. Upp is now Head of the Assistant-Teaching in the Poultry IndusPoultry Industry Department which was try Department of Louisiana State Uniestablished as a separate department at versity. Louisiana State University July 1, 1948. Previously the poultry teaching activities Dr. A. R. Robblee (B.S., M.S., Univerhad been affiliated with the Animal In- sity of Alberta; Ph.D., University of Wisdustry Department. Mr. A. B. Watts consin) has been appointed Assistant Pro(B.S., S.L.I., 1939; M.S., L.S.U., 1941) fessor in Poultry Husbandry at the is on leave to pursue work toward the doc- University of Alberta, Edmonton. His torate in nutrition. Mr. H. E. Hathaway duties will include teaching and research (B.S., Oklahoma A. & M., 1940; M.S., work in poultry nutrition. Michigan State College, 1942) has been appointed Assistant Poultry HusbandryGeorge T. Davis, formerly of the Deman and Instructor in Poultry Industry. partment of Poultry Husbandry, OklaMr. J. C. Gilbreath (B.S., Oklahoma A. homa A. & M. College, has recently been {Continued on page 821)
Downloaded from http://ps.oxfordjournals.org/ at Florida International University on June 9, 2015
Body temperature was affected severely when the air temperature rose above 90°F. Feed consumption was reduced at high air temperature, but the results were not consistent. Water consumption at 95°F. was.double that at 70°F. The heart rate was lower at the higher environmental temperatures. Respiration increased when the air temperature reached 80°F., and at 105°F. was very high.
817