Physiological Response of Domestic Fowl to Abrupt Changes of Ambient Air Temperature1

Physiological Response of Domestic Fowl to Abrupt Changes of Ambient Air Temperature 1 P. C. HARRISON 2 ' 3 AND H. V. BIELLIER Department of Poultry Husbandry, University of Missouri, Columbia, Missouri 65201 (Received for publication November 30, 1968)

C

Cardiovascular activity has been found to follow seasonal trends. Blood pressure is elevated during winter months and lowered during summer months (Vogel and Sturkie, 1963; Weiss et al., 1957). Heart rate is not greatly affected until conditions become severe enough to cause 1 Contribution from the Missouri Agricultural Experiment Station, Journal Series No. 5550. 2 Present address: Department of Animal Sciences, Washington State University, Pullman 3 Supported in part by N I H Research Fellowship Award No. 906-03.

a change in body temperature. As body temperature decreases, there is a decrease in heart rate and blood pressure until a terminal body temperature of around 26°C. is attained (Rodbard and Tolpin, 1947; Weiss, 1960). When body temperature increased due to high environmental temperature, an increase in heart rate was observed followed by an increase in blood pressure until a body temperature of approximately 45°C. was reached in chickens (Frankel et al., 1962; Linsley and Burger, 1964; Rodbard and Tolpin, 1947; and Whittow et al, 1964). The respiratory rate of chickens increases upon exposure to high temperature and it appears to be related to the increase in body temperature (Randall and Hiestand, 1939; Frankel el al., 1962; Linsley and Burger, 1964; Calder and SchmidtNielsen, 1968). When environmental temperature is decreased, especially from high temperatures, a decrease in respiratory rate has been observed (Hillerman and Wilson, 1955; Weiss, 1960). Body temperature is one of the most obvious parameters that displays the general response pattern and indicates the process of acclimation (Edholm et al., 1963). When an animal is exposed to a cold environment, body temperature drops rapidly at first, then plateaus at a temperature lower than at the previous temperature. The opposite effect on body temperature has been reported after exposure to high temperature (Davis, 1963; Edholm et al., 1963; Lind and Bass, 1963; Slonim, 1963).

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ONSIDERABLE research has been conducted on physiological processes of the domestic fowl while exposed to stressful environmental temperatures. However, relatively few investigations have been conducted during the period immediately following exposure. This experiment was designed to determine the effect of an abrupt change in ambient temperature on heart rate, blood pressure, respiratory rate, and body temperature. Of special interest was the time relationship between initial response to a changed ambient temperature and the new level of function. Prosser (1964) refers to this as the "time course of physiological variation in rate function." When an animal is exposed to a stressing temperature, there is a rapid initial change in level of metabolism and other physiological parameters. Following this period of rapid change, which generally shows an overshoot or undershoot, there is a plateauing of functional level but at a different level than at the previous temperature.

PHYSIOLOGICAL RESPONSE TO TEMPERATURE

MATERIALS AND METHODS

Heart rate, blood pressure, respiratory rate, and body temperature were taken simultaneously on individual birds at each time exposure period during each treatment. Five birds were used for each experimental temperature change except from 5°C. to 21°C. and from 5°C. to 35°C. where four birds were used. During the time when these parameters were being measured, the bird was removed from the cage and placed upright in a sling. Holes were cut in the sling so that the legs could be readily accessible for obtaining pulse rate and blood pressure readings. Following transfer of the birds to a different environmental temperature, measurements were made on each bird throughout the first 30 minutes of exposure. During this period the bird remained in the sling with all measurement apparatus connected. In all subsequent measurements the parameter readings were taken over a fiveminute span of time. Pulse rate was measured by a crystalline sound transducer taped to the shank two centimeters below the hock joint and recorded on a Model 7 Grass polygraph. The mean pulse rate was obtained by counting the number of pen cycles recorded by the polygraph for three tensecond periods during the time of measurement. Blood pressure was measured indirectly by use of a sphygmomanometer. The pressure cuff was four inches long and one inch wide and of the type described by Weiss and Sturkie (1951). Three separate cuff wraps, two centimeters above the hock joint, were made and the average of the readings represented the blood pressure for a single point. Respiratory rate was obtained by counting the number of respirations in four separate 25-second periods throughout the time of measurement. Respirations were recorded on the polygraph

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Single Comb White Leghorn hens approximately 20 months of age from the University of Missouri intraflock population were used in order to reduce variation caused by immature birds which would still be growing and/or beginning reproductive activity. Temperature treatments were conducted in three separate temperaturecontrol chambers. The hens were kept in individual 10 X16 X 18-inch cages in which the birds had access to feed and water at all times. Continuous incandescent light with an intensity of five to seven foot candles at the bird level was maintained in all chambers. Environmental temperature treatments consisted of abrupt changes in temperature by moving the birds from one chamber kept at a constant (±2°C.) temperature to an adjacent one at a different constant temperature. Changes in temperature were: (1) 21°C. to 35°C; (2) 5°C. to 35°C; (3) 5°C. to 21°C; (4) 21°C. to 5°C; (5) 35°C. to 5°C; and (6) 35°C. to 21°C. Relative humidity ranged from 34 to 46% in the 35°C. chamber, 44 to 52% in the 21°C. chamber, and 56 to 68% in the 5°C. chamber. Prior to making a change in temperature, the birds were placed at the original temperature for not less than 14 days. During this 14-day period, three to five consecutive daily physiological measurements were taken in order to accustom the birds to handling and equipment required for measurement purposes. Just prior to moving the birds to the new temperatures, all physiological parameters were measured, and this point was used as time "zero" functional level. The physiological parameters which were measured consisted of pulse rate, blood pressure, respiratory rate, body temperature, and oxygen consumption.

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P. C. HARRISON AND H. V. BIELLIER

that the birds had access to both feed and water at all times. Between each of the daily measurement periods, the birds were returned to their individual cages and had access to both feed and water. RESULTS AND DISCUSSION

Decrease in Environmental Temperature. Following a change from 21°C. to 5°C. environmental temperature, initial responses were: an increase in pulse (heart) rate, little change in blood pressure, little change in respiratory rate, slight decrease in body temperature, and an increase in oxygen consumption (Figure 1). The stability of the blood pressure, during a period of increased heart rate, is different from the response in man. Others working with the fowl at extreme temperatures have observed blood pressure to be fairly constant and not greatly related to heart rate response until critical body temperatures are attained (Frankel et al., 1962; Rodbard and Tolpin, 1947; and Weiss, 1960). Since in this treatment body temperatures decreased only slightly, the relatively small decrease in blood pressure seems to be consistent with other research. In the group shifted from 35°C. to 5°C, there was an increase in pulse rate, again only a slight change in blood pressure, a rapid drop in respiration rate, decrease in body temperature, and an initial increase followed by a decrease in oxygen consumption (Figure 2). Even though the decrease in temperature was greater in this treatment, heart rate and blood pressure changes were of about the same magnitude as seen in the 21°C. to 5°C. change. On the other hand, decrease in respiratory rate was greatly accentuated. This respiratory response upon exposure to cold appears to be controlled separately from response in body temperature. The decrease in respiratory rate occurred within seconds to minutes following

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chart by use of a bellows-type pneumograph which was connected to a volumetric pressure transducer. Body temperature was read directly from a rectal thermometer. The thermometer was inserted into the rectum to a depth of six centimeters and held in place at least two minutes prior to recording body temperature. An open system of measuring oxygen consumption was used. This system employed a metal box mounted on casters with dimensions of 27X24Xl9-inches with a single air inlet and exhaust, a ball gas flowmeter, and a positive-pressure air pump as component parts. The box accomodated two hens at a time and provided a glass front for observing the birds. Room air was drawn through a calcium chloride dessicant and pumped through the box at the rate of approximately 6.55 liters per minute. Forty-milliliter samples of intake and exhaust air were analyzed separately for oxygen content. A Fisher Model 25V gas partitioner and a Fisher 1-millivolt laboratory recorder were utilized to determine percent oxygen in the samples. Four birds were used in determining the consumption of oxygen at each temperature treatment. Oxygen consumption determination was taken just prior to shifting birds to a different environmental temperature. The empty box was then moved to the new environmental temperature and the air pump again placed in operation. When the box temperature became the same as that in the chamber to which it had been moved, the birds were placed in the box. Following a 45-minute period of equilibration, oxygen analyses were made every two hours for the first 12 hours of exposure followed by longer intervals throughout the remainder of the exposure period. Feed and water containers were mounted inside the oxygen box so

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PHYSIOLOGICAL RESPONSE TO TEMPERATURE PR

BP

RR P o l l * Ralr

450

170.

200 430

(btiuli/min)

(P«)

•

Blood P r r i i u i r (mm H „ )

(BP)

O

Rt-ipiiulory Ralr

(RR)

*


Q

Body T i - i i i | > c K i l u f f

(broatliy'min) (°C)

Oxyu*"Con>umplion(ml/min/100uB.W.)

ISO

(Oj)

190-

410

130180-

390.

1 10 170.

370^

?l)l

350-

70-

l.C-41

150-

50-

330140-

310

30-

i±A

o i

7

3

4

5

6

? i

i

rts—rt—fo—^-—\—}—J—i—i—i—>—h—h-

hours

dayi Exposure Time

I'K Uf' HU HT

1.00 7.48 4.4 J 0.20

6.36 0.20

7.96 «.04 2.60 0.18

8.11 5.21 1.61 0.16

5.74 6.65 2.86 0.21

4.00 5.55 4.62 0.18

11.69 6.50 5.00 0.22

FIG. 1. Effect on some physiological parameters of five Leghorn hens following an abrupt decrease in environmental temperature from 21°C. to 5°C. Standard errors are shown at selected exposure times.

transfer from high temperature to decreased temperature, whereas body temperature declined over a period of one to two hours. Again in the 35°C. to 5°C. group there appears to be a close relationship between body temperature and oxygen consumption. Upon exposure of the birds to 5°C. room temperature, body temperature decreased and oxygen consumption increased, however, after the first two hours, oxygen consumption decreased. During the period from two hours to 48 hours of exposure, oxygen consumption remained low. Body temperature of the birds began to increase after 12 hours of exposure. Between 48 and 72 hours after shifting the birds, both parameters had again increased to near the plateaued

level. During this period of low body temperature and low oxygen consumption, spasmic shivering was observed. Following the period of 72 hours of exposure, spasmic shivering decreased. From this evidence of increase in body temperature to plateaued level at 48 hours, increase in oxygen consumption to plateaued level at 72 hours, and decrease in cold shivering followed 72 hours, it appears that between 48 and 72 hours some degree of nonshivering thermogenesis may be occurring. In the group decreased from 35° C. to 21°C, the same relationships existed as in the other treatments but were of less magnitude (Figure 3). The greatest change was observed in respiratory rate which followed much the same pattern as did the

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160'

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P. C. HARRISON AND H. V. BIELLIER

(PR)

Poise Role (beots/min) Blood Pressure (mm Hg)

(BP)

Respiratory Rote (breaths/m

(RR)

Body Temperature (°C)

(BT)

Oxygen Consumption (ml/min/100 gB.W.) ( 0 2 )

.00 .37 4.98 0.13

4.96 0.20

5.10 0.16

3.95 0.22

3.07 0.07

FIG. 2. Effect on some physiological parameters of five Leghorn hens following an abrupt decrease in environmental temperature from 35°C. to 5°C. Standard errors are shown at selected exposure times.

decrease from 35°C. to 5°C. Body temperature decreased for the first four hours, then rose to a plateaued level within 12 hours of exposure. The slight change in oxygen consumption may have been somewhat affected by the rapid decrease in respiratory rate. The increase in pulse rate in these treatments may also be related to the decrease in respiratory rate. Covino and Heghauer (1955) have shown that the decrease in respiratory rate in hypothermic dogs was great enough to produce acidosis. Along with the acidosis, there were alterations in all phases of ECG recordings and ventricular arrythmia occurred. However, this relationship of respiratory rate decrease and heart rate increase was not apparent in the group transferred from 21°C. to 5°C. In the

other two treatments 35°C. to 5°C. and 35°C. to 21°C, there was a higher initial respiratory rate, and the decrease was more of a return to the normal level. Increase in Environmental Temperature. When birds were moved from 21°C. to 35°C. and from 5°C. to 35°C. environmental temperatures, the relationship of response in rate functions were similar. In these two temperature changes pulse (heart) rate and blood pressure decreased slowly, respiratory rate and body temperature increased, and oxygen consumption increased initially then decreased later in the exposure period (Figures 4 and 5). Ahmad et al. (1967) reported that body temperature increased as ambient temperature was increased from 21.0°C to

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1.0 - 4 1 . 0

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PHYSIOLOGICAL RESPONSE TO TEMPERATURE PR

RR

>P

450-

42. o

170200-

430-

150190-

410.

130-

Pulse Rate (beats/min)

(PR)

•

Blood Pressure (mm Hg)

(BP)

O

Respiratory Rate (breaths/min)

(RR)

A

Body Temperature (°C)

(»T)

a

Oxygen Consumption (ml/mir/100 gB.W.) ( O j )

•

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10

11

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1

2

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5 days

6

7

8

Exposure Time .

PR BP RR BT

9.25 10.26 1.95 0.11

11.32 11.43 1.84 0.10

17.02 15.07 2.10 0.08 Standard Error

17.01 12.23 1.96 0.08

10.44 11.94 2.65 0.06

6.23 10.68 3.90 0.04

FIG. 3 Effect on some physiological parameters of five Leghorn hens following an abrupt decrease in environmental temperature from 35°C. to 21°C. Standard errors are shown at selected exposure times.

29.4°C and 35.0°C. Oxygen consumption was significantly reduced at 35.0°C. for 13-month old S.C. White Leghorn hens but not for 15 and 18-month old birds. The decrease in pulse rate upon exposure to high temperature is somewhat different than the response in many species. The normal trend in mammals is for pulse rate to show an increase as environmental and body temperature begin to rise. However, Hutchinson and Sykes (1953) have shown heart rate in the fowl to be inverse to the increase in environmental temperature until a body temperature of 110°F. was attained. After attaining a 110°F. body temperature, a Qio type response was seen in heart rate, which caused an increase of 30 beats per minute for each degree rise in body tem-

perature. Since the highest mean body temperature in these trials was 43.11°C. (109.6°F.), only the inverse relationship would be expected. In the group that was transferred from 5°C. to 35°C, the decrease in blood pressure started to occur 14 to 18 hours after the lowest pulse rate was obtained. These results indicate that a change in vascular capacity affects blood pressure more than change in heart rate following an increase in temperature. Respiratory rate response was again shown to be inversely related to the response of pulse rate. Upon exposure to 35°C, both temperature changes showed an increase in level of respiratory rate and a decrease in pulse rate. This relationship may also reflect a cause and effect rela-

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370.

1040 BP

PR

P . C. H A R R I S O N AND H. V. RK 170-

450 200430 -

BIELLIER

150-

Pulse Rate (beots/min)

(PR)

Blood Pressure (mm Hg) Respiratory Rate (breaths/min)

(8P) o (RR) A

Body Temperature ( C)

(BT)

•

D

Oxygen Consumption (ml/min/100 gB.W.) (O2)

190410-

130180-

390-

110170-

370-

90-

350-

70150-

330.

50WO-

i

3oj

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>UL

5

6 hours

7 Exposure Time

BP RR BT

10.71 16.13 2.87 0.15

21.54 16.35 10.34 0.02

17.13 10.55 6.53 0.09

11.51 9.02 23.09 0.09

19.95 12.66 10.61 0.06

9.27 8.30 31.03 0.10

16.10 9.49 31.55 0.13

FIG. 4. Effect on some physiological parameters of five Leghorn hens following an abrupt increase in environmental temperature from 21°C. to 35°C. Standard errors are shown at selected exposure times.

tionship between the two parameters. A disruption of acid-base balance, due to birds panting, could have an effect on cardiac activity. A profound respiratory alkalosis was found to be induced by hyperthermic polypnea in m a t u r e Leghorn males (Linsley and Burger, 1964). Weakness of the egg shell resulting from hyperventilation has been demonstrated in the pigeon b y Calder and Schmidt-Nielsen (1966). Mueller (1966) reported t h a t a temperature increase from 13 to 34°C. induced a respiratory alkalosis in the laying hen sufficient to reduce the shell thickness by approximately 12 percent. An acid-base imbalance b y the increase in number eggs produced at the 35°C. ture. I t was of interest to

was indicated of thin shelled room temperadetermine if a

decrease in egg shell weight (specific gravity) 1 occurred soon enough after exposure to high temperature to be related to increased respiratory rate and decreased pulse rate. T o determine the effect of an increase or decrease in environmental temperature on egg specific gravity, five White Leghorn pullets which were in 80 to 90 percent production were placed in the 21°C. chamber. After a five-day period the pullets were subjected to an a b r u p t change in temperature from 21°C. to 35°C. for a period of 28 days and then returned to 21°C. A very rapid decrease in specific gravity of eggs was observed (Figure 6). Within the first day of exposure to 35°C. 1 Specific gravity values were obtained by immersing eggs in sodium chloride solutions of graded concentrations.

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160-

PHYSIOLOGICAL R E S P O N S E TO T E M P E R A T U R E

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19.9 8 7.44 24.04 0.11

15.59 7.89 14.93 0.07

17.14 7.49 36.70 0.10

10.08 3.94 12.40 0.22

4.16 7.47 11.96 0.11

Standard Error

FIG. 5. Effect on some physiological parameters of four Leghorn hens following an abrupt increase in environmental temperature from 5°C. to 35°C. Standard errors are shown at selected exposure times.

room temperature, specific gravity of the eggs decreased from 1.0750 to 1.0625 with no change in egg weight. This sudden change could be an indication t h a t soon after panting begins the birds develop a respiratory alkalosis and this is compensated for by a renal excretion of calcium bases (Mongin, 1968). T h e rapid change in specific gravity indicates rapid changes in calcium metabolism occurring soon after exposure of birds to high environmental temperatures. In both treatments in which birds were placed in the 35°C. room temperature, there was a close relationship between initial responses of respiratory rate and oxygen consumption to the increase in body temperature. I n the 21°C. to 35°C. treatment panting occurred between 41.94°C. and 42.72°C. body tem-

perature, and in the group increased from 5°C. to 35°C. panting began between 42.72°C. and 43.11°C. In both treatments panting started when body temperature had increased 1.22°C. above the initial level, and both began panting between 30 minutes and 2 hours of exposure. Periodic panting following the plateau in respiratory rate accounted for the variation of respiratory rate. Since these periods of panting occurred a t body temperatures lower t h a n those required to initiate the initial panting response, a possible decrease in threshold of panting is indicated. The increase in oxygen consumption attained its maximum at the four-hour measurement period following a shift from 21°C. to 35°C. and at the two-hour measurement period for those shifted from

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Exposure Time

2.45 2.24 4.93 0.15

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P. C. HARRISON AND H. V. BIELLIER

8

10

12

14

16

18

20

22

24

26

28

30

32

34

36

38

40

Experimental Time (days) FIG.

6. Effect of abrupt increase and decrease in environmental temperature on specific gravity of eggs from five Leghorn pullets.

5°C. to 35° C. This initial increase in oxygen consumption appears to be a Qio type response in metabolism caused by the increase in body temperature. In the 21°C. to 35°C. temperature change there was a 35.4 percent increase in oxygen consumption for each 1.0°C. rise in body temperature (calculated at the highest points of increase). In the 5°C. to 35°C. group there was a 41.4 percent increase in oxygen consumption for each 1.0°C. rise in body temperature. In the 5°C. to 21°C. temperature change the pattern and relationship of responses were less defined and of much less magnitude. In this treatment there was only a slight decrease in pulse rate, a slight decrease in respiratory rate, slight increase in body temperature, and oxygen

consumption remained relatively steady (Figure 7). The increase in blood pressure with a decrease in pulse rate again indicates that following a change in temperature the change in vascular system exerts a greater influence on blood pressure than heart rate. SUMMARY

White Leghorn hens were subjected to six different abrupt changes in environmental temperature in order to determine the effect of an abrupt decrease or increase in environmental temperature on physiological variations in rate function. Changes in temperature were: 21°C. to 5°C, 35°C. to 5°C, 35°C. to 21°C, 21°C. to 35°C, 5°C. to 35°C, and 5°C. to 21°C. Five physiological parameters were mea-

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6

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PHYSIOLOGICAL RESPONSE TO TEMPERATURE

Pulse Rale (beats/min) Blood Pressure (mm Hg)

(PR) • (HP) o

Respiratory Rate (breaths/min) Body Temperature (°C)

(RR) A (BT) •

Oxygen Consumption (ml/min/100 g8.W.) ( 0 2 )

6 Hours

7

10

1

fr^—I

i

i

I

I

i

7 i

» ill

days Exposure Time

20.35 4.80 4.36 0.06

22.30 9.04 4.36 0.05

24.41 7.40

15.68 5.05 3.88 0.0S

15.87 6.40 2.96 0.07

13.66 5.72 4.24 0.12

19.94 5.60 2.79 0.13

Standard Error

FIG. 7. Effect on some physiological parameters of four Leghorn hens following an abrupt increase in environmental temperature from 5°C. to 21°C. Standard errors are shown at selected exposure times.

sured over a period of ten days: pulse rate, blood pressure, respiratory rate, body temperature, and oxygen consumption. Following the abrupt increase or decrease in environmental temperature, there were alterations in functional rates of the physiological parameters. The general pattern of response was a rapid initial change in rate function, which was followed by a plateau in rate function. This plateau was generally at a different functional rate than at the previous temperature. Depending on the parameter and the type of change in temperature, there was generally an overshoot or undershoot of the plateaued or acclimated functional level. When the birds were transferred from 35°C. and 21°C. to 5°C. ambient temperatures there was a rapid increase in pulse

rate. Pulse rate showed the opposite response when the birds were transferred from 5°C. and 21°C. to 35°C. Blood pressure showed the most stable functional level during both increase and decrease in environmental temperature. A decrease in blood pressure was indicated at both high and low temperatures. Respiratory rate response was inversely related to pulse rate in birds exposed to a decrease or increase in room temperature. The plateaued level of respiratory rate at 35°C. was irregular due to periodic panting of the birds throughout the exposure time. Periodic panting at the 35°C. environment, at body temperatures lower than those which initiated panting, indicated a possible lowering of the panting threshold in birds acclimated to high temperature. However, the decrease in

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5

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P. C. HARRISON AND H. V. BIELLIER

REFERENCES Ahmad, M. M., R. E. Moreng and H. D. Muller, 1967. Breed responses in body temperature to elevated environmental temperature and ascorbic acid. Poultry Sci. 46: 6-15. Calder, W. A., and K. Schmidt-Nielsen, 1968. Panting and blood carbon dioxide in birds. Am. J. Physiol. 215:477-482. Calder, W. A., and K. Schmidt-Nielsen, 1966. Evaporative cooling and respiratory alkalosis in the pigeon. Proc. Natl. Acad. Sci. US 55: 750-756.

Covino, B. J., and A. H. Heghauer, 1955. Ventricular excitability during hypothermia and rewarming in the dog. Proc. Soc. Exp. Biol. 89: 659-662. Davis, T. R. A., 1963. Nonshivering thermogenesis. Federation Proc. 22 (No. 3, Part I): 777-782. Edholm, O. G., R. H. Fox, J. M. Adam and R. Goldsmith, 1963. Comparison of artificial and natural acclimatization. Federation Proc. 22 (No. 3, P a r t i ) : 709-715. Frankel, H., K. Holland and H. S. Weiss, 1962. Respiratory and circulatory responses of hyperthermic chickens. Arch. Intern. De Physiol. De Biochim. 70: 555-563. Hillerman, J. P., and W. O. Wilson, 1955. Acclimation of adult chickens to environmental temperature changes. Am. J. Physiol. 180: 591-595. Hutchinson, J. C. D., and A. H. Sykes, 1953. Physiological acclimatization of fowls to a hot humid environment. J. Agr. Sci. 43: 294-321. Lind, A. R., and D. E. Bass, 1963. Optimal exposure time for development of acclimatization to heat. Federation Proc. 22 (No. 3, Part I) 705708. Linsley, J. G., and R. E. Burger, 1964. Respiratory and cardiovascular responses in the hyperthermic domestic cock. Poultry Sci. 43: 291-305. Mongin, P., 1968. Role of acid-base balance in the physiology of egg shell formation. World's Poultry Sci. J. 24: 200-230. Mueller, W. J., 1966. Effect of rapid temperature changes on acid-base balance in shell quality Poultry Sci. 45: 1109. Prosser, C. L., 1964. Handbook of Physiology Section 4: Adaptation to the Environment (D. B. Dill, E. F. Adolph, C. G. Wilber, eds.) Waverly Press, Inc., Baltimore, Md. Randall, C. W., and W. A. Hiestand, 1939. Panting and temperature regulation in the chicken. Am. J. Physiol. 127:761-767. Rodbard, S., and M. Tolpin, 1947. A relationship between body temperature and blood pressure in the chicken. Am. J. Physiol. 151: 509-515. Slonim, A. D., 1963. Nervous mechanisms in cold acclimation. Federation Proc. 22 (No. 3, Part I) 732-733. Vogel, J. A., and P. D. Sturkie, 1963. Cardiovascular responses of the chicken to seasonal and induced temperature changes. Science, 140:1404-1406. Weiss, H. S., 1960. Cardiovascular reactions to immersion hypothermia with a note on prefeeding reserpine. Poultry Sci. 39: 1304. Weiss, H. S., R. K. Ringer and P. D. Sturkie, 1957. Development of the sex difference in blood pressure of the chick. Am. J. Physiol. 188:1404-1406. Weiss, H. S., and P. D. Sturkie, 1951. An indirect

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respiratory rate upon exposure to a decrease in environmental temperature appeared to be independent of decrease in body temperature. Change in body temperature best reflected the general response pattern when birds were subjected to either an increase or decrease of environmental temperature. Body temperature not only depicted the general pattern of response, but also the magnitude of response reflected the magnitude of change in environmental temperature. Oxygen consumption increased in those groups transferred to 5°C. from 21°C. and 35° C. ambient temperatures. When the birds were changed from 21°C. and 5°C. to 35°C. ambient temperatures, they showed an initial increase in oxygen consumption that was related to increase in body temperature and respiratory rate. The rapid decrease in the specific gravity of eggs from hens changed from 21°C. to 35°C. ambient temperature indicated an acid-base imbalance of the blood which may represent a "cause-effect" relationship between respiratory rate and pulse rate. Most all parameters approached a plateaued or acclimated functional level within 12 to 24 hours following exposure of the birds to either an increase or decrease in ambient temperature. In the group changed from 35°C. to 5°C, body temperature and oxygen consumption approached plateaued levels at 48 and 72 hours of exposure, respectively.

PHYSIOLOGICAL RESPONSE TO TEMPERATURE method for measuring blood pressure in the fowl. Poultry Sci. 30:587-592. Whittow, G. C , P. D. Sturkie and G. Stein, Jr.,

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1964. Cardiovascular changes associated with thermal polypnea in the chicken. Am. J. Physiol. 207: 1349-1353.

The Relative Value of Rapeseed and Soybean Oils in Chick Starter Diets R. E. SALMON

(Received for publication December 2, 1968)

T

HE beneficial effect of dietary fat in improving weight gains and feed efficiency of chickens and turkeys has been adequately demonstrated. Vermeersch and Vanschoubroek (1968) have reviewed the relevant literature since 1954. Though the benefits of dietary fat are recognized, there is conflicting evidence relating to the value of rapeseed oil (RSO) in poultry diets. Sell and Hodgson (1962) found that 4 or 8% RSO in a chick starter diet promoted growth and feed efficiency as effectively as similar levels of soybean oil (SBO), sunflower oil or tallow. Tsang et al. (1962) reported that oil from rapeseed screenings was as satisfactory as stabilized yellow grease in promoting growth of broiler chicks. Joshi and Sell (1964) showed that diets containing 5 or 10% RSO depressed growth and feed consumption of turkeys to 6 weeks as compared with a low-fat basal diet or with diets containing 5 or 10% SBO, sunflower oil, or animal tallow. Salmon (1969) found that 9% RSO depressed the early growth, feed conversion and dietary metabolizable energy (ME), of turkeys as compared to 9% SBO; mixtures of RSO with 1/3 or more SBO or with less than 1/3 beef tallow gave equal performance to 9% SBO. The literature reports cited here suggest that chicks and poults respond dif-

ferently to RSO in starter diets. This paper reports the results of two experiments with chicks using RSO from the same supply as that fed previously to turkeys and reported by Salmon (1969). Experiment 1. Day-old male chicks of a commercial meat strain were randomized into 20 compartments of an electrically heated battery brooder. At 18 days of age the birds were moved to unheated cages, where the room temperature was thermostatically controlled. The initial temperature of 30°C. was reduced by 3°C. at weekly intervals. Feed and water were available at all times. The experimental diets contained 24.4% crude protein by analysis (NX6.25), and varied only in the proportion of SBO and RSO, which totalled 10% of the diet in each case (Tables 1 and 2). Each diet was fed to 4 groups of 15 chicks. Body weights of individual chicks and feed consumption by groups were recorded on the 13th, 27th and 41st day. Dietary ME was determined during the second and sixth weeks of the experiment when samples of excreta were collected on three consecutive days during each assay period. The daily collections from each pen were pooled for each 3-day period and assayed for ME as described by Blakely and MacGregor

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Research Station, Research Branch, Canada Agriculture, Swift Current, Saskatchewan, Canada