Some Physiological Effects of High Environmental Temperatures on the Laying Hen

912

P. B. HAMILTON AND J. R. HARRIS

Wiseman, H. G., W. C. Jacobson and W. C. Harmeyer, 1967. Note on removal of pigments from chloroform extracts of aflatoxin cultures with copper carbonate. J. Assoc. Off. Agri. Chem. SO: 982-983.

Yacowitz, H., S. Wind, W. P. Jambor, N. P. Willett and J. F. Pagano, 1959. Use of mycostatin for the prevention of moniliasis (crop mycosis) in chicks and turkeys. Poultry Sci. 38: 653-660.

A. J. SMITH AND J. OLIVER Department of Agriculture, University of Rhodesia, P.O. Box MP. 167, Mount Pleasant, Salisbury, Rhodesia (Received for publication November 19, 1970)

HOMEOTHERMY conductance of the tissues, the body surIRDS are homeotherms and so are less face area and the degree of subcutaneous vulnerable to environmental temper- vasodilation. The second stage involves both ature changes than poikilotherms in respect the transfer of sensible heat from the skin of both functional efficiency and danger of surface, through the feathers and boundary tissue damage. The price that has to be layer of still air to the outside environment paid for the benefits conferred by homeo- by conduction, convection or radiation or thermy is that body temperature cannot be the loss of insensible heat, by evaporation allowed to fluctuate beyond relatively nar- from the skin and the lungs. row limits without deterioration in normal The mechanism of thermoregulation in functional efficiency. Within a limited, if ill poultry has not been fully elucidated. In defined, environmental temperature range, humans the thermoregulatory centre of the the laying hen is able to balance thermo- body, which is located in the hypothalagenesis and thermolysis so that its body mus, is comprised of two anatomically distemperature remains at the optimum for tinct subcentres, one of which is responsinormal body functions. ble for heat conservation (e.g. by cutaneComplete uniformity of body tempera- ous vaso-constriction and shivering) while ture is possible only if no heat exchange oc- the other is concerned with heat dissipation curs between the body and its environment. (e.g. by vaso-dilation and sweating) (LeitBirds, however, constantly produce heat head and Lind, 1964). Leithhead and Lind and lose it to the environment so that there suggest that the hypothalamus responds diis a thermal gradient from the warm inte- rectly to local brain temperature changes rior (core) to the cooler surface (shell). induced by variations in the temperature of Sensible heat constantly flows from the the blood supplying the brain, as well as to deep body centre to the outside in two indirect afferent impulses from thermorestages, from the core to the surface of the ceptors. This suggestion was confirmed by body and from the skin surface to the am- Bligh (1966) who reviewed the literature bient air. The rate of flow in the first stage dealing with thermoregulation in mammals. is dependent upon the temperature gradient He concluded that the thermosensitivity of between the deep centre and the skin, the well defined areas, within the hypothalmic

B

Downloaded from http://ps.oxfordjournals.org/ at Ernst Mayr Library of the Museum Comp Zoology, Harvard University on June 10, 2014

Some Physiological Effects of High Environmental Temperatures on the Laying Hen

HIGH ENVIRONMENTAL TEMPERATURES

The average body temperature of the adult fowl is probably 41.9°C. (King and Farner, 1961) but Heywang (1938) noted that the range of body temperatures of individual non-broody hens ranged from 39.8°C. to 43.6°C. Payne (1966a) suggested that body temperature of hens is not constant even within the zone of thermoneutrality but varies continuously as the environmental temperature is changed. The amount of the variation in body temperature of individuals is small, probably not more than ± 0.5°C. (Lincoln, 1964). Several factors influence body temperature of the laying hen; breed, egg production (Heywang, 1938), activity (Hutchinson, 1954), feed intake and plane of nutrition (Robinson and Lee, 1947), environmental temperature (Heywang, 1938; and Wilson, 1948) and the natural diurnal rhythm of the body (Heywang, 1938; and Wilson, 1948). Diurnal fluctuations in body temperature cannot be entirely explained in terms of variations in body activity or environmental temperature (Wilson, 1948). In an environment with natural diurnal fluctuation in environmental tem-

perature, Heywang (1938) found that body temperatures were highest at four in the afternoon and lowest at midnight. Body temperatures were highest during the hottest part of the day but not lowest during the coolest part of the night. This rhythm is normally independent of the diurnal rhythm of environmental temperature (Hutchinson, 1954). The increase in body temperature from the active period to the inactive period is about 1°C. in hens (Hutchinson, 1954). The amplitude of this rhythm can be reduced by injecting thiouracil, which indicates that the activity of the thyroid is involved (Siegel, 1968). A similar rhythm seems to occur in all birds, except that in nocturnal species the period of highest body temperature occurs at night (Sturkie, 1965). The factor which is most likely to alter body temperature of laying hens is change in environmental temperature, particularly if it is increased above 32°C. (Wilson, 1948). Thus although the hen is a homeotherm its body temperature can fluctuate within a limited range without it suffering any harmful effects. The physical and chemical means by which the laying hen maintains a relatively constant body temperature will now be discussed. THERMOGENESIS AND THERMOLYSIS IN BIRDS

a) Introduction. Birds normally have higher body temperatures than mammals, which makes them comparatively less prone to heat stress (Dawson and SchmidtNielson, 1964). The upper lethal body temperature is 47.3°C. (Moreng and Shaffner, 1951) and the lower is 23.4°C. (Sturkie, 1946; and Moreng and Shaffner, 1951). The environmental temperature range within which the laying hen can maintain its body temperature within the lethal lim-

Downloaded from http://ps.oxfordjournals.org/ at Ernst Mayr Library of the Museum Comp Zoology, Harvard University on June 10, 2014

structure, require local temperature changes of only 0.2°C. to 0.5°C. to produce a thermoregulatory response. He stated "While there is still no direct evidence that changes in hypothalmic temperature intervene in normal temperature regulation, it is now evident that the thermosensitivity of structures is sufficiently fine to presume that they do." The central control system may predominate in birds. King and Farner (1964) produced evidence to show that panting in birds is stimulated by elevation of temperature of the panting centre in the anteriodorsal wall of the midbrain and not by stimulation of peripheral receptors. However Siegel (1968) states that the entire panting response can be abolished by bilateral vagotomy in chickens.

913

914

A. J. SMITH AND J. OLIVER

SUMMIT METABOLISM s^~~^f^J '

s<

OS

OLO. u_ u j

«

>•

N.

\

lE SO

N. \ EXTRA\ HEAT \ NECESSARY \ TO KEEP \ BODY WARM N.

*'

DEATH FROM HYPERTHERMIA 1

^CRITICAL \VEMP.

~z_

—,r-

MOSTLY CHEMICAL REGULATION

o \~ "3

o a.

<

J—

MINIMAL HEAT PRODUCTION

\

TEMPERATURE /VAN'THOFF OF HYPERTHERMAL/ EFFECT RISE

t

\

EXCESS HEAT \ (GIVEN OFF BY MOSTLY \ EVAPORATION PHYSICAL V OF WATER). REGULATION X 1

N

ZONE OF THERMO NEUTRALITY

< <

•CO

l \

UJ

X

\

\

INCREASING BODY TEMPERATURE

\ N

CD

\ t

INCREASING ENVIRONMENTAL TEMPERATURE

BODY TEMP

FIG. 1. Basal heat production by adult birds as affected by changes in environmental temperature.

its is comparatively wide. The upper lethal environmental temperature is in the region of 40.5°C. for White Leghorns. Above this temperature heat production exceeds heat loss so that body temperature eventually rises uncontrollably (Lee et al., 1945; and Wilson, 1948). However, hens can withstand short periods of exposure to higher environmental temperatures. For example Squibb (1959) noted that hens could withstand temperature of 44°C. for one hour. The lower lethal ambient temperature has not been denned precisely, nor is a precise definition possible; however laying hens maintained homeothermy for 3.3 to 29.5 hours at an environmental temperature of - 3 4 ° C . to - 3 7 ° C . (Sturkie, 1946; and Horvath ei aZ., 1948). According to conventional concepts there is a narrow range of temperatures within which basal heat production by the bird is minimal and body temperature is controlled by variations in heat loss (physical temperature regulation) (Romijn and

Lokhorst, 1966). (Fig. 1). This range, which lies between what are called the upper and lower critical temperatures, is known as the zone of thermoneutrality. The lower critical temperature of the adult hen is within the range 16.5°C. to 20°C. (Dukes, 1947; Romijn and Lokhorst, 1966; King and Farner, 1964). The upper critical temperature has not been precisely defined as yet. Various temperatures have been suggested, i.e. 26°C. (King and Farner, 1964), 27.5°C. (Dukes, 1947; and Wilson, 1948) and 34°C. (Romijn and Lokhorst, 1966). The zone of thermoneutrality may be much narrower than is indicated above and under a given set of circumstances there may only be one environmental temperature at which pullets expend the least amount of energy in maintaining body temperature. Such a concept was suggested by Barott and Pringle (1946). These workers found that this temperature was 35°C. for chicks of up to two weeks of age and de-

Downloaded from http://ps.oxfordjournals.org/ at Ernst Mayr Library of the Museum Comp Zoology, Harvard University on June 10, 2014

DECREASING BODY TEMPERATURE

HIGH ENVIRONMENTAL TEMPERATURES

lethal temperature (King and Farner, 1961). At temperatures above the upper critical temperature body temperature increases. Wilson (1948) found that rectal temperature increased at environmental temperatures above 26.5°C. although the increases were small until the environmental temperature was 32.3°C. Lee et al. (1945) noted that up to an environmental temperature of 29.5°C. rectal temperature was unaffected but that an environmental temperature of 32.3°C. increased body temperature by 0.20°C. to 0.83°C. The exact temperature at which body temperature rises above normal depends on the relative humidity of the atmosphere and the degree of acclimatization of the bird. b) Thermo genesis. Heat produced by the laying fowl accrues as a result of basal metabolism, feeding (or digestion), egg production and activity (Fig. 2). Basal metabolic rate was defined by Kleiber (1965) as the rate of heat production (of animals) in a postabsorptive condition, in a comfortable microclimate and at rest. With birds as with other farm animals, a state of complete relaxation can rarely be achieved. Although fasting may limit activity even the small activity represented by standing as opposed to lying is sufficient to increase heat production by about 12 percent (McDonald et al., 1966). Consequently, the term fasting metabolism is probably preferable for use with farm animals, although many workers use the terms basal or standard metabolic rate. Thus, although the term basal metabolism is used in this review the figures quoted probably do not reflect the true basal metabolism of birds. Basal heat production is not related directly to body weight nor to the surface area of the body (W0-87). Results obtained from homeotherms ranging from mice to cattle indicate that basal metabolic rate per unit of surface area increases as weight

Downloaded from http://ps.oxfordjournals.org/ at Ernst Mayr Library of the Museum Comp Zoology, Harvard University on June 10, 2014

creased to 21° for one year old Rhode Island Red pullets. However, they, like other research workers, failed to allow their birds sufficient time to adapt to their experimental temperatures (Shannon and Brown, 1969) and consequently underestimated the temperature at which minimum basal metabolic rate took place. When a two to three week adaptation period was allowed Waring and Brown (1967) found that fasting metabolic rate of White Leghorn hens decreased until ambient temperature reached 29°C, the highest temperature used in their experiment. This result is confirmed by the work of Spencer Davis and Tribe (1969) which showed that the basal metabolic rates of the homeotherms they tested were never temperature independent. Thus it has not been established whether or not a true thermal neutral zone exists, or whether as now seems more likely, there is a range of temperatures within which rate of change of basal metabolic rate with change of environmental temperature occurs more slowly than at more extreme temperatures. What is known is that outside a certain range of temperatures, delimited by 'critical' temperatures, the adult chicken exhibits certain distinct characteristics. Below the lower critical temperature the laying hen becomes more active and consumes more feed than she does at temperatures within the thermal-neutral zone (i.e. chemical control of body temperature, Freeman, 1966). As environmental temperature falls, body heat production rises until it reaches a maximum (summit metabolism) (Fig. 1). If environmental temperature falls further, heat loss can no longer be balanced by heat production, body temperature decreases and metabolic intensity declines in accordance with the van t' Hoff relationship. Death due to hypothemia will eventually result at the lower

91S

916

A. J. SMITH AND J. OLIVER

THERMOGENESIS

THERMOLYSIS /INFLUENCED

BY *.

BODY 'HEAT PRODUCTION

\

NORMAL BODY

COVERING,

COLOUR

CONVECTION IN PERFORMANCE OF

AREA

AND

SENSIBLE HEAT '

/

EMISSIVITY

PROCESSES/ /CONDUCTION

HEAT

RESERVES OR FOOD^

UNG

I SOLAR RADIATION

FROM BODY INCREASED ME1ABCMSM DUE TO EGG PRODUCTION

\

A N D

H£AT

FRQM

SURROUNDINGS

^EVAPORATION

INSENSIBLE

HEAy/

INFLUENCED BY SURROUNDINGS

ic.

HEAT PRODUCED DUE \TO

MOISTURE

VAPORATION

)

THERMAL

CONDUCTION

AIR

TEMPERATURE

OF TISSUE

AND

AIR

HUMIDITY

PERIFERAL

BU0O0

ACTIVITY AIR MOVEMENT

V

FLOW.

A f t e r F i n d l a y (1950)

FIG. 2. Sources of heat production and heat loss in the laying fowl (adapted from Findlay, 1950).

increases (Kleiber, 1961). Kleiber recommends that the three-fourths power of body weight (W0-75) be used as representative of metabolic body weight. Under standard conditions the basal metabolic rate of adult homeotherms from mice to cattle is 70 kcal./kg.°-75/day on average. Romijn and Lokhorst (1966) working with hens found that this formula fitted their data very well. Berman and Snapir (1965) also found that metabolic rate was highly correlated with W0-75. There would seem to be however some discrepancy between Kleiber's predictions and the actual basal metabolic heat production of hens. The predicted basal metabolic rate of hens weighing 1.6 to 2.0 kg. using Kleiber's formula is 62.0 to 58.8 kcal. /kg ./day but experimental results show that basal heat production can vary considerably from these predicted figures. The basal heat output of medium heavy (approx. 2.0 kg.) laying hens maintained at 22°C. to 24°C. that had been fasted for a

day was 72.7 kcal./kg./day (Waring and Brown, 1965). The comparable figure for non-laying hens was 60.6 kcal./kg./day. They indicate that laying hens have a higher basal metabolic rate than the nonlayers because the above differences could not be explained in terms of increased physical activity by laying hens. There would also appear to be a difference in basal metabolic rate between breeds. White Leghorns (approx. 1.6 kg.) in lay kept at 22°C. were found to have a basal metabolic rate of 94.2 kcal./kg./day (Waring and Brown, 1967). Feeding a maintenance diet to White Leghorn hens increased their heat output by 4.9 kcal./kg./day and feeding an ad libitum diet by 30.8 kcal./kg./day above basal metabolic rate (Waring and Brown, 1967). This latter figure agrees fairly closely with that of Benedict et al. (1932) also obtained with ad libitum feeding, namely 39.8 kcal./kg./day. It is not possible to apportion heat pro-

Downloaded from http://ps.oxfordjournals.org/ at Ernst Mayr Library of the Museum Comp Zoology, Harvard University on June 10, 2014

| BODY SURFACE

HIGH ENVIRONMENTAL TEMPERATURES

tion of metabolisable energy. Consequently it is not possible at out present stage of knowledge to predict precisely the heat output of all types of laying hen under all management conditions, although a reasonable estimate can be made from existing data. c) Thermolysis. As the laying hen has no sweat glands and is normally covered with feathers, at high environmental temperatures it must rely mainly on its respiratory system for thermolysis. Heat is lost from the body both as sensible heat (heat that raises the temperature of the surroundings) and insensible heat (which does not) (Fig. 2). As environmental temperature increases heat loss in the insensible form becomes progressively more important (Ota et al., 1953), although vasodilation causes an increase in heat loss from unfeathered extremities at high environmental temperatures (Siegel, 1968). Longhouse et al. (1960) found that pullets kept at 32.3° C, lost 60 percent of their body heat by evaporation. The actual proportion of heat lost by this means also depends on the humidity of the air. Romijn and Lokhorst (1966) noted that at 34°C. hens lost 80 percent of their total heat loss in the insensible form when the R.H. was 40 percent, but only 39 percent when the R.H. was 90 percent. Total heat loss from the laying hen due to respiration is relatively constant below 26.7°C. ambient. Between 26.7°C. and 32°C. it increases rapidly. Above 32°C. the rate of increase declines, indicating a breakdown in the body temperature control mechanism (Barott and Pringle, 1941). At an environmental temperature of 40°C. or higher, heat lost by evaporation is generally much less than total heat production in wild birds (Dawson and Schmidt-Nielsen, 1964). Since heat loss by transfer is reduced or eliminated at these temperatures, heat is stored in the body and body tem-

Downloaded from http://ps.oxfordjournals.org/ at Ernst Mayr Library of the Museum Comp Zoology, Harvard University on June 10, 2014

duction accurately to the various aspects of laying hen activity. For example some of the extra heat production associated with ad libitum feeding could possibly be due to increased egg production or additional movement or both. Although increments due to movement, 29 kcal./kg./day (Deighton and Hutchinson, 1940), and to egg production, 7 kcal./kg./day (Mitchell and Kelly, 1933) for hens producing one egg every two days, have been calculated, these must be treated with caution because they are probably unreliable. From the above data heat production of hens kept at an environmental temperature of 22°C. to 24°C. varies from 60 to 125 kcal./kg./day. The amount of heat produced depends on breed, body size, productivity and feed intake. Breed differences apparently exist in metabolic heat production at different environmental temperatures. Romijn and Lokhorst (1966) found that North Holland Blue (a heavy breed) had a constant heat output in the thermal-neutral zone (20°C. to 34°C), but the heat production of White Leghorns fed on a maintenance ration decreased from 99.2 to 89.2 kcal./kg./ day when the environmental temperature was raised from 22°C. to 29°C. (Waring and Brown, 1967). However, it is possible that the North Holland Blue chickens were given insufficient time to adapt to the various environmental temperatures used in the experiment. Other factors can confuse the issue still further. For example amino acid inadequacies (in particular methionine) in the diet have been shown to lead to increased heat production by chicks due to their ability to use metabolizable energy for productive purposes being impaired (Baldini, 1961; and Shoji et al., 1966). The latter workers noted that correcting a methionine deficiency in a chick diet reduced heat production and increased the efficiency of utilisa-

917

918

A. J. SMITH AND J. OLIVER

Panting itself generates heat. Dawson (1958) estimated that the cardinal (Richmondea cardinalis) at an environmental temperature of 40°C. produced one cal./ h./g. body weight for each 2.5 cal./h./g. dissipated. The amount of heat lost by panting is related to the amount of water in the expired air. The rate of water loss from the body of the chicken is fairly constant at temperatures below 23.9°C. (Barott and Pringle, 1941). These workers showed that at temperatures higher than 23.9°C. the rate of water elimination begins to increase slowly at first and then more rapidly above 26.7° C. Above 32.3°C. there is only a slight increase and above 35°C. virtually none, indicating that the hen is reaching the limit of her ability to lose heat. However, their results are contradicted by Lee et al. (1945) who found that the rate of increase in water elimination was small up to 32.3° C. and increased thereafter especially above 37.8°C. The results of Lee et al. (1945) agree closely with those obtained by Dawson (1958) working with the cardinal (Richmondea cardinalis). The amount of the increase of water loss by hens can be from 5 g. per hour at normal temperatures up to 30 g. per hour when the bird is panting (Lee et al., 1945). Water intake by the bird is also affected by environmental temperature. The amount of water consumed is lowest in the range 10°C. to 15.6°C. (Ota et al., 1953). Below this range feed intake increases and extra water is needed to assist the passage of the feed through the intestine. Above this range feed intake declines but water intake increases because more is needed for evaporative cooling. When environmental temperature is increased water intake by hens increases. The amount of water consumed per day is more on days immediately after the temperature rise than it is a few days later. For exam-

Downloaded from http://ps.oxfordjournals.org/ at Ernst Mayr Library of the Museum Comp Zoology, Harvard University on June 10, 2014

perature increases from by two to four centigrade degrees. Within limits, storing of heat in this way improves the position of birds with regard to heat exchange with the environment especially by curtailing the amount of water expended in temperature regulation. Under natural conditions this stored heat would probably be dissipated passively by heat transfer when ambient temperature is lowered (Dawson and Bartholomew, 1968). The increase in heat loss by birds at high environmental temperatures is associated with an increased rate of respiration. Panting is initiated by the increase in temperature of blood flowing to the brain (Randall, 1943). Panting beings when body temperature rises by 0.1°C. to 0.4°C. above normal (Randall and Hiestand, 1939). Environmental temperatures of 26.6°C. and above cause body temperature to increase and therefore panting is normally initiated at this temperature (Wilson, 1948). Lee et al. (194S) observed that respiratory rate rose in fairly close relationship with rectal temperature. However, although the laying hen is able to increase its respiration rate up to 25 times normal in hyperthermia, the respiration effort is only increased fourfold, indicating that breathing in polypnoea is shallow (Hutchinson, 1954). Despite this reduction in tidal volume and the presence of the largely non vascular abdominal air sacs there is a loss of carbon dioxide in the blood and considerable alkalosis. This indicates that there is an increased passage of air through the gaseous exchange areas of the lungs (Calder and Schmidt-Nielsen, 1966). Respiratory rate reaches a maximum of 140 to 170 respirations per minute at a body temperature of 44° C. in the chicken (Siegel, 1968). When body temperature exceeds this maximum, respiration rate begins to decline and tidal volume again decreases.

HIGH ENVIRONMENTAL TEMPERATURES

that wetting the heads of hens reduced body temperature by about 0.11°C. However, the combs and wattles seem to play little direct part in thermolysis since varnishing them makes no difference to the hens reaction to high ambient temperature (Leeetal., 1945). Under conditions of high temperature stress the laying hen seems to depend mainly on the respiratory processes as a means of losing body heat. Furthermore most of the loss above 32.3°C. is by vaporization of water from the respiratory passages (insensible heat loss). Some disagreement between workers exists about the laying hen's ability to expel water vapour at high environmental temperatures. This might be connected with differences in relative humidity of the atmosphere and the duration of exposure to temperature stress when the measurements were made. FACTORS AFFECTING THE TOLERANCE OF LAYING BIRDS TO HIGH ENVIRONMENTAL TEMPERATURES

a) Limits of heat tolerance. In temperate climates there is a danger that hens will die of heat stroke if suddenly exposed to high environmental temperatures for prolonged periods of time (Hutt, 1938; Fox, 1951). Fox (1951) estimated that 100,000 birds died in New England during a heat wave which lasted four days. The highest environmental temperature recorded was 37.8°C. and the average relative humidity was 70 percent. On the other hand in Izatnagar, India, where maximum temperatures of over 43.3°C. are frequently recorded and where many fowls of European breeds are kept along with indigenous birds, heat stroke is not a serious cause of loss to poultry keepers (Iyer, 1952). Experimental results indicate that induced temperature acclimatization is not sufficient to account for the difference in heat tolerance between the American and

Downloaded from http://ps.oxfordjournals.org/ at Ernst Mayr Library of the Museum Comp Zoology, Harvard University on June 10, 2014

pie, the rate of water consumption was doubled immediately after environmental temperature was increased from 21.2°C. to 37.8°C. (Wilson, 1949). However, when water consumption was measured for one week after this rise in temperature it was only 35 percent greater at 37.8°C. than at 21.2°C. A high initial increase in the intake of water also took place when the ambient temperature was raised from 21.2°C. to 26.6°C. and from 26.6°C. to 32.3°C. respectively (Wilson, 1949). The actual quantity of water consumed is dependent, however, on many factors, i.e. body weight, physical activity, rate of egg production as well as environmental temperature (Longhouse et al., 1960). These workers found that laying hens consumed 1.5 to 1.7 times as much water as feed in the environmental temperature range 6.7°C. to 4.5°C. and about five times as much water as feed at 37.8°C. Similarly Wilson (1949) found that the ratio by weight of water to feed consumed was 2.6:1 at 21.2°C, 3:1 at 26.6°C, 4.1:1 at 32.2°C. and 8.3:1 at 37.8°C. The above observations were confirmed indirectly by Wilson et al. (1957) who noted that the ratio of wet manure voided to feed consumed was about 1.3:1 for hens kept at 18.4°C. and 2.6:1 for hens kept at 35°C. Hillerman and Wilson (1955) showed that birds that consumed the most water, withstood the highest temperatures, while Fox (1951) observed that survival time of fowls at high environmental temperature (42°C.) was positively correlated with the persistency with which birds continued to drink. This effect according to Fox was due in part to the cool water in the alimentary tract cooling the bird by conduction of heat from the tissues. He also postulated that hens given free access to drinking water, splash it over their heads and are cooled by evaporation. This theory is supported by the fact that Wilson et al. (1952) showed

919

920

A. J. SMITH AND J. OLIVER

C. could be attained for a few minutes without having any permanent ill effect on the hen. The lethal body temperature of both young and adult fowls is 47.3°C. (Moreng and Shaffner, 1951). b) Acclimatization to high environmental temperatures. Acclimatization, the complex of processes which adapt a bird to the environment in which it has to live, has been shown by Gelineo (1964) to alter the magnitude of heat output and the position of both the lower critical temperature and the temperature of hyperthermal rise in many species of birds. Thus, if laying birds are maintained at different temperatures for long periods, acclimatization alters both the magnitude of their heat output and the temperature at which hyperthermal rise begins. Hutchinson and Sykes (1953) demonstrated that the fowl can tolerate heat stress more readily after a series of short exposures to high temperature or after continuous residence in a warm climate. These workers were able to increase the tolerance to high temperature by exposing birds for twenty-four successive days to short periods (up to 4 h.) at 37.2°C. After acclimatization, residence by birds at an air temperature of 40°C. was equivalent to 37.2°C. in the unacclimatized state in day-time tests. At night the figure for the acclimatized birds was 39.2°C. The acclimatization observed was not due to loss of condition, change in body weight, egg yield, feather cover or permanent endogenous secular changes in the birds. Evaporative loss was reduced on acclimatization and although respiratory rate was not significantly affected, polypnoea appeared less laboured and shallower. It may be that the process of acclimatization is mainly associated with low basal metabolic rate at high ambient temperatures. The fasting metabolism of White Leghorn hens was reduced by 15 percent

Downloaded from http://ps.oxfordjournals.org/ at Ernst Mayr Library of the Museum Comp Zoology, Harvard University on June 10, 2014

Indian fowls (Hutchinson and Sykes, 1953). Hutchinson (1954) suggested that the microclimates experienced by fowls in hot countries are more favourable than local meteorological station information indicates. Diurnal variation in temperature may also be an important factor influencing the survival ability of the Indian hens. Squibb (1959) has shown how important this factor is in Guatemala. However, neither Iyer nor Fox give sufficient information about their local meteorological conditions for the validity of this hypothesis to be tested. The maximum constant environmental temperature that a laying hen can withstand is affected by the humidity of the atmosphere. Although below 29.5°C. relative humidity has little effect on the rectal temperature of hens, above this temperature the effect is considerable (Yeates et al., 1941). At an environmental temperature of 40.6°C. with a relative humidity of 75 percent, body temperatures of laying hens was 47.8°C. as compared to 40°C. at 55 percent relative humidity (Yeates et al., 1941). Working with unacclimatized White Leghorns, Wilson (1948) found that even at comparatively low relative humidities (50 percent) that some birds died within six hours if exposed to an air temperature of 40.6°C. A similar result was obtained by Lee et al. (1945) who in addition found that Leghorns and Australorps could only withstand an environmental ambient temperature of 43.4°C. for one to two hours. Hens are able to withstand quite large increases in body temperature, but when the rectal temperature reaches 45°C. they are in danger of succumbing to heat stroke (Lee et al, 1945; Wilson, 1948; and Hutchinson and Sykes, 1953). Higher rectal temperatures than this can be tolerated for short periods. Hutchinson and Sykes showed that a rectal temperature of 46.1°

H I G H ENVIRONMENTAL

921

hour with a night-time minimum of 24°C. without egg production being affected. The average daily temperature was 27.1°C. There were, however, signs of thermal stress (rapid respiration and spreading of the wings) during the period of highest temperature. Under these conditions, egg production, feed consumption, mortality and body weight were not significantly affected when compared with hens kept at more moderate temperatures (17.5-18.7° C). Squibb and Wogan (1960) suggest that several characteristics of the changing temperature pattern (absolute maximum, duration of peak temperature, rate of change and the pattern of diurnal variation preceding the period of change) are important factors governing the effects of high temperatures on laying fowls. Squibb explained the tolerance of his experimental birds to high temperatures in terms of the ameliorating effect of wide diurnal temperature and humidity fluctuation. Recent work indicates that diurnal fluctuations within moderate limits may be beneficial and actually stimulate hen productivity. The optimum temperature range should include a minimum temperature of no more than 15°C. (Payne, 1966b; and Peterson et al., 1960). Where minimum temperature was 24°C. hens produced up to seven percent more eggs than where the minimum temperature was 10°C. The data of Mueller (1961), Payne (1964) and Payne (1966c) indicate that hens are highly productive when kept in an environment in which the diurnal temperature fluctuates between 15°C. and 20°C. to 30°C. Diurnal temperature fluctuations similar to those in Payne's experiments appear to encourage hens to produce a larger total egg mass than most constant temperature regimes. The difference is normally due to an increase in egg numbers but is occasion-

Downloaded from http://ps.oxfordjournals.org/ at Ernst Mayr Library of the Museum Comp Zoology, Harvard University on June 10, 2014

when constant temperature was increased from 22°C. to 28°C. (Shannon and Brown, 1969). Similarly, Hoffman and Shaffner (1950) observed that the basal metabolic rate of 11-week old chicks, reared at high temperatures (26.5°C.) from seven weeks of age, was less than that of chicks reared at more moderate (7.2°C.) temperatures. This change was associated with changes in size of the thyroid gland and rate of thyroid secretion. Also, Wallgren (1954) noted that three weeks after the environmental temperature was increased from 22.5°C. to 32.5°C. the basal metabolic rate of Emberiza hortulana had decreased by 18 percent. However, its basal metabolic rate was not lowered when exposed to alternate periods of 16 hours at 32.5°C. followed by 8 hours at 10°C. to 14°C. (Wallgren, 1954). In view of the findings of Hutchinson and Sykes referred to above (namely that fowls can be acclimatized by short exposure to high temperatures), this may indicate that acclimatization is not caused by changed basal metabolic rate alone. From the evidence available it is not clear precisely what mechanisms are involved when hens become acclimatized to high environmental temperatures. However, whatever changes are induced in the hen by acclimatization they are effective for a much longer period than the actual period of initial exposure to heat stress (Payne, 1966c). c) Diurnal temperature variation. Sharp increases in temperature following days of more moderate conditions can result in hens dying from heat stress (Hutt, 1938; Fox, 1951; and Squibb and Wogan, 1960). Conversely, diurnal temperature fluctuations can enable laying hens to withstand day-time heat stress (Squibb, 1959; and Squibb et al., 1959). Squibb working in Guatemala observed that hens (New Hampshires) could withstand environmental temperatures of up to 44° C. for one

TEMPERATURES

922

A. J. SMITH AND J. OLIVER

Hampshires laid significantly fewer eggs at 32.4°C. There was no significant correlation between body temperature and egg production for White Leghorns, but for the other two breeds there were highly significant negative correlations. Each 0.055°C. rise in body temperature of White Plymouth Rocks was associated with a decrease of 2.78 eggs per hen per month. Susceptibility to heat stress also increases with age (Hutt, 1938; Rollo et al., 1963; and Ota and McNally, 1963). The latter workers found that within an environmental temperature range of 32.3°C. to 35°C. and 75 percent relative humidity, although pullets produced small eggs and lost 25 percent of their original body weight, they continued to lay eggs at near normal rates. Under similar conditions hens in their second egg laying year tended to stop laying and then moult. Strain differences in heat tolerance also appear to exist within the White Leghorn breed. Family differences in survival time at 40.8°C. were observed by Wilson et al. (1966). Thus, the White Leghorn breed appears to be the most heat tolerant of the present commercial breeds, although it is less tolerant than the Red Jungle Fowl (Hillerman and Wilson, 1955). However the reasons for its superiority are imperfectly understood. CONCLUSION Homeothermy in the laying hen is controlled by regions of the hypothalamus which are probably stimulated both by peripheral receptors and by blood temperature. As with other non sweating homeotherms the laying hens main short-term defence against hyperthermia is increased thermolysis (mainly by the loss of moisture from lungs). But over an extended period heat production can be reduced both by decreased feed intake and a lowering of basal

Downloaded from http://ps.oxfordjournals.org/ at Ernst Mayr Library of the Museum Comp Zoology, Harvard University on June 10, 2014

ally due to an increase in egg size. Egg weight, when compared to eggs from hens on other treatments, was relatively larger when temperature was increased during the hours of darkness (Payne, 1966c), or when it was decreased in the last three hours of daylight. (Payne, 1966b). d) Genetic difference between breeds and individuals. White Leghorns are more heat tolerant than other commercial breeds (Hutt, 1938; Fox, 1951; Huston et al., 1957; and Ahmad et al., 1967). Hutt (1938), for example, showed that deaths from heat prostration, when environmental temperature of 38°C. to 40°C. were recorded on three successive days, were three times as numerous in Rhode Island Reds and White Plymouth Rocks as in White Leghorns. Heat tolerance may be negatively associated with body weight. Berman and Snapir (1965) noted that at high environmental temperatures (29°C. to 31°C.) both the fasting and resting metabolic rates per unit of metabolic body size were lower for White Leghorns than for White Plymouth Rocks. Conversely, under ad libitum feeding Huston et al. (1962) and Ota and McNally (1961) found that White Leghorns have higher metabolic rates than Plymouth Rocks, New Hampshires X Cornish respectively. This apparent contradiction can perhaps be explained in terms of the voracious appetite of White Leghorns per unit of body weight compared with other breeds (Waring and Brown, 1967). Berman and Snapir (1965), suggested that White Leghorns may be able to tolerate larger increases in body temperature than other breeds without this affecting their metabolic rate adversely. The study of Huston et al. (1957) in which birds were acclimatized to 32.4°C, showed that White Leghorns laid as well at 32.3°C. as they did within the range 5.9°C. to 16.0°C. but White Plymouth Rocks and New

H I G H ENVIRONMENTAL TEMPERATURES

REFERENCES Ahmad, N. M., R. E. Moreng and H. D. MuUer, 1967. Breed responses in body temperature to elevated environmental temperature and ascorbic acid. Poultry Sci. 46: 6-15. Baldini, J. T., 1961. The effect of dietary deficiency on the energy metabolism of the chick. Poultry Sci. 40: 1177-1183. Barrott, H. G., and E. M. Pringle, 1941. Energy and gaseous metabolism of the hen affected by temperature. J. Nutr. 22: 273-286. Barrott, H. G., and E. M. Pringle, 1946. Energy and gaseous metabolism of the chicken from hatch to maturity as affected by temperature. J. Nutr. 3 1 : 35-50. Benedict, F. G., W. Landauer and E. L. Fox, 1932. The physiology of the normal and frizzle fowl with special reference to the basal metabolism. Connecticut Agricultural Experimental Station. Bulletin 117: 13-101. Cited by Stewart and Hinkle (1959). Berman, A., and N. Snapir, 1965. The relation of fasting and resting metabolic rates to heat tolerance in the domestic fowl. Brit. Poultry Sci. 6: 207-216. Bligh, J., 1966. The thermosensitivity of the hypothalamus and thermoregulation in mammals. Biol. Rev. 41:317-367. Calder, W. A., and K. Schmidt-Nielsen, 1966. Evaporative cooling and respiratory alkalosis in the pigeon. Proc. Nat. Acad. Sci. 55: 750-756. Dawson, W. R., 1958. Relation of oxygen consumption and evaporative water loss to temperature in the cardinal. Physiol. Zool. 3 1 : 37-48. Dawson, W. R., and G. A. Bartholomew, 1968. Temperature regulation and water economy of desert birds. I n : Desert Biology 1: 357-389. Ed. G. W. Brown, Jr., Academic Press, N.Y. and London. Dawson, W. R., and K. Schmidt-Nielsen, 1964. Terrestial animals in dry heat: desert birds. Handbook of Physiology, Section 4 : 481^92, Ed. D. B. Dill, Washington.

Deighton, T., and J. C. D. Hutchinson, 1940. Studies on metabolism of fowls. I I : The effect of activity on metabolism. J. Agric. Sci. Camb. 30: 141-159. Dukes, H. H., 1947. The Physiology of Domestic Animals. 6th ed., Comstock, N.Y. Findlay, J. D., 1950. Bull. Hannah Dairy Res. Inst., No. 9 (cited by Findlay, J. D., and W. R. Beakly, 1954). I n : Progress in the Physiology of Farm Animals, vol. 1, 252-298. Ed. J. Hammond, Butterworths, London. Fox, T. W., 1951. Studies on heat tolerance in domestic fowl. Poultry Sci. 30: 477-483. Freeman, B. N., 1966. Physiological responses of the adult fowls to environmental temperature. Worlds Poultry Sci. J. 22: 140-145. Gelineo, S., 1864. Organ systems in adaption—the temperature regulating system. Handbook of Physiology. Section 4 : 259-282. Ed. D. B. Dill, Washington. Heywang, B. W., 1938. Effect of some factors on the body temperature of hens. Poultry Sci. 17: 317-323. Hillerman, J. P., and W. O. Wilson, 1955. Acclimatisation of adult chickens to environmental temperature changes. Am. J. Physiol. 180: 591595. Hoffman, E., and C. S. Shaffner, 1950. Thyroid weight and function as influenced by environmental temperature. Poultry Sci. 29: 365-376. Horvath, S. M., G. E. Folk, F. N. Craig and W. Fleischmann, 1948. Survival time of various warm blooded animals in extreme cold. Science, 107: 171-172. Huston, T. M., W. P. Joiner and J. L. Carmon, 1957. Breed differences in egg production of domestic fowl held at high environmental temperature. Poultry Sci. 36: 1247-1254. Huston, T. M., T. N. Cotton and J. L. Carmon, 1962. The influence of high environmental temperature on the oxygen consumption of mature domestic fowl. Poultry Sci. 4 1 : 179-183. Hutchinson, J. C. D., 1954. Heat regulation in birds. I n : Progress in the Physiology of Farm Animals, 299-3 S8. Ed. J. Hammond, Butterworth, London. Hutchinson, J. C. D., and A. H. Sykes, 1953. Physiological acclimatisation of fowls to a hot humid environment. J. Agric. Sci. Camb. 43 : 294-322. Hutt, F. B., 1938. Genetics of the fowl. VII: Breed differences in susceptibility to extreme heat. Poultry Sci. 17: 454-462. Iyer, 1952. (cited by Hutchinson and Sykes, 1953).

Downloaded from http://ps.oxfordjournals.org/ at Ernst Mayr Library of the Museum Comp Zoology, Harvard University on June 10, 2014

metabolic rate. No thermal neutral zone as such appears to exist. The body temperature of laying hens is fairly labile and they can tolerate, at least for short periods of time, considerable rises in body temperature. Under hot climatic conditions where diurnal temperature fluctuation is considerable the storage of heat in the body is common.

923

924

A. J. SMITH AND J. OLIVER Academy, Bologna. Payne, C. G., 1966a. Developments in the use of artificial heating for the control of the animal environment. 1-11. The Electricity Council (E. D. A. division). Rural Electrification Conference, 1966. Payne, C. G., 1966b. Practical aspects of environmental temperature for laying hens. Worlds Poultry Sci. J. 22: 126-139. Payne, C. G., 1966c. Environmental temperature and egg production. In: Physiology of the Fowl. pp. 235-241. Ed. C. Horton Smith, and E. C. Amoroso. Oliver and Boyd, Edingburgh, London. Peterson, C. F., E. A. Sauter, D. E. Conrad and C. E. Lampman, 1960. The effect of energy level and laying house temperature on the performance of White Leghorn pullets. Poultry Sci. 39 : 1010-1018. Randall, W. C , and W. A. Heistand, 1939. Panting and temperature regulation in chickens. Am. J. Phys ; ol. 127: 761-767. (cited by Wilson, 1948). Randall, W. C , 1943. Hypothermia in chickens. Proc. Soc. Exp. Biol. Med. 52: 240-243. Robinson, K. W., and D. H. K. Lee, 1947. The effect of the nutritional plane upon the reactions of animals to heat. J. Anim. Sci. 6: 182194. Rollo, C. A., W. Grub and J. R. Howes, 1963. The effects of high constant environmental temperatures upon caged White Leghorn pullets and hens. Presented at the 1963 Annual Meeting Am. Soc. Agric. Engrs. Paper no. 63, 401. Romijn, C , and W. Lokhorst, 1966. Heat regulation and energy metabolism in the domestic fowl. I n : Physiology of the Fowl, 211-227. Ed. C. Horton Smith, and E. C. Amoroso, Oliver and Boyd, Edinburgh, London. Shannon, D. W. F., and W. O. Brown, 1969. The period of adaption of the fasting metabolic rate of the common fowl to an increase in environmental temperature from 22°C. to 28°C. Brit. Poultry Sci. 10: 13-18. Stewart, R. D., and C. N. Hinkle, 19S9. Environmental requirements for poultry shelter design. Agric. Engng. 40: 532-535. Shoji, K., K. Totsuka and M. Tajima, 1966. The effect of methionine deficiency on energy metabolism in chicks. Jap. J. Zootech. Sci. 37: 246. Nutr. Abstr. Rev. 37: 941. Siegel, H. S., 1968. Adaption in poultry. In: Adaptation of Domestic Animals, 292-309. Ed. E. S. E. Hafez, Lea and Febiger, Philadelphia. Spencer Davis, P., and M. A. Tribe, 1969. Temper-

Downloaded from http://ps.oxfordjournals.org/ at Ernst Mayr Library of the Museum Comp Zoology, Harvard University on June 10, 2014

King, J. R., and D. S. Farner, 1961. Energy metabolism thermoregulation and body temperature. I n : Biology and Comparative Physiology of Birds, 2: 215-279. Ed. A. J. Marshall, Academic Press, N.Y. King, J. R., and D. S. Farner, 1964. Terrestial animals in humid heat: birds. I n : Handbook of Physiology, section 4 : 603-624. Ed. D. B. Dill. Kleiber, M., 1961. The Fire of Life. John Wiley & Sons, N.Y., London. Kleiber, M., 1965. Metabolic body size. In: Energy Metabolism, 427-435. Ed. E. L. Blaxter, Academic Press, London, N.Y. Lee, D. H. K., E. W. Robinson, N. I. M. Yeates and M. R. Scott, 1945. Poultry husbandry in hot climates. Experimental enquiries. Poultry Sci. 24: 195-207. Leithead, C. S., and A. R. Lind, 1964. Heat Stress and Heat Disorders. Cassell, London. Lincoln, D. W., 1964. The effect of environmental temperature on the ovulation-oviposition cycle of the domestic fowl. B.Sc. Thesis, Univ. Nottingham. Longhouse, A. D., N. Ota and W. Ashby, 1960. Heat and moisture design data for poultry housing. Agric. Engng. 4 1 : 567-576. McDonald, P., E. W. Edwards and J. F. D. Greenhalgh, 1966. Animal Nutrition. Oliver and Boyd, Edinburgh, London. Mitchell, H. H., and M. A. R. Kelly, 1933. Estimated data on the energy, gaseous and water metabolism of poultry for use in planning the ventilation of poultry houses. J. Agric. Res. 47: 735-748. Moreng, R. E., and C. S. Shaffner, 1951. Lethal internal temperatures for the chicken (from fertile egg to mature bird). Poultry Sci. 30: 255266. Mueller, W. J., 1961. The effect of constant and fluctuating environmental temperatures on the biological performance of laying pullets. Poultry Sci. 40: 1562-1571. Ota, H., H. L. Garver and W. Ashby, 1953. Heat and moisture production of laying hens. Agric. Engng. 34: 163-167. Ota, H., and E. H. McNally, 1961. Poultry respiration calorimetric studies of laying hens. U.S. Dept. Agric. Res. Service Publ. 42. Ota, H., and E. H. McNally, 1963. Poultry studies with respiration calorimeters. Trans. Am. Soc. Agric. Engrs. 6: 129-135. Payne, C. G., 1964. The influence of environmental temperature on poultry performance. World's Poultry Sci. Asscn. Report of the 2nd European Conf., pp. 117-120. National Agricultural

HIGH ENVIRONMENTAL TEMPERATURES

Waring, J. J., and W. O. Brown, 1967. Calorimetric studies on the utilisation of dietary energy by the laying White Leghorn hen in relation to plane of nutrition and environmental temperature. J. Agric. Sci. 68: 149-155. Wilson, H. R., A. E. Armas, I. S. Ross, R. W. Dorminey and C. J. Wilcox, 1966. Familial differences of Single Comb White Leghorn chickens in tolerance to high ambient temperature. Poultry Sci. 45: 784-788. Wilson, W. O., 1948. Some effects of increasing environmental temperature on pullets. Poultry Sci. 27: 813-817. Wilson, W. O., 1949. High environmental temperature as affecting the reaction of laying hens to iodised casein. Poultry Sci. 28: 581-592. Wilson, W. O., J. P. Hillerman and W. H. Edwards, 1952. The relation of high environmental temperature to feather and skin temperatures of laying pullets. Poultry Sci. 3 1 : 843-850. Wilson, W. O., E. G. McNally and H. Ota, 1957. Temperature and calorimeter study on hens in individual cages. Poultry Sci. 36: 1254-1261. Yeates, N. T. N., D. H. K. Lee and R. J. G. Hines, 1941. Reactions of domestic fowls to hot atmospheres. Proc. Roy. Soc. Qd. 53: 105-128.

Rofenaid1 Treatment of Arizona (Paracolon) 7:1,7,8 and Salmonella typhimurium Infections in Young Turkeys2 J. F. STEPHENS AND SHARON HARPSTER Department of Poultry Science, The Ohio State University, Columbus, Ohio 43210 AND

C.

T.

ORTON

Hoffmann-La Roche, Inc., N-utley, New Jersey 07110 (Received for publication November 20, 1970)

R

OFENAID is the Hoffmann-LaRoche trademark for the compound containing sulfadimethoxine and ormetoprim in a 5:3 ratio. The efficacy of sulfadimethoxine against several species of chicken 1

Hoffmann-La Roche trade name for a compound containing sulfadimethoxine and 2,4-diamino-5(4,5-dimethoxy-2-methylbenzyl) pyrimidine. 2 This project was supported by a grant from Hoffmann-La Roche, Inc., Nutley, N. J.

and turkey coccidia has been demonstrated (Mitrovic and Bauemfeind, 1967; Mitrovic, 1968). Mitrovic (1967) also reported the compound to be effective in preventing fowl cholera and infectious coryza in chickens. Sulfadimethoxine in combination with ormetoprim was reported more effective against coccidiosis than sulfadimethoxine alone (Mitrovic et al., 1969b). This combination product (Rofenaid) was also found

Downloaded from http://ps.oxfordjournals.org/ at Ernst Mayr Library of the Museum Comp Zoology, Harvard University on June 10, 2014

ature dependence of metabolic rate in animals. Nature, 224-225. Squibb, R. L., 1959. Relation of diurnal temperature and humidity ranges to egg production and feed efficiency of New Hampshire hens. J. Agric. Sci. 52: 217-222. Squibb, R. L., G. N. Wogan and C. H. Reed, 1959. Production of White Leghorn hens subjected to high environmental temperatures with wide diurnal fluctuations. Poultry Sci. 38: 1182-1183. Squibb, R. L., and G. N. Wogan, 1960. Ambient environmental conditions associated with reported spontaneous occurrence of thermal death in poultry. World's Poultry Sci. J. 16: 126-137. Sturkie, P. D., 1946. Tolerance of adult chickens to hypothermia. Am. J. Physiol. 147: 531-540. Sturkie, P. D., 1965. Avian Physiology. Cornell University Press, Ithaca, New York. Wallgren, H., 1954. Energy metabolism of two species of the genus Emberisa as correlated with distribution and migration. Acta Zool. 84: 1. (cited by King and Farner, 1961). Waring, J. J., and W. O. Brown, 1965. A respiration chamber for the study of energy utilisation for maintenance and production in the laying hen. J. Agric. Sci. 65 : 139-146.

925