CLOACAL AND SURFACE TEMPERATURES OF BROILER CHICKS IN FIRST WEEK

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1 Q'MOO Applied Poultry Science, Inc ENVIRONMENTAL TEMPERATURE AND LOAAL AND SURFAE TEMPERATURES OF BROILER HIKS IN FIRST WEEK POSTHATH R. D. MALHEIROS, K M. B. MOWS, L. D. G. BRUNP, E. B. MALHEIROS, R. L. FURLAN and M. MAARI Departamento de Morfo1og.a e Fisiologia Animal, Faculdade de i2nciar Agrhrias e Veterinanas de Jaboticabal, UNESP, EP , Jaboticabal, Sdo Paulo, Brazil Phone: , Ext: 234 FAX; macm'@fcav.unesp.br Primary Audience: Broiler Supervisors, Broiler Growers, Hatcheries, Researchers, Extension Agents DESRIPTION OF PROBLEM The thermoneutral environmental temperature for broiler chicks during the 1st wk posthatch should be between 32 and 35 and ambient temperatures higher than this induce hyperthermia followed by dehydration, reducing feed intake and body weight gain [l]. On the other hand, environmental temperatures much lower than these cause hypothermia and seem to be one important factor causing the high incidence of pulmonary hypertension syndrome (ascites) in broilers reared in cold weather [2]. Van der He1 et al. [3] reported that the upper critical temperature for newly hatched broiler chicks ranges between 36 and 37T, and that water loss increased from 1.8 to 4.4 g 1 To whom correspondence should be address ed

2 112 BROILER HIK HEAT LOSS as ambient temperature rises from 30.8 to 38.8", with the main increase occurring after exposure to 35. The effect of cold challenge on thermoregulatory responses has not been intensively investigated in broiler chicks. Espira and Evans [4] showed that energy saved by vocalization (heat conserving behavior from parent or surrogate) during 20 exposure did not affect body temperature in 3dayold chicks, but the thermal gradient between body and ambient temperature was reduced. The objective of this study was to investigate the extent to which environmental temperature affects the cloacal and surface (back, head, Wings, and shanks) temperatures as well as sensible heat loss of broiler chicks reared at 35, 25, or 20 during the 1st wk posthatch. MATERIALS AND METHODS Male, dayold chicks of the obb strain were used in this trial.the chicks were kept in three climatic chambers (80 birds per temperature) in which environmental temperature (") and relative air humidity (%) were: 20", 80%; W, 69%; and 35", 73%, respectively. Ten birds per temperature treatment were sampled at random every day up to 7 days of age, and cloacal temperature was measured by inserting a thermistor probe connected to a 6channel telethermometer to a depth of 3 cm into the cloaca (Yellow Spring Instruments, Model 46 TU, Yellow Spring, OH). Surface temperature was measured at four different sites (back, head, wing, and shank) using an infrared thermometer (Horiba 33oT, Japan). Mean surface temperature (") was calculated according to the chick body area proportionally as follows (equation adapted from Richards [5]): Tms =0.03Th Tb Ts % where: Tms =mean surface temperature Th =head temperature Tb =back temperature Ts = shank temperature 'h = wing temperature Heat loss by radiation was calculated according to Hardy [6]: HLR =&I. &2. A. (Tm4 Ta4) where: HLR =heat loss by radiation (Watts) emissivity of air ( = 1) &2 = emissivity of feathers ( = 0.94) =StephanBoltzman constant (5.67 x 10" Wm2 OK4) A = surface area (m2) Tms = mean surface temperature (OK) Ta = ambient temperature (OK) The surface area of the chicks was cal culated according to Esmay [I: A = 9.85 x where: A = surface area ( cm2) P =body weight (g) The broiler chicks' volume (cm3) was also measured by inserting the birds (after sacrifice with an overdose of anaesthetic) into a measuring cylinder partially filled with tap water. For each age a randomized complete design was used with three treatments (rearing temperature: 20,25, and 35 ) and 10 replicates. Data for all variables was subjected to an analysis of variance using the General Linear Model procedure of SAS [8]. RESULTS AND DISUSSION The rectal and surface temperatures of the chicks raised at different environmental temperatures during the 1st wk posthatch appear in Table 1. loacal temperature increased from the 1st to the 7th day posthatch independent of ambient temperature. For the chicks kept at 20 the cloacal temperature was lower (P <.Ol) compared to the birds kept in a thermoneutral(35") or cool environment (25 ). Back, head, and wing temperatures were also affected by chick living temperature (P e.01). hicks reared at 20 had a surface temperature almost 3 lower (P <.01) than did birds reared at cool or thermoneutral temperatures (25 and 35", respectively) independent of the birds' age. Surface temperatures in these parts of the body were 1 to 2 higher for the chicks at 35 than for those at 25. It is well known that feathers provide a thick layer of insulation and that the temperature of the

3 MALHEIROS et al. Research Report 113 AMBIENT AGE (Days) TEMPERATURE " LOAAL TEMPERATURE (") ' 41.1a 41.2' b ab b 40.6b 40.8b r b b b 40.eb 40.4' ** ** ** ** PA I I NS 1 ** I NS 1 I BAKTEMPERATURE Y3 I I F cv (%) *F=Test of Fischer. 'V= oefficient ofvariation (%I. 33.0b 335' 32.5' 35.0' 34.6b 34.4b 35.1b 31.2' ' 32.T 32.T ** ** ** ** ** ** ** weans with the same superscript in the columns (for each parameter) are not significantly different (P >.OS). **P< or

4 114 BROILER HIK HEAT LOSS skin changes little over a wide range of ambient temperatures [9]. Thus, despite the difference in surface temperature found in the chicks in these feathered areas, the difference was well below that found in the shank (nonfeathered area). The most striking difference in surface temperature was observed in the chick shank. The difference (Pc.Ol) in surface temperature reached 10 comparing buds living at 20 and 35. The naked skin plays an important role in maintaining core temperature, so skin temperature of feathered parts rose 2 to 5 when ambient temperature varied from 20 to 40", while the nonfeathered regions showed an increase of up to 20 [SI. Yahav et al. [lo], using thermography, showed an increased radiation heat loss in nakedneck chickens at 8 wk of age, giving evidence of the importance of external insulation in heatconserving mechanisms. Mean surface temperature, which was calculated proportionally, also differed significantly (P c.01) among the chicks kept at different environmental temperatures, with higher values verified for the chicks at 35. The changes in skin temperature are related to the responses of the cardiovascular system. Yahav et al. [ll] suggested that regulatory hemodynamic changes are necessary to cope with thermal stress. Dawson and Hudson [12] reported that thermal conductance increased by a factor of two or three when ambient temperature rose from 20 to 4O", implying an increase in peripheral blood flow. Thus, the increased or decreased blood flow to the periphery might be the determinant factor to establish the surface temperature during exposure to different environmental temperatures. Wolfenson [l3] reported that arterio venous anastomoses appeared mostly in unfeathered skin, and contributed 17 to 83% of the total blood flow under cold and hot conditions, respectively. Body weight data of chicks reared at three environment a1 temperatures appears in Table 2. It was observed that chicks reared at a lower environmental temperature (20 ) showed lower body weight at the 6th and 7th days of age; however, the body weight of the chicks reared at 25 was similar to that of buds reared at thermoneutral temperatures (35 ). This lower weight might be related to the heatconserving behavior of these birds, since at low ambient temperatures they aggregate to avoid heat loss and the frequency of use of the feeder and drinker declined. Since the chicks seem to have an energy reserve in the yolk sac for at least 3 days [14,15], the reduced body weight at low ambient temperatures was more evident 6 days after hatching. Nitsan et al. [16] showed that the yolk sac content contributes 50% and 40% of total energy and protein during the 1st day posthatch and 2% and 6% on the 4th day of life, respectively. Figure 1 shows the findings of sensible heat loss. Analysis of the data showed a significant effect (P c.ol). The magnitude of the radiation heat loss (W) values revealed that chicks kept at 35 do not lose heat, but by decreasing rearing ambient temperature to 20", heat loss increased almost nine times. This increase is related in part to surface:volume area that was higher for dayold chick and decreased with age (Table 2) and to the gradient between skin and ambient temperature, since for dayold birds the gradient was 11.14" for chicks living at 20 and 0.29" for chicks at 35.

5 MALHEIROS et al. Research Report 115 TABLE 2. Body weight, volume, area, and area:volume ratio of broiler chicks reared at different environmental L (%> I AF=Test of Fischer. B ~ oefficient = of variation (%I. bmeans with the same superscript in the columns (for each parameter) are not significantly different (P >.OS). *Pc.OS; ** Pc.01.

6 116 J 2o'c +25' +35' b c P BROILER HIK HEAT LOSS a b A AGE (DAYS) FIGURE 1. Radiation heat loss (W) for chicks reared at different environmental temperatures (35, 25, or 20 ) during the 1st wk posthatch, For each point, means with the same letters are not significantlydifferent (P >.05). ONLUSIONS AND APPLIATIONS 1. hicks reared at an ambient temperature of 20 had lower body weight at 7 days of age. 2. By reducing the ambient temperature from 35 to 20 there was an increase of nine times in radiation heat loss in 7dayold chicks. 3. The maintenance of the chick at thermoneutral temperature is critical to avoid hypothermia, increasing the physiological cost of thermal homeostasis. 1. Mickelbcrry, W.., J.. Rogler, and WJ. Siadelman, The influence of dietary fat and environmental temperature upon chick owth and carcass composition. Poultry Sci. 45:31>32f? 2. Maxwell. M.H. and G.W. Robertson UK su& of brozer ascites and sudden death syndromes in Br. Poultq Sei Van der Hel, W., M.W.A. Verslegen, A.M. Henken, and H.A. Brandsman, The u per critical ambient tem rature in neonatal chicks. Boultry Sci r 4. Espira, A. and RM. Evans, Ener savings from vocal regulation of ambient temperaturety 3dayold domestic chick. anadian J. Zoology Richards, S.A., The significance of changes in the temperature of the skin and b core of the chicken in the regulation of the heat loss. 8hysiol. 216:l Hardy, J.D., Heat transfer. Pages in: Physiology of Heat Regulation and the hence of lothing. LH. Newburgh, ed. W.B. Saunders, Philadelphia, PA. 7. &may, M.L, Poultry and their environment. Pa es in: Principles of Animal Environment. M.& Esmay, ed. AVI Publishing o., Westport, T. REFERENES AND NOTES 8. SAS Institute, SAS (Statistical Anal is User's Guide: Statistics. SAS Institute, gc., 9. Wilson, W.O., J.P. Hillerman, and W.H. Edwanls, The relation of hieh environmental temderatures to feather and skin temgratures of laying pulfets. Poultry Sci. 31: Yahav, S., D. Luger, A ahaner, M. Dotan, M. Rusal, and S. Hurwitz, Thermoregulation in naked neck chickens sub'ected to different ambient temperatures. Br. Poultry ki. 39: Yahav, S., A. Strasehow, I. Pladk, and S. Hlllwitq 1997.Effects of diurnallycyclin versus constant tern ratures on chicken growth and food intake. Br. pourry Sei. 314%~. 12. Dmon, W.R and J.W. Hudson, Birds. Pages in: omparative Physiology of Thermoregulation, Vol. I: Invertebrates and Nonmammalian Vertebrates. G.. Whittow, ed. Academic Press, New York, NY. 13. Wolfenson, D., Blood flow through arteriovenous anastomoses and its thermal function in the laying hens. J. Physiol. 3M Reis, LH., LT. Gama, and M. haveiro %ares, Effects of short storage conditions and broiler breeder age on hatchability, hatching time, and chick weights. Poultry Sci T

7 Research Report MALHEIROS et al Uni, Z., S. Ganot, and D. Sklan, Posthatch development of mucosal function in the broiler small intestine. PoultIy Sci. m NitsPn, Z, G. BernAvrahan, Z. Zoref, and I. Nlr, Growth and development of the digestive organs and some enzymes in broiler chicks after hatching. Br. Poultry Sci AKNOWLEDGEMENT The authors would like to thank FundaGBo de Am ro a Pesquisa do Estado de SzLo Paulo (FAPESP) for Eancial support.