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Research Note: Evaporative Cooling for Increased Production of Large Broiler Chickens
Research Note: Evaporative Cooling for Increased Production of Large Broiler Chickens J. D. SIMMONS and J. W. DEATON USDA, Agricultural Research Service, South Central Poultry Research Laboratory, Mississippi State, Mississippi 39762 (Received for publication August 29, 1988) ABSTRACT Environmental chambers were used to simulate pad and fan evaporative cooling for rearing broilers to heavy weights during hot summer conditions of the southeastern US. Broilers were reared in the chambers from 4 to 9 wk of age. Treatments included 1) constant 21 C with a 10-C dewpoint (positive control), 2) simulating pad and fan evaporative cooling by cycling temperature from 24 to 29 to 24 C once each 24-h period with a dewpoint cycle from 21 to 23 to 21 C, and 3) simulating hot summer conditions by cycling temperature from 24 to 38 to 24 C once each 24-h period with a constant 21C dewpoint. The objective of the research was to determine if body weight and feed conversion changed as a result of using evaporative cooling when rearing large broilers in high ambient temperatures. Results show that at 6 and 9 wk of age, evaporative cooling improved body weight and feed conversion compared with rearing under typical summer conditions. The constant temperature control treatment group weighed significantly more at 9 wk of age when compared with the other two treatment groups. The use of evaporative cooling can increase body weight and improve feed conversion at both 6 and 9 wk when compared with results of rearing broilers under hot summer conditions. (Key words: broilers, body weight, feed conversion, evaporative cooling, temperature) 1989 Poultry Science 68:839-841 INTRODUCTION
Evaporative cooling is a process in which the heat in the air is used to evaporate water put in contact with the air. The result is a lowering of the temperature and an increase in the humidity of the air being conditioned. The process works best in hot, dry climates and has been used in the familiar pad and fan form for years in the arid West and Southwest (Reece et al, 1970). Pad and fan evaporative cooling is now used quite often in layer houses in the more humid Southeast although the potential for cooling is less due to the higher humidity of the ambient air (Trumbull et al, 1986). Pad and fan cooling is characterized by an 8 to 9-degree reduction in temperature, and acceptable increases in humidity of the air (Timmons and Baughman, 1983). Evaporatively cooled interiors have temperature cycles that reflect ambient conditions. Although it has the largest potential to cool, pad and fan has the greatest initial cost of all the forms of evaporative cooling. This expense has precluded widespread use in commercial broiler production. Broiler growth rate is reduced and feed conversion can suffer in a high temperature
environment (Reece et al, 1972). A heavy broiler is now being marketed at 8 to 9 wk for further processing, and the larger broiler may be especially susceptible to hot weather problems. The potential exists for increased body weight and improved feed conversion of large broilers during the summer months by using pad and fan evaporative cooling. The objective of this research was to determine if body weight and feed conversion changed as a result of using evaporative cooling for rearing large broilers in high ambient temperatures. MATERIALS AND METHODS
Two trials were conducted. In each trial, male broilers were reared in an environmentally controlled house with a brooding regimen of 29 C the 1st wk, 27 C the 2nd wk, 24 C the 3rd wk, and 21 C the 4th wk. For the first 3 wk, all chicks were fed a starter diet calculated to contain 21% protein and 3,142 kcal ME/kg. Thereafter, the broilers were fed a finisher diet calculated to contain 18.4% protein and 3,109 kcal ME/kg. Feed and water were provided ad libitum. At 4 wk of age the broilers were weighed and divided into six groups of equal weight of
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70 birds each, and placed on new litter in environmental chambers as described by Reece and Deaton (1969). Each bird was provided with an area of 836 cm2 and 9 lx of continuous light. Control of these chambers could be programmed to vary both the temperature and humidity. The broilers were reared in the chambers from 4 to 9 wk of age and birds and residual feed were weighed each week. Two chambers (two replications) were used to simulate each of three environments: control cooled, evaporative cooling, and hot summer. The control was kept at a constant 21 C dry bulb temperature, with a 10 C dewpoint. To simulate evaporative cooling, the dry-bulb temperature was cycled from 24 to 29 to 24 C, with a dewpoint cycle from 21 to 23 to 21 C. To simulate hot summer conditions, the drybulb temperature was cycled from 24 to 38 to 24 C with a 21 C dewpoint. The temperature cycles peaked at 1500 h and reached their minimum at 0600 h, generally approximating a sine wave. The experiment was designed as a split-plot design, with a main plot consisting of trial and chamber, and the sub-plot being the simulated environments. An ANOVA (Snedecor and Cochran, 1956) was conducted for body weight and feed conversion (grams of feed/ gram body weight). Significantly different treatment means were separated by the multiple range test of Duncan (1955). RESULTS
At 6 wk, broilers reared under control conditions were not significantly heavier than those reared with simulated evaporative cooling, but both groups were significantly heavier than those reared under simulated hot summer conditions (Table 1). At 6 wk, broilers reared with simulated evaporative cooling had a significantly lower feed conversion rate than those reared under control conditions or simulated hot summer conditions. At 9 wk, broilers reared under control conditions were significantly heavier than those reared with simulated evaporative cooling or under simulated hot summer conditions (Table 1). At 9 wk, broilers reared under simulated evaporative cooling were significandy heavier than those reared under simulated hot summer conditions. However, at 9 wk, broilers reared under simulated hot summer conditions had a significantly poorer feed
841
RESEARCH NOTE
conversion rate than those reared with the other two treatments. The feed conversion rate for broilers reared under control conditions was the same as that for broilers reared under simulated evaporative cooling. During the treatment period (4 to 9 wk of age) 23 broilers (2.7%) died in the two trials (13 in Trial 1 and 10 in Trial 2), but the deaths were not related to treatment. DISCUSSION
At 6 wk, the best feed conversion rate resulted from the treatment that also produced the highest weight gain; this occurred with simulated evaporative cooling. Yet the controlcooled environment produced the best weight gains; the feed conversion results appear to be inconsistent. However, work done by Deaton et al. (1978) demonstrated that when rearing broilers at distinct temperatures, production of optimum feed conversion does not always coincide with optimum temperature for weight gain. At 9 wk, the best feed conversion rate resulted from the treatment (control cooled) that also produced the highest weight gain, but the same feed conversion rate was recorded with a different treatment (simulated evaporative cooling). An explanation is offered by Reece and Lott (1983). They noted that for each 50-g difference in body weight, it required approximately .015 g feed/g BW of the "feed conversion ratio" (due to feed) to equate weights. Therefore, if body weights were equated at 9 wk for broilers reared under control-cooled conditions vs. those reared under simulated evaporative cooling, the feed conversion for the latter group would be 2.33 rather than 2.28, as the weight difference between the two was 151 g. Poor feed conversion rates under simulated hot summer conditions were not unexpected. Dale and Fuller (1980) noted that during periods of high temperature, chickens will dissipate heat by lifting wings and panting; these mechanisms require an expenditure of energy, with a resulting higher value of feed conversion.
Results of this test suggest that at both 6 and 9 wk, broilers reared under evaporative cooling can achieve higher body weights than under hot summer conditions. Further cooling to a constant 21 C may not increase the weight gain of 6-wk-old broilers, but the larger 9-wkold is more responsive to the temperature of its environment. Therefore, if a choice existed, a 21 C temperature would be favored over the other treatments for the larger broiler. Pan and fan evaporative cooling may be considered as an option to the industry when marketing a 6wk-old broiler, but when marketing at 9 wk, a cooling system with that amount of capacity may be needed to get the desired weight on the larger broiler. REFERENCES Dale, N. M , and H. L. Fuller, 1980. Effect of diet composition on feed intake and growth of chicks under heat stress. II. Constant vs. cycling temperatures. Poultry Sci. 59:1434-1441. Deaton, J. W., F. N. Reece, and J. L. McNaughton, 1978. The effect of temperature during the growing period on broiler performance. Poultry Sci. 57:1070-1074. Duncan, D. B., 1955. Multiple range and multiple F tests. Biometrics 11:1-42. Reece, F. N., and J. W. Deaton, 1969. Environmental control for poultry research. Agric. Eng. 50:670-671. Reece, F. N., J. W. Deaton, and L. F. Kubena, 1972. Effects of high temperature and humidity on heat prostration of broiler chickens. Poultry Sci. 51:2021-2025. Reece, F. N., J. W. Deaton, and B. D. Lott, 1970. Use of evaporative cooling for broiler chicken production in areas of moderate and high relative humidity. Am. Soc. Agric. Eng. (ASAE) Paper No. 70-412. ASAE, St. Joseph, MI. Reece, F. N., and B. D. Lott, 1983. The effects of temperature and age on body weight and feed efficiency of broiler chickens. Poultry Sci. 62:1906-1908. Snedecor, G. W., and W. G. Cochran, 1956. Statistical Methods. The Iowa State College Press, Ames, IA. Timmons, M. B., and G. R. Baughman, 1983. Experimental evaluation of poultry mist-fog systems. Trans. ASAE 26:207-210. Trumbull, R. D., J. L. Koon, and C. A. Flood, 1986. Potential for use of evaporative cooling systems. Am. Soc. Agric. Eng. (ASAE) Paper No. 86-4048. ASAE, St. Joseph, MI.
Evaporative cooling is a process in which the heat in the air is used to evaporate water put in contact with the air. The result is a lowering of the temperature and an increase in the humidity of the air being conditioned. The process works best in hot, dry climates and has been used in the familiar pad and fan form for years in the arid West and Southwest (Reece et al, 1970). Pad and fan evaporative cooling is now used quite often in layer houses in the more humid Southeast although the potential for cooling is less due to the higher humidity of the ambient air (Trumbull et al, 1986). Pad and fan cooling is characterized by an 8 to 9-degree reduction in temperature, and acceptable increases in humidity of the air (Timmons and Baughman, 1983). Evaporatively cooled interiors have temperature cycles that reflect ambient conditions. Although it has the largest potential to cool, pad and fan has the greatest initial cost of all the forms of evaporative cooling. This expense has precluded widespread use in commercial broiler production. Broiler growth rate is reduced and feed conversion can suffer in a high temperature
environment (Reece et al, 1972). A heavy broiler is now being marketed at 8 to 9 wk for further processing, and the larger broiler may be especially susceptible to hot weather problems. The potential exists for increased body weight and improved feed conversion of large broilers during the summer months by using pad and fan evaporative cooling. The objective of this research was to determine if body weight and feed conversion changed as a result of using evaporative cooling for rearing large broilers in high ambient temperatures. MATERIALS AND METHODS
Two trials were conducted. In each trial, male broilers were reared in an environmentally controlled house with a brooding regimen of 29 C the 1st wk, 27 C the 2nd wk, 24 C the 3rd wk, and 21 C the 4th wk. For the first 3 wk, all chicks were fed a starter diet calculated to contain 21% protein and 3,142 kcal ME/kg. Thereafter, the broilers were fed a finisher diet calculated to contain 18.4% protein and 3,109 kcal ME/kg. Feed and water were provided ad libitum. At 4 wk of age the broilers were weighed and divided into six groups of equal weight of
839
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70 birds each, and placed on new litter in environmental chambers as described by Reece and Deaton (1969). Each bird was provided with an area of 836 cm2 and 9 lx of continuous light. Control of these chambers could be programmed to vary both the temperature and humidity. The broilers were reared in the chambers from 4 to 9 wk of age and birds and residual feed were weighed each week. Two chambers (two replications) were used to simulate each of three environments: control cooled, evaporative cooling, and hot summer. The control was kept at a constant 21 C dry bulb temperature, with a 10 C dewpoint. To simulate evaporative cooling, the dry-bulb temperature was cycled from 24 to 29 to 24 C, with a dewpoint cycle from 21 to 23 to 21 C. To simulate hot summer conditions, the drybulb temperature was cycled from 24 to 38 to 24 C with a 21 C dewpoint. The temperature cycles peaked at 1500 h and reached their minimum at 0600 h, generally approximating a sine wave. The experiment was designed as a split-plot design, with a main plot consisting of trial and chamber, and the sub-plot being the simulated environments. An ANOVA (Snedecor and Cochran, 1956) was conducted for body weight and feed conversion (grams of feed/ gram body weight). Significantly different treatment means were separated by the multiple range test of Duncan (1955). RESULTS
At 6 wk, broilers reared under control conditions were not significantly heavier than those reared with simulated evaporative cooling, but both groups were significantly heavier than those reared under simulated hot summer conditions (Table 1). At 6 wk, broilers reared with simulated evaporative cooling had a significantly lower feed conversion rate than those reared under control conditions or simulated hot summer conditions. At 9 wk, broilers reared under control conditions were significantly heavier than those reared with simulated evaporative cooling or under simulated hot summer conditions (Table 1). At 9 wk, broilers reared under simulated evaporative cooling were significandy heavier than those reared under simulated hot summer conditions. However, at 9 wk, broilers reared under simulated hot summer conditions had a significantly poorer feed
841
RESEARCH NOTE
conversion rate than those reared with the other two treatments. The feed conversion rate for broilers reared under control conditions was the same as that for broilers reared under simulated evaporative cooling. During the treatment period (4 to 9 wk of age) 23 broilers (2.7%) died in the two trials (13 in Trial 1 and 10 in Trial 2), but the deaths were not related to treatment. DISCUSSION
At 6 wk, the best feed conversion rate resulted from the treatment that also produced the highest weight gain; this occurred with simulated evaporative cooling. Yet the controlcooled environment produced the best weight gains; the feed conversion results appear to be inconsistent. However, work done by Deaton et al. (1978) demonstrated that when rearing broilers at distinct temperatures, production of optimum feed conversion does not always coincide with optimum temperature for weight gain. At 9 wk, the best feed conversion rate resulted from the treatment (control cooled) that also produced the highest weight gain, but the same feed conversion rate was recorded with a different treatment (simulated evaporative cooling). An explanation is offered by Reece and Lott (1983). They noted that for each 50-g difference in body weight, it required approximately .015 g feed/g BW of the "feed conversion ratio" (due to feed) to equate weights. Therefore, if body weights were equated at 9 wk for broilers reared under control-cooled conditions vs. those reared under simulated evaporative cooling, the feed conversion for the latter group would be 2.33 rather than 2.28, as the weight difference between the two was 151 g. Poor feed conversion rates under simulated hot summer conditions were not unexpected. Dale and Fuller (1980) noted that during periods of high temperature, chickens will dissipate heat by lifting wings and panting; these mechanisms require an expenditure of energy, with a resulting higher value of feed conversion.
Results of this test suggest that at both 6 and 9 wk, broilers reared under evaporative cooling can achieve higher body weights than under hot summer conditions. Further cooling to a constant 21 C may not increase the weight gain of 6-wk-old broilers, but the larger 9-wkold is more responsive to the temperature of its environment. Therefore, if a choice existed, a 21 C temperature would be favored over the other treatments for the larger broiler. Pan and fan evaporative cooling may be considered as an option to the industry when marketing a 6wk-old broiler, but when marketing at 9 wk, a cooling system with that amount of capacity may be needed to get the desired weight on the larger broiler. REFERENCES Dale, N. M , and H. L. Fuller, 1980. Effect of diet composition on feed intake and growth of chicks under heat stress. II. Constant vs. cycling temperatures. Poultry Sci. 59:1434-1441. Deaton, J. W., F. N. Reece, and J. L. McNaughton, 1978. The effect of temperature during the growing period on broiler performance. Poultry Sci. 57:1070-1074. Duncan, D. B., 1955. Multiple range and multiple F tests. Biometrics 11:1-42. Reece, F. N., and J. W. Deaton, 1969. Environmental control for poultry research. Agric. Eng. 50:670-671. Reece, F. N., J. W. Deaton, and L. F. Kubena, 1972. Effects of high temperature and humidity on heat prostration of broiler chickens. Poultry Sci. 51:2021-2025. Reece, F. N., J. W. Deaton, and B. D. Lott, 1970. Use of evaporative cooling for broiler chicken production in areas of moderate and high relative humidity. Am. Soc. Agric. Eng. (ASAE) Paper No. 70-412. ASAE, St. Joseph, MI. Reece, F. N., and B. D. Lott, 1983. The effects of temperature and age on body weight and feed efficiency of broiler chickens. Poultry Sci. 62:1906-1908. Snedecor, G. W., and W. G. Cochran, 1956. Statistical Methods. The Iowa State College Press, Ames, IA. Timmons, M. B., and G. R. Baughman, 1983. Experimental evaluation of poultry mist-fog systems. Trans. ASAE 26:207-210. Trumbull, R. D., J. L. Koon, and C. A. Flood, 1986. Potential for use of evaporative cooling systems. Am. Soc. Agric. Eng. (ASAE) Paper No. 86-4048. ASAE, St. Joseph, MI.