Performance and preference of broiler chickens exposed to different lighting sources

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1 2013 Poultry Science Association, Inc. Performance and preference of broiler chickens exposed to different lighting sources Angélica Signor Mendes,* 1 Sandro José Paixão,* Rasiel Restelatto,* Gabriela Munhoz Morello, Daniella Jorge de Moura, and Jean Carlo Possenti * * Animal Science Department, Technological Federal University of Paraná (UTFPR), Campus Dois Vizinhos, Paraná, , Brazil; Animal Sciences Department, Purdue University, West Lafayette, IN 47906; and Agricultural Engineering Department, State University of Campinas (UNICAMP), Campinas, São Paulo, Brazil Primary Audience: Researchers, Animal Scientists, Agricultural Engineers, Veterinarians, Complex Managers, Broiler Farm Personnel DESCRIPTION OF PROBLEM Lighting is a critical component of the environment of commercial broiler chicken facilities that can influence the health, productivity, and welfare of confined broiler chickens [1]. Lighting has been shown to affect the physiology and behavior of domestic fowl. The progenitors of SUMMARY Vision is important in poultry behavior and welfare. Poultry have highly specialized visual systems, and the majority of their behavior is mediated by vision. In the present study, we evaluated the lighting preference of broiler chickens exposed to different lighting sources and their production performance. In the first portion of the study, we evaluated the preference of birds for white and yellow lighting provided by light-emitting diode (LED) bulbs. Bird preference was assessed by videos recorded during the experiment. In the second portion of the study, we evaluated the performance of broiler chickens exposed to LED and compact fluorescent lamps (CFL). Performance was assessed in terms of mortality rate, bird BW, daily BW gain, feed consumption, and feed conversion. The chickens occupied environments with yellow and white LED lighting evenly and did not show any behavioral sign of preference for one of the environments. However, birds presented greater feed consumption at 21, 28, and 35 d of age when exposed to white LED lighting. Generally, birds exposed to LED lighting presented better production performance than birds under the CFL. Seven-day-old male chickens presented better feed conversion under LED illumination than did males of the same age under CFL. Key words: bird preference, illumination, light-emitting diode, poultry production 2013 J. Appl. Poult. Res. 22 : /japr broiler chickens lived in a natural environment, where the natural lighting was substantially different from the artificial lighting used inside commercial poultry facilities today. First, the natural light intensity on a sunny day may be as high as 100,000 lx [2], whereas the light intensity found in broiler barns may be less than 5 lx at the bird level [3], despite the illumination 1 Corresponding author: angelica@utfpr.edu.br

2 Mendes et al.: EXPOSURE TO DIFFERENT LIGHTING SOURCES 63 recommendations of the Farm Animal Welfare Council [4] of at least 20 lx. Moreover, the spectrum of natural light provides a uniform energy distribution with wavelengths between 350 and 700 nm, whereas artificial light sources provide a narrower spectrum of wavelengths, thus providing light of a different color than natural light [3]. Poultry producers have begun switching from tungsten-filament (incandescent) bulbs to more energy-efficient and longer-lasting light sources. The efficient light sources most commonly used in agriculture include low-pressure mercury (fluorescent) and high-pressure sodium discharge bulbs, which are generally 4 to 5 times more luminous efficient and last 10 to 30 times longer than incandescent bulbs. One advantage of the discharge lamps is that they can be manufactured to produce light with distinct spectral characteristics. However, producers should be careful when choosing a new lighting source because some fluorescent lights can be emitted at frequencies that may be perceived by birds as discontinuous [5]. In most studies done to evaluate the relationship between environmental lighting and behavior in poultry, researchers have used 2 distinct approaches: preference tests and behavioral observations of birds exposed to different light sources. Bird preference has been assessed in response to exposure to different light intensities [6], light sources [7, 8], light colors [9], and flickering frequencies [10].The visual ability of birds and their behavior and welfare have been investigated under exposure to artificial lighting [11]. In various experiments using poultry, researchers have tried to establish whether housing using fluorescent light sources is detrimental to the performance of commercially raised birds. Fluorescent lighting has been shown to be preferred to incandescent lighting by hens (Gallus gallus) and turkeys (Meleagris gallopavo) [7, 12]. Some evidence also exists that housing under different light sources alters bird behavior. Denbow et al. [13] found that the type of lighting significantly affected the degree to which turkeys peck and pull feathers. In addition, Boshouwers and Nicaise [14] found that laying hens were more active under fluorescent, as compared with incandescent, lighting. The preference test allows birds to choose between several environments that may differ in only one characteristic. The birds can thus indicate their perceptions about the environment by demonstrating whether they have any attraction or aversion to that characteristic [15]. An underlying principle is that animals, including poultry, generally behave in a way that maximizes their fitness [16]; thus, they preferentially choose features that will most likely satisfy their requirements, regardless of whether these are perceptible to humans. The objective of this study was to investigate the preference of domestic broilers of different sexes and ages for commercially available light sources and to evaluate bird performance. The first portion of the study evaluated the preference of 4 groups of 34 broiler chickens, ranging from 1 to 6 wk of age, for white and yellow lighting from light-emitting diode (LED) bulbs. The second portion of the study evaluated the performance of 12 groups of 30 broiler chickens exposed to 2 different lighting sources: LED and compact fluorescent lamps (CFL). MATERIALS AND METHODS The study was conducted at the Technological University of Paraná, Brazil, in accordance with the principles and specific guidelines of the Federation of Animal Science Societies [17], during August and September of A total of 496 broiler chickens were provided by the local broiler hatchery, Pluma Agroavícola [18], integrated by Cobb, and were used in the present study. The chickens were raised for 40 d. Water was provided ad libitum through bell drinkers, with 1.5 cm of drinker space per bird. A 4-stage commercial diet was provided to the chickens in tube feeders (2.5 cm of feeder space/bird) 3 times a day, at 0700, 1300, and 1800 h, following the feeding program recommendations from Cobb. The bedding material consisted of wood shavings that were turned daily to avoid the formation of solid blocks of compacted bedding material caused by high moisture concentrations in these spots. The birds were placed in cm pens located in a 13 8 m poultry barn. The barn was equipped with 2 space heaters located outside the pens containing the birds. Five additional

3 64 JAPR: Research Report Figure 1. Poultry barn, top view (not to scale): 5 brooders, 2 space heaters. Experiment 1: 4 preference test apparatuses, each containing groups of 34 chickens and 2 chambers; experiment 2: treatments (sex and light source) were randomly assigned to the 12 pens, each containing groups of 30 chickens. brooders were also placed outside the pens during the growing period, as shown in Figure 1. The dry bulb temperature and RH were measured once every minute at the bird level, in the center of each pen, by using data loggers to ensure that the temperature and RH conditions were similar in all pens. The light regimen used in this study consisted of 19 h of light and 5 h of dark. Two light bulbs, spaced 100 cm apart, were hung from the ceiling of each chamber at a height of 175 cm from the ground. The study was conducted as 2 distinct experiments at the same time. The first experiment evaluated the preference of broiler chickens for white and yellow lighting from LED lamps, whereas the second experiment evaluated the performance of broiler chickens exposed to 2 different lighting sources: LED and CFL illumination. The light intensities provided by the LED and CFL sources were 20 lx for 1-wk-old birds and 5 lx for 2- to 6-wk-old birds. Table 1 shows the specifications of the light bulbs. Experiment 1: Bird Preference for 2 Distinct Light Colors A total of 68 male and 68 female broiler chickens were provided by Pluma Agroavícola [18] hatchery and dorsally marked with an individual symbol using a nontoxic marker to differentiate Table 1. Specifications for the light-emitting diode (LED) and compact fluorescent lamp (CFL) bulbs: Voltage, power consumption, amperage, color temperature, light intensity, luminous efficiency, dimensions, and manufacturers information Light source 1 Specifications CFL 127 V; 15 W (equivalent to a regular 60-W incandescent bulb); 203 ma; color temperature of 6,400 K (white); light intensity: lm; luminous efficiency: 53.4 lm/w; size: 52 mm in diameter, 150 mm in length LED, white 220 V; 5 W; 50 ma; color: 500 nm; light intensity: 280 lm; luminous efficiency: 17 lm/w; size: 70 mm in diameter, 65 mm in length LED, yellow 220 V; 5 W; 50 ma; color: 635 nm; light intensity: 180 lm; luminous efficiency: 17 lm/w; size: 70 mm in diameter, 65 mm in length 1 CFL (Philips, Barueri, São Paulo, Brazil; white and yellow LED (Inobram, Pato Branco, Paraná, Brazil;

4 Mendes et al.: EXPOSURE TO DIFFERENT LIGHTING SOURCES 65 Figure 2. Preference test setup, top view (not to scale): birds were initially placed in the center tunnel (dark, with no feed or water), which gave easy access to a chamber equipped with yellow light-emitting diode (LED) bulbs (right) and to another chamber equipped with white LED bulbs (left). Both chambers were equipped with a feeder and a drinker. the sexes. The chickens were separated into 4 groups of 34 birds (17 males and 17 females) and were placed in 4 preference test apparatuses (Figure 1), each composed of 2 distinct chambers (floor area of 2 m 2 ) connected through an access tunnel ( cm) that allowed the birds to move back and forth, according to their preference (Figure 2). One of the chambers was equipped with white LED lamps, and the other was equipped with yellow LED lamps. Each group (replicate, experimental unit) of 34 chickens was initially placed in the access tunnel, which did not offer any light, water, or food to discourage the birds from remaining in this area and to motivate them to choose one of the chambers. Bird preference was assessed through videos captured by polychromatic video cameras located on the ceiling of each chamber. Fifteen-minute videos were recorded daily at 3 distinct times of the day, 0800, 1300, and 2000 h, according to the methodologies proposed by Bizeray et al. [19] and Estevez et al. [20]. The number of males and females in each chamber was recorded at each assessment. Feed intake was measured weekly for each chamber. The chambers were cleaned once a day and food, water, and wood shavings were replaced daily to prevent any preferences by the birds caused by familiar odors. Air temperature and RH measurements helped to ensure that any preference for a particular compartment occurred because of the light environment and not the temperature or RH conditions. Therefore, the environment in each chamber was identical with the exception of the light sources. Data were evaluated through ANOVA, and means were compared through the Tukey and Fisher tests, considering a 95% confidence level, by using the computer software SANEST [21]. Experiment 2: Bird Performance at 2 Distinct Light Sources A total of 360 one-day-old Cobb broiler chickens (180 males and 180 females) were obtained from a local commercial supplier and randomly distributed into 12 pens ( cm), each containing 30 chickens (6 pens with males and 6 pens with females). The sex and light treatments were randomly assigned to the 12 pens, as illustrated in Figure 1. The pens were identical in every aspect, with the exception of the light environment; half of the pens were equipped with white LED bulbs and the other half were equipped with CFL bulbs. All pens were surrounded with a black fabric, which prevented the lighting of one pen from affecting the next pens. Chicken performance was assessed for each of the light environments. The chickens (subsampling) remained within their pens (experimental units) from d 1 through 41. The performance parameters mortality rate, bird BW, BW gain, feed intake, and feed conversion were measured weekly, according to the methodology proposed by Miragliotta [22]. The structure of experiment 2 was a completely randomized design with 3 replicates and a 2 (light source) 2 (sex) factorial arrangement of treatments. Data were evaluated through ANOVA, and means were compared by Tukey s test, considering a 95% confidence level. The analysis was done using the computer software SANEST [21]. RESULTS AND DISCUSSION Experiment 1: Bird Preference for the 2 Distinct Light Colors Figure 3 shows the mean percentage of birds in each of the light environments (white vs. yellow LED) at the time of the assessments. No significant (P > 0.05) differences were found between the number of male and female birds occupying each of the light environments (white vs. yellow LED) for all assessment events (morning, 0800 h; afternoon, 1300 h; and evening, 2000 h), as illustrated in Figure 3. The distribution of birds seemed to be uniform between the 2 chambers. However, feed intake was significantly (P < 0.05) different between chambers when chick-

5 66 JAPR: Research Report Figure 3. Mean percentage of male and female birds present in each light environment [white vs. yellow lightemitting diode (LED)], during the 3 assessment times (0800 h, morning; 1300 h, afternoon and 2000 h, evening). ens were 21, 28, and 35 d old. Birds at these ages ate substantially more in the chamber equipped with white LED lamps (Table 2). There was also an indication that the younger birds ate more in the environment with the white LED lamps, with exception of those at 14 d of age. Nevertheless, no statistical difference was observed in feed intake for younger birds between the chambers. The difference in feed intake may also be attributed to the spectral sensitivity of the chickens. Chickens have the ability to see colored light differently from humans [23]. Chickens are less sensitive than humans to the blue-green Table 2. Comparison of the effects of light source [white vs. yellow light-emitting diode (LED)] on feed intake (kg of feed/bird) of broiler chickens within each of the age groups (7 through 40 d of age) Age, d LED, white LED, yellow ± 0.01 a ± 0.01 a ± 0.01 a ± 0.01 a ± 0.01 a ± 0.01 b ± 0.02 a ± 0.01 b ± 0.02 a ± b ± 0.01 a ± 0.01 a a,b Means followed by different superscript letters within the same line are different by Tukey s test (P < 0.05). color range and much more sensitive to orangered wavelengths (600 to 650 nm). In addition, they can see UV light (350 to 450 nm), which humans cannot detect. Therefore, the chickens under white LED exposure may have perceived an increase in brightness from these light bulbs, which caused their feed intake to increase. Others have suggested that birds prefer specific types of lighting sources. Kristensen et al. [24] evaluated the preference of 4 groups of 6 chickens each (1 to 6 d old) to 4 distinct lighting sources (Biolux, incandescent, warm white, and spectral sensitivity-matched light) and 2 different light intensities. The authors found that 6-wk-old birds preferred Biolux and warm white light bulbs over the other light sources studied, independently of light intensity. In addition, broiler chickens foraged significantly more and stood significantly less under low light intensity (5 lx) than under high light intensity (100 lx), regardless of the lighting type. In several studies, researchers examined the behavior of chickens under different light sources or colors that produced different light intensities. Vandenberg and Widowski [8] examined hens preferences for high-intensity high-pressure sodium (HPS) lighting compared

6 Mendes et al.: EXPOSURE TO DIFFERENT LIGHTING SOURCES 67 with low-intensity incandescent lighting. They observed that hens spent significantly more time preening, nesting, and pecking in the HPS light than in the incandescent light environment and significantly more time sitting and eating in the incandescent light than in the HPS environment. However, hens sat more often in the dark central compartment of the preference setup, suggesting that they may prefer to rest in a darker environment. Light color has also been shown to affect bird behavior. Broiler chickens were found to be less active in blue and green light than in red or white light, and they chose to spend more time under the blue and green light during a preference test [9, 25]. Laying hens preferred fluorescent to incandescent light [7], probably because of the difference in wavelengths between the 2 sources. In the present study, we did not evaluate which specific light characteristics (e.g., intensity, wavelength, or variation) were the most preferred by the birds. Prayitno et al. [9] showed that broilers had an immediate preference for the light color to which they were accustomed. The authors considered the birds general preferences, as well as their rearing experience. Prescott et al. [11] suggested that exposure to natural light would be an ideal solution to many lighting problems and that natural light would generally increase the welfare of domestic fowl. Experiment 2: Bird Performance at 2 Distinct Light Sources Table 3 shows the mean values for feed intake per bird, BW gain, and BW for broiler chickens of different ages and sexes. Significant differences between sexes were found among all response variables (Table 3). Male chickens had significantly higher feed intakes than females after 21 d of age (P < 0.05) and had increased live weight (P < 0.05) and better feed conversion (P < 0.05). Overall, male chickens presented better production performance than did females, as expected. Mortality rate was not statistically different between treatments. These results agree with those of Goldflus [26]. Light source (white LED vs. CFL) alone did not significantly (P > 0.05) influence bird performance. However, significant (P < 0.05) interactions were found between the sex and light source treatments for different chicken ages. Table 4 shows the interaction results between sex and light source for each distinct bird age. Table 3. Comparison of the effects of sex (female vs. male) and light source [light-emitting diode (LED) vs. compact fluorescent lamp (CFL)] on mean values for feed intake (kg/bird), live weight (kg), and feed conversion (kg/kg) of broiler chickens within each of the age groups (7 through 40 d of age) Factor Age, d Feed intake, kg/bird Male 5.87 ± 0.15 a ± 0.24 a ± 1.59ª 32.6 ± 2.91 a ± 3.44 a ± 3.36 a Female 6.04 ± 0.19 a ± 1.44 a ± 1.41 b ± 0.73 b ± 2.37 b ± 0.68 b LED, white 5.98 ± 0.24 a ± 0.56 a ± 2.77 a 29.7 ± 2.04 a ± 3.60 a ± 3.01 a CFL 5.92 ± 0.13 a ± 1.27 a ± 0.80 a ± 3.44 a ± 3.54 a ± 1.46 a CV, % Live weight, kg Male 0.19 ± 0.01 a 0.52 ± 0.01 a 0.99 ± 0.04 a 1.76 ± 0.09 a 2.37 ± 0.12 a 2.77 ± 0.16 a Female 0.18 ± 0.01 b 0.48 ± 0.05 a 0.87 ± 0.07 b 1.57 ± 0.09 b 2.06 ± 0.08 b 2.42 ± 0.06 b LED, white 0.19 ± 0.01 a 0.51 ± 0.05 a 0.93 ± 0.09 a 1.66 ± 0.16 a 2.21 ± 0.17 a 2.6 ± 0.23 a CFL 0.19 ± 0.01 a 0.5 ± 0.04 a 0.93 ± 0.07 a 1.67 ± 0.10 a 2.21 ± 0.22 a 2.6 ± 0.23 a CV, % Feed conversion, kg/kg Male 1.23 ± 0.06 b 1.51 ± 0.09 a 2.17 ± 0.17 a 2.61 ± 0.17 a 2.47 ± 0.60 a 1.97 ± 0.34 a Female 1.33 ± 0.04 a 1.72 ± 0.33 a 2.54 ± 0.47 a 2.62 ± 0.18 a 2.66 ± 0.55 a 2.28 ± 0.37 a LED, white 1.27 ± a 1.56 ± 0.26 a 2.34 ± 0.47 a 2.63 ± 0.12 a 2.62 ± 0.54 a 2.14 ± 0.47 a CFL 1.29 ± 0.03 a 1.67 ± 0.27 a 2.37 ± 0.33 a 2.67 ± 0.22 a 2.51 ± 0.62 a 2.11 ± 0.30 a CV (%) a,b Means followed by different superscript letters within a row are significantly different by Tukey s test (P < 0.05).

7 68 JAPR: Research Report Table 4. Comparison of the effects of sex (female vs. male) and light source [light-emitting diode (LED) vs. compact fluorescent lamp (CFL)] on feed intake (kg), live weight (kg), and feed conversion (kg/kg) results, accounting for the interaction between sex and light source, within each of the age groups (7 through 40 d of age) Item LED, white CFL Feed intake, kg/bird 7 d of age Male 5.82 ± 0.29 a,b 5.92 ± 0.31 a,a Female 6.14 ± 0.22 a,a 5.93 ± 0.31 a,a 14 d of age Male ± 0.90 a,a 12.6 ± 0.55 a,a Female ± 0.58 a,a ± 1.01 a,a 21 d of age Male ± 1.29 a,a ± 1.30 a,a Female ± 1.11 a,b ± 1.08 b,a 28 d of age Male ± 2.02 a,a ± 2.30 a,a Female ± 1.80 a,a ± 1.89 a,b 35 d of age Male ± 2.00 a,a ± 1.99 a,a Female 33.4 ± 1.80 a,a 30.9 ± 1.50 a,a 40 d of age Male ± 0.90 a,a ± 0.85 a,a Female ± 0.90 a,a ± 0.95 a,a Live weight, kg 7 d of age Male 0.19 ± 0.02 a,a 0.19 ± 0.03 a,a Female 0.18 ± 0.02 a,a 0.18 ± 0.02 b,a 14 d of age Male 0.52 ± 0.02 a,a 0.53 ± 0.03 a,a Female 0.5 ± 0.03 a,a 0.47 ± 0.02 b,a 21 d of age Male 1.00 ± 0.01 a,a 0.97 ± 0.01 a,a Female 0.86 ± 0.01 a,b 0.89 ± 0.02 a,a 28 d of age Male 1.8 ± 0.05 a,a 2.73 ± 0.19 a,a Female 1.53 ± 0.04 a,b 2.61 ± 0.19 a,a 35 d of age Male 2.32 ± 0.20 a,a 2.42 ± 0.50 a,a Female 2.1 ± 0.20 a,a 2.02 ± 0.45 a,a 40 d of age Male 2.75 ± 0.60 a,a 2.79 ± 0.60 a,a Female 2.44 ± 0.55 a,a 2.39 ± 0.50 a,a Feed conversion, kg/kg 7 d of age Male 1.19 ± 0.20 b,b 1.27 ± 0.22 a,a Female 1.36 ± 0.21 a,a 1.3 ± 0.22 a,a 14 d of age Male 1.53 ± 0.11 a,a 1.49 ± 0.21 a,a Female 1.58 ± 0.12 a,a 1.86 ± 0.22 a,a 21 d of age Male 2.19 ± 0.55 a,a 2.16 ± 0.50 a,a Female 2.48 ± 0.60 a,a 2.59 ± 0.60 a,a 28 d of age Male 1.57 ± 0.30 a,a 2.79 ± 0.60 a,a Female 1.69 ± 0.33 a,a 2.55 ± 0.50 a,a Continued Table 4 (Continued). Comparison of the effects of sex (female vs. male) and light source [light-emitting diode (LED) vs. compact fluorescent lamp (CFL)] on feed intake (kg), live weight (kg), and feed conversion (kg/kg) results, accounting for the interaction between sex and light source, within each of the age groups (7 through 40 d of age) Item LED, white CFL 35 d of age Male 2.86 ± 0.60 a,a 2.10 ± 0.60 a,a Female 2.38 ± 0.58 a,a 2.95 ± 0.58 a,a 40 d of age Male 2.02 ± 0.70 a,a 1.93 ± 0.60 a,a Female 2.27 ± 0.65 a,a 2.29 ± 0.65 a,a a,b Means followed by different superscript lowercase letters within a column and within age are different by Tukey s test (P < 0.05). A,B Means followed by different superscript uppercase letters within a row are different by Tukey s test (P < 0.05). When raised under exposure to CFL, male chickens presented significantly (P < 0.05) higher live weights than did female chickens at 7 and 14 d of age. However, live weight was not significantly different between sexes for the remaining ages and for birds raised under the white LED bulbs. Feed conversion was significantly (P < 0.05) lower for 7-d-old male chickens exposed to white LED bulbs. These results suggest that the CFL may have had a negative effect on the feed conversion of 7-d-old male birds, whereas feed conversion was not affected by the light source in older birds (Table 4). Male chickens generally consumed more feed than did female chickens at 21 d when exposed to CFL (P < 0.05). However, no significant effects of light source were observed relative to BW and feed conversion for this age of bird. These results indicate that, under white LED lamps, 21-d-old male chickens ate less and had the same performance results as birds exposed to CFL. Feed intake and live weight were significantly (P < 0.05) higher for 21- and 28-d-old female birds raised under CFL. However, light source did not affect the feed conversion of these birds, indicating that the LED lamps resulted in better performance with the same feed conversion as for the 21- and 28-d-old female birds raised under CFL. The LED bulbs used in this study are currently available on the global market. The major benefits of LED lamps compared with other

8 Mendes et al.: EXPOSURE TO DIFFERENT LIGHTING SOURCES 69 light sources commonly used in agriculture are their good luminous efficiency, long operating life, resistance to moisture, and availability in different peak wavelengths. However, although researchers have been studying the effect of different light intensities [1, 27, 28] and the use of dimmers [29] on bird performance, data are lacking in the literature on the effect of LED lighting on the performance and welfare of agricultural animals and poultry. Others [30] have suggested that green LED lighting enhances broiler growth at an early age, whereas blue LED lighting enhances growth at older ages. Switching lighting from blue to green at 20 d of age also improved growth as compared with white light (CFL). The average FE and mortality rate did not differ between groups. Light has been shown to affect bird performance. Nevertheless, researchers indicate wide variation in performance results attributable to lighting effects, especially with respect to the use of colored light. This variation in results may be due to differences in light source and light schedule, as well as age, species, and breed of experimental animals. CONCLUSIONS AND APPLICATIONS 1. The distribution of broiler chickens was uniform and even between the 2 chambers; thus, the birds did not show any preference for white vs. yellow LED environments. 2. Feed intake was significantly (P < 0.05) higher in the chamber equipped with white LED lights when chickens were 21, 28, and 35 d old. 3. Seven-day-old male chickens raised under LED bulbs had better feed conversion than did chickens of the same age raised under CFL. 4. Generally, the chickens raised under white LED bulbs had better production performance than did chickens raised under CFL. REFERENCES AND NOTES 1. Olanrewaju, H. A., J. P. Thaxton, W. A. Dozier, J. Purswell, W. B. Roush, and S. L. Branton A review of lighting programs for broiler production. Int. J. Poult. Sci. 5: Théry, M Forest light and its influence on habitat selection. Plant Ecol. 153: Prescott, N. B., and C. M. Wathes Reflective properties of domestic fowl (Gallus g. domesticus), the fabric of their housing and the characteristics of the light environment in environmentally controlled poultry houses. Br. Poult. Sci. 40: Farm Animal Welfare Council Report on the Welfare of Broiler Chickens. Ministry of Agriculture, Fisheries and Food, London, UK. 5. Lewis, P. D., and T. Morris Poultry Lighting The Theory and Practice. Nottingham Univ. Press, Nottingham, UK. 6. Davis, N. J., N. B. Prescott, C. J. Savory, and C. M. Wathes Preferences of growing fowls for different light intensities in relation to age, strain and behaviour. Anim. Welf. 8: Widowski, T. M., L. J. Keeling, and I. J. H. Duncan The preferences of hens for compact fluorescent over incandescent lighting. Can. J. Anim. Sci. 72: Vandenberg, C., and T. M. Widowski Hens preferences for high-intensity high-pressure sodium or lowintensity incandescent lighting. J. Appl. Poult. Res. 9: Prayitno, D. S., C. J. C. Phillips, and H. Omed The effects of color of lighting on the behavior and production of meat chickens. Poult. Sci. 76: Widowski, T. M., and I. J. H. Duncan Laying hens do not have a preference for high-frequency versus low-frequency compact fluorescent light sources. Can. J. Anim. Sci. 76: Prescott, N. B., C. M. Wathes, and J. R. Jarvis Light, vision and the welfare of poultry. Anim. Welf. 12: Sherwin, C. M Light intensity preferences of domestic male turkeys. Appl. Anim. Behav. Sci. 58: Denbow, D. M., A. T. Leighton, and R. M. Hulet Effect of light sources and light intensity on growth, performance, and behaviour of female turkeys. Br. Poult. Sci. 31: Boshouwers, F. M. G., and E. Nicaise Artificial light sources and their influences on physical activity and energy expenditure of laying hens. Br. Poult. Sci. 34: Duncan, I. J. H Designing environments for animals Not for public perceptions. Br. Vet. J. 148: Dawkins, M. S From an animal s point of view: Motivation, fitness, and animal welfare. Behav. Brain Sci. 13: Federation of Animal Science Societies Guide for the Care and Use of Agricultural Animals in Research and Teaching. 3rd ed. Fed. Anim. Sci. Soc., Champaign, IL. 18. Pluma Agroavícola, Linha Santo Izidoro, Dois Vizinhos, Paraná State, Brazil. 19. Bizeray, D., I. Estevez, C. Leterrier, and F. M. Faure Effects of increasing environmental complexity on the physical activity of broiler chickens. Appl. Anim. Behav. Sci. 79:27 41.

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