Photostimulation of Japanese quail

Photostimulation of Japanese quail A. B. Molino, 1 E. A. Garcia, G. C. Santos, J. A. Vieira Filho, G. A. A. Baldo, and I. C. L. Almeida Paz Department of Animal Production, FMVZ, Unesp-Botucatu/SP, Brazil ABSTRACT To adapt commercial poultry production to a new scenario of energy savings and to develop specific practices for quail production aimed at reducing costs while maintaining or improving productivity, four experiments were conducted. In the first experiment, birds were allocated to four treatments (photoperiod duration): T1: 14L:10D; T2: 15L:9D; T3: 16L:8D; and T4: 17L:7D. In the second experiment, birds were subjected to four levels of brightness: T1: 5 lux; T2: 10 lux; T3: 15 lux; and T4: 22 lux (control). In the third experiment, four types of lamps were evaluated: T1: compact fluorescent lamp (color temperature: 6,500K); T2: compact fluorescent lamp (color temperature: 2,700K); T3: incandescent lamp; and T4: yellow LED. In the last experiment, four lighting programs were compared: T1: continuous program (control), in which there was a single photoperiod of 15 h; the other treatments consisted of intermittent lighting programs, as follows: T2: 1 h of light provided 1 h after dusk; T3: 1 h of light provided 2 h before dawn; T4: half an hour of light provided 1 h after dusk and half an hour of light provided 1.5 h before dawn. In each experiment, 1,296 Japanese quail were evaluated for four 28-d cycles, totaling 112 experimental days. A completely randomized experimental design of 4 treatments with 12 replicates of 27 birds each was applied in all trials. Performance and egg quality were evaluated in each experiment. Higher egg production and adequate egg quality, as well as energy savings, can be obtained with Japanese quail using compact fluorescent lamps or LEDs and a photoperiod of 15 h/d supplied using an intermittent lighting program, with 1 h of artificial light 2 h before dawn at a brightness of 5lux. Key words: ambience, egg production, energy savings, management of quail 2015 Poultry Science 94:156 161 http://dx.doi.org/10.3382/ps/peu039 INTRODUCTION Japanese quail production has increased since its start as a commercial poultry activity. The reasons for this success are the excellent meat quality and the high nutritional value and pleasant flavor of Japanese quail eggs, which has resulted in wide acceptance by consumers. However, its production faces some challenges (Martins, 2002), such as the lack of research on farm and environmental management practices. The literature does not provide a manual for the raising of Japanese quail that contains information on the ideal weight for each phase, nutritional requirements, lighting management, and other aspects. In this context, producers have utilized manuals on laying hens, and despite the good results obtained, there is a need for research studies related to the raising of quail in order to develop a specific manual such as those that already exist for hens, breeders, and broiler chickens. Thus, few works evaluate the photostimulation of quail, a fact that necessitates presenting reviews and results from other authors with other species to enable confir- C 2015 Poultry Science Association Inc. Received April 15, 2014. Accepted October 24, 2014. 1 Corresponding author: molinoab@fmvz.unesp.br mation of the diverging results when utilizing manuals for other species in the raising of quail. Artificial lighting is routinely applied in intensive egg production. Lighting can be used to delay or accelerate age at sexual maturity and to stimulate egg laying because long photoperiods stimulate the sexual function of layers and optimize egg production (Freitas et al., 2005). Continuous photoperiods of approximately 16 17 h daily have been used for many years in commercial egg production. Light is commonly supplied using incandescent lamps, with a brightness of 22 lux, and in tropical countries, where hens are generally kept in open-sided houses, artificial light is used only to complement the natural photoperiod. Lewis et al. (1997) reported that under photoperiods of 8 13 h, white and brown laying hens increase egg production by an average of 1% for each hour of increase in the photoperiod. The same lighting management started to be applied to Japanese quail on the assumption that their laying behavior would be similar to that of laying hens. However, despite the physiological similarities of Japanese quail and hens, the direct application of such a lighting regime to Japanese quail needs to be studied. Brightness may influence both age at sexual maturity and egg production. According to Etches (1996), 156

PHOTOSTIMULATION OF JAPANESE QUAIL 157 brightness during the photoperiod (light phase) and the scotoperiod (dark phase) affects the circadian rhythm that controls the time of lay. Incandescent lamps are commonly used to light poultry houses; however, their rate of conversion of electrical energy into light energy is low, and they have low durability (1,000 h average life), which increases production costs (Jordan & Tavares, 2005). Nevertheless, environmental lighting technology has greatly advanced in the last few years, and traditional incandescent lamps is being steadily replaced by light-emitting diodes (LEDs). The main advantage of LEDs is their energy savings (they consume 80% less energy than incandescent lamps and 50% less than fluorescent lamps), their longer life, and a wavelength that permits them to be used in the photostimulation of diverse types of poultry. Araújo et al. (2011) report that compact fluorescent lamps have higher installation costs but use 70% less energy and live longer (8 10 times longer) than incandescent lamps. An interesting aspect of the physiology of egg-laying poultry is the fact that they do not need to be continuously subjected to long days. This phenomenon is called a subjective day, when adult hens in lay ignore periods of dark between the 14 16 h of light stimulation (Gewehr, 2003). When the period of light occurs during the night, before dawn, the bird understands this period as the beginning of the day, ignoring the subsequent period of dark between the period of light and dawn. This also happens after dusk; if there is a period of light at a determined time of the night, the period between dusk and the period of light is ignored. The technological modernization of commercial poultry production that has occurred in recent decades has not taken into account the possible limitations of electrical energy, and solutions are now being sought to reduce the consumption of electrical energy. To adapt commercial poultry production to the new scenario of energy savings and to develop specific practices for quail production aimed at reducing costs while maintaining or improving productivity, research on the lighting of Japanese quail houses is required. This is the objective of the present study. MATERIALS AND METHODS Four experiments were carried out at the School of Veterinary Medicine and Animal Science of Universidade Estadual Paulista Júlio de Mesquita Filho, Botucatu campus, Brazil. Up to 7 weeks of age, birds were subjected to a natural photoperiod. When 5% of production was achieved, weekly increases in illumination of 30 min were administered up to 14 h of light per day, with the artificial illumination being provided by incandescent lamps. When the production peak was reached, the birds were selected. Body weight was not controlled since there is no manual in the literature on the lineage specifying a suitable level for this parameter. Thus, the birds were selected only for their productivity, and the unproductive ones were discarded. After being distributed in accordance with the treatments, only after 28 d was the experiment begun in the production house so that adaptation to the changed environment would not influence the results. In each experiment, 1,296 Japanese quail, with an initial age of 15 weeks, were evaluated for four 28-d cycles, totaling 112 experimental days. A completely randomized experimental design of 4 treatments with 12 replicates of 27 birds each was applied in all trials. A70 10 m open-sided house with a drop ceiling was divided into 8 environments using black plastic canvas to prevent the passage of light from one environment to the others. Birds were housed in battery cages (one per environment). Each battery contained 6 metal cages, housing 27 birds each, at a density of 135.1 cm 2 /bird. Each cage was equipped with a trough feeder and a nipple drinker placed in front of the cage. Feed was based on corn and soybean meal, formulated according to the recommendations of the NRC (1994), and offered ad libitum during the entire experimental period. Mortality and the number of intact and cracked eggs were recorded daily. Feed residues were weighed each week for each cage to estimate the average feed intake per bird housed. During the preexperimental adaptation phase, all birds were submitted to 14 h of light per day. Before the beginning of each experiment, flocks were selected by culling nonproductive birds. In the first experiment, birds were subjected to 4 treatments (photoperiod duration): T1: 14 h of light and 10 h of dark (14L:10D); T2: 15 h of light and 9 h of dark (15L:9D); T3: 16 h of light and 8 h of dark (16L:8D); and T4: 17 h of light and 7 h of dark (17L:7D). The natural photoperiod ranged between 11 h 30 min and 13 h 30 min, and the artificial light suppliedineachtreatmentwasequallydividedbetweenthe morning and afternoon periods. The brightness of the artificial lighting to complement the natural photoperiod was 22 lux. Incandescent lamps and a continuous lighting program were used. In the second experiment, birds were subjected to 4 levels of brightness. The following treatments were applied: T1: 5 lux; T2: 10 lux; T3: 15 lux; and T4: 22 lux (control). In each treatment, brightness was measured using a luximeter placed at the height of the birds head. The natural photoperiod ranged between 10h45min and 12h30min, and the amount of hours of artificial light supplied in each treatment was equally divided between the morning and afternoon periods to supply 15 h of continuous light per day, which was the best result obtained in the previous experiment. Incandescent lamps were used in all treatments. In the third experiment, four types of lamp were evaluated, as follows: T1: compact fluorescent lamp

158 MOLINO ET AL. (color temperature: 6,500K); T2: compact fluorescent lamp (color temperature: 2,700K); T3: incandescent lamp; and T4: LED (color temperature: 2,700K). During the entire experimental period, the natural photoperiod ranged between 12h45min and 10h30min, and the number of hours of artificial light supplied in each treatment was equally divided between the morning and afternoon periods to supply 15 h of continuous light per day. Birds were submitted to 15 continuous hours of light per day, and the artificial brightness of the artificial light used to complement the natural photoperiod was 5 lux because these were the best results obtained in the 2 previous experiments. In the last experiment, 4 lighting programs were compared. The first treatment consisted of a continuous program (control) in which a continuous photoperiod was supplied for 15 h from 6 am to 9 pm (natural + artificial light). The second treatment consisted of an intermittent program in which the lamps were turned on at 6am and off at 7am, when natural lighting commenced; subsequently, the lamps were turned on at 6pm and off at 7pm, then turned on again at 8pm and off at 9pm. The third treatment employed an intermittent program in which the lamps were turned on at 6am and off at 7am, when natural lighting commenced; afterwards, the lamps were turned on at 6pm and off at 7pm and again turned on at 4am and off at 5am. The fourth treatment employed an intermittent program wherein the lamps were turned on at 6am and off at 7am, when natural lighting commenced; subsequently, the lamps were turned on at 6pm and off at 7pm and on again at 8pm and off at 8:30pm, then once more turned on at 4:30am and off at 5am. Considering the concept of subjective day of Sauveur (1996), all intermittent lighting programs provided a 15-h photoperiod and an artificial brightness of 5 lux using a fluorescent compact lamp because these were the best results obtained in the 3 previous experiments. The following parameters were evaluated in each experiment: feed intake, egg production percentage, percentage of intact eggs, egg weight, egg mass, feed conversion ratio per dozen eggs and per egg mass, and livability. In each 28-d period, 2 eggs per replicate were collected for 3 consecutive days for analysis, totaling 24 eggs per treatment in each analysis. The following egg-quality parameters were evaluated: egg specific gravity, analyzed according to the recommendations of Moreng & Avens (1990) and expressed in grams per cubic centimeter; egg breaking strength, using a texturmeter (TA.XT plus Texture analyzer) with a 75-mm (P/75) breaking probe; eggshell percentage was calculated as the ratio between eggshell weight and egg weight; and eggshell thickness was calculated as the average of 3 measurements made at 3 points equidistant from the shell equator using a digital pachymeter and expressed in millimeters. Eggshell weight per surface area (EWSA) was determined according to the following equation: EWSA = (eggshell weight/3.9782 egg weight 0.7056 ) 1000, and expressed in milligrams per square centimeter. Data were subjected to analysis of variance, and means were compared by the test of Tukey (P < 0.05), using the SISVAR statistical package (2000, Ferreira, D.F. Lavras: UFLA/DEX). RESULTS AND DISCUSSION Table 1 presents the performance results of the new lighting regime with the Japanese quail in the four experiments. As shown in Table 1, in the first experiment, photoperiod duration influenced only egg production percentage. Birds that received 14 h of light per day produced fewer eggs than those subjected to the other treatments. Lewis et al. (1997) subjected white and brown laying hens to photoperiods of 8, 10, 13, or 16 h of light per day and observed an increasing linear effect of photoperiod on egg production and feed intake. The authors concluded that both layer types increased their egg production by 1% for each hour of increase in photoperiod, which differs from the results of the present study, confirming that the laying hens and quail can present divergent responses when subjected to the same photoperiod. Brightness and lamp type did not influence any of the evaluated performance parameters. Although the literature contains reports that chickens require a 10 difference in brightness to able to differentiate day from night, Robinson & Renema (1999) found that 0.47 lux are not sufficient to stimulate the activity of broiler breeders; at least 5 lux were required also to allow them to differentiate day from night. Given what was observed in the results of the present study, the quail, as well as the breeders, require only 5 lux. This reinforces the hypothesis that manuals for laying hens should not be used in the raising of quail since the recommendation for the former is 22 lux, while for quail only 5 lux is sufficient. Lamp type had no effect on production performance. In addition, Gewehr (2003) found no egg production differences in Japanese quail when using fluorescent or incandescent lamps. Jácome et al. (2012) compared colored LED (white, orange, or yellow) with incandescent lamps, and concluded that, independently of color, lamp type did not influence the production performance of Japanese quail. In our study lighting programs influenced only egg production and egg mass. The continuous program (T1) and T3 (lamps were turned on at 6am and off at 7am, when natural lighting commenced; subsequently, the lamps were turned on at 6pm and off at 7pm and again turned on at 4am and off at 5am) provided better results than the T4 (lamps were turned on at 6am and off at 7am, when natural lighting commenced; subsequently, the lamps were turned on at 6pm and off at 7pm and again turned on at 8pm and off at 8:30pm,

PHOTOSTIMULATION OF JAPANESE QUAIL 159 Table 1. Performance of Japanese quail submitted to the experimental treatments. Treatment FI (g) EP (%) EW (g) EM (g) FCRdz (g/dz) FCRem (g/g) Int (%) Liv (%) PHOTOPERIOD LENGTH 14L:10D 29.83 89.16 B 11.17 9.97 0.40 3.01 98.84 100.00 15L:9D 28.89 92.18 A 11.19 10.31 0.38 2.81 99.43 99.74 16L:8D 28.68 91.59 A 11.16 10.23 0.37 2.81 99.20 99.73 17L:7D 29.11 92.71 A 11.26 10.44 0.38 2.79 99.31 99.87 CV (%) 3.45 3.51 1.63 4.45 4.40 5.23 0.84 0.21 P-value 0.252 0.031 0.816 0.363 0.079 0.074 0.303 0.134 BRIGHTNESS 5 lux 31.39 92.77 11.16 10.35 0.41 3.04 99.51 100.00 10 lux 30.97 91.18 11.09 10.12 0.41 3.09 99.43 99.85 15 lux 30.40 92.35 11.12 10.27 0.40 2.97 99.61 99.84 22 lux 31.24 93.13 11.07 10.31 0.40 3.04 99.75 100.00 CV (%) 2.48 3.62 1.63 4.37 3.99 4.48 0.92 0.17 P-value 0.167 0.762 0.842 0.820 0.321 0.534 0.238 0.216 LAMP TYPES CF 1 29.84 93.35 10.98 10.25 0.39 2.96 98.74 99.84 CF 2 28.85 91.28 11.13 10.17 0.38 2.89 99.50 99.84 Incand 29.63 92.78 11.13 10.33 0.39 2.92 99.52 99.75 LED 29.95 93.85 11.09 10.41 0.39 2.92 99.31 99.84 CV (%) 3.69 3.19 1.80 3.90 5.32 5.13 0.78 0.25 P-value 0.322 0.487 0.557 0.761 0.975 0.890 0.299 0.897 LIGHTING PROGRAM T1 28.87 89.97 A 10.41 9.36 A 0.39 3.11 99.13 99.23 T2 27.48 85.53 AB 10.35 8.85 AB 0.39 3.14 99.26 99.01 T3 27.94 88.18 A 10.23 9.02 A 0.39 3.15 98.81 99.03 T4 27.69 84.09 B 10.39 8.74 B 0.40 3.21 98.73 99.60 CV (%) 5.26 3.85 1.79 4.19 4.83 4.29 0.83 0.84 P-value 0.391 0.022 0.348 0.042 0.583 0.657 0.648 0.602 Means followed by different letters in the same column are statistically different by the test of Tukey (P < 0.05). FI: feed intake/bird/day; EP: egg production percentage; EW: egg weight; EM: egg mass; FCRdz: feed conversion ratio per dozen eggs; FCRem: feed conversion ratio per egg mass; Int: percentage of intact eggs; Liv: livability. CF1: compact fluorescent lamp (color temperature: 6,500K); CF2: compact fluorescent lamp (color temperature: 2,700K). Incand: incandescent lamp. T1: continuous program; T2: lamps were turned on at 6am and off at 7am, when natural lighting commenced; subsequently, the lamps were turned on at 6pm and off at 7pm, then turned on again at 8pm and off at 9pm. T3: lamps were turned on at 6am and off at 7am, when natural lighting commenced; subsequently, the lamps were turned on at 6pm and off at 7pm and again turned on at 4am and off at 5am. T4: lamps were turned on at 6am and off at 7am, when natural lighting commenced; subsequently, the lamps were turned on at 6pm and off at 7pm and again turned on at 8pm and off at 8:30pm, then turned on once more at 4:30am and off at 5am. then turned on once more at 4:30am and turned at 5am). The T2 program (lamps were turned on at 6am and off at 7am, when natural lighting commenced; subsequently, the lamps were turned on at 6pm and off at 7pm, then turned on again at 8pm and off at 9pm) provided intermediate results and was not different from the others. Gewehr et al. (2005) observed no differences in egg production and egg mass when comparing a continuous lighting program with two intermittent lighting programs (one with half an hour of light before dawn, the other with half an hour of light before dawn and half an hour of light after dusk), all totaling 15h30min of light/day. Therefore, the reported differences in lighting effects on commercial laying hens, broilers, and Japanese quail need to be taken into account, stressing the importance of studying specific rearing practices for each poultry type because each type may respond differently to the same rearing conditions. Table 2 presents the egg-quality results of quail in the four experiments. The absence of significant effects of photoperiod length on the quality of eggs shows that the variation in light quantity supplied has a greater effect on egg production without influencing the internal and external quality of the eggs. The purpose of this study was to maintain egg production and egg quality while at the same time saving electrical energy. Therefore, the lack of effects of brightness on egg production and quality is considered positive because birds maintained at the lowest intensity tested achieved the same performance and egg quality indices as those kept at higher intensities and, in addition, required less energy use. The absence of an effect of lamp type obtained in the present study indicates that when adequate light length and intensity are supplied, lamp type does not change Japanese quail performance or egg quality, but it may provide energy savings because LED lamps are twice as economical as compact fluorescent lamps, which in turn are 70% more economical than incandescent lamps (Borille et al., 2012). According to the data in Table 2, lighting programs influenced only eggshell thickness. The continuous program (T1) and T3 (lamps were turned on at 6am and turned at 7am, when natural lighting commenced; subsequently, the lamps were turned on at 6pm and off at 7pm and turned on again at 4am and off at 5am) provided better results than the T4 program (lamps were

160 MOLINO ET AL. Table 2. Egg quality of Japanese quail submitted to experimental treatments Treat. ESG (mg/cm 3 ) Strength (gf) Eggshell (%) Thickness (mm)(mm) EWSA (mg/cm 3 ) PHOTOPERIOD LENGTH 14L:10D 1.076 1.283 8.13 0.224 41.74 15L:9D 1.077 1.294 8.19 0.224 41.87 16L:8D 1.077 1.333 8.23 0.222 41.98 17L:7D 1.076 1.265 7.99 0.219 40.82 CV (%) 0.17 8.03 2.89 2.31 2.66 P-value 0.109 0.437 0.088 0.076 0.069 BRIGHTNESS 5 lux 1.075 1.350 8.09 0.221 41.27 10 lux 1.075 1.344 8.08 0.219 41.42 15 lux 1.074 1.242 8.07 0.218 41.28 22 lux 1.075 1.310 8.03 0.219 41.44 CV (%) 0.14 8.89 3.34 2.49 3.35 P-value 0.481 0.115 0.944 0.703 0.994 LAMP TYPE CF 1 1.077 1.347 7.94 0.211 41.54 CF 2 1.076 1.212 7.82 0.211 40.61 Incand 1.078 1.315 8.01 0.209 41.87 LED 1.076 1.202 7.76 0.208 40.13 CV (%) 0.44 11.16 4.39 3.56 7.09 P-value 0.372 0.078 0.253 0.130 0.434 LIGHTING PROGRAM T1 1.074 1.492 8.19 0.226 A 41.25 T2 1.075 1.514 8.12 0.215 AB 41.19 T3 1.074 1.421 8.07 0.225 A 41.15 T4 1.074 1.494 8.01 0.208 B 40.99 CV (%) 0.66 12.92 4.49 4.64 8.03 P-value 0.991 0.523 0.747 0.017 0.992 Means followed by different letters in the same column are statistically different by the test of Tukey (P < 0.05). ESG: egg specific gravity; Strength: eggshell breaking strength; Eggshell: eggshell percentage; Thickness: eggshell thickness; EWSA: eggshell weight per surface area. CF1: compact fluorescent lamp (color temperature: 6,500K), CF2: compact fluorescent lamp (color temperature: 2,700K); Incand: incandescent lamp. T1: continuous program; T2: lamps were turned on at 6am and off at 7am, when natural lighting commenced; subsequently, the lamps were turned on at 6pm and off at 7pm, then turned on again at 8pm and off at 9pm. T3: lamps were turned on at 6am and off at 7am, when natural lighting commenced; subsequently, the lamps were turned on at 6pm and off at 7pm and again turned on at 4am and off at 5am. T4: lamps were turned on at 6am and off at 7am, when natural lighting commenced; subsequently, the lamps were turned on at 6pm and off at 7pm and again turned on at 8pm and off at 8:30pm, then once more turned on at 4:30am and off at 5am. turned on at 6am and off at 7am, when natural lighting commenced; subsequently, the lamps were turned on at 6pm and turned off at 7pm and again turned on at 8pm and off at 8:30pm, then turned on once more at 4:30am and off at 5am). The T2 program (lamps were turned on at 6am and off at 7am, when natural lighting commenced; subsequently, the lamps were turned on at 6pm and off at 7pm, then turned on again at 8pm and off at 9pm) results were not different from those of the other programs. The differences in eggshell thickness may be due to differences in egg production and egg mass because the birds that produced more and heavier eggs also produced eggs with thicker eggshells. Eggshell synthesis depends on the endocrine interaction among certain organs. Therefore, several factors may influence eggshell thickness. As hens age, in addition to reduced estrogen and 1,25 dihydroxycholecalciferol production, eggshell thickness is also influenced by parathyroid action (parathormone synthesis), calcium absorption rate, acid base balance, ion balance, respiratory activity, dietary nutritional levels, blood phosphorus level, egg size and weight, and environmental temperature (Lesson & Summers, 1997). Our results are consistent with the findings of Gewehr et al. (2005), who also observed differences in the eggshell thickness of Japanese quail eggs when comparing a continuous lighting program with 2 intermittent lighting programs (program 1 provided half an hour of light to an hour before dawn, whereas program 2 provided half an hour of light before dawn and half an hour of light after dusk), all of which provided 15h30m of light/day. In their study, birds in program 2 produced eggs with thicker eggshells compared with the continuous program, whereas program 1 was not different from the others. Higher egg production and adequate egg quality, as well as energy savings, can be obtained with Japanese quail using compact fluorescent lamps or LEDs and a photoperiod of 15 h/d supplied using an intermittent lighting program, with 1 h of artificial light 2 h before dawn at a brightness of 5 lux.

PHOTOSTIMULATION OF JAPANESE QUAIL 161 ACKNOWLEDGMENTS This research was supported by Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP), São Paulo, Brazil. REFERENCES Araújo, W. A. G., L. F. T. Albino, F. C. Tavernari, and M. J. S. Godoy. 2011. Programa de luz na avicultura de postura. Rev. CFMV. 52:58 65. Borille, R., R. G. Garcia, A. F. B. Royer, I. C. L. A. Paz, F. R. Caldara, I. A. Nääs, and I. M. D. T. Jácome. 2012. LED: Uma nova luz para a avicultura moderna. Rev. Ov. 7:14 18. Etches, R. J. 1996. Reproducción aviaria. 1st rev. ed. S. A. Acribia España, Zaragoza. Freitas, H. J., J. T. B. Cotta, A. I. G. Oliveira, and C. E. Gewher. 2005. Avaliação de programas de iluminação sobre o desempenho zootécnico de poedeiras leves. Cienc. Agrotec. 29(2): 424 428. Gewehr, C. E. 2003. Avaliação de programas de iluminação em codornas (Coturnix coturnix). PhD Diss. Univ. Federal de Lavras, Minas Gerais. Gewehr, C. E., J. T. B. Cotta, A. I. G. Oliveira, and H. J. Freitas. 2005. Efeitos de programas de iluminação na produção de ovos de codornas (Coturnix coturnix). Cienc. Agrotec. 29(4):857 865. Jácome, I. M. D. T., R. Borille, L. A. Rossi, D.W. Rizzotto, J. A. Becker, and C. F. R. Sampaio. 2012. Desempenho produtivo de codornas alojadas em diferentes sistemas de iluminação artificial. Arch. Zootec. 61(235):449 456. Jordan, R. A., and M. H. F. Tavares, 2005. Análise de diferentes sistemas de iluminação para aviários de produção de ovos férteis. Rev. Bras. Eng. Agric. Ambient. 9(3):420 423. Lesson, S., and J. D. Summers. 1997. Commercial poultry nutrition. ed. University Books, Guelph, Canada. Lewis, P. D., G. C. Perry, and T. R. Morris. 1997. Effect of size and timing of photoperiod increase on age at first egg and subsequent performance of two breeds of laying hen. Brit. Poult. Sci. 38(2):142 150. Martins, E. N. 2002. Perspectivas do melhoramento genético de codornas no Brasil. Proc. Simp. Int. Cot. 1:204 208. Moreng,R.E.,andJ.S.Avens.1990.Ciência e produção de aves. 1st rev. ed. Roca, São Paulo, SP, Brazil. National Research Council. 1994. Nutrient requirement of poultry. 9th rev. ed. Natl. Acad. Press, Washington, DC. Robinson, F. E., and R. A. Renema. 1999. Principles of photoperiod management in female broiler breeders. Tech News. 7(1):1 6. Sauveur, B. 1996. Photopériodisme et reproduction des oiseaux domestiques femelles. Anim. Prod. 9(1):25 34.