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Effect of embryonic photostimulation on the posthatch growth of turkey poults
Effect of Embryonic Photostimulation on the Posthatch Growth of Turkey Poults I. Rozenboim,*,1 R. Huisinga,† O. Halevy,* and M. E. El Halawani‡ *Hebrew University of Jerusalem, Faculty of Agriculture, Department of Animal Science, PO Box 12, Rehovot 76100, Israel; †Willmar Poultry Corporation, Inc., Willmar, Minnesota 56201; and ‡University of Minnesota, Department of Animal Science, 1988 Fitch Ave., St. Paul, Minnesota 55108 ABSTRACT Artificial illumination, including light quality, is important in modern meat-type poultry management. In the present study, the effect of in ovo monochromatic green light photostimulation on posthatch growth of turkey poults was investigated. In experiment 1, 182 turkey eggs were divided into two light treatment groups (n = 91). The first group was intermittently photostimulated (3 min on and 3 min off) with green light provided by five light-emitting diodes (LED) per egg at 0.1 W/m2 at the upper eggshell surface. The second group was incubated in the dark and served as the control. Posthatch BW were recorded at 0, 2, 6, 13, 20, 28, 35, and 59 d of age. A heavier BW, occurring at 28 d of age and persisting until the end of the experiment (59 d of age), was observed in the in ovo green light stimulated females as compared to their corresponding controls. In experiment 2, 273 turkey eggs were divided into three light treatment groups (n = 91). The first group was intermit-
tently photostimulated (15 min on and 15 min off) with green light provided by seven LED per egg at 0.14 W/ m2. The second group was photostimulated with white light provided by one mini-incandescent lamp per egg at light intensity and schedule similar to the first group. Eggs of the third group were incubated in the dark and served as controls. Posthatch BW were recorded at 0, 7, 14, 28, 42, 56, and 79 d of age. No differences were found among the BW of males incubated under different light conditions. As in experiment 1, female turkeys with stimulated green light in ovo had greater BW compared to their corresponding control and white light groups from 28 d of age until termination of the experiment at 79 d of age. Breast muscle weight was greater in female turkeys incubated under green light when compared to white and dark incubation treatment groups. We suggest that in ovo green light photostimulation enhances the posthatch BW of female turkey poults.
(Key words: turkey embryo, photostimulation, muscle growth, monochromatic light, incubation) 2003 Poultry Science 82:1181–1187
INTRODUCTION In the closed and controlled environment of modern commercial poultry houses, birds are exposed to artificial light only. Thus, photoperiod, intensity, sprectra, and sources of light are major factors influencing current poultry management (Andrews and Zimmerman, 1990). The effects of different artificial light sources on the growth of meat-type birds have been tested in a number of experimental studies (Zimmerman, 1988; Andrews and Zimmerman, 1990; Scheideler, 1990). One of the principal differences among artificial light sources is spectral output. The light spectrum can affect growth in birds. Broilers reared under blue or green fluorescent lamps (Wabeck and Skoglund, 1974) or light-emitting
2003 Poultry Science Association, Inc. Received for publication March 18, 2002. Accepted for publication November 27, 2002. 1 To whom correspondence should be addressed: rozenboi@ agri.huji.ac.il.
diodes (LED; Rozenboim et al., 1999) gained significantly more weight than birds reared under red or white light, whereas feed conversion and mortality were unchanged. Similar results with red and green lights have been observed in quail (Phogat et al., 1985). Although green light enhances BW (Lauber and McGinnis, 1961; Ookawa, 1970; Foss et al., 1972; Wabeck and Skoglund, 1974; Lauber, 1975), mature female Japanese quail weigh less when raised under green and blue light as compared to those raised under red or white light (Woodward et al., 1969). Turkeys grow faster under blue light until 16 wk of age, but by 24 wk those reared under red and white lights are heavier (Leighton and Mason, 1976). These contradictory findings are probably due to wide variability in the types of light sources (Goodman, 1983), in differing methods for measuring light dosage (Blum, 1964), and in species, breed, gender, and age of the experimental birds (Woodward et al., 1969; Ookawa, 1970; Foss et al., 1972).
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Abbreviation Key: LED = light-emitting diodes.
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In our studies, a pure monochromatic light source based upon LED was used (Rozenboim et al., 1998, 1999). Broilers, reared from d 1 under monochromatic green and blue lights, have greater body and muscle growth than birds reared under red and white lights (Rozenboim et al., 1999). These growth parameters are highly correlated with enhanced satellite cell proliferation in chicks (Halevy et al., 1998). The effect on growth and satellite cell proliferation was significant by 3 d of age, suggesting that green light especially, but also blue light, positively affects early processes in posthatch muscle growth. Because the enhancement in muscle growth due to green light stimulation can be detected as early as 3 d of age, taken together with the fact that muscle development peaks during the last third of embryonic development (Harvey and Marshall, 2000), it seemed logical to study the effects of subjecting embryos to monochromatic green light. The effect of light on embryonic development was investigated several decades ago. Several investigators reported that white light illumination accelerates embryonic development in White Rock chickens (Siegel et al., 1969), turkeys (Cooper, 1972), broilers (Walter and Voitle, 1972), White Leghorn chickens (Coleman and McDaniel, 1976), and quail (Walter and Voitle, 1973). Eggs incubated beneath white light hatch approximately 1 d earlier than those incubated in the dark (Siegel et al., 1969; Walter and Voitle, 1972; Coleman and McDaniel, 1976). However, another experiment showed that in ovo illumination has no effect on hatching time or posthatch weight at 4 and 8 wk of age (Walter and Voitle, 1972). It has also been reported that photostimulation of turkey embryos with white incandescent illumination for 12 h causes significant acceleration in hatching time without affecting hatchability or BW on hatching day (Fairchild and Christensen, 2000), suggesting embryonic photostimulation as a tool for shortening the hatching period. None of these studies analyzed the effects of pure monochromatic light on embryonic development in general and on muscle development in particular. Therefore, the objective of this study was to determine the effect of pure monochromatic green light (560 nm) photostimulation during egg incubation on posthatch development of turkey poults.
TABLE 1. Fertility and hatchability of large white turkey eggs incubated under green light or dark (experiment 1) or green light, white light, or dark conditions (experiment 2) Treatment
Experiment
n
Hatchability (%)
Green light Dark Green light Dark White
1 1 2 2 2
91 91 91 91 91
93.4 92.3 93.4 92.3 90.1
equipped with a drum-tilted egg setter) located in a darkened room. All eggs were set at one level in the incubator. Trays with different light treatments were isolated by cardboard panels to eliminate any crossover stimulation. After 15 d of incubation, the eggs were candled and fertility was recorded. After 25 d of incubation, eggs were transferred to nontilting hatching trays located at the same level as the egg set trays. Time of hatching was recorded, and poults were weighed, wingbanded, and transferred to four brooding rooms heated to 32°C. Each treatment group was equally distributed among the four rooms. Birds were reared according to primary breeder’s recommendations. Feed and water were provided ad libitum.
Experiment 1 One hundred eighty-two turkey eggs were used. Eggs were weighed, numbered, and divided equally into two light treatment groups. The first group was stimulated with green light, from the first day of incubation until hatching. Green light was provided by five LED (peak wavelength 560 nm, half band 15 nm) located above each egg. Light intensity was 0.1 W/m2 at the top surface of the eggs4 and was intermittent at 3 min on and 3 min off, to avoid overheating the eggs. The second group was incubated under dark conditions and served as the control. Dark conditions were verified by measuring for zero light intensity over the setting trays. Body weights were recorded at 0, 2, 6, 13, 20, 28, 35, and 59 d of age. At the end of the experiment all birds were killed, and sex was determined.
Experiment 2 MATERIALS AND METHODS Birds Fertile eggs from large white Nicholas turkeys were provided by the Willmar Poultry Corporation.2 Eggs were selected by weight (between 85 and 90 g) and placed in a commercial incubator (Robbins 17H,3
2
Willmar Poultry Corporation, Inc., PO Box 753, Willmar, MN. Robbins Incubator Company, Denver, CO. 4 Li-COR Pyranometer Sensor, Lincoln, NE. 5 Osram, Germany. 3
Two hundred seventy-three turkey eggs were used. Eggs were weighed, numbered, and divided equally into three light treatment groups. The first group was photostimulated with green light provided by seven LED (peak wavelength 560 nm, half band 15 nm) located above each egg. Light intensity was 0.14 W/m2 at the top surface of the eggs and was intermittent at 15 min on and 15 min off. The second group was photostimulated with white light provided by one mini-incandescent lamp (full spectrum light5 located above each egg; light intensity was 0.14 W/m2 at the top surface of the eggs and was intermittent at 15 min on and 15 min off. The third group was incubated under dark conditions
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FIGURE 1. Hatching time of large white Nicholas turkey eggs incubated under green light or dark conditions.
and served as the control. Body weights were recorded at 0, 7, 14, 28, 42, 56, and 79 d of age. At the end of the experiment all of the birds were killed, sex was determined, and the breast muscles (Pectoralis major and minor) were removed from the sternum bone, cleaned of connective tissue, and weighed. Data were analyzed by a two-way analysis of variance, using light treatment and sex as the variables. Hatching time was analyzed by the CATMOD procedure of SAS software (SAS, 1987).
had similar hatch times at 27 d and 9 h (Figure 3). An increase in BW of birds incubated under green light was detected after 28 d of age (Figure 4). This weight increase
RESULTS Experiment 1 There were no differences between the two groups regarding hatchability (Table 1). Hatching time was also similar between the two groups (Figure 1). The BW of the males were the same in both treatment groups (Figure 2a). However, there was an increase in the BW of the females incubated under the green light. This BW increase was evident at 28 d of age and remained elevated until the end of the experiment at 59 d of age (Figure 2b). Mortality for the entire experiment was 9.5% for the green lighted group and 13% for the control group.
Experiment 2 There were no differences between the three groups regarding hatchability (Table 1). Eggs incubated beneath the white light hatched slightly sooner than the other groups, but the difference was not significant. Both the green-light-incubated and the dark-incubated eggs
FIGURE 2. Body weights of turkey toms (a) and turkey hens (b) incubated under green light or dark conditions. Bars represent mean ± SEM. a,bValues marked with different letters differ at P < 0.05.
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FIGURE 3. Hatching time of turkey poults incubated under green, white, or dark light conditions.
in the green-light group persisted until the end of the experiment at 79 d of age. When BW was analyzed by sex, no differences were found in the BW of males incubated under the different light conditions (Figure 5a). However, females incubated under green light were heavier than all other experimental groups from 28 d of age until the end of the experiment at 79 d of age
(Figure 5b). A noticeable depression in breast muscle weight in males incubated under dark conditions was detected; however, when breast muscle weight was presented as a percentage of BW, differences were not significant (Figure 6a,b). An increase in breast muscle weight was found in females incubated under green light, as compared to white-light- and dark-incubated
FIGURE 4. Body weights of straight run poults incubated under green light, white light, or dark conditions. Bars represent mean ± SEM. Values marked with different letters differ at P < 0.05.
a,b
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FIGURE 5. Body weights of male (a) and female (b) turkey poults incubated under green light, white light, or dark conditions. Bars represent mean ± SEM. a,bValues marked with different letters differ at P < 0.05.
birds. In addition, there was an increase in the percentage of breast muscle weight as compared to BW in the females incubated under green light. Mortality over the period was 7.4, 13.8, and 15.8 for the green light, dark, and white light treatments, respectively.
DISCUSSION The present study shows that embryonic exposure to monochromatic green light will stimulate posthatch growth in turkeys. The results of both experiments revealed that the increase in BW due to incubation under green light was limited to females only. The mechanisms underlying this phenomenon are presently unknown. Photostimulation of broilers after hatching with monochromatic green light was found to enhance BW (Wa-
beck and Skoglund, 1974), and quail raised beneath blue or green fluorescent lamps gained more weight than those reared under red or white fluorescent lamps (Phogat et al., 1985). It has been demonstrated that green light stimulates growth primarily at an early age, and blue light enhances growth at a later age when compared to birds reared under full-spectrum light or red light (Rozenboim et al., 1999). Green light may stimulate growth at an early age by enhancing the proliferation of skeletal muscle satellite cells (Halevy et al., 1998). Satellite cells are highly correlated with muscle growth and development and can be manipulated via different growth factors or by green light stimulation (Halevy et al., 1996, 1998). In ovo photostimulation with artificial light was linked to acceleration in embryo development and early
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Lama et al., 1998). Tissue synthesis of insulin-like growth factor-I (IGF-I) is differentially regulated within a given tissue and stage of incubation during embryogenesis of the turkeys (McMurtry and Brocht, 1997) and broilers (Kocamis et al., 2000). These findings taken together with the present results suggest that female turkeys are more receptive to in ovo photostimulation by green light as compared to turkey males. Further studies are needed in order to determine the mechanism involved in such differences to light photostimulation. The results of the present study indicate that growth may be augmented by manipulation of the light spectrum to the benefit of the poultry grower.
REFERENCES
FIGURE 6. Breast muscle weight (a) and percentage of breast muscle weight compared to body weight of turkey poults at 79 d of age and (b) incubated under green light, white light, or dark conditions. Bars represent mean ± SEM. a,bValues marked with different letters differ at P < 0.05.
hatching (Coleman and MacDaniel, 1975a,b, 1976). Advanced hatching was found in embryos photostimulated with white light, which appeared to be due to an increase in egg temperature (for details, see Romanoff, 1960). Preliminary experiments (unpublished data) in our laboratory showed that photostimulation of eggs for 30 min with various wavelengths, at an intensity of 0.1 W/m2, caused an elevation in yolk temperature of 0.15°C, resulting in an early hatch of broiler chicks and turkey poults. This observation led us to use intermittent lighting, which eliminated the early hatch associated with increased egg temperature. In our second experiment, although we illuminated intermittently, early hatch was detected in the white-light-treated birds, suggesting overheating of the eggs due to better penetration of the long wavelength emitted by the mini-incandescent lamps. It has been shown that photostimulation of turkey eggs with incandescent lamps causes early hatch, with no residual effects on hatchability, embryonic survival, liver or heart growth, or glycogen content (Fairchild and Christensen, 2000). In the present study, increased early posthatch mortality was encountered in the group incubated under white light, suggesting that the embryonic heating effect had a carryover impact on survival of the poults. Sexual dimorphism in growth, associated with growth hormone stimulation, was previously found in rats. Female rats responded to growth hormone stimulation with a better growth rate than male rats (Rol de
Andrews, D. K., and N. G. Zimmerman, 1990. A comparison of energy efficient broiler house lighting source and photoperiods. Poult. Sci. 69:1471–1479. Blum, H. 1964. Photodynamic Action and Diseases Caused by Light. Hafner, New York. Coleman, M. A., and G. R. McDaniel. 1975a. Photoacceleration of embryonic development in depigmented Japanese quail eggs. Poult. Sci. 54:1849–1855. Coleman, M. A., G. R. McDaniel. 1975b. The effect of light and specific gravity on embryo weight and embryonic mortality. Poult. Sci. 54:1415–1421. Coleman, M. A., and G. R. McDaniel. 1976. Light alterated changes in the embroynic age versus incubation age of White Leghorn embryos. Poult. Sci. 55:2483–2485. Cooper, J. B. 1972. Effect of light during incubation on hatchability of turkey eggs. Poult. Sci. 51:1105–1108. Fairchild, B. D., and V. L. Christensen. 2000. Photostimulation of turkey eggs accelerates hatching times without affecting hatchability, liver or heart growth, or glycogen content. Poult. Sci. 79:1627–1631. Foss, C. D., L. B. Carew, and E. L. Arnold. 1972. Physiological development of cockerels as influenced by selected wavelengths of environmental light. Poult. Sci. 51:1922–1927. Goodman, G. 1983. Physiological responses of the cockerel to light quality: Growth and sexual development. Ph.D. Thesis. Hebrew University, Jerusalem, Israel. Halevy O., I. Biran, and I. Rozenboim. 1998. Various light source treatments affect body and skeletal muscle growth by affecting skeletal muscle satellite cell proliferation in broilers. Comp. Biochem. Physiol. A Mol. Integr. Physiol. 120:317–323. Halevy O., V. Hodik, and A. Mett. 1996. The effects of growth hormone on avian skeletal muscle satellite cell proliferation and differentiation. Gen. Comp. Endocrinol. 101:43–52. Harvey, A. L., and I. G. Marshall. 2000. Skeletal muscle. Pages 123–139 in Sturkie’s Avian Physiology. G. C. Wittow, ed. Academic Press, San Diego. Kocamis H., Y. N. Yeni, C. U. Brown, P. B. Kenney, D. C. Kirkpatrick-Keller, and J. Killefer. 2000. Effect of in ovo administration of insulin-like growth factor-I on composition and mechanical properties of chicken bone. Poult. Sci. 79:1345–1350. Lauber, J. K. 1975. Photoacceleration of avian embryogenesis. Comp. Biochem. Physiol. 51A:903–907. Lauber, J. K., and J. MacGinnis. 1961. Spectral sensitivity of avian growth and reproduction processes. Fed. Proc. 24:701. Leighton, A. T., and J. P. Mason 1976. Environmental factors affecting growth performance of turkeys. Am. Soc. Agric. Eng. 76:4508. (Abstr.) McMurtry J. P., and D. M. Brocht 1997. Developmental changes in embryonic and extra-embryonic insulin-like growth fac-
PHOTOSTIMULATION OF TURKEY EMBRYOS tor-I tissue concentrations in the turkey embryo. Poult. Sci. 76:894–900. Ookawa, T. 1970. Effects of bilateral optic enucleation on body growth and gonad in young male chicks. Poult. Sci. 49:333–334. Phogat, S. B., C. K. Aggarwal, and S. K. Chopra. 1985. Effect of red and green lights on growth of quail. Indian J. Poult. Sci. 20:126–128. Rol de Lama, M. A., A. Perez-Romero, M. Hermanussen, C. Ariznavarreta, and J. A. Tresguerres. 1998. Sexual dimorphism in growth as measured by microknemometry: different responses to GH deficiency and exogenous GH administration. Neuroendocrinology 68:210–219. Romanoff, A. L. 1960. The Avian Embryo: Structural and Functional Development. MacMillan, New York. Rozenboim I., Y. Zilberman, and G. Gvaryahu. 1998. New monochromatic light source for laying hens. Poult. Sci. 77:1695–1698. Rozenboim, I., I. Biran, Z. Uni, B. Robinzon, and O. Halevy. 1999. The effect of monochromatic light on broiler growth and development. Poult. Sci. 78:135–138.
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SAS. 1987. User’s Guide: Version 7. SAS Institute Inc., Cary, NC. Scheideler, S. E. 1990. Research Note: Effect of various light sources on broiler performance and efficiency of production under commercial conditions. Poult. Sci. 69:1030–1033. Siegel, P. B., S. T. Isakson, F. N. Coleman, and B. J. Huffman. 1969. Photoacceleration of development in chick embryo. Comp. Biochem. Physiol. 28:753–758. Wabeck, C. J., and W. C. Skoglund. 1974. Influence of radiant energy from fluorescent light source on growth, mortality and feed conversion of broilers. Poult. Sci. 53:2055–2059. Walter, J. H., and R. A. Voitle. 1972. Effects of photoperiod during incubation on embryonic and post-embryonic development of broilers. Poult. Sci. 51:1122–1226. Walter, J. H., and R. A. Voitle. 1973. Effects of photoperiod during incubation on embryonic and post-embryonic development of quail and chickens. Br. Poult. Sci. 14:533–540. Woodward, A. E., J. A. Moore, and W. O. Wilson. 1969. Effect of wavelength of light on growth and reproduction in Japanese quail (Coturnix Coturnix Japonica). Poult. Sci. 48:118– 123. Zimmermann, N. G. 1988. Broiler performance when reared under various light sources. Poult. Sci. 67:43–51.
tently photostimulated (15 min on and 15 min off) with green light provided by seven LED per egg at 0.14 W/ m2. The second group was photostimulated with white light provided by one mini-incandescent lamp per egg at light intensity and schedule similar to the first group. Eggs of the third group were incubated in the dark and served as controls. Posthatch BW were recorded at 0, 7, 14, 28, 42, 56, and 79 d of age. No differences were found among the BW of males incubated under different light conditions. As in experiment 1, female turkeys with stimulated green light in ovo had greater BW compared to their corresponding control and white light groups from 28 d of age until termination of the experiment at 79 d of age. Breast muscle weight was greater in female turkeys incubated under green light when compared to white and dark incubation treatment groups. We suggest that in ovo green light photostimulation enhances the posthatch BW of female turkey poults.
(Key words: turkey embryo, photostimulation, muscle growth, monochromatic light, incubation) 2003 Poultry Science 82:1181–1187
INTRODUCTION In the closed and controlled environment of modern commercial poultry houses, birds are exposed to artificial light only. Thus, photoperiod, intensity, sprectra, and sources of light are major factors influencing current poultry management (Andrews and Zimmerman, 1990). The effects of different artificial light sources on the growth of meat-type birds have been tested in a number of experimental studies (Zimmerman, 1988; Andrews and Zimmerman, 1990; Scheideler, 1990). One of the principal differences among artificial light sources is spectral output. The light spectrum can affect growth in birds. Broilers reared under blue or green fluorescent lamps (Wabeck and Skoglund, 1974) or light-emitting
2003 Poultry Science Association, Inc. Received for publication March 18, 2002. Accepted for publication November 27, 2002. 1 To whom correspondence should be addressed: rozenboi@ agri.huji.ac.il.
diodes (LED; Rozenboim et al., 1999) gained significantly more weight than birds reared under red or white light, whereas feed conversion and mortality were unchanged. Similar results with red and green lights have been observed in quail (Phogat et al., 1985). Although green light enhances BW (Lauber and McGinnis, 1961; Ookawa, 1970; Foss et al., 1972; Wabeck and Skoglund, 1974; Lauber, 1975), mature female Japanese quail weigh less when raised under green and blue light as compared to those raised under red or white light (Woodward et al., 1969). Turkeys grow faster under blue light until 16 wk of age, but by 24 wk those reared under red and white lights are heavier (Leighton and Mason, 1976). These contradictory findings are probably due to wide variability in the types of light sources (Goodman, 1983), in differing methods for measuring light dosage (Blum, 1964), and in species, breed, gender, and age of the experimental birds (Woodward et al., 1969; Ookawa, 1970; Foss et al., 1972).
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Abbreviation Key: LED = light-emitting diodes.
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In our studies, a pure monochromatic light source based upon LED was used (Rozenboim et al., 1998, 1999). Broilers, reared from d 1 under monochromatic green and blue lights, have greater body and muscle growth than birds reared under red and white lights (Rozenboim et al., 1999). These growth parameters are highly correlated with enhanced satellite cell proliferation in chicks (Halevy et al., 1998). The effect on growth and satellite cell proliferation was significant by 3 d of age, suggesting that green light especially, but also blue light, positively affects early processes in posthatch muscle growth. Because the enhancement in muscle growth due to green light stimulation can be detected as early as 3 d of age, taken together with the fact that muscle development peaks during the last third of embryonic development (Harvey and Marshall, 2000), it seemed logical to study the effects of subjecting embryos to monochromatic green light. The effect of light on embryonic development was investigated several decades ago. Several investigators reported that white light illumination accelerates embryonic development in White Rock chickens (Siegel et al., 1969), turkeys (Cooper, 1972), broilers (Walter and Voitle, 1972), White Leghorn chickens (Coleman and McDaniel, 1976), and quail (Walter and Voitle, 1973). Eggs incubated beneath white light hatch approximately 1 d earlier than those incubated in the dark (Siegel et al., 1969; Walter and Voitle, 1972; Coleman and McDaniel, 1976). However, another experiment showed that in ovo illumination has no effect on hatching time or posthatch weight at 4 and 8 wk of age (Walter and Voitle, 1972). It has also been reported that photostimulation of turkey embryos with white incandescent illumination for 12 h causes significant acceleration in hatching time without affecting hatchability or BW on hatching day (Fairchild and Christensen, 2000), suggesting embryonic photostimulation as a tool for shortening the hatching period. None of these studies analyzed the effects of pure monochromatic light on embryonic development in general and on muscle development in particular. Therefore, the objective of this study was to determine the effect of pure monochromatic green light (560 nm) photostimulation during egg incubation on posthatch development of turkey poults.
TABLE 1. Fertility and hatchability of large white turkey eggs incubated under green light or dark (experiment 1) or green light, white light, or dark conditions (experiment 2) Treatment
Experiment
n
Hatchability (%)
Green light Dark Green light Dark White
1 1 2 2 2
91 91 91 91 91
93.4 92.3 93.4 92.3 90.1
equipped with a drum-tilted egg setter) located in a darkened room. All eggs were set at one level in the incubator. Trays with different light treatments were isolated by cardboard panels to eliminate any crossover stimulation. After 15 d of incubation, the eggs were candled and fertility was recorded. After 25 d of incubation, eggs were transferred to nontilting hatching trays located at the same level as the egg set trays. Time of hatching was recorded, and poults were weighed, wingbanded, and transferred to four brooding rooms heated to 32°C. Each treatment group was equally distributed among the four rooms. Birds were reared according to primary breeder’s recommendations. Feed and water were provided ad libitum.
Experiment 1 One hundred eighty-two turkey eggs were used. Eggs were weighed, numbered, and divided equally into two light treatment groups. The first group was stimulated with green light, from the first day of incubation until hatching. Green light was provided by five LED (peak wavelength 560 nm, half band 15 nm) located above each egg. Light intensity was 0.1 W/m2 at the top surface of the eggs4 and was intermittent at 3 min on and 3 min off, to avoid overheating the eggs. The second group was incubated under dark conditions and served as the control. Dark conditions were verified by measuring for zero light intensity over the setting trays. Body weights were recorded at 0, 2, 6, 13, 20, 28, 35, and 59 d of age. At the end of the experiment all birds were killed, and sex was determined.
Experiment 2 MATERIALS AND METHODS Birds Fertile eggs from large white Nicholas turkeys were provided by the Willmar Poultry Corporation.2 Eggs were selected by weight (between 85 and 90 g) and placed in a commercial incubator (Robbins 17H,3
2
Willmar Poultry Corporation, Inc., PO Box 753, Willmar, MN. Robbins Incubator Company, Denver, CO. 4 Li-COR Pyranometer Sensor, Lincoln, NE. 5 Osram, Germany. 3
Two hundred seventy-three turkey eggs were used. Eggs were weighed, numbered, and divided equally into three light treatment groups. The first group was photostimulated with green light provided by seven LED (peak wavelength 560 nm, half band 15 nm) located above each egg. Light intensity was 0.14 W/m2 at the top surface of the eggs and was intermittent at 15 min on and 15 min off. The second group was photostimulated with white light provided by one mini-incandescent lamp (full spectrum light5 located above each egg; light intensity was 0.14 W/m2 at the top surface of the eggs and was intermittent at 15 min on and 15 min off. The third group was incubated under dark conditions
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FIGURE 1. Hatching time of large white Nicholas turkey eggs incubated under green light or dark conditions.
and served as the control. Body weights were recorded at 0, 7, 14, 28, 42, 56, and 79 d of age. At the end of the experiment all of the birds were killed, sex was determined, and the breast muscles (Pectoralis major and minor) were removed from the sternum bone, cleaned of connective tissue, and weighed. Data were analyzed by a two-way analysis of variance, using light treatment and sex as the variables. Hatching time was analyzed by the CATMOD procedure of SAS software (SAS, 1987).
had similar hatch times at 27 d and 9 h (Figure 3). An increase in BW of birds incubated under green light was detected after 28 d of age (Figure 4). This weight increase
RESULTS Experiment 1 There were no differences between the two groups regarding hatchability (Table 1). Hatching time was also similar between the two groups (Figure 1). The BW of the males were the same in both treatment groups (Figure 2a). However, there was an increase in the BW of the females incubated under the green light. This BW increase was evident at 28 d of age and remained elevated until the end of the experiment at 59 d of age (Figure 2b). Mortality for the entire experiment was 9.5% for the green lighted group and 13% for the control group.
Experiment 2 There were no differences between the three groups regarding hatchability (Table 1). Eggs incubated beneath the white light hatched slightly sooner than the other groups, but the difference was not significant. Both the green-light-incubated and the dark-incubated eggs
FIGURE 2. Body weights of turkey toms (a) and turkey hens (b) incubated under green light or dark conditions. Bars represent mean ± SEM. a,bValues marked with different letters differ at P < 0.05.
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FIGURE 3. Hatching time of turkey poults incubated under green, white, or dark light conditions.
in the green-light group persisted until the end of the experiment at 79 d of age. When BW was analyzed by sex, no differences were found in the BW of males incubated under the different light conditions (Figure 5a). However, females incubated under green light were heavier than all other experimental groups from 28 d of age until the end of the experiment at 79 d of age
(Figure 5b). A noticeable depression in breast muscle weight in males incubated under dark conditions was detected; however, when breast muscle weight was presented as a percentage of BW, differences were not significant (Figure 6a,b). An increase in breast muscle weight was found in females incubated under green light, as compared to white-light- and dark-incubated
FIGURE 4. Body weights of straight run poults incubated under green light, white light, or dark conditions. Bars represent mean ± SEM. Values marked with different letters differ at P < 0.05.
a,b
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FIGURE 5. Body weights of male (a) and female (b) turkey poults incubated under green light, white light, or dark conditions. Bars represent mean ± SEM. a,bValues marked with different letters differ at P < 0.05.
birds. In addition, there was an increase in the percentage of breast muscle weight as compared to BW in the females incubated under green light. Mortality over the period was 7.4, 13.8, and 15.8 for the green light, dark, and white light treatments, respectively.
DISCUSSION The present study shows that embryonic exposure to monochromatic green light will stimulate posthatch growth in turkeys. The results of both experiments revealed that the increase in BW due to incubation under green light was limited to females only. The mechanisms underlying this phenomenon are presently unknown. Photostimulation of broilers after hatching with monochromatic green light was found to enhance BW (Wa-
beck and Skoglund, 1974), and quail raised beneath blue or green fluorescent lamps gained more weight than those reared under red or white fluorescent lamps (Phogat et al., 1985). It has been demonstrated that green light stimulates growth primarily at an early age, and blue light enhances growth at a later age when compared to birds reared under full-spectrum light or red light (Rozenboim et al., 1999). Green light may stimulate growth at an early age by enhancing the proliferation of skeletal muscle satellite cells (Halevy et al., 1998). Satellite cells are highly correlated with muscle growth and development and can be manipulated via different growth factors or by green light stimulation (Halevy et al., 1996, 1998). In ovo photostimulation with artificial light was linked to acceleration in embryo development and early
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Lama et al., 1998). Tissue synthesis of insulin-like growth factor-I (IGF-I) is differentially regulated within a given tissue and stage of incubation during embryogenesis of the turkeys (McMurtry and Brocht, 1997) and broilers (Kocamis et al., 2000). These findings taken together with the present results suggest that female turkeys are more receptive to in ovo photostimulation by green light as compared to turkey males. Further studies are needed in order to determine the mechanism involved in such differences to light photostimulation. The results of the present study indicate that growth may be augmented by manipulation of the light spectrum to the benefit of the poultry grower.
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FIGURE 6. Breast muscle weight (a) and percentage of breast muscle weight compared to body weight of turkey poults at 79 d of age and (b) incubated under green light, white light, or dark conditions. Bars represent mean ± SEM. a,bValues marked with different letters differ at P < 0.05.
hatching (Coleman and MacDaniel, 1975a,b, 1976). Advanced hatching was found in embryos photostimulated with white light, which appeared to be due to an increase in egg temperature (for details, see Romanoff, 1960). Preliminary experiments (unpublished data) in our laboratory showed that photostimulation of eggs for 30 min with various wavelengths, at an intensity of 0.1 W/m2, caused an elevation in yolk temperature of 0.15°C, resulting in an early hatch of broiler chicks and turkey poults. This observation led us to use intermittent lighting, which eliminated the early hatch associated with increased egg temperature. In our second experiment, although we illuminated intermittently, early hatch was detected in the white-light-treated birds, suggesting overheating of the eggs due to better penetration of the long wavelength emitted by the mini-incandescent lamps. It has been shown that photostimulation of turkey eggs with incandescent lamps causes early hatch, with no residual effects on hatchability, embryonic survival, liver or heart growth, or glycogen content (Fairchild and Christensen, 2000). In the present study, increased early posthatch mortality was encountered in the group incubated under white light, suggesting that the embryonic heating effect had a carryover impact on survival of the poults. Sexual dimorphism in growth, associated with growth hormone stimulation, was previously found in rats. Female rats responded to growth hormone stimulation with a better growth rate than male rats (Rol de
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