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The Influence of Light Quality on Initiation of Egg Laying by Hens
The Influence of Light Quality on Initiation of Egg Laying by Hens R. PYRZAK, N. SNAPIR, 1 G. GOODMAN, E. ARNON.and M. PEREK Department of Animal Science, Faculty ofAgriculture, The Hebrew University of Jerusalem, POB 12, Rehovot 76100, Israel (Received for publication June 19, 1984)
1986 Poultry Science 65:190-193 INTRODUCTION
Maturation in pullets is advanced primarily by an increase (King, 1961, Shutze et al., 1961) in light hours or is delayed by a decrease (Morris and Fox, 1958a,b; Morris and Owen, 1960) in light hours. Rate of sexual maturation or regression is proportional to rate of change of daylength. Harrison et al. (1969a) reported that the earlier the exposure of pullets to longer photoperiods, the younger the age at first egg. At a given photoperiod, greater light intensity (.2 to 32.2 lx) also advanced maturity (Dorminey et al, 1970). Wavelength of light also influences sexual maturation. Harrison et al. (1969b) reported that blue and green lights stimulated early reproductive development in pullets and cockerels; those reared in red or clear light matured later. However, Woodward et al. (1969) and Scott and Payne (1937) reported that red light hastened maturation in Coturnix quail and in turkeys, respectively. Siopes and Wilson (1980) suggested that the difference in spectral composition between fluorescent and incandescent light was re-
1
sponsible for unequal rates of maturation of quail. Oishi and Lauber (1971) indicated that wavelength per se, not radiant energy level or photon number, was important in the response of quail to light. However, Vriend and Lauber (1973) pointed out that in environments of equal radiant energy, photon irradiance (number of photons per unit area and time) increases with wavelength. This study examined the effect of irradiation with narrow bands of visual light or with white light from different commercial sources, each with a specific spectrum, on initiation of egg laying in juvenile and molted adult hens. Light levels were equalized between treatments on the basis of photon irradiance.
From whom reprints should be requested.
190
MATERIALS AND METHODS
Sixty day-old Single Comb White Leghorn x Rhode Island Red female chicks were randomly assigned to each of six light-treatment rooms and maintained in a controlled environment in the absence of natural light. At four weeks, the pullets under each treatment were housed in colony cages in the same room, five pullets/ cage. At 16 weeks, 34 pullets were randomly chosen and caged individually. Water and a standard commercial diet (14.6% protein, 2815
Downloaded from http://ps.oxfordjournals.org/ at Florida Atlantic University on January 28, 2015
ABSTRACT Female chicks of an egg-laying strain were irradiated (.6 juE photons/m^/sec) from day-old to termination of the experiment at 672 days of age with narrow-band blue (B), green (G), or red (R) fluorescent light, or with white light from cool white (C) or sunlight-simulating (V) fluorescent tubes or from tungsten (T) incandescent lamps. The effect on initiation of egg laying by juvenile hens and on renewal of laying after molting was studied. There was no significant effect of light source on average days to first egg for initiating egg production. After molting, it took an average of 45, 28, and 16 days for hens in the B, G, and R groups, respectively, to begin to lay after light stimulation. The C group started to lay again after 32 days as compared to 19 and 21 days for the T and V groups. The relative weights of the abdominal fat of maturing hens under the monochromatic treatments were in inverse ratio to wavelength. There was no difference between the wide-spectrum sources. At a given level of photon irradiation, light quality was not a factor in the initiation of egg production but influenced renewal of egg laying following molting in the domestic hen. Light quality may also be involved in fat metabolism prior to maturity. (Key words: light quality, maturation, egg production, molting, fat deposition)
LIGHT AND EGG LAYING IN HENS 100 1
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20
400
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500 600 WAVELENGTH (nm)
—
, N 700
FIG. 1. The spectrum of photon (quantum) irradiance from six light sources, each analyzed relative (%) to the peak band. B = Blue, G = green, R = red, C = cool white, V = sunlight-simulating (Vita-lite) fluorescent tubes, and T = tungsten incandescent bulbs.
kcal/kg ME, 3.27% Ca) were supplied ad libitum during the experiment. Birds were treated from 1-day-old with light from either red (R), green (G), blue (B), sunlight-simulating (V) (all, Duro-Test Corp. NJ, USA), standard cool white 40-W fluorescent tubes (C), or from standard 60 W-tungsten (T) incandescent bulbs. Calculated from manufacturer's data, the spectrum of photon irradiance relative to the peak band is shown in Figure 1. Treatments were equalized at .6 /lE photons/m^/sec at head level of the pullets by partial covering of tubes with black plastic or by varying height of lamps. Illuminance (lx) was also recorded (Table 1). Light was measured with a Ll-Cor battery-operated light meter (Model LI-185A, Lambda Instrument Corp., NE) equipped with a quantum sensor cell of flat response between 400 to 700 nm, or with a photometric (lx) sensor. From 0 to 15 weeks of age, pullets received 10 hr of light/ day, which was followed by equal weekly increments to total 17 hr (0500 to 2200 hr) by the 24th week. This was maintained to forced molting after 50 weeks of egg laying.
The average age (days) when each hen within a treatment produced her first egg indicated achievement of juvenile sexual maturation. Reinitiation of laying after molting was assessed for each treatment by the average period of time (days) needed after renewal of light stimulation for the appearance of the first egg of each hen. The body weight reduction (North, 1977) necessary for molt, accompanied by a consistent cessation of laying, was achieved by feed withdrawal for 10 days, the first 3 together with water deprivation. Feed was then restricted to 60, 70, and 80 g/hen/day for the 1st, 2nd, and 3rd weeks, respectively, and thereafter supplied ad libitum. Daily light was reduced to 6 hr for 6 weeks at commencement of molting, then increased to 12 hr, followed by weekly increments of 1 hr to a total of 17 hr. Body weight was recorded at maturity (16, 20 weeks) and before and after molting. At 16 and 20 weeks of age, five hens from each treatment were taken randomly for autopsy. Abdominal fat weight was recorded as a percentage of body weight. Data were assessed by Student's t-test or analysis of variance, as appropriate means were separated in the latter case by Duncans' multiple range test (Snedecor and Cochrane, 1971). RESULTS AND DISCUSSION
Average age of first lay did not differ significantly between treatments (Table 2). First eggs to appear under the monochromatic treatments (B, G, R; 124 days of age ± 2)
TABLE 1. Light intensity under six light treatments Light treatments
B G R C T V
Photon irradiance1
Illuminance 1
(pE m^ sec)
(lx)
.60 .59 .64 .63 .64 .64
13 56 12 38 32 32
+ ± ± ± ± +
.03 .03 .04 .03 .04 .03
+ + ± + ± +
2 6 2 4 4 4
1 Mean (± SE) of measurements at six different points in each pen. 2 B = Blue, G = green, R = red, C = cool white, V = sunlight-simulating (Vita-lite) fluorescent lamps, and T = tungsten incandescent bulbs.
Downloaded from http://ps.oxfordjournals.org/ at Florida Atlantic University on January 28, 2015
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80-
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40-
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191
192
PYRZAK ET AL. TABLE 2. Effect of light quality (X ± SE) on initiation of egg laying in hens (n = 24)
Light treatments'
Average period between postmolt light stimulation and first egg
Average age at first egg
/
± ± ± + ± ±
6 7a 6a 5a 5a 5a
.
45 28 16 32 19 21
N
± ± ± ± ± ±
3a 2b 2e 3b 2C 2^
' ' Different letters in a column indicate significant (P<.05) differences between treatments. 1
B = Blue, G = green, R = red, C = cool white, V = sunlight-simulating (Vita-lite) fluorescent lamps, and T = tungsten incandescent bulbs.
significantly preceded those under wide spectrum radiation (C, V, T; 131 days + 1). Scott and Payne (1937) suggested that the extension of natural daylength by an additional period of R light was more stimulatory to turkey hens than B light. However, there was a large difference in intensity between wavelengths which may have masked any effect of light quality. Harrison et al. (1969b) reported slightly greater stimulation of maturation by short wavelengths in comparison to long wavelengths in pullets and cockerels. In con-
TABLE 3. Body weight (g) of mature hens (X ± SE) before and after molt and abdominal fat (%) at maturation B o d y weight Light treatments'
16 w e e k s
B G R C T V
1350 ± 1360± 1400 + 1390± 1570 ± 1390+ a
2
60b 30b 60b 30b 40a 50b
20 w e e k s
Before molt, 54 w e e k s 3
2
(&>
1580± 60b 1700± 150ab 1730± 8 0 a b 1690 ± 5 0 b 1740 ± 1 7 0 a b 1850± 50a
2312 + 9 1 a 2450 ± 8 5 a 2396 ± 8 0 a 2225 + 6 6 a 2304±96a 2417 ± 9 5 a
A b d ominal fat
After m o l t , 62 w e e k s 3
16 w e e k s 2
1801± 60a 1990± 75a 1860 ± 8 0 a 1910± 80a 1851 ± 8 1 a 1010 ± 1 0 5 a
2.6 2.4 1.6 2.1 1.8 2.1
± ± ± ± ± ±
.8a .3a .3a ,6a .3a .7a
20 weeks 2
4.7 3.1 2.7 3.3 2.7 3.0
± ± + ± ± ±
.8a .7ab .6b .3ab .7b .5b
' Different letters in a column indicate significant (P-C05) differences between treatments. B = Blue, G = green, R = red, C = cool white, V = sunlight-simulating (Vita-lite) fluorescent tubes, and T tungsten incandescent bulbs. 1
3
n = 20 to 24.
Downloaded from http://ps.oxfordjournals.org/ at Florida Atlantic University on January 28, 2015
150 160 149 148 152 147
B G R C T V
a
trast, Woodward et al. (1969) found reproductive development in quail to be greater under R than under B or G light. Following restimulation by light after molting, average period to first egg was significantly longer under B light (Table 2) compared to all the other sources. The time required under R, T, and V radiation was significantly less than that required for B, G, C, with B being greater than G or C. The R, T, V, and C light sources are rich in red light compared to the G and B tubes (Fig. 1). Thus, in the postmolting period, response to light quality under the complex spectral sources can not be explained simply in terms of response to the narrow light bands. The influence of wavelengths was greater after molting than it was during pubertal maturation. If laying is primarily dependent on direct light stimulation of the hypothalamus (Benoit, 1964), the relative influence of longer wavelength light may increase because of its greater penetrability and the possibly increased opacity of tissues to intracranial light transmission with age. Compared to T light, body weight under B and G light was less at 16 and 20 weeks (Table 3) despite greater fatness in the B treatment at 20 weeks of age. Woodward et al. (1969) observed lower weights under B or G in quail at maturity when compared to white or R light. Body weight of turkeys was also lower at maturity under B light as compared to R light (Leighton and Mason, 1976). Body weight
LIGHT AND EGG LAYING IN HENS
REFERENCES Benoit, J., 1964. The role of the eyes and the hypothalamus in the photo-stimulation of the gonads of the duck. Ann. NY Acad. Sci. 117: 204-216. Dorminey, R. W„ J. E. Parker, and W. H. McClusky, 1970. Effect of light intensity on leghorn pullets during the development and laying periods. Poultry Sci. 49:1657-1661. Harrison, P. C , 1972. Extraretinal photocontrol of reproductive responses of leghorn hens to photoperiods of different length and spectrum. Poultry Sci. 51:2060-2064. Harrison,P. C , J. McGinnis, G. Schumaier, and J. K. Lauber, 1969a. Sexual maturity and subsequent
reproductive performance of White Leghorn chickens subjected to different parts of the light spectrum. Poultry Sci. 48:878-883. Harrison,P. C , G. Schumaier, and J. McGinnis, 1969b. Sexual maturity and subsequent reproductive performance of White Leghorn chickens subjected to different parts of the light spectrum. Poultry Sci. 48:878-883. King,D. E., 1961. Effects of increasing, decreasing and constant light treatment on growing pullets. Poultry Sci. 40:479-484. Leighton, A. T., Jr., and J. P. Mason, 1976. Environmental factors affecting growth performance of turkeys. Am. Soc. Agric. Eng. Paper No. 76— 4508. Menaker, M., and H. Underwood, 1976. Extraretinal photoreception in birds. Photochem. Photobiol. 23:299-306. Morris, T. R., and S. Fox, 1958a. Light and sexual maturity in the domestic fowl. Nature 181: 1453-1454. Morris,T. R., and S. Fox, 1958b. Artificial light and sexual maturity in the fowl. Nature 182:1522— 1523. Morris,T. R., and V. M. Owen, 1960. The effect of light intensity on egg production. Pages 458—461 in Proc. 13th World's Poultry Congress. North, M. O., 1977. Commercial Chicken Production Manual. Avi Publishing Co., New York, NY. Oishi,T., and J. K. Lauber, 1973. Photoreception in the photosexual response of quail. II. Effect of intensity and wavelength. Am. J. Physiol. 225: 880-886. Scott,H. M., and L. F. Payne, 1937. Light in relation to the experimental modification of the breeding season of turkeys. Poultry Sci. 16:90—96. Shutze,J. V., W. E. Matson, and J. McGinnis, 1961. Influence of different photoperiods during brooding and rearing on subsequent productive characteristics in chickens. Poultry Sci. 40: 1604-1611. Siopes.T. D., and W. O. Wilson, 1980. Participation of the eyes in the photosexual response of Japanese quail. Biol. Reprod. 23:352-257. Snedecor.G. W., and W. G. Cochrane, 1971. Statistical Methods. Iowa State Univ. Press, Ames, IA. Vriend.J., and J. K. Lauber, 1973. Effects of light intensity, wavelength and quanta on gonads and spleen of the deer mouse. Nature 244:37—38. 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). Poultry Sci. 48:118—123.
Downloaded from http://ps.oxfordjournals.org/ at Florida Atlantic University on January 28, 2015
was not significantly different between R and B light in this study. Postmolt body weights did not differ significantly, despite differences in time required for reinitiation of laying (Table 2). Abdominal fat, relative to body weight, declined with the increase in wavelength both at 16 and 20 weeks (Table 3). At 20 weeks, the relative weight of fat under B light was 50% (P>.05) and 72% (P<.05) greater than under G or R, respectively, and 74% (P<.05), 58% (P<.05), and 41% (P>.05) greater than under T, V, or C light, respectively. All treatments in the present experiment were at the same level of photon irradiance (Table 1). Additionally, illuminances of the B and R sources were similar, as were those of the C, T, and V sources of white light. Therefore, the differences between treatments confirm that light quality is a factor in renewal of egg laying following molting. Relatively greater intracranial penetration of longwave photons (Benoit, 1964) to an extraretinal photoresponsive mechanism, located in the brain (Oishi and Lauber, 1973; Menaker and Underwood, 1976) may be involved in mediating the effect of light on ovarian development (Harrison, 1972). This is supported by the findings reported herein.
193
1986 Poultry Science 65:190-193 INTRODUCTION
Maturation in pullets is advanced primarily by an increase (King, 1961, Shutze et al., 1961) in light hours or is delayed by a decrease (Morris and Fox, 1958a,b; Morris and Owen, 1960) in light hours. Rate of sexual maturation or regression is proportional to rate of change of daylength. Harrison et al. (1969a) reported that the earlier the exposure of pullets to longer photoperiods, the younger the age at first egg. At a given photoperiod, greater light intensity (.2 to 32.2 lx) also advanced maturity (Dorminey et al, 1970). Wavelength of light also influences sexual maturation. Harrison et al. (1969b) reported that blue and green lights stimulated early reproductive development in pullets and cockerels; those reared in red or clear light matured later. However, Woodward et al. (1969) and Scott and Payne (1937) reported that red light hastened maturation in Coturnix quail and in turkeys, respectively. Siopes and Wilson (1980) suggested that the difference in spectral composition between fluorescent and incandescent light was re-
1
sponsible for unequal rates of maturation of quail. Oishi and Lauber (1971) indicated that wavelength per se, not radiant energy level or photon number, was important in the response of quail to light. However, Vriend and Lauber (1973) pointed out that in environments of equal radiant energy, photon irradiance (number of photons per unit area and time) increases with wavelength. This study examined the effect of irradiation with narrow bands of visual light or with white light from different commercial sources, each with a specific spectrum, on initiation of egg laying in juvenile and molted adult hens. Light levels were equalized between treatments on the basis of photon irradiance.
From whom reprints should be requested.
190
MATERIALS AND METHODS
Sixty day-old Single Comb White Leghorn x Rhode Island Red female chicks were randomly assigned to each of six light-treatment rooms and maintained in a controlled environment in the absence of natural light. At four weeks, the pullets under each treatment were housed in colony cages in the same room, five pullets/ cage. At 16 weeks, 34 pullets were randomly chosen and caged individually. Water and a standard commercial diet (14.6% protein, 2815
Downloaded from http://ps.oxfordjournals.org/ at Florida Atlantic University on January 28, 2015
ABSTRACT Female chicks of an egg-laying strain were irradiated (.6 juE photons/m^/sec) from day-old to termination of the experiment at 672 days of age with narrow-band blue (B), green (G), or red (R) fluorescent light, or with white light from cool white (C) or sunlight-simulating (V) fluorescent tubes or from tungsten (T) incandescent lamps. The effect on initiation of egg laying by juvenile hens and on renewal of laying after molting was studied. There was no significant effect of light source on average days to first egg for initiating egg production. After molting, it took an average of 45, 28, and 16 days for hens in the B, G, and R groups, respectively, to begin to lay after light stimulation. The C group started to lay again after 32 days as compared to 19 and 21 days for the T and V groups. The relative weights of the abdominal fat of maturing hens under the monochromatic treatments were in inverse ratio to wavelength. There was no difference between the wide-spectrum sources. At a given level of photon irradiation, light quality was not a factor in the initiation of egg production but influenced renewal of egg laying following molting in the domestic hen. Light quality may also be involved in fat metabolism prior to maturity. (Key words: light quality, maturation, egg production, molting, fat deposition)
LIGHT AND EGG LAYING IN HENS 100 1
'A1
_®
•
\
3 60
1 \G
B
\|
'
!iR
-
11 '
\
,'
:'00r
2
\\
2 60 z
g
••' / Vx C/
g 40
''1
/ T
\
''
\
•
20
400
"i
•-
\
i
i
500 600 WAVELENGTH (nm)
—
, N 700
FIG. 1. The spectrum of photon (quantum) irradiance from six light sources, each analyzed relative (%) to the peak band. B = Blue, G = green, R = red, C = cool white, V = sunlight-simulating (Vita-lite) fluorescent tubes, and T = tungsten incandescent bulbs.
kcal/kg ME, 3.27% Ca) were supplied ad libitum during the experiment. Birds were treated from 1-day-old with light from either red (R), green (G), blue (B), sunlight-simulating (V) (all, Duro-Test Corp. NJ, USA), standard cool white 40-W fluorescent tubes (C), or from standard 60 W-tungsten (T) incandescent bulbs. Calculated from manufacturer's data, the spectrum of photon irradiance relative to the peak band is shown in Figure 1. Treatments were equalized at .6 /lE photons/m^/sec at head level of the pullets by partial covering of tubes with black plastic or by varying height of lamps. Illuminance (lx) was also recorded (Table 1). Light was measured with a Ll-Cor battery-operated light meter (Model LI-185A, Lambda Instrument Corp., NE) equipped with a quantum sensor cell of flat response between 400 to 700 nm, or with a photometric (lx) sensor. From 0 to 15 weeks of age, pullets received 10 hr of light/ day, which was followed by equal weekly increments to total 17 hr (0500 to 2200 hr) by the 24th week. This was maintained to forced molting after 50 weeks of egg laying.
The average age (days) when each hen within a treatment produced her first egg indicated achievement of juvenile sexual maturation. Reinitiation of laying after molting was assessed for each treatment by the average period of time (days) needed after renewal of light stimulation for the appearance of the first egg of each hen. The body weight reduction (North, 1977) necessary for molt, accompanied by a consistent cessation of laying, was achieved by feed withdrawal for 10 days, the first 3 together with water deprivation. Feed was then restricted to 60, 70, and 80 g/hen/day for the 1st, 2nd, and 3rd weeks, respectively, and thereafter supplied ad libitum. Daily light was reduced to 6 hr for 6 weeks at commencement of molting, then increased to 12 hr, followed by weekly increments of 1 hr to a total of 17 hr. Body weight was recorded at maturity (16, 20 weeks) and before and after molting. At 16 and 20 weeks of age, five hens from each treatment were taken randomly for autopsy. Abdominal fat weight was recorded as a percentage of body weight. Data were assessed by Student's t-test or analysis of variance, as appropriate means were separated in the latter case by Duncans' multiple range test (Snedecor and Cochrane, 1971). RESULTS AND DISCUSSION
Average age of first lay did not differ significantly between treatments (Table 2). First eggs to appear under the monochromatic treatments (B, G, R; 124 days of age ± 2)
TABLE 1. Light intensity under six light treatments Light treatments
B G R C T V
Photon irradiance1
Illuminance 1
(pE m^ sec)
(lx)
.60 .59 .64 .63 .64 .64
13 56 12 38 32 32
+ ± ± ± ± +
.03 .03 .04 .03 .04 .03
+ + ± + ± +
2 6 2 4 4 4
1 Mean (± SE) of measurements at six different points in each pen. 2 B = Blue, G = green, R = red, C = cool white, V = sunlight-simulating (Vita-lite) fluorescent lamps, and T = tungsten incandescent bulbs.
Downloaded from http://ps.oxfordjournals.org/ at Florida Atlantic University on January 28, 2015
AA
~®
80-
"300
'
\l \
40-
20 -
'
191
192
PYRZAK ET AL. TABLE 2. Effect of light quality (X ± SE) on initiation of egg laying in hens (n = 24)
Light treatments'
Average period between postmolt light stimulation and first egg
Average age at first egg
/
± ± ± + ± ±
6 7a 6a 5a 5a 5a
.
45 28 16 32 19 21
N
± ± ± ± ± ±
3a 2b 2e 3b 2C 2^
' ' Different letters in a column indicate significant (P<.05) differences between treatments. 1
B = Blue, G = green, R = red, C = cool white, V = sunlight-simulating (Vita-lite) fluorescent lamps, and T = tungsten incandescent bulbs.
significantly preceded those under wide spectrum radiation (C, V, T; 131 days + 1). Scott and Payne (1937) suggested that the extension of natural daylength by an additional period of R light was more stimulatory to turkey hens than B light. However, there was a large difference in intensity between wavelengths which may have masked any effect of light quality. Harrison et al. (1969b) reported slightly greater stimulation of maturation by short wavelengths in comparison to long wavelengths in pullets and cockerels. In con-
TABLE 3. Body weight (g) of mature hens (X ± SE) before and after molt and abdominal fat (%) at maturation B o d y weight Light treatments'
16 w e e k s
B G R C T V
1350 ± 1360± 1400 + 1390± 1570 ± 1390+ a
2
60b 30b 60b 30b 40a 50b
20 w e e k s
Before molt, 54 w e e k s 3
2
(&>
1580± 60b 1700± 150ab 1730± 8 0 a b 1690 ± 5 0 b 1740 ± 1 7 0 a b 1850± 50a
2312 + 9 1 a 2450 ± 8 5 a 2396 ± 8 0 a 2225 + 6 6 a 2304±96a 2417 ± 9 5 a
A b d ominal fat
After m o l t , 62 w e e k s 3
16 w e e k s 2
1801± 60a 1990± 75a 1860 ± 8 0 a 1910± 80a 1851 ± 8 1 a 1010 ± 1 0 5 a
2.6 2.4 1.6 2.1 1.8 2.1
± ± ± ± ± ±
.8a .3a .3a ,6a .3a .7a
20 weeks 2
4.7 3.1 2.7 3.3 2.7 3.0
± ± + ± ± ±
.8a .7ab .6b .3ab .7b .5b
' Different letters in a column indicate significant (P-C05) differences between treatments. B = Blue, G = green, R = red, C = cool white, V = sunlight-simulating (Vita-lite) fluorescent tubes, and T tungsten incandescent bulbs. 1
3
n = 20 to 24.
Downloaded from http://ps.oxfordjournals.org/ at Florida Atlantic University on January 28, 2015
150 160 149 148 152 147
B G R C T V
a
trast, Woodward et al. (1969) found reproductive development in quail to be greater under R than under B or G light. Following restimulation by light after molting, average period to first egg was significantly longer under B light (Table 2) compared to all the other sources. The time required under R, T, and V radiation was significantly less than that required for B, G, C, with B being greater than G or C. The R, T, V, and C light sources are rich in red light compared to the G and B tubes (Fig. 1). Thus, in the postmolting period, response to light quality under the complex spectral sources can not be explained simply in terms of response to the narrow light bands. The influence of wavelengths was greater after molting than it was during pubertal maturation. If laying is primarily dependent on direct light stimulation of the hypothalamus (Benoit, 1964), the relative influence of longer wavelength light may increase because of its greater penetrability and the possibly increased opacity of tissues to intracranial light transmission with age. Compared to T light, body weight under B and G light was less at 16 and 20 weeks (Table 3) despite greater fatness in the B treatment at 20 weeks of age. Woodward et al. (1969) observed lower weights under B or G in quail at maturity when compared to white or R light. Body weight of turkeys was also lower at maturity under B light as compared to R light (Leighton and Mason, 1976). Body weight
LIGHT AND EGG LAYING IN HENS
REFERENCES Benoit, J., 1964. The role of the eyes and the hypothalamus in the photo-stimulation of the gonads of the duck. Ann. NY Acad. Sci. 117: 204-216. Dorminey, R. W„ J. E. Parker, and W. H. McClusky, 1970. Effect of light intensity on leghorn pullets during the development and laying periods. Poultry Sci. 49:1657-1661. Harrison, P. C , 1972. Extraretinal photocontrol of reproductive responses of leghorn hens to photoperiods of different length and spectrum. Poultry Sci. 51:2060-2064. Harrison,P. C , J. McGinnis, G. Schumaier, and J. K. Lauber, 1969a. Sexual maturity and subsequent
reproductive performance of White Leghorn chickens subjected to different parts of the light spectrum. Poultry Sci. 48:878-883. Harrison,P. C , G. Schumaier, and J. McGinnis, 1969b. Sexual maturity and subsequent reproductive performance of White Leghorn chickens subjected to different parts of the light spectrum. Poultry Sci. 48:878-883. King,D. E., 1961. Effects of increasing, decreasing and constant light treatment on growing pullets. Poultry Sci. 40:479-484. Leighton, A. T., Jr., and J. P. Mason, 1976. Environmental factors affecting growth performance of turkeys. Am. Soc. Agric. Eng. Paper No. 76— 4508. Menaker, M., and H. Underwood, 1976. Extraretinal photoreception in birds. Photochem. Photobiol. 23:299-306. Morris, T. R., and S. Fox, 1958a. Light and sexual maturity in the domestic fowl. Nature 181: 1453-1454. Morris,T. R., and S. Fox, 1958b. Artificial light and sexual maturity in the fowl. Nature 182:1522— 1523. Morris,T. R., and V. M. Owen, 1960. The effect of light intensity on egg production. Pages 458—461 in Proc. 13th World's Poultry Congress. North, M. O., 1977. Commercial Chicken Production Manual. Avi Publishing Co., New York, NY. Oishi,T., and J. K. Lauber, 1973. Photoreception in the photosexual response of quail. II. Effect of intensity and wavelength. Am. J. Physiol. 225: 880-886. Scott,H. M., and L. F. Payne, 1937. Light in relation to the experimental modification of the breeding season of turkeys. Poultry Sci. 16:90—96. Shutze,J. V., W. E. Matson, and J. McGinnis, 1961. Influence of different photoperiods during brooding and rearing on subsequent productive characteristics in chickens. Poultry Sci. 40: 1604-1611. Siopes.T. D., and W. O. Wilson, 1980. Participation of the eyes in the photosexual response of Japanese quail. Biol. Reprod. 23:352-257. Snedecor.G. W., and W. G. Cochrane, 1971. Statistical Methods. Iowa State Univ. Press, Ames, IA. Vriend.J., and J. K. Lauber, 1973. Effects of light intensity, wavelength and quanta on gonads and spleen of the deer mouse. Nature 244:37—38. 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). Poultry Sci. 48:118—123.
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was not significantly different between R and B light in this study. Postmolt body weights did not differ significantly, despite differences in time required for reinitiation of laying (Table 2). Abdominal fat, relative to body weight, declined with the increase in wavelength both at 16 and 20 weeks (Table 3). At 20 weeks, the relative weight of fat under B light was 50% (P>.05) and 72% (P<.05) greater than under G or R, respectively, and 74% (P<.05), 58% (P<.05), and 41% (P>.05) greater than under T, V, or C light, respectively. All treatments in the present experiment were at the same level of photon irradiance (Table 1). Additionally, illuminances of the B and R sources were similar, as were those of the C, T, and V sources of white light. Therefore, the differences between treatments confirm that light quality is a factor in renewal of egg laying following molting. Relatively greater intracranial penetration of longwave photons (Benoit, 1964) to an extraretinal photoresponsive mechanism, located in the brain (Oishi and Lauber, 1973; Menaker and Underwood, 1976) may be involved in mediating the effect of light on ovarian development (Harrison, 1972). This is supported by the findings reported herein.
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