Kasetsart J. (Nat. Sci.) 46 : 51 - 63 (2012)

Effects of Red Light Illumination on Productivity, Fertility, Hatchability and Energy Effi ciency of Thai Indigenous Hens

Nirat Gongruttananun* and Pannapat Guntapa

ABSTACT

This study was conducted to determine the effects of red light exposure on the productivity, fertility and hatching characteristics in Thai native hens (Gallus domesticus). A total of 120 birds aged 18 wk were housed in an open-sided shed and exposed to one of the following lighting treatments: 1) natural daylight supplemented with fl uorescent light (Control), 2) natural daylight supplemented with red light (NR) and 3) red light as the sole light source (R). The red light was produced by light- emitting diodes. All treatments were provided with a daily light:dark photoperiod of 16:8 hr over a 28-week egg-laying period, and there were four replicate pens of 10 hens for each treatment. Photostimulation of the light sources was initiated at age 18 wk and any subsequent effects on the live performance and reproductive traits were observed during the experimental period. Feed and water were available at all times. Body weights, feed consumption and mortality rates were similar among the treatment groups. The age at fi rst egg of the NR birds (130.7 d) was comparable to that of the R birds (129.2 d) which was signifi cantly less than that of the control hens (134.7 d). During the fi rst week of the laying period, R hens produced more eggs than did hens in the control treatment (P < 0.05), whereas the NR birds exhibited an intermediate value between those groups. At 2 wk after photostimulation, the serum estradiol concentration was signifi cantly higher for hens in the R treatment compared to those of the control and NR treatments. The hematocrit values of the birds in the R treatment tended to be lower than those of the other two treatments in some periods of the study. During the lighting period from weeks 6 to 8, a signifi cantly improved feed conversion ratio was observed in the R and NR treatments compared to that of the control treatment. No signifi cant differences in egg weight, egg and eggshell quality or any parameters of hatching occurred between the R and control groups. The weights of the ovary, pituitary gland, spleen and the abdominal fat were similar for all light treatments. It was concluded that photostimulation by red light resulted in an acceleration of sexual development in Thai native hens compared to hens exposed to full-spectrum lighting; however, live performance, egg production, egg and eggshell quality, and fertility were not affected whatever the light treatment. The light-emitting diode lighting regimens could be benefi cial for energy conservation and the reduction of rearing costs in laying hens. Keywords: Thai native hen, red light, sexual maturity, estradiol, hatchability

Department of Animal Science, Faculty of Agriculture, Kasetsart University, Bangkok 10900, Thailand. * Corresponding author, e-mail: agrnig@ku.ac.th

Received date : 21/07/11 Accepted date : 28/12/11

Kasetsart J. (Nat. Sci.) 46(1)52

INTRODUCTION

In Thailand, the commercial poultry industry has reached an advanced stage and the country is now self-suffi cient in poultry meat and egg production. Meanwhile, the government policy is to promote the raising of indigenous chickens by small holders to increase their household income and keep this local strain for the conservation of genetic resources (Aini, 1990). However, the reproductive effi ciency of the birds is very low, as under commercial farm conditions, cumulative annual egg production of birds was less than 90 eggs per hen (Kongruttananun, 1993) and the peak production was approximately 38% hen-day egg production (Gongruttananun and Chotesangasa, 2005). This is a costly problem for the producers, resulting in substantial losses in egg and chicken production. Light is an important environmental factor for the birds, as it not only allows vision but infl uences important physiological responses such as activity and behavior. The reproductive performance of the domestic fowl is highly dependent on appropriate light manipulation, involving both the quantity (duration and intensity); the quality (color or wavelength) of light and the effects of the spectrum (color of light) on reproductive performance of the domestic fowl have been the subject of a number of studies. It is well documented that light from the red spectrum has a gonadal activating effect whereas blue and green spectra have little or no effect on the organs (Woodard et al., 1969; Harrison et al., 1970; Pryzak et al., 1987). However, the infl uence of the wavelength of light on reproductive performance in the domestic fowl is equivocal. Jones et al. (1982) did not fi nd any benefi cial effects of red light for egg production in laying hens. Rozenboim et al. (1998) demonstrated that egg production could be adversely affected by exposing laying hens to light with a wavelength of 880 nm. Two types of photoreceptors were reported in birds—retinal

photoreceptors and extra-retinal photoreceptors (Harrison, 1972). Growth and behavior responses depend principally on the retinal photoreceptors, whereas photosexual responses are mainly influenced by the extra-retinal light receptors (Lewis and Morris, 2000). Photostimulation of extra-retinal photoreceptors which are located in several parts of the brain and are sensitive to red light, stimulates reproductive activity in male chickens (Foss et al., 1972) and quails (Oishi and Lauber, 1973). Recently, Mobarkey et al. (2010) reporting on broiler breeder hens stated that photostimulation of the retinal photoreceptors resulted in depressed reproductive function, whereas the activating effect was controlled by the stimulation of the extra-retinal photoreceptors. In Thailand, information about the effect of the color of light on reproductive performance in laying hens is lacking. Therefore, the objective of the present study was to determine the infl uence of red monochromatic light applied from 18 to 46 wk of age on the live performance, egg production, fertility and hatching characteristics in Thai native hens.

MATERIALS AND METHODS

Experimental birds and lighting regimens The experimental animals and procedures

used in this study were approved by the Animal

Ethics Committee of Kasetsart University,

Thailand. A total of 120 Thai native hens were

used in the study. The birds were hatched in

January 2010 and reared in a curtain-sided growout

house exposed to natural day lengths. All pullets

were moved into slat-floor pens situated in a

conventional open-sided layer shed at 18 wk of

age. The birds were randomly divided into three

groups, each group consisting of four replicates

of 10 birds per replicate. Groups 1 (Control)

and 2 (NR) were raised under natural daylight

supplemented with 4 hr of white fluorescent or

red light, respectively, operated from 18:00 to

Kasetsart J. (Nat. Sci.) 46(1) 53

22:00 hours daily by an autonomic time clock.

Group 3 (R) was placed in identical pens that

were enclosed with PVC (polyvinyl chloride)

black plastic, so that the light could be controlled

and the birds in these pens were exposed to red

light as the sole light source for 16 hr per day.

This lighting operated continuously from 06:00

to 22:00 hours daily throughout the study. Each

light treatment was separated from the others by

means of PVC black plastic partitions. Each pen

was 2.9 × 2.9 × 3.0 m (width × height × length), and

mechanically ventilated. Ambient temperature in

the pens was recorded daily. Throughout the study,

the temperatures (mean ± SE) of the control, NR

and R groups were 33.3 ± 3.6, 32.7 ± 3.7 and 32.6

± 2.2 °C, respectively. Feed and fresh water were

provided ad libitum. The feed was a commercial

layer diet calculated to contain 17% crude protein,

2,800 kcal of metabolizable energy per kilogram

of feed and 3.5% calcium.

Lighting devices In each pen of the control treatment,

artificial light was provided from one 13-watt

white fluorescent tube hung from the ceiling in the

middle part of the pen. The red light used in the

NR and R treatments was produced from a light

emitting diode (LED). The LED lamp was made

by using 20 diodes installed in two parallel lines

4.5 cm apart on a plastic board (7 cm × 10.5 cm,

width × length). The LED lamp was hung from the

ceiling in the middle part of each pen subjected

to the NR and R treatments. The light intensity

was measured with a luxmeter (model TES-1330,

TES Electrical Electronic, Corp., Taiwan) with a

measuring range of 1 × 10-2 to 1 × 105 lx and an

accuracy of ± 3% at the level of the heads of the

birds at five locations within each pen. The light

intensity measurements were taken on a weekly

basis, recorded at noon and repeated at 20:00

hours to establish a pen mean light intensity, over

the 26-week experimental period. The mean light

intensity of the control, NR and R treatments were

583.4, 440.2 and 74.2 lx, respectively. The physical

characteristics of these light sources are detailed

in Table 1.

Sexual maturat ion and performance variables During the experimental period, the following data were obtained: body weights at the beginning and termination of the study, feed consumption, rate of sexual maturity, egg production, egg weight, egg quality and mortality rate. Egg production and egg weight were recorded daily and determined on a weekly basis to 36 wk of age. The rate of sexual maturity was the age at fi rst egg following photostimulation. The feed intake data were recorded on a biweekly basis to 36 wk of age. All eggs from each replicate laid on the last day of the week were collected in each 2-week period for egg and eggshell quality measurement. The eggs were broken at the equatorial region, and the interior contents were allowed to drain out. The internal quality of eggs was assessed according to albumen height and yolk color by using specialized equipment (Technical Services and Supplies, U.K.). The yolk weight was determined after it was separated from adhering albumen and then weighed on an electric balance (Model

Table 1 Radiometric and electrical characteristics of the two light sources used in the experiment.

Wavelength (nm) Luminous Power Peak Range intensity (lumen.watt-1) dissipation (watt)LED1 632 612-652 11.5 0.1Fluorescent2 - - 37.0 13.01 Model 5 mm round ultra bright red LED (ENGINEO Co., Ltd., Chiang Mai, Thailand).2 Model EFD 13D/6D-E 2U (Toshiba Co., Ltd., Bangkok, Thailand).

Light type

Kasetsart J. (Nat. Sci.) 46(1)54

PB1501, Mettler Toledo, Columbus, OH, USA). The eggshell along with membranes was washed with tap water and dried at room temperature for 1 wk. After drying, the eggshell was weighed and shell thickness was measured in millimeters using a digimatic micrometer (Mitutoyo Corporation, Kanagawa, Japan). Three measurements were taken on the equator region for each egg shell, and the mean of the three measurements was calculated. The albumen weight was determined by subtracting the yolk plus shell weight from the total egg weight. The specifi c gravity of eggs was determined using sodium chloride solutions ranging in specifi c gravity from 1.064 to 1.100 in increments of 0.004 units as described by Keshavarz and Nakajima (1993).

Hematological studies Blood samples (5 mL) were obtained

from the brachial vein from two hens from each

replicate at 2 wk following photostimulation. The

time of bleeding was between 09:00 and 11:00

hours. The hematocrit value was determined using

heparinized microcapillary tubes by centrifuging

in a Hettich Microliter centrifuge (Hettich,

Tuttlingen, Germany) for 5 min at 21,382× g at

25 °C (Campbell, 1995). Next, the remainder

was centrifuged for 15 min at 1,096× g at 25 °C.

Serum estradiol and prolactin concentrations were

measured by chemiluminescent microparticle

immunoassay on an ARCHITECT® System Model

I 2000SR (Abbott Laboratories, Abbott Park, IL,

USA). In brief, the analytical sensitivity of the

assay was less than or equal to 10 pg/mL and 0.6

ng/mL for estradiol and prolactin, respectively.

Accuracy was 99.30% for estradiol and 99.97% for

prolactin. The intra-assay coefficient of variation

was 4.8% for estradiol and 3.2% for prolactin,

whereas the inter-assay coefficient was 7.1 and

4.4% for estradiol and prolactin, respectively. The

hematocrit measurement was repeated when the

birds were aged 26 and 44 wk.

Fertility and hatchability Hatching performance was determined

when the hens were aged 40 wk. The hens in

each replication were naturally mated with one

Thai native male aged 48 wk. Hatching eggs were

collected after the hens had been mated with the

cockerels for 7 d. The eggs were picked up from the

nests, placed in incubator trays and received at the

hatchery at 16:30 hours. Then, eggs that were dirty,

cracked or misshapen were removed. All eggs were

fumigated with formaldehyde gas for 30 min and

stored in the hatching room for 5 d at 18.0 ± 2.0

°C at 75.0 ± 5.0% relative humidity. On the fifth

day after collection, the eggs were pre-warmed

for 6 hr at room temperature and 65% relative

humidity, allowed to sweat and dry, and weighed to

0.01 g accuracy just before the incubation period.

All eggs were fumigated again in the incubator on

the day of setting. Incubating trays representing

each treatment were distributed throughout all

positions in the setter (Model Multiplo electric

incubator, The Multiplo Incubator & Brooder

Pty. Ltd., Sydney, NSW, Australia) to minimize

any possible machine position effects. The eggs

were turned hourly through 90° and incubated at

37.4 ± 0.02 °C dry bulb temperature and 38.9 ±

0.02 °C wet bulb temperature. The hatcher (Model

Multiplo, The Multiplo Incubator & Brooder Pty.

Ltd., Sydney, NSW, Australia) was operated at

37.2 ± 0.02 °C dry bulb temperature and 30.0 ±

0.02 °C wet bulb temperature.

On the eighth day of incubation, the

eggs were candled in the candling room (around

28.5 °C and 80% relative humidity). „Clear‰ eggs

were removed and broken in order to identify early

dead embryos from infertile eggs as described

by Lourens et al. (2006). The eggs were candled

repeatedly on day 19 of incubation to remove

middle embryonic mortalities and weighed in order

to determine egg weight loss at the transferring

time. About 2 hr after removal from the setter, eggs

with apparently living embryos were transferred to

hatching baskets and randomly distributed in the

Kasetsart J. (Nat. Sci.) 46(1) 55

hatcher to reduce any possible machine position

effects. All chicks were taken off at 21 d and 12

hr postincubation. Hatched chicks were weighed

on a treatment basis to 0.01 g accuracy. The

fertility (number of fertile eggs per all eggs set ×

100) and hatchability (number of chicks hatched

per all fertile eggs × 100), and early embryonic

mortality (number of embryos dying from day 1

to 7 per number of fertile eggs set × 100), middle

embryonic mortality (number of embryos dying

from day 8 to 18 per number of fertile eggs set

× 100) and late embryonic mortality (number of

embryos dying from day 19 to 21 per number of

fertile eggs set × 100) were calculated.

The hens in all treatments were mated by

the roosters thoroughly to minimize any possible

effects of the males. This was done by exchanging

the cockerels among treatments when the hens

were aged 42 and 44 wk to produce hatching eggs

for batches II and III, respectively. In each batch,

the roosters in the control treatment were removed

and placed in the NR treatment and replaced with

the male birds taken from the R treatment. In turn,

the cockerels in the R treatment were replaced

with the roosters that had been mated with hens

in the NR treatment. Incubation practices and data

collection were operated under the same conditions

as those in batch I. The average of the three batches

was calculated for each replication.

Autopsies At the termination of the study, two birds from each replicate were sacrifi ced for observation of reproductive and internal organs. The birds were killed by cervical dislocation, and the ovary and oviduct were removed and measured for weight and length. Pituitary glands were excised and weighed immediately following their removal to the nearest 0.0001 mg with an analytical balance (Model AB 104, Mettler-Toledo Ltd., Bangkok, Thailand). The spleen, liver and abdominal fat were removed and weighed on an electric balance (Model PB 1501, Mettler Toledo, Columbus, OH, USA).

Statistical analysis The experiment was conducted as a completely randomized design with three treatments. Data were analyzed using the statistical software package SAS (version 9.0; SAS Institute, 2002). The GLM procedure was used to analyze the effect of the treatment on live performance, egg production, egg and eggshell quality, hematological parameters, hatching performances and internal organ weights. The arcsine transformation was used for all percentage data. When the means of the GLM procedure were statistically different, these means were further compared between the control and the experimental groups using Duncan’s multiple range test. Signifi cance was based on P < 0.05. The experimental unit was a group of 10 hens for all traits studied. For the determination of the hematological values and morphological characteristics of the internal organs, only two hens per replicate were used. Data were presented as means and the pooled standard error of the mean.

RESULTS

Live performance, sexual maturation and egg production The effects of the experimental lighting regimens on body weight, feed intake, and mortality rate are presented in Table 2. There were no signifi cant differences in initial body weight, fi nal weight, feed consumption or mortality rate among the treatment groups. Figure 1 shows the effect of the light treatments on age at fi rst egg of the experimental birds. Pullets in the NR and R treatment groups commenced egg production when the birds were aged 130.7 and 129.2 d, respectively, which were signifi cantly earlier than for the birds in the control group (134.7 d). Weekly egg production (presented as hen day percentage), is presented in Figure 2 for birds reared under different light sources. During the fi rst week of egg laying, the birds in the R treatment had a signifi cantly higher rate of egg production than

Kasetsart J. (Nat. Sci.) 46(1)56

Table 2 Body weight, feed consumption and mortality rate of the experimental hens during 18 weeks of photostimulation.

Body weight Group Initial Final Weight gain Feed intake Mortality rate weight weight (kg) (kg) (kg) (g.bird-1.d-1) (%)Control 1.37 1.71 0.345 80.5 11.30NR 1.36 1.70 0.343 78.4 10.71R 1.37 1.66 0.289 72.4 12.94SEM 0.06 0.13 0.158 5.9 12.72P-value 0.943 0.865 0.854 0.195 0.967Control = Daylight supplemented with 4 hr of fl uorescent light; NR = Daylight supplemented with 4 hr of red light; R = Red light for 16 h.d-1.SEM = Pooled standard error of the mean (4 replicates of 10 hens each per treatment).There are no signifi cant differences (P < 0.05) among the means within the same column.

b

b

a

128129130131132133134135136

Control NR R

Treatment

Age

at f

irst

egg

(day

s)

Figure 1 Effects of light treatment on age at fi rst egg of the experimental hens maintained under natural daylight supplemented with 4 hr of fl uorescent (Control) or red (NR) light compared to that of the hens photostimulated only with 16 hr of red light (R) per day. Values marked with no common letters are signifi cantly different at P < 0.05 (P = 0.029; Pooled standard error of the mean = 2.45).

the control birds (9.68 versus 0.51%, respectively), whereas egg production rate of the birds in the NR treatment (4.08%) exhibited an intermediate value. Thereafter, there was no signifi cant difference in the rate of egg production among the three bird groups throughout the experimental period. Figure 3 represents the biweekly averages for the feed conversion ratio of the experimental hens as affected by the lighting treatments. During 24-26 wk of age, a signifi cantly higher level of feed

conversion ratio was observed in the control group (7.49 kg feed per kg egg weight) as compared to those of the NR and R treatment groups with values of 5.58 and 4.78 kg feed per kg egg weight, respectively.

Reproductive hormones and hematocrit values The treatment effects on estradiol and prolactin concentrations in the blood and

Kasetsart J. (Nat. Sci.) 46(1) 57

Figure 2 Rate of egg production on Thai native hens maintained under natural daylight supplemented

with 4 hr of fluorescent (Control) or red (NR) light compared to that of the hens photostimulated

only with 16 hr of red light (R) per day. ∗ = Statistical significance among groups at P < 0.05

(P = 0.025, Pooled standard error of the mean = 3.87).

0

10

20

30

40

50

60

70

80

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18Weeks of photostimulation

Perc

enta

ge p

rodu

ctio

n

ControlNRR

0

1

2

3

4

5

6

7

8

9

10

4 6 8 10 12 14 16 18

Weeks of photostimulation

FCR

(kg

feed

/kg

egg

wei

ght)

ControlNRR

∗

Figure 3 Effects of light treatment on mean feed conversion ratio (FCR) of hens maintained under natural

daylight supplemented with 4 hr of fluorescent (Control) or red (NR) light compared to that of

the hens photostimulated only with 16 hr of red light (R) per day. ∗ = Statistical significance

among groups at P < 0.05 (P = 0.012, Pooled standard error of the mean = 1.01).

Kasetsart J. (Nat. Sci.) 46(1)58

hematocrit values are given in Table 3. At 20 wk of age, hens in the R group (175.50 pg.mL-1) had a signifi cantly (P = 0.010) higher level of serum estradiol concentrations than those in the control and NR groups with values of 42.75 and 48.25 pg.mL-1, respectively. On the other hand, the concentration of prolactin was similar among the treatment groups. The treatment effect was not signifi cant (P = 0.05) for the percentage of packed cell volume at 26 wk of age.

Egg and egg shell quality Means of egg weight, yolk weight, yolk color, albumen weight, albumen height, shell weight, shell thickness and egg specifi c gravity over the experimental period are summarized in Table 4. No effect of lighting treatment was found within the hen performance criteria of egg weight, egg and egg shell quality or egg specifi c gravity among the treatment groups.

Table 3 Effects of light treatment on blood concentrations of reproductive hormones and hematocrit values measured at various ages of hens maintained under natural daylight supplemented with 4 hr of fl uorescent (Control) or red (NR) light compared to that of the hens photostimulated only with 16 hr of red light (R) per day.

Estradiol (pg.mL-1) Prolactin (ng.mL-1) Hematocrit (%)Group 20 wk 20 wk 20 wk 26 wk 36 wkControl 42.75b 0.93 27.73 38.61 32.27NR 48.25b 0.41 26.82 34.89 33.43R 175.50a 0.81 25.74 31.48 32.61SEM 53.44 0.62 2.73 5.42 1.99P-value 0.010 0.495 0.362 0.050 0.923Control = Daylight supplemented with 4 hr of fl uorescent light; NR = Daylight supplemented with 4 hr of red light; R = Red light for 16 h.d-1.a,b = Means within the same column without a common superscript are signifi cantly different (P < 0.05). SEM = Pooled standard error of the mean (4 replicates of 2 samples each per treatment).

Table 4 Effects of the lighting treatments on egg and egg shell quality of Thai native hens throughout the study (age 20 to 46 wk).

Group Item Control NR R SEM P-valueEgg weight (g) 38.0 36.6 37.2 1.4 0.566Yolk weight (%) 29.3 28.7 28.8 1.1 0.751Yolk color (Roche scores) 7.0 6.8 6.7 0.3 0.391Albumen weight (%) 60.7 61.3 61.1 1.2 0.091Albumen height (mm) 5.5 5.9 5.8 0.50 0.571Shell weight (%) 9.9 9.9 10.0 0.19 0.485Shell thickness (mm) 0.32 0.31 0.31 0.01 0.074Egg specifi c gravity 1.086 1.085 1.086 0.001 0.495Control = Daylight supplemented with 4 hr of fl uorescent light; NR = Daylight supplemented with 4 hr of red light; R = Red light for 16 h.d-1.SEM = Pooled standard error of the mean (4 replicates of 10 hens each per treatment).

Kasetsart J. (Nat. Sci.) 46(1) 59

Table 5 Effects of light treatment on fertility and hatching performances of the experimental hens. Group Item Control NR R SEM P-valueNumber of setting eggs 212 255 255 Setting egg weight (g) 44.1 43.3 43.0 2.3 0.793Fertility (%) 97.0 98.0 95.1 2.5 0.314Egg weight loss (%) Day 1-7 3.9 4.3 3.9 0.4 0.372 Day 1-18 11.2 11.7 10.2 2.3 0.662Hatchability (%) 72.4b 81.8a 72.3b 5.1 0.045Embryonic mortality (%) Early dead (1-7 d) 17.9 8.3 18.5 7.7 0.170 Middle dead (8-18 d) 3.1 0.7 0.4 2.2 0.217 Late dead (19-21 d) 6.5 9.0 8.6 4.9 0.737Hatched chick weight (g) 30.7 29.4 30.5 1.2 0.315Control = Daylight supplemented with 4 hr of fl uorescent light; NR = Daylight supplemented with 4 hr of red light; R = Red light for 16 h.d-1.a,b = Means within the same row without common superscripts are signifi cantly different (P < 0.05).Hatchability = (number of chicks / number of fertile eggs) × 100.

Early dead = (number of embryos dying from day 1 to 7 / number of fertile eggs set) × 100.

Middle dead = (number of embryos dying from day 8 to 18 / number of fertile eggs set) × 100.

Late dead = (number of embryos dying from day 19 to 21 / number of fertile eggs set) × 100.

SEM = Pooled standard error of the mean.

Hatching performances Mean values indicating the effect of the light treatments on fertility, egg weight loss, hatchability, embryonic mortality and hatched chick weight are summarized in Table 5. There were no signifi cant differences in fertility, egg weight loss, embryonic mortality and hatched chick weight among the three experimental bird groups. The hatchability of chicks in the NR group was 81.8%, which was signifi cantly higher than those of chicks in the control (72.4%) and R (72.3%) treatment groups.

Morphological characteristics of gonads and internal organs A summary of the morphological characteristics of gonads and internal organs of the experimental birds sacrifi ced at the termination of the study is shown in Table 6. No signifi cant differences in weights of the ovary, pituitary gland, spleen or abdominal fat occurred among

the treatment groups. The weight and length of the oviduct of the birds in the NR treatment were signifi cantly greater than those of the hens in the control and R treatments. Similar observations were also found for the means of liver weight among the experimental birds. From the results of the present study, it was apparent that the average feed conversion ratio of the control birds was greater than those of the NR and R birds in most of the studied periods; a signifi cant difference occurred during the period from age 24-26 wk (Figure 3). As a consequence, feed savings could be obtained by using the LED lighting regimen compared to the cost of the birds under fl uorescent lighting (Table 7). The calculation based on 40 hens (10 hens per replication) in the R treatment, indicated a reduction in rearing costs (-10.2% in feed and -38.4% in light energy costs). Approximately 2.7 and 84.6% of the feed and light energy savings, respectively, were in the NR treatment. This was in

Kasetsart J. (Nat. Sci.) 46(1)60

Table 6 Effects of light treatment on morphology of gonads and internal organ weights of the

experimental hens determined at the end of the study.

Ovary Oviduct Pituitary Spleen Liver AbdominalGroup weight weight length glands (g/kg BW) (g/kg BW) fat (g/kg BW) (g/kg BW) (cm/kg BW) (mg/kg BW) (g/kg BW) Control 5.44 5.96b 20.73b 3.96 1.13 11.04b 37.54NR 16.10 18.28a 35.22a 3.13 1.24 16.12a 27.09R 5.63 2.79b 21.89b 4.11 0.85 11.80b 25.50SEM 8.30 5.53 6.37 1.58 0.40 2.61 13.75P-value 0.188 0.006 0.018 0.754 0.418 0.046 0.438Control = Daylight supplemented with 4 hr of fl uorescent light; NR = Daylight supplemented with 4 hr of red light; R = Red light for 16 h.d-1.BW = Bodyweight.a,b = Means within the same column without common superscripts are signifi cantly different (P < 0.05).SEM = Pooled standard error of the mean (4 replicates of 2 samples each per treatment).

Table 7 Cost effectiveness of LED device (632 nm) compared to that of fl uorescent light tube (13W) used in the experiment.

Energy FeedGroup Energy consumption Savings Feed intake Savings (W.d-1) (%) (kg.d-1) (%)Control 208 - 3.221 -NR 32 84.6 3.132 2.7R 128 38.4 2.893 10.2Control = 4 hr of one 13 W fluorescent tube per day per replication ; NR = 4 hr of one 2 W LED lamp per day per replication ;

R = 16 hr of one 2 W LED lamp per day per replication.180.5 g feed.d-1 × 40 hens.278.4 g feed.d-1 × 40 hens.372.4 g feed.d-1 × 40 hens.

agreement with the result reported by Rozenboim et al. (1998) who suggested that a reduction in the rearing costs of laying hens could be obtained by using an LED lighting system.

DISCUSSION

The main fi nding of the present study was that photostimulation of Thai native hens with red light resulted in an acceleration of the rate of sexual development of the birds. As shown in Figure 1, pullets in the NR and R light treatments signifi cantly accelerated the time to laying of the fi rst egg by 4.0 and 5.5 days, respectively, from

that which occurred in the control treatment. The results indicated more progressive development of ovarian follicles in hens exposed to red light, especially as the birds were illuminated only with red light in closed confi nement. This was confi rmed by evidence of increased blood estradiol concentrations in the birds in the R treatment (Table 3). Estradiol is an ovarian hormone that has a variety of reproductive functions in domestic hens, including the regulation of calcium metabolism for egg shell formation (Etches, 1987), enhancement of growth of the oviduct and induction of the albumen secretion (Palmiter, 1972) and stimulation of the yolk precursor

Kasetsart J. (Nat. Sci.) 46(1) 61

synthesis (Deely et al., 1975). There were no signifi cant differences among treatments in terms of the hematocrit values, although the mean of birds in the R treatment at 26 wk of age tended to be lower than those of hens in the control and NR treatments. Presumably, these differences were a refl ection of the different reproductive status of the birds. Proudman and Wentworth (1977) reported a lower packed cell volume in turkey hens compared with non-laying hens and suggested the hematocrit value as an indicator of egg laying status of the birds. In the present study, hens in the control and NR treatments were raised under natural daylight in open-sided pens, the light intensity was very high (greater than 400 lx) in all portions of the visible electromagnetic spectrum. On the other hand, for hens in the R lighting regimen, who were reared in closed pens and exposed only to the spectral output of red light (632 nm), the light intensity was relatively low (less than 80 lx). Siopes (1984) stated that a quantifi cation of the light energy in the 600 to 700 nm range is important in evaluating the effects of different light intensities and light with different color outputs. In the present study, the total amount of light energy either in the visible spectrum or in the 600 to 700 nm range of spectra was not measured. However, it is of interest to note that hens in the control and NR treatments were reared under the same natural daylight period except for 4 hr of supplementary artifi cial light; the NR hens were illuminated with red light whereas the control hens were exposed to fl uorescent light. Mobarkey et al. (2010) reported that photostimulation of extra-retinal photoreceptors activated the reproductive function in broiler breeder hens whereas the stimulation of retinal photoreceptors had an inhibitory role. In the present study, the red light provided for the NR and R treatments had a peak wavelength of 632 nm. Hartwig and van Veen (1979) demonstrated that only wavelengths of light greater than 600 nm penetrated to the diencephalon

where photosexual responses are located. It seems likely that the stimulatory effect of red light on sexual development occurred in the present study as a result of a combination of the inhibition of the photostimulation of the retinal photoreceptors and the stimulation of the photostimulation of the extra-retinal photoreceptiors. The greater effect was noticeable hens in the R treatment which involved red light radiation as the sole light source for 16 hr a day throughout the experimental period. However, the total egg production throughout the experimental period did not differ signifi cantly among those treatment groups exposed to the polychromatic or monochromatic lighting regimens. The lack of significant differences suggests that suffi cient photostimulatory light energy was present in all treatments to induce a maximum response, although the light source and intensity varied considerably among the treatment groups. Clearly, it was apparent from the present study that red light radiation did not adversely affect the fertility and hatchability of Thai indigenous hens (Table 5). The mean hatchability of chicks in the R treatment was comparable to that of chicks in the control treatment, which was signifi cantly lower than that of chicks in the NR treatment. This occurrence would be due to post-oviposition factors rather than treatment effects. Brooding behavior was observed in the control and R groups during the hatching egg collecting period. This phenomenon might lead to cessation of laying and sitting on eggs by the broody hens, resulting in failure of chicken embryonic development in the incubator. The atrophy of the oviduct and reduction of the liver weight of the hens in the control and R groups (Table 6) indicated the inactive status of the reproductive organs of the hens.

CONCLUSION

Thai native hens exposed to red light can maintain the normal characteristics of live

Kasetsart J. (Nat. Sci.) 46(1)62

performance and have a reproductive performance comparable to those obtained in hens reared under natural daylight supplemented with full-spectrum fl uorescent lighting except for an acceleration in sexual maturation. LED lighting regimens could be benefi cial for reducing rearing costs and energy consumption.

ACKNOWLEDGEMENTS

The research project was funded by the Kasetsart University Research and Development Institute (KURDI), Kasetsart University, Bangkok, Thailand.

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