Use of Artificial Lighting to Increase Photoperiod Length for Pasture-Raised Laying Hens to Improve Egg Productivity and Quality

Final Report for GS14-138

Project Type: Graduate Student
Funds awarded in 2014: $10,997.00
Projected End Date: 12/31/2015
Grant Recipient: Texas A&M University-Commerce
Region: Southern
State: Texas
Graduate Student:
Major Professor:
Dr. Jackie Wahrmund
University of Kentucky
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Project Information


This project investigated the effects of commercial-style photoperiod in a sustainable-style management practice on laying hen deposition rate. Twenty-seven hens were raised in identical conditions.  Three breeds were represented by nine hens each.   Within each breed, three hens were randomly assigned to one of three groups, resulting in three groups of nine hens. Each group was randomly assigned to a coop, and each coop was assigned a management system treatment.  Treatments included: commercial (COM), pasture-raised (PAST) and pasture-raised with an extended, commercial-style photoperiod (PEP). The COM hens were raised indoors with ad libitum feed and a photoperiod of twelve to fourteen hours. This photoperiod became progressively longer as the study progressed. Housing for the PAST hens was identical to that of the COM hens; however, PAST hens had no extended photoperiod and were provided additional access to ten square meters of pasture per hen. Housing for the PEP hens was identical to that of the PAST hens with an additional photoperiod of twelve to fourteen hours. Hen deposition rate was measured once per week over a 56-day period.  Egg quality was measured periodically throughout the experiment.


The purpose of this project is to investigate a novel method of increasing the productivity of pasture-raised laying hens.  With increasing feed costs, high animal welfare standards preferred by the public, and a movement toward sustainable and natural production practices, poultry scientists and producers are exploring the viability and effectiveness of new production practices.  In the late 1990’s, a directive was introduced to the European Community to ban the use of battery cages for layers by 2012 (Mugnai et al., 2009). Similar legislation has also been passed in the United States such as California’s Prop 2 in 2008, which dramatically increases the minimal amount of square inches per hen in a hen house and also mandates that eggs imported into California from other states meet these same requirements (California Proposition 2, 2008). This law was implemented in 2014. As a result, researchers should investigate alternative and cost-effective egg production practices outside of the usual commercial practices.

Raising hens on pasture is a popular alternative for many small poultry producers; however, egg production is generally lower in this management system.  Researchers have demonstrated that hens raised on pasture can maintain similar deposition rates as commercial hens in the spring when pastures are generally high in nutrients and daylight hours are long. However, they struggle to maintain the same deposition rate in late summer, autumn and winter (Van Elswyk, 1997; Bubier, 1998; Mugnai et al., 2009; Castellini et al., 2012; Mugnai et al., 2012).  Researchers have also demonstrated that egg quality and nutrient levels are improved when hens are raised on pasture (Mugnai et al., 2009; Mugnai et al., 2012).  Sustainable egg producers will find benefit in maintaining high deposition rates throughout the year while also maintaining high egg quality standards. In addition, the alternative production systems, including pasture production systems, are widely considered to be more humane than caged and free range production systems (Appleby and Hughes, 1991).

Photoperiod is the length of time within a day that a hen is exposed to sunlight or a broad-spectrum light source. Hens perform at peak production during times of a lengthening or long photoperiod (Sharp, 1993). Commercially-raised hens are commonly kept indoors under artificial lighting for fourteen to sixteen hours per day.  As pasture-raised hens do not have a controlled photoperiod, egg deposition declines during times of the year when day length or photoperiod is short.  It is hypothesized that egg deposition rate will increase in pasture-raised hens if artificial light is added to coops to mimic long days during periods of decreasing day light.

Costs of egg production can be reduced in a pasture management system because hens may obtain nutrients from natural sources such as forage and arthropods that crawl or fly into hens’ designated pasture area. These hens require fewer nutrient inputs in the form of commercially available feed (Buchanan et al., 2007).  Additionally, the hens will return nutrients to the pasture via waste products (Moore et al., 1995).  Therefore, a pasture-raised hen can contribute to the overall sustainability of poultry production by recycling nutrients between the animal itself and its surrounding ecosystem.  It is hypothesized that the nutrient profile of the pastures where hens are housed will be more desirable for producers. Furthermore, the hens’ outputs, in the form of eggs, will be more desirable for consumers.

Raising hens on pasture enhances sustainability of agriculture by directly linking the hens to the environment in which they live.  This link is achieved through nutrient exchange from the hen to the soil and then back to the hen again.  However, there are environmental aspects in this management system which cannot be controlled. These include diet, light, temperature, and other weather factors.  This is in great contrast to the housing conditions of commercially-raised laying hens.  The environment for commercially-raised hens is completely controlled, from the room temperature to the lighting and the feed.  It is well-recognized among agriculturalists that providing a consistent, safe environment results in profitable production.  However, commercial systems are not considered to be sustainable as every nutrient input must be obtained and delivered, and every nutrient output must be handled and removed appropriately.  There is no direct link between the animal and its surrounding environment.

Eggs from pasture-raised hens are a popular sustainable alternative to commercially-produced eggs.  However, certain environmental aspects, such as short day length in the fall and winter, may depress overall productivity and profitability.  One way to control the hens’ environment without removing the hens from their ecosystem is to provide additional lighting (Lewis et al., 1997).  It is hypothesized that this will essentially “trick” the hens’ systems into believing they are in a perpetual spring, when egg production is at its peak. Timed lights are a simple addition to any coop. Therefore, producers may find much benefit in including this artificial environmental stimulus.  Any practice that increases the efficiency of pasture-raised hens at minimal cost will encourage agriculturalists to produce a sustainable, humane product without limiting output.  This will increase the quantity not only of sustainable egg products available for consumers but also of sustainable agricultural practices for producers.  The increased quantity should have a favorable effect on the price for consumers and producers, thereby making the sustainable option a more popular choice.

Project Objectives:

The experiment has been completed.  This is the Final Report.


Click linked name(s) to expand/collapse or show everyone's info
  • Margaret Morgan
  • Dr. Jackie Wahrmund


Materials and methods:

All experimental procedures were approved by the Texas A&M University-Commerce Institutional Animal Care and Use Committee (Protocol #P14-05-01).

This experiment utilized twenty-seven laying hens in a randomized block design.  The representative breeds were Cuckoo Marans (CM), Easter Egger Hybrids (EEH) and Silkie pullets (SP). The SP used in this study were raised in the same conditions as the CM and EEH, however they were twelve weeks younger than the CM and EEH hens. The eggshell color of these hens was varied such that eggs could be clearly identified with the hen from which they came. The egg colors were dark brown for CM, green for EEH, and white for SP. The CM and EEH laying hens were raised in an identical manner for ten weeks. They were maintained on vitamin supplement in their water and unmedicated chick starter/grower crumbles. After ten weeks of growth, the CM and EEH pullets were moved outdoors to a grazer coop. They had access to native grasses and ad libitum feed and water. At sixteen weeks the CM and EEH hens were moved into their designated treatment groups.  Hens continued to be maintained in identical environments with equal access to light, feed and pasture as they became accustomed to the new social conditions. At this time, young SP were being raised in identical conditions to the CM and EEH. After eight weeks, the SP were randomly added to the treatment groups. Once pecking order was established within groups (roughly thirty days), the experiment began. A commercially-available layer diet and water were provided ad libitum for hens in all treatment groups each day. 

Within breed, three hens were randomly assigned to one of three groups, resulting in three groups of nine hens. Each group was randomly assigned to a coop, and each coop was assigned a management system treatment. Treatments included: commercial (COM), pasture-raised (PAST) and pasture-raised with an extended, commercial-style photoperiod (PEP). The COM hens were raised indoors with ad libitum feed and a twelve to fourteen hour photoperiod, which became progressively longer as the study progressed. Housing for the PAST hens was identical to that of the COM hens; however, PAST hens had no extended photoperiod, and were provided additional access to ten square meters of pasture per hen. Housing for the PEP hens was identical to that of the PAST hens with additional twelve to fourteen-hour photoperiod. Hen deposition rate was measured once per week over a 56-day period, beginning in mid-October until mid-December.

Indoor enclosures (coops) were identical for all treatment groups, and provided 0.495 square meters of floor space per hen.  Coops were equipped with perches, laying boxes, and three walls of windows for optimum sunlight exposure. 

The COM group was maintained in the indoor enclosure at all times, and was exposed to natural and supplemental light totaling twelve to fourteen hours per day.  Photoperiod increased as the study progressed to mimic the onset of spring and summer in Northeast Texas. The Yeti Solar Light Passage Light (YetiSolar, Virginia) was used to adjust the photoperiod for the COM hens. The Yeti Solar Light Passage Light (YSLPL) and Light Passage Light Timer (YSLPLT), 12V direct-current systems included 5-Watt solar panels, charge controllers, 12 Volt 4 amp-hour batteries, and bright LED light fixtures. The 12 Volt timers, designed to work with the YSLPL, controlled the lights. This particular system was chosen because of the included broad-spectrum LED light that came close to mimicking sunlight. The light is useable four or more hours every day when the solar panel is located properly. This allowed the COM hens to receive at least fourteen hours of light per day, even in December.

The hens assigned to the PAST treatment had access to the outdoors from sunrise until sunset.  The outdoor enclosure provided ten square meters of pasture per hen.  Hens were housed in the indoor enclosure from sunset to sunrise to protect them from predators and to allow hens to exercise natural roosting behavior.  No additional lighting was provided.  A Pullet Shut Automatic Coop Door (PSACD) (, Lockhart, Texas,) and Solar Sensor, running from a 12 volt DC power supply, were used to keep the hens in the coop at night and to keep the predators out. Because the coops were in an area with full sun, the solar panel was placed on the south-facing side of the coop roof to ensure the door had an adequate power supply.  The solar panel and trickle charger included a piggy-back connector, so the door was able to operate at dawn with the voltage stored in the battery.  The solar sensor allowed the door to automatically open with the morning sunlight and close just after dark with no concerns regarding seasonal changing times of sunrise and sunset.

The hens assigned to the PEP treatment had access to the outdoors from sunrise until sunset.  The outdoor enclosure provided ten square meters of pasture per hen.  Hens were housed in the indoor enclosure from sunset to sunrise to protect them from predators and to allow hens to exercise natural roosting behavior.  Lighting was provided in the indoor enclosure before dawn so that hens were exposed to light for twelve to fourteen hours per day, increasing as the study progressed to mimic the onset of spring and summer in North Texas.  The combination of the YSLPL, YSLPLT and PSACD allowed the PEP hens to have exposure to multiple hours of light before dawn (totaling twelve to fourteen hours per day), access to pasture at dawn and safety at night.   

Three identical sections of 10-meter by 10-meter pasture were sectioned off and identical coops were placed in the center of each enclosed area. The research area sat in the middle of a 100-acre plot of unfertilized and uncut forage. The forage had not been treated, hayed or modified for at least one full calendar year before the study began. At the onset of the study, pastures were about 18 inches tall and ranged from growing native coastal and Bermuda grasses to dead stalks. Toward the end of the study, pastures died due to cold weather and the weather conditions in late fall in North Texas.   The number of arthropods entering and exiting the hen enclosure was not controlled for any treatment. Therefore it is possible that various arthropods became part of the hens’ diet.

All eggs were collected and counted daily. Weekly egg deposition for each breed was totaled on days 7, 14, 21, 28, 35, 42, 49 and 56. Eggs laid on days 30 and 31, 37 and 38, and on days 51 and 52 of the study were analyzed using the Egg Analyzer (Okra Technology, Israel) on days 32, 39 and 53 respectively. Yolk color, egg mass, albumen height, Haugh unit and egg quality grade were measured by the Egg Analyzer machine.

Data were analyzed using the MIXED procedure of SAS (version 9.3; SAS Institute, Cary, NC).  The experimental unit was hen. Main effects included treatment, week, and treatment × week; the random effect was hen within treatment.  Dependent variables included egg deposition rate and egg quality measures.  Least squares means were calculated, and when means differed at the (P ≤ 0.05) level, means were separated using pairwise comparisons.

Neither the CMH PAST nor any SP hens in any treatment laid an egg during the study; therefore, they were excluded from data analysis.

Research results and discussion:

The results of yolk color are shown in Table 1. There was no breed effect (P > 0.05). There was a treatment effect where PEP had darker (P = 0.003) yolks than COM. There was no estimate for PAST due to the extremely low numbers of PAST eggs produced during the study. There was also a breed × treatment effect where EEH PAST eggs had the darkest (P = .031) yolks followed by EEH PEP, CMH PEP, CMH COM, and finally EEH COM.

It is well established that hens with varied diets and access to dark green forage produce eggs with darker yolks than hens on standard, non-supplemented diets. The darker yolks in PEP is likely attributed to their exposure to a varied diet and the natural carotenoids, vitamins and minerals present in the dark green forage that was available to them until week 5 of the study when the first major cold weather spell occurred. Additionally, it is possible that hens in the PAST and PEP systems had access to arthropods that also contributed to their overall nutrient profile. The extended photoperiod was the same for COM and PEP eggs; therefore, the resulting improved egg quality (as measured by yolk color) in PEP eggs was not due to the extra light provided in the treatment. The results of darker PEP yolks are in agreement with previous research including results reported by Karadas et al. (2006) that indicated poultry fed natural carotenoids had higher yolk nutrient content and darker yolk color than hens in their control group.

The breed × treatment interaction, where the EEH laid eggs with darker yolks than the CMH , may be due in part to the hybrid breeding of the EEH. Their hybrid vigor may have allowed them to more efficiently utilize the available nutrients across all treatments, laying darker yolks than CMH when pasture was available and lighter yolks on the commercial diet. These results are in agreement with results reported by Küçüky?lmaz et al. (2012) where hens of two different egg color genotypes, a hybrid commercial white strain and a native heritage breed brown strain, showed different egg quality effects when housed in cage free compared to caged environments. Küçüky?lmaz et al. (2012) reported that commercial white egg layers produced eggs of greater quality than the native brown laying strain. Though there were significant results for this quality measure, the overall number of observations was low across the study and likely contributed to the minimal amount of significance observed in the data.

The results for albumen height are shown in Table 2. There was no breed effect, treatment effect or breed × treatment effect (P > 0.10). Although not significant, EEH PEP eggs had numerically greater albumen height than other breed and treatment combinations. The overall number of observations was low across the study and likely contributed to the minimal amount of significance observed in the data.

Albumen height is a measure of the quality and freshness of an egg. A higher the albumen indicates improved freshness of the egg and a more desirable albumenoid protein structure. Low albumen heights are an indication that proteins in the albumen have begun to denature due to age, or were not formed properly due to the availability of amino acids in hens’ diet. The increased amino acid, vitamin and mineral availability in fresh forage and available arthropods is associated with increased egg quality (Horsted et al., 2006). Hens will consume available forage, adding to their overall metabolizable energy intake (Horsted et al., 2006). Though there are few available studies on the subject, hens in the PAST and PEP systems likely consumed various arthropods as there was no way to control for their entrance into and egress from the production system pasture area. The literature, especially in regards to the study completed by Horsted et al. in 2006, is in agreement with the higher albumen heights observed in PAST and PEP treatments where hens had daily access to ad libitum pasture compared to the COM treatment where hens did not have access to more amino acids, vitamins and minerals available in the forage.

The results for treatment and breed on egg weight are shown in Table 3 and the results for treatment on egg weight are shown in Table 4. There was no breed effect (P > 0.10). There was a treatment effect where PEP eggs weighed more than COM eggs (P = 0.005). There was no estimate for PAST eggs. There was no breed × treatment interaction (P > 0.10).

Egg weight is one of the primary measures of egg quality. Larger eggs are more valuable to producers and consumers. Usually the age of the hen has the most direct effect on egg size. However, when all hens are the same age, egg weight can be affected by diet and possibly the size of the enclosure. Keshavarz and Nakajima (1995) have established that egg weight can be changed significantly by increasing either protein or fat in the hens’ ration. The larger egg mass observed in PEP eggs may be attributed to the additional levels of gross energy they were provided through consumption of forage and arthropods, while their basic dietary needs were being met by the commercial layer diet they were also provided.

Egg quality traits have also been linked to number of square meters of pasture available per hen (Mugnai et al. 2009). In a study by Mugnai et al. (2009) hens allowed to forage on 10 square meters of pasture per hen exhibited greater shell weight and percentage, darker yolk color and higher α-tocopherol, carotenoid and polyphenol contents than hens only allowed 4 square meters of pasture. This may also help explain why COM hens, which were allowed no extra space for forage, laid smaller eggs than PEP hens, which did have access to 10 square meters of pasture per hen.

PEP hens had access to a varied diet including extra forage and arthropods, as well as access to a larger space than COM hens. The literature is in line with the current findings that the PEP treatment resulted in about 10% larger eggs compared to the COM treatment.

The results for Haugh unit measurement are shown in Table 5. There was neither a breed (P > 0.566) nor a treatment effect (P > 0.584). There was no breed × treatment interaction (P > 0.451). However, according to the means, EEH PEP eggs had numerically greater Haugh units than other breed and treatment combinations. The overall number of observations was low across the study and likely contributed to the minimal amount of significance observed in the data.

Haugh units (HU) are a quality measure of eggs that is calculated by combining the albumen height and the egg weight in a logarithmic formula with other constants. As HU measurement increases, egg freshness and quality also increases.

The Equation for Haugh units is included below:

HU = 100 * log(h - 1.7w^0.37 + 7.6)

  • HU = Haugh unit
  • h = observed height of the albumen in millimeters
  • w = weight of the egg in grams


The results for the effect of week and treatment on egg deposition rate are shown in Table 6. There was a week × treatment interaction (P < 0.001) for egg deposition rate.  During week 1, the COM hens tended to have a greater deposition rate than PEP (P = 0.066) and PAST (P = 0.093) hens. The deposition rates of PEP and PAST did not differ (P = 0.862). In week 2 the COM hens had a greater deposition rate than the PAST (P = 0.015) and PEP (P = 0.047) hens. The PAST and PEP hens’ deposition rate did not differ (P = 0.603) in week 2. In week 3, PEP tended to have a greater deposition rate (P = 0.093) than PAST. During week 4, PEP had greater deposition rate (P = 0.010) than PAST. The COM deposition rate did not differ (P = 0.388) from PAST in week 4, and the PEP hens tended to have a greater deposition rate (P > 0.066) than COM. The deposition rates for COM, PAST and PEP did not differ during weeks 5 to 8 (P > 0.128).

The main purpose of this study was to discover the effects of a commercial-style lighting system on a pasture-style production system compared to traditional commercial-style and pasture-style production systems. Therefore the study measured deposition rate or the number of eggs laid per week within each treatment by all breeds of hen. Previous research indicates that increased photoperiod yields increased egg production (Lewis et al., 1997). Both COM and PEP hens experienced increased photoperiod. These hens were exposed to 12-14 hours of light per day while PAST hens received increasingly less light per day averaging closer to 10 hours a per day. In weeks 1 to 4 the results are in line with previous research. A cold-spell with temperatures in the teens and twenties struck during week 5, which accounts for the low production across the board at that time. During week 6, the Yeti Solar light system failed in the PEP coop, lowering deposition rate for those hens. During weeks 7 and 8 these hens had trouble recovering from this brief lack of supplemental light. The decreased egg production by the PEP hens also contributed to an overall lower number of eggs laid after week 6. This made achieving significance within the number of eggs deposited each week more difficult. However, for the first four weeks of the study it is clear that increased photoperiod caused increased egg deposition in both commercial and pasture-style production systems.

Participation Summary

Educational & Outreach Activities

Participation Summary:

Education/outreach description:

These data are published in the thesis titled “Use of Artificial Lighting to Increase Photoperiod Length For Pasture-Raised Laying hens To Improve Egg Productivity and Quality” by M. Katie Morgan Michelsohn at Texas A&M University-Commerce.  A manuscript is being prepared for peer-reviewed publication. 

Project Outcomes

Project outcomes:

Overall this study demonstrated that supplemental artificial lighting system to increase photoperiod will improve egg productivity in both commercial and pasture-style laying hen production systems. Given the increase in egg quality measurements that pasture-raised eggs exhibit over commercial-style eggs such as yolk color, albumen height, and egg weight, it is concluded that pasture-raised eggs can provide benefits to the producer and the consumer. It is also concluded that combining a pasture system with a commercial-style lighting regime, which results in greater egg deposition rate, contributes to a more desirable overall production system for the producer and the consumer.  Providing supplemental lighting to pasture-raised laying hens is a simple practice for poultry producers.  This has great potential to increase both quantity and quality of egg products for producers seeking sustainable alternatives for their hen production systems.

Economic Analysis

Pasture-raised eggs easily sell for $6.00 per dozen eggs in Northeast Texas during the fall and winter at local farmers markets.  Therefore, for this economic analysis the value of one egg is estimated at $0.50.  The cost associated with adding artificial light to a chicken coop is about $40.00.  Most traditional-sized coops comfortably house 10 hens.

In this study the weekly deposition rate of PAST hens was 0.25 eggs per hen, and the weekly deposition rate of PEP hens was 1.125 eggs per hen, resulting in 0.875 more eggs per hen per week in the PEP system compared to PAST.  It should be reiterated that these data were obtained during the fall and winter.  If a producer has ten hens and one coop, the breakeven point for the cost of the light would occur during the eighth week of production.  From October through March, when hen productivity is generally lower, this added light could result in $65 greater gross income for a producer compared to the PAST system.

If a producer has fifty hens in five coops these data are even more advantageous to the producer with supplemental lights.  The breakeven point for covering the cost of five coop lights ($200 total) would also occur during the eighth week of production.  However, at the end of the 24-week fall and winter seasons the additional lights will result in an increased gross income of $325 compared to the PAST system.

The added economic benefit across an entire fall and winter period is $0.2708 per hen per week.  The added economic benefit past the breakeven point is $0.40625 per hen per week.

These figures are based on the $40.00 cost of lighting.  Cheaper alternatives may be available, but the producer is cautioned to only choose lights that are intended for use around poultry that can be safely secured inside a coop.

Farmer Adoption

These methods can be easily adapted by poultry farmers of any size scale.  For every coop, a light should be provided such that the photoperiod for the hens totals 14 hours.  It is recommended that these additional hours be provided in the morning before sunrise.  This will ensure hens return to their coop at sundown to be safe from predators that emerge at nightfall.  Using this method, the time the lights should come on varies as the days become shorter then longer throughout the fall and winter seasons.  This can be accomplished by either turning the lights on every day, or by setting the lights to a timer.  Timers add convenience, but also add cost.  Producers are encouraged to weigh costs and benefits based on their individual operations.


Areas needing additional study

The failure of the light for the PEP day in Week 6 was an unfortunate event.  This experiment should be repeated to increase the robustness of the data.  Any follow-up studies would best be completed with multiple treatment replications.

This experiment has revealed other opportunities for further research.  Additional breed and crossbreed differences could be observed, particularly in varying climates.  This study took place in Northeast Texas.  Results would likely differ in other climates, such as those that are particularly cold or those in tropical or subtropical regions.

An aspect of this experiment that likely contributed to treatment differences was the access to pasture for the PAST and PEP hens.  However, we did not design this experiment to determine any differences in arthropod intake by the hens.  A follow-up study could examine how arthropod populations differ when chickens are present, and correlate any of these population differences with resulting egg quality changes.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.