fl
.5 ,,

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Ammts mm summon 0+- nzsuns AND
METHODS REPORTED IN THE LITERATURE on
Poumv mam-ma AND mvesmmon or

1mm mansmss son noon-m AND msmc

05 WHITE ROCK HENS

finds:- {at tho Deg!» oi M. 5.
meme»: STATE uwwmsm
Allan Frederick Bufchbakor
1960‘

Think;

This is to certify that the

thesis entitled

Analysis and Evaluation of Results and
Methods Reported in the Literature on
Poultry Lighting and Investigation of
Light Intensities for Roasting and Rising of White Rock Hens

presented by
Allen Frederick Butchbaker

has been accepted towards fulfillment
of the requirements for

_L§:__degree in Mural Engineering

' \‘ A“ l \

Major professor

 

Date November 18, 1960

 

0-169

 

LIBRARY

Michigan Sta»

University

 

 

 

 

ANALYSIS AND EVALUATION OF RESULTS AND METHODS
REPORTED IN THE LITERATURE ON POULTRY LIGHTING
AND INVESTIGATION OF LIGHT INTENSITIES FOR
ROOSTING AND RISING 0!“ WHITE ROCK HENS

 

“a
i
i
by 4
Allen Frederick Butchhaker 9
ABSTRACT

submitted to the Colleges of Agriculture and Engineering
of Michigan State University of Agriculture and
Applied Science in partial fulfillment of
the requirements for the degree of

MASTER OF SCIENCE
IN
AGRICULTURAL ENGINEERING

Department of Agricultural Engineering

\

1960
Approval é gjw

 

2
ALLEN FREDERICK.BUTCHBAKER ABSTRACT

Since 1900, the use of artificial lights to supple-
ment natural daylength has improved the egg production
of hens. Research in the 1930's found that the increased
egg production was not a result of the increased time to
feed, but a physiological response. Because of the pre-
ponderance of applied research rather than basic research,
fundamental information is needed on the effect of light
on certain responses of chickens under carefully control-
led conditions.

.A review of the many articles on poultry lighting
revealed some contradictory results. The most outstanding
difference between experiments was in light intensity.
This difference may be accounted for by lack of uniformity
in pen design, lamp wattage, lamp location, luminaire,
or season of year. Methods of measuring light intensity
may not have been comparable.

In this study, preliminary investigations of roosting
and rising of White Rock hens under natural light condi-
tions showed that the time of roosting did not correlate

with sunset time. The chickens tended to roost at a

3
ALLEN FREDERICK BUTCHBAKER ABSTRACT

light intensity dependent upon the degree of cloudiness.

The time of rising correlated with sunrise time.
investigations with artificial lights showed that

chickens roosted at a light intensity dependent upon

the light intensity to which they had become adapted.

With no light at night, significant differences did not

exist between the various light intensity treatments

for rising.

Chickens see mainly reflected light, therefore
reflectance measurements should be the criteria for
measuring light intensity within a poultry house. inci-
dent light readings in footcandles averaged about five
times higher than comparable reflectance readings in
footlamberts. A.brightness meter showed that white
chickens reflect the most light of any objects in the
pen which fact might account for some of the behavior

of chickens.

ANALYSIS AND EVALUATION OF RESULTS AND METHODS
REPORTED IN THE LITERATURE ON POULTRY LIGHTING
AND INVESTIGATION or LlGH’l‘ INTENSITIES FOR
ROOSTlNG AND RISING or WHITE .ROCK HENS

by

Allen Frederick gutchbaker

A THESIS

Submitted to the Colleges of Agriculture and Engineering
of Michigan State University of Agriculture and
Applied Science in partial fulfillment of
the requirements for the degree of

MASTER or SCIENCE
IN
AGRICULTURAL ENGINEERING

Department of Agricultural Engineering

1960

r.
G 14?”, W J

J

.3;'

ACKNOWLEDGEMENTS

The author wishes to express his sincere appreciation
and gratitude to the following:

Professor D. E. Wiant, Agricultural Engineering
Department, under whose guidance and inspiration this
study has been conducted.

Mr. J. P. Ditchman of the General Electric Company
for suggesting the problem and encouraging the study.

Dr. D. P. Brown,.Agricultural Engineering Department
for his suggestions and assistance in the early phases
of the study.

Professor J. A. Davidson, Poultry Science Depart-
ment for his suggestions and cooperation in making
arrangements for chickens and pens for the experiments.

Mr. J. B. Cawood, Mr. G. Shiffer, and Mr. W. H.
Brockbank of the Research Laboratory in the Agricultural
Engineering Department for their assistance and sugges-
tions in the construction of apparatus used in the

experiments.

ii

Dr. F. H. Buelow,‘Agricultural Engineering Depart-
ment for his assistance in designing and testing the
apparatus.

Michigan State Highway Department for their assist-
ance in the calibration of the phototube.

Michigan Committee on Rural Electrification for
financing the study.

Mr. E. J. Niemala, Poultry Plant Foreman for his
interest and assistance in the study and for caring
for the chickens used in the experiment.

My wife, Nancy, for typing the manuscript and her
encouragement and valuable help throughout this study

and thesis preparation.

iii

TABLE OF CONTENTS

Page
LIST OF FIGURES. . . . . . . . . . . vii
LIST OF TABLES . . . . . . . . . . . ix
INTRODUCTION. . . . . . . . . . . . 1
OBJECTIVES . . . . . . . . . . . . 3
LITERATURE REVIEW . . . . . . . . . . 9
History . . . . . . . . . . . 9
Day Length . . . . . . . . . . 12
Light Intensity. . . . . . . . . 19
Wavelength . . . . . . . . . . 22
Frequency of Lighting Periods . . . . 23
Activity . . . . . . . . . . . 33
Time of Lay . . . . . . . . . . 35
Physiology of the Eye. . . . . . . 37
Retina . . . . . . . . . . 38
Photochemistry of Vision . . . . no
DISCUSSION OF LITERATURE REVIEw . . . . . A9
General Discussion. . . . . . . . 55
Daylength. . . . . . . . . . . 57
Light Intensity. . . . . . . . . 59

iv

Wavelength of Light. . . .

Frequency of Light Periods .

PRELIMINARY STUDIES OF LIGHT INTENSITIES AT

ROOSTING AND RISING. . . .
Location and Apparatus. . .
Light Sensing Apparatus . .
Calibration of Phototube . .

Infrared Sensing Equipment .

0

Results of Roosting Investigations.

Analysis of Roosting Time vs Sunset

Time a e e e e o 0

.Analysis of Roasting Light Intensity.

Results of Rising Investigations . . .

Analysis of Rising Time vs Sunrise

Time . . . . . . .

,Analysis of Rising Light Intensity

Comparison of Rising vs Roosting Inten-

Slty O O O O O O 0

Variation of Light Intensity in Pen 205

Conclusion. . . . . . .

INVESTIGATION OF RISING.AND ROOSTING LIGHT

INTENSITY . . . . . . .
Design of the Equipment . .

V

Page
61

62

61+
6h
67
72
73
75

75
79
82

82

85

87
87

88

91

92

Location .
Artificial
Apparatus.
Calibration of
Procedure . .
Daily Results.

Results. . .

Light Intensity vs Volts

Discussion of Results .

CCMPARISON OF INCIDENT LIGHT AND REFLECTED

LIGHT . o .

CONCLUSIONS . e e

FUTURE INVESTIGATIONS .

REFERENCES. 0 . .

.1
I

Vi

Page

92
92
93
95
95
96
98

103
106
110

112

Ill}.

Figure

I.

2.

3.

9.

10.

11.

LIST OF FIGURES

Sketch of pen 205 showing location of
equ1pment e e e e o e e e e e a

Light measuring apparatus consisting of
microammeter, d-c power supply, and
phOtOtlee e e e o a e e e e e 0

Spectral response curve for RCA 926 photo-
tube 0 O O O O O O O O O O O 0

Calibration curve for RCA 926 phototube
and microammeter . . . . . . . . .

Roasting time versus day of month under
natural light conditions for periods from
.April lh-ZS and April 30-May 6 . . . .

Light intensity and number of chickens on
roost during roosting time for a clear day

Light intensity and number of chickens on
roost during roosting time for an overcast

day 0 O O O O O O O O O O O C

Rising time of median chicken versus day
of month under natural conditions for
periods from‘April 15-23 and April 30- May

6 O O O O O O O O O O O O O 0

Light intensity and number of chickens
off roost during rising time for an over-
CCSt day. a a a e e e e e o e a

Light intensity and number of chickens
off roost during rising time for a clear

day . . . . . . . . . . . . .

variation of light intensity in pen 205
for a uniformly overcast day (April 26,
1960) with the phototube reading 3.0 foot-
candles . . . . . . . . . . . .

vii

Page

66

68

70

71+

77

80

80

83

86

86

Figure
12.

13.

1h.

15.

16.

Experimental poultry house with black plas-

tic over windows of test pens.

Voltage control apparatus used at roasting

and rising times . . .

Calibration of light intensities of various
lamp wattages in pens of Experimental House
Readings taken six inches

versus voltage.

above floor directly under lamps.

Summary of significant difference between

light treatments for roosting.

Location of footcandle readings in pens

of Experimental House .

viii

Page

9’4

91»

97

100

108

Table ,

II.

III.

IV.

VI.

VII.

VIII.

IX.

XI.

.XII.

XIII.

.XI\/.

LIST OF TABLES

Dakan's Results of Effect of Color an Egg
PrOdUCtion O O O O 0 O O O O O 0

Summary of Results of Articles in the
Literature on Rate of Lay . . . . . .

Summary of Results of Articles in the
Literature on Total Annual Egg Production.

Summary of Results of Articles in the
Literature an Age At Maturity. . . . .

Summary of Results of Articles in the
Literature on ACtiVity a a e a a a a

Summary of Results of.Articles in the
Literature on Malting . . . . . . .

Results of Roasting Investigations With
Natural Light . . . . . . . . . .

Comparison of Roasting Light Intensities
For Clear Days and Cloudy Days . . . .

Results Of Rising Investigations With
Natural Light . . . . . . . . . .

Wattage of Lamp Used in Each Pen For Tests

Sample of Daily Results for Chickens
Roasting in Pen Number 2 With 150 Watt
meSe 0 O O O O O O O O O O 0

Results of Roasting Experiment With
Artificial Light . . . . . . . . .

Results of Rising Experiments With Arti-
ficial Light . . . . . . . . . .

Footcandle Readings at Locations Shown in
Fig. 16 for the Various Lamp Wattages.

Footcandle Meter was held Perpendicular to
Light Source at Level of Litter and Equip-
ment in Pen. . . . . . . . . . .

ix

Page

2h
50
Si
52
53
51+
76
81

81+
93

96

99

103

108

Table Page

XV. Faatlambert Readings of Selected Objects
in Test Pens of Experimental Poultry
House. a a e a a e a a o e a o 109

INTRODUCTION

And God said, Let there be light: and there was
light. .And God saw the light, that it was good:
and God divided the light from the darkness.
And God called the light Day, and the darkness
he called.Night.

Genesis 1: 3-5

This is the biblical explanation of the beginning of
light. Light is truly one of the greatest phenomenas in
nature. Nearly all life is either directly or indirectly
dependent upon light. Plants use light through the pro-
cess of photosynthesis to synthesize sugars from carbon
dioxide and water. Higher forms of life, such as the
vertebrate animals, use plants as their food supply.
Some of the highest forms of animals use other animals
or both animals and plants for their food.

Light not only sustains life through the process of
photosynthesis, but also permits animals to see their‘
surroundings. The awareness of most animals of their
surroundings or changes in their surroundings, is the
result of reflection or emission of light toward them
by external objects.and the reception of this light by

special photoreceptive organs, (Walls, l9hl). In the

2
higher forms of animal life these organs are called eyes.
The eyes do not See the objects but animals see through
the use of eyes. Seeing is a phenomenon of the mind
plus the eye and not of the eye alone.

Vision is a complex and sometimes deceptive product
of the interaction of the simple information which tra-
vels along the optic nerve, and the manipulations which
this information undergoes in the brain, before it is
presented to the cansiousness for action or other dis-
posal. "Nothing is in the mind which is not first in
the senses" but the sense organs, and particularly the
eye, may offer the mind much more than the latter can
assimilate. It is this interpretation that is the cause
of much research by physiologists and psychologists. we
do not know what animals see in their minds. We can not
adequately interpret results for animals, as the human
eye and mind visions objects. Animals may see only
blurs of objects and not distinct colors, whereas the
{human eye may distinguish the same objects very clearly.
‘Therefore, one should not interpret what an animal sees

in terms of a person's photoreceptiveness in either

 

 

color, sensitivity, or acuity.

There is much evidence to indicate that light con-
trols many of the reproductive cycles in plants and
animals. For instance some plants are called short-day
plants and others long-day plants. Many animals also
exhibit this phatoperiadicity. Some insects go into a
dormant stage of life due to changes in day length.

The hair of a Snowshoe Hare changes to white when days
are shortening. Birds migrate towards the North during
the spring in the Northern hemisphere when days became
longer.

Domestic chickens exhibit a phatoperiadic perform-
ance. In order to increase egg production, artificial
lights are used to lengthen the natural day.

The effect of light on the performance of chickens
has been the interest of many experimenters. Duration
of light, rate of change of daylength, light intensity,
and wavelength have been the main points of investiga-
tion.

The optimum length af day has been the main interest‘

<>f researchers. There are many conflicting reports in

h
the literature, but many researchers claim that 13 to IE
hours of light achieves the highest egg production.

The second point frequently investigated is the
intensity of light needed for poultry. The usual recom-
mended light intensity is one footcandle which is pri-
marily based upon some investigations performed in l92h.
However, the full lighting regime was not investigated.
Most investigations stopped before a light intensity of
no footcandles was reached.

The effect of wavelength of light on egg production
has not been investigated very thoroughly. Most experi-
ments in this phase of research failed to balance the
energy for different parts of the chlcken's visible
spectrum. Red and yellow light appear to be the most
desirable, and blue light the least desirable.

Many investigators noticed that egg production falls
off during periods of downward changing daylengths, and'
increases during increasing daylengths. Other investi-
gators used this fact to delay the sexual maturity of
pullets and increase egg production and egg quality.

Physical factors, other than light, may also have

 

 

 

a bearing on the reactions of chickens. .Air temperature
and wall temperatures have an effect on the dissipation
of heat by chickens. Humidity, either directly or
indirectly, may affect chickens in certain responses.
Chickens are easily frightened, so strange or familiar
noises may also affect their behavior.

When conducting an experiment with chickens one
should recognize several physiological and sodialo-
glcal factors. Different breeds or strains may react
to a stimulus in different ways. The birds may react

_differently depending on their age. The previous his-
tory of chickens may affect their reactions to a certain
stimulus. Chicks grown under different types of light-
ing conditions may react differently to the same stimu-
lus when mature. Chickens have a definite peck order
(social order). The top chicken will peck at all of
the other chickens and so on down the order until the
bottom chicken in the social order is pecked at by all
of the others. This social order may affect an experi-

Inent wherever a group of chickens is studied.

The performance of chickens may be measured in

several different ways: total egg production, feed con-
sumption, age at maturity, rate of lay, time of lay,
clutch length, activity, mortality, molt, egg size, egg
quality, live weight, and physical reaction (response)
to a stimulus.

There are several contradictions in the literature
as to the effect of light on some of the performance
_l'responses of chickens. .Also, some of the recommendae.
tions of poultry specialists are based upon research
conducted several years ago. Most of the experiments
reported in the literature were conducted as an applied
type of research rather than basic research.

The aim of this thesis is to provide more basic
information on the effect of light on the habits
of chickens. One way to investigate the effects of
light on chickens is to study the actions of chickens
under natural light conditions. .A conspicuous point
to investigate is the act of rising and roosting of
chickens. under natural conditions, chickens rise when
the light intensity increases from darkness, and roast

upon the approach of sunset. This study will investigate

 

 

7

the effect of light on chickens at the time of rising
and the time of roosting.

Another aim of this thesis is to investigate the
environment of a poultry house as a chicken sees it.
Since chickens see objects because of light reflected
from the objects, measurements of the light reflected
from.objects in a poultry house will be made,

.After considering the above aims, definite objectives
can be set up. Broad objectives are made as well as
objectives concerned with the investigations included

in this thesis.

The

OBJECTIVES

objectives of this study are divided into two

sections: overall and specific.

The

(l)

(2)

The

(l)

(2)

(3)

overall objectives are:

Ultimate goal by the use of light of increasing
the performance of chickens, i.e., egg produc-
tion, growth, feed conversion. 8
Increase the knowledge about the influence

of light on chickens.

specific objectives are:

Evaluate articles in the literature concerning
the effect of light on poultry.

Investigate the effect of a changing light
intensity on chickens at rising and roosting.
InveStigate the environment of a poultry house

as a chicken sees it.

LITERATURE REVIEW

The articles in the literature on the subject of
light for poultry are innumerable. Many of the arti-
Cles of a more technical nature are presented in this
literature review, whereas, the non-technical articles
(trade and popular farm.magazine articles) are generally
omitted.

The review is presented in nine sections: History,
Daylength, Light Intensity, Wavelength of Light, Fre-
quency of Lighting Periods, Activity of Chickens, Time
of Lay, Physiology of the Eye, and PhotochemiStry of

Vision.

History

A paper presented by Roberts and Carver in l9hl at
an American Society of Agricultural Engineers meeting
states that the first use of artificial lighting of
poultry houses in this country dates to the backyard
experiments of Dr. E. C. Waldorf in Buffalo, New York,
in 1889.‘ In these early experiments gas burners were
Lased as a source of light. Press notices of this work

czreated a sensation when it was reported that for a

10

three month period, each hen laid an average of ten eggs
per week. Roberts and Carver also mention that the
first commercial application of artificial lighting is
credited to Mr. and Mrs. George Shoup (1918), formerly
in charge of the Poultry Department of the Western
Washington Experiment Station, Puyallup. The experiment
started in 1912, and continued for six years.

George G. Newell (1916), an auditor, wrote a book
entitled, ”A.Revolution in Egg Production.” His use
of electric lights to further the chickens' "business
day” created a lot of unfavorable, derogatory, and
sarcastic publicity in the newspapers for tampering
with the chickens' normal living habits. He used two
chicken houses in the backyard of his Brookfieid,
lllinols home (a suburb of Chicago).. He noticed that
there was a difference of six hours and twelve minutes
between the maximum daylight hours in June and the
.minimum in December. This affected the chickens'
"business day." He solved the problem of low egg pro-
‘duction during the winter months by installing electric

{lights‘on January 21, l9lh. He used two sockets in

11
each house. One Benjamin socket (contains two outlets)
held one eight candle power lamp and one sixty candle
power tungsten lamp. The eight candle power lamps were
to simulate dusk to promote roosting of the hens, but
they had to be replaced with two candle power lamps.

By lengthening the day he doubled the output of the hens
in 12 days.

Daugherty (1917) reported that morning lights were
as satisfactory as either evening or a combination of
morning and evening.

Curtis (1920) reported that Professor Rice of
Cornell University carried on experiments to determine
the optimum intensity of illumination.

Credit for first use of all-night lighting for
laying hens is given to J. E. Morris in Southeastern
Ohio in 1925 (Kennard, 1929). He used natural gas for
lighting his poultry house. unable to turn off the gas
automatically, he left the lights on all night with
satisfactory results. The egg production of the hens

izncreased from 10 percent to hO-SO percent.

12

Day Length

The effect of natural day length on the domestic
fowl has been known for several years. Lewis, et al.,
(1919) noted the seasonal variations in egg production
and hours of daylight for hens kept through two laying
years. Whetham (1933) described the correlation between
day length and rate of egg production for fowls over a
wide range of latitudes under natural conditions. Maxi-
.mum production accompanied seasons with longest days.

Many of the early experimenters merely studied the
effects of artificial lighting on the chickens. increase
in egg production during the winter months without
regard to why the chickens produced more eggs. They
tried to approach the natural day length where the egg
production is greatest, normally a 13 to in hour light
day. Kable (1926) used two pens of yearling White Leg-
horn hens for a laying experiment. He lighted one pen
and left one pen unlighted. He gives feed cost, power
<:ost, and egg production curves, but does not mention
the type of lamps, the number of lamps, light intensity,

01* the length of operating time used in the experiments.

13
There have been many experiments, such as Kable's, to
determine if egg production increased by using artifi-
cial light.

Fairbanks and Rice (l92u) recommended a morning
and evening lighting schedule. This provided a uniform
day of 13 to 1k hours of light despite changes in the
times of sunrise and sunset throughout the season. One
common practice was to turn the lights on at uzoo a.m.
and off at daylight.

Ebbel (19u0) subjected hens of several breeds to
artificial illumination during a period from December
to March, thereby increasing winter egg production and
consequently the number of early chicks.

Byerly and Moore (l9ul) described the effect of
several different light periods (normal day and night,
6 hours light - 18 darkness, continuous in hours of
light - l2 darkness) on length of clutch and rate of
egg production of a cross of New Hampshire-Barred
Plymouth Rock chickensT’ The in hour light - 12 hour dark

period lengthened the clutches without a following decline

in egg production. Continuously lighted birds

114
produced well at first but soon declined. The birds
receiving 6 hours light - 18 darkness began to molt
heavily and ceased laying early. The light intensity
was approximately 11 footcandles in each group.

One of the most extensive investigations on day
length was conducted by Roberts and Carver (l9hl).

The experiments were conducted in a windowless poultry
house using artificial light only. No mention was made
of the breed, but they say that birds of similar breed-
ing were used. With a 7.5 footcandle light intensity,
they found that 13 hours of light was optimum for egg
production. There appeared to be no significant dif-
ference between 13 and 19 hours of light. .Anything
below 13 hours of light resulted in a decrease in rate
of egg production.

Riley and Byerly (19h3) concluded that while
increased light periods are capable of stimulating re-
productive activity in yearling Rhode island Red hens,
which have not finished melting, the progress of molt
is not affected. Warren, et al., (1950) summarized

the performance of laying hens under varying environmental

15

conditions. Molting was inhibited or delayed for birds
receiving 12 hours of light daily throughout the laying
year. .

Mueller, et al., (1951) states that sexual maturity
was attained earliest by pullets receiving more than 12
hours of light per day. Pullets kept under controlled
light conditions, but subjected to variation in tempera-
ture, laid as well as pullets for which both light and
temperature were controlled at constant levels.

0. c. Hennard (1929) used allénight lights for Leg-
horn pullets in 1928-29. He reported a prompt response
in egg production for each of the test groups and no
ill effects. The peak production with continuous light
occurred in October, November, and December. No mention
is made of the annual egg production.

.Penquite and Thompson (1933) studied the influence
of continuous light on Leghorns. They found that con-
tinuous light did not increase or decrease to a signif-
icant degree the total number of eggs laid annually.
‘The hens with lights laid more eggs in November, Decem-

t>er, and January than the controls, the peak of production

16
coming in November and December. The peak for the con-
trols came in March and.April. Apparently, the contin-
uous light did not have a deleterious effect upon the
birds.

Weinmiller and Mantel (19h0) treated hens with
all-night lights from.November 1 to May 31 and reported
a marked increase in egg production for the first four
months of the experimental period. They also report
a significant reduction of molt of illuminated birds.

Ryan, et al., (1959) conducted a h8 week experi-
ment to find the effect of all night lighting vs a in
hour day on pullet egg production using S.C.W.L., W.
P.R., B.P.R., Cr. Bd., R.l.R., and Conn..Controls.

They found that for the first 12 weeks rate of lay for
the all-night group was 5 percent higher than the In
hour group. The advantage declined to 1.8 percent for
the h8 week period. There was evidence of a variation
to the two light treatments among strains and breeds.

No mention is made of the previous lighting history or
the age of the pullets at start of the experiment. Also,

the light intensity is not mentioned.

l7

Heywang (19h6) found that chicks reared to 12 weeks
of age under continuous light showed greater weight
gains than chicks reared under the usual daylight and
night conditions.

in England, Hutchinson and Taylor (1957) studied the
seasonal variation in the egg production of fowls. They
concluded that a downward change of day length can
induce molting and cause cessation of laying even when
the final absolute day length is adequate.

Sykes (1956) studied the effect of short, unchanging
daylength of six hours on age at sexual maturity and
egg production. He concluded that age at sexual matu-
rity is not affected by the absolute length of the day,
but egg production is affected both by the absolute
length and rate of change in length of day.

Callenbach, et al., (l9hh) studied the influence
of light on age at sexual maturity and ovulation rate
of White Leghorn pullets. They found that the continuous
2h hours per day illumination during the growing period
did not result in sexual maturity at a younger age.

Constant 2h hours per day illumination during the growing

18

period and thereafter appeared to inhibit the expres-
sion of sexual maturity of a considerable number of
exposed pullets and prevented a high rate of ovulation
during_tha entire laying period. Growth, feed consump-
tion, and mortality were either entirely unaffected by
variations in light treatment or indirectly influenced
by reproductive activity.

Tomhave, (195h) investigated the influence of
artificial lights during the growing periOd upon the
sexual maturity and subsequent egg production of October
hatched New Hampshire chicks.r He found that sexual .

‘1‘ I my

maturity was delayed 7 to in days by the use of arti-
ficial lights.. '
T. C. Byerly (1957) developed an egg laying equation
which uses light as one of the dependent variables.
R=A+(B) loglo X+CY+DZ

Where:

R equals the monthly rate of egg production in
percent of total number of hen-days

.A, B, C, a D are constants calculated by the
method of least squares

Log10 of X is the logarithm of the length of
daily light period in hours

19
Y is length of the night or dark period in hours

2 is the number of months elapsed since laying
commenced.

The rate of production is proportional to the daily
light period and the daily dark period so the maximum
production is reached at 13 to 1h hours of illumina-

tion.

In England, Cole: (1959) showed that the relative
amount of light is more important than the absolute
amount of light. He compared chickens receiving 12
hours of light after the start of laying with chickens
receiving 23% hours of light. After two months the
chickens under 23* hours of light were cut back to 12
hours of light. The reduction in hours of light caused

a fall in egg production and an increase in molt.

Light intensigz
One of the earliest reports of light intensity
investigations is published in a bulletin on the arti-
ficial illumination of poultry houses for winter egg
production by Fairbanks and Rice (1921;). They investi-

szated the threshold intensity of light on the floor

20
above which the activity of chickens would be increased,
and below which the activity would be decreased. They
revealed that the general illumination of the pen was
quite as important as the illumination of the floor.
it was determined that the intensity of light on the
floor necessary for active feeding was from eight-tenths
(0.8) to one (1.0) footcandle. They said that a no watt
Mazda bulb with a 16 inch reflector six feet from the
floor would give sufficient lighting for approximately
200 square feet of floor area. No mention was made of
the breed of hens used in the experiment.

Roberts and Carver (l9ul) observed rate of egg pro-
duction with light intensities of 1.0 to 31.3 footcandles
at the feed troughs with 13 hours of light per day. They
found no significant difference due to increasing the
intensity of light over 1.0 footcandle. However, no
mention is made of the breed of hens used in the tests,
or the instrument used for measuring light intensity.

Nicholas, et al., (l9hh) found that varying the
Intensity of illumination from 0.5 to 38.0 footcandles

aat.a.central point in the "working area" and from 0.0

21
to 27.0 at a central point on the roosting perches had
no effect on the degree of reproductive response.
Variable intensity did not cause variable egg production.

.A study by Moreng, et al., (1956) indicated that a
limited light environment may be more stimulating to
the anterior pituitary function of chicks than an
abundant light environment.

Wilson, et al., (1958) studied the effect upon egg
production of keeping chickens in darkness. Single
Comb White Leghorn hens kept in continuous darkness for
five weeks continued to lay eggs. Some of the hens did
not cease egg production, while others, previously
pausing, started to lay again. The hens that paused
for no longer than five days, laid at a rate of 60.2
and 77.1 percent in two tests. The decline in egg
production was greatest in the hens losing the largeSt
percentage of body weight. An intensity of 0.0002
footcandles was determined by exposing film in the
room for one hour and then developing it. .A hen does
not need light for either ovulation or oviposition.

‘The psychic factors regulating ovulation and oviposition

22

are more important than the amount of light a bird receives.

Wavelength

Piper (1905) found that vertebrates such as the hen
and buzzard, gave maximal responses to a wavelength of
600 millimicrons both when light adapted and dark adap-
ted. He recorded the retinal currents under monochro-
matic lights.

Hess (1912) believed that birds are blind to violet
and blue. By sprinkling rice grains in a spectrum pro-
Jected upon a white floor, he found that fowls would
eat the rice from the red end to the Junction of the
green and blue, but would peck no grains in the blue
and violet.

Hahn, Honlgmann, and Blasser (1916, 1926) painted
a different picture by staining rice grains with dif-
ferent dyes or by illuminating them with colored lights,
gluing down the grains to which it was desired to train
the birds negatively. They said that the domestic hen
has partial blue-blindness which increases during
growth. They contended that the hen must be convinced

that blue objects are good to eat. in other words,

23
there is "no blue food in nature."

Watson and Lashley (1915 and 1916) used superlative
apparatus giving brilliant beams of pure spectral lights.
Watson fixed the spectral limits of the chick as lying
between 700 and 715 millimicrons at one end and between
395 and h05 millimicrons at the other.

Lashley trained his bantam cocks to discriminate
various wavelength bands and found that they had about
the same number of maxima hue-discrimination, and in
about the same locations as the corresponding graph for
man. Man distinguished 160 spectral segments in this
visible spectrum whereas a bird, such as a pigeon
(Hamilton and Coleman, 1933) can discriminate only 20
spectralisegments between 700 millimicrons and A60
millimicrons.

Laurens (1923) found that the pigeon has a PurkinJe
phenomenon, but that it takes all of hS minutes for any
discernable effects of dark-adaptation to manifest them-
selves. Piper had not waited long enough to get actual
dark-adaptation, and consequently missed the Purkinje

phenomenon; nor had he, like Laurens, used light beams

21+
of equal energy content, and he therefore obtained fal-
laclous maxima. With equalized lights, Laurens found
that the pupil of the light-adapted pigeon responded
between 70h.millimlcrons and h2h.millimicrons, maximally
at 56k millimicrons. Scotopically, the spectrum was
shortened at the red end to 66h.5 millimicrons and the
maximum was shifted to 52h.5 millimicrons.

Dakan (l93h) studied the effect of light on feed
consumption and the urge of hens to lay. He used light
filters from the Corning Glass Company for the colored
light source. .All daylight was excluded from the
experimental pens. He found that red was the best light
source for laying.

Table l Dakan's Results of Effect of Color on

Egg Production
Total Production

 

Pen No. Color August 1 - January 15
1 White 70.5
2 Red 78.0
3 Yellow 69.9
h Blue 56.0

Dakan does not mention the intensity of the light
source, reflectance characteristics of the walls, trans-

ndttance characteristics of filters, the distribution of

25

the light in the pen, or the breed of chicken used in
the testS. He states also that the gonadal activity was
increased by red absorption as indicated by Bissonette
(1932) and Rowan (1938).

Dobie, et al., (19h6) in one of their experiments
tried different types of lights. They tried Mazda
incandescent, Mazda plus CX ultraviolet, Ruby Red, and
Red fluorescent lighting. The egg production was
re5pectlvely: 71.2%. 72.9%, 69.8%. and 71.0%. This
experiment was conducted with 13 hours of light and six
footcandles at the feed trough.

Hammond and Titus (19h1) studied the effect of
colored light and colored walls on the growth and
mortality of Rhode island Red chicks. They used 16
pens with no day-old chicks in each pen. The floors
were painted medium gray and were covered with shavings.
The walls and ceilings were painted as follows: h white,-
2 violet-blue, 2 flat-black, 2 gray, 2 yellowish-green,
2 red (carmine) and dark green. Tungsten filament lamps
were used in most of the rooms.

it was observed that from 15 to 60 percent of the

26
the chicks in the black, blue, and red rooms never ate;
they never learned to eat. This was consistent through-
out five tests. Rooms of these colors had lower light
intensities. Chicks do not learn to eat readily in a
low light intensity environment.

They concluded that the color of light in the envi-
ronment of growing chickens is less important than the
intensity of the light. .Also, neither the color nor
the intensity of the light to which pullets are sub-
Jected during the first 16 weeks of their life, affect
the live weight, egg production, egg fertility, or
hatchability of eggs.

it appears that the spectral effects on chicks had not
been tested thoroughly. The effect in some pens was of
low intensities rather than a direct consequence of the
color. Chicks may be receiving enough light from thet
desirable portion of the spectrum from the light source
for adequate growth, etc. The spectral reflectance of
the walls was not fully known so even the walls may

have been reflecting the desirable wavelengths.

Dim red lights were used to maintain winter egg

27
production of White Leghorn pullets in New Jersey as
reported by Platt (1953). This was prompted by the war
blackout along the coastline. .All night lighting was
accomplished by using 15 watt red bulbs centered 18
inches above the perch spaced four (h) feet apart. Ten
watt bulbs used 8 hours, from 8 p.m. to h a.mu.were Just
as satisfactory in maintaining winter egg production as
the standard incandescent filament lamps for a 1h hour
day.

Carson, et al., (1958) studied sexual maturity and
productivity in the chicken as affected by the quality
of illumination during the growing period. Their find-
ings did not agree with Callenbach (l9hh) and Hutt et
al., (1955) in that one of the effects of lengthening
the day of pullets with artificial light was a decrease
in the rate of lay after maturity. The chickens were
illuminated from 15 weeks through maturity with red,
gold, green, blue, soft white, or cool white fluores-
cent for 2h hours per day. Controls of continuous
lighting with 60 watt incandescent and of normal day-

light were used. There was no evidence to show that

28
continuous illumination with 60 watt incandescent from
day-old through maturity produced any harmful effects
on livability or subsequent egg production. Any quality
of light stimulated the onset of egg production as
evidenced by the fact that all lighted pullets reached
50 percent production at least three weeks prior to the

unlighted control.

Frequency_of Lighting Periods

 

Common lighting practices provide a day length of
approximately 13 hours of continuous light. Roberts
and Carver (l9h1) reported that 3 hours of intermittent
light daily (1 light, 5 dark - 1 light, h dark - 1 light,
12 dark) yielded production above that of 10 hours
continuous light.

Wilson and Abplanalp (1956) studied the effect of
lntenmittent light stimuli on egg production of Single
Comb White Leghorn pullets. The intermittent light was
provided at regular cycles of four hours. Quantity of
light was set at 90, 60, u5, 15, 2, and 1 minutes in a
series of tests. They made the following conclusions:

(1) intermittent lighting generally gave higher

(2)

(3)

(LL)

(5)

(6)

29
egg production than the same amount of con-
tinuous lighting.

Egg production obtained under short photo-
periods was not proportionate to the amount
of light.

The minimum amount of light needed for an
all-or-none response for maintaining egg
production in pullets is probably less than
six evenly spaced one-minute photoperiods in
2h hours.

Hens were more susceptible than pullets to
light changes and possibly to other environ-
mental factors.

Good layers were more resistant to shocks
from light changes than poor layers.

The time of oviposition is influenced by

light and management factors.

Wilson explains that a considerable variation in light

intensities existed in the rooms so it might be con-

ceivable that some of the results might be due to the

combination of time and intensity or Just of intensity.

30

High-intensity light for one or a few short periods
(5 to 20 seconds) during the night has been shown to
stimulate or maintain high egg production in the hen
(Staffe, 1950, 1951; Weber, 1951). This effect is '
comparable to those with.more conventional foams of
intermittent lighting, though intensity possibly plays
a role‘with this method.

At the university of Nottingham, Nightall (1955)
increased egg production 5 to 6 percent by using flash
lighting. His method was to produce light periods
of 20 seconds duration at 2:00, 3:25, and h:50 a.m."

He used a car battery and 25 volt lamps with hO, 60,
and 100 watt ratings.

Shutze, et al., (1959) used continuous lighting on
New Hampshire pullets for the first 8 weeks, then
reared them on the range, The pullets came into produc-
tion at a slower rate and peaked at 59.2 percent as
compared to 73.2 percent for pullets on 12 hour light,
12 hour dark period from hatching to 8 weeks. They found
that continuous light to either 8 weeks or 20 weeks

depressed the subsequent egg production.

31

At Edinburgh, Coles (1959) conducted experiments
with day-old chicks receiving six hours of light to
maturity and then gradually increased amounts of light
per day until 18 months of age. This resulted in a
consistently high egg production pattern. A.practical
means of achieving this lighting plan is to rear
November-hatched chicks under the natural short days
until April. At the point of lay increase the light
by 15 minutes per day each week. Thus, the birds are
subjected to the increasing light pattern.

Stimulight is a term applied to a method of raising
pullets on restricted light. D. F. King (1959) developed
this method of lighting by working with White Leghorn
pullets. The method consists of restricting the light
to six hours per day until the pullets reach 21 weeks
of age. Then 18 minutes of light are added each week
until the total amount of light reaches 21} hours per
day.

The chief advantages claimed for this method of
.lighting are more eggs than in hour lighting schedule,

less feed per dozen eggs, larger eggs, stronger shells,

32

i

and greater hatchability.

An article in the December, 1959 issue of the Farm
Journal, "How Stimulight is Working Out," says that
Harold Biellier, university of Missouri, got the same
result as King, but other researchers failed to verify
the results. C. E. Ostrander, Cornell university,
reported no increase in total production by “Stimulight”
in either the light or heavy breeds. W. C. Skoglund,
New Hampshire, did not get the same result as King but
got the most eggs from "normal" light (1h hour day).

Nothing is mentioned about the intensity of light
during the light cycle or dark cycle. in other words,
was the dark cycle actually dark or was some light
infiltrating the building? Did the researchers have
their experiments on a comparable basis?

McClary (1960), a geneticist for a commercial
hatchery firm, conducted tests with a step-down step-up
lighting plan using Leghorn pullets. Conversion of
existing structures to follow the lighting plan is
{accomplished easier than in King's plan since natural

daylight can be used to its fullest extent. No windowless

33
houses are needed in this plan. The light per day is
decreased in increments of 15 to 20 minutes per week
until the pullets are 22 weeks old. Then, the procedure
is reversed, and the light-period is stepped-up each
week to stimulate pullets into production.

The results of step-down step-up lighting, as
compared to constant 15 hour per day lighting showed
that:

(1) Sexual maturity was delayed two to three

weeks.

(2) Pullets gaVe a significant increase in

rate of lay after nine months.

(3) There was a significant reduction in mor-

tality.

(h) It resulted in an increased egg weight of

1 ounce per dozen at 7 to 8 months and

fi ounce per dozen advantage at nine months.

Activity

The effectiveness of supplemental light on egg pro-

iduction for many years was believed to afford increased

3h
topportunity of the chickens to feed. Fairbanks and Rice
(19214.) assumed that egg production depended on the activ-
ity of the chickens (speed of feeding). Goodale (1923)
questioned this view; Whetham (1933) suggested stimula-
tion through the anterior pituitary body. ,About the same
time Bissonette (1933) came to a similar conclusion,
reasoning from his experiments on the EurOpean starling.
Dakan (l93h) says that birds can eat all the feed
they need in ten hours. He found no difference in egg
production between two pens; one at ten hours of light
and hoppers covered and the other with light at night
and uncovered hoppers. The stimulatory effects of light
were shown by Rider (1938) to be independent of the
availability of feed during hours of artificial light-
lng. Rider's results were confirmed by Callenbach, 1
et al., (19h3). They state that a daily feeding period
of 10 hours was adequate for maximal egg production.
Therefore, light is a positive physiological influence
stimulating reproductive activity in mature female
chickens.

Wilbur O. Wilson (1958) experimented with the effect

35
of light on egg production and growth. He says that
light per se (by itself) rather than the increase in

feeding time is the factor affecting growth and egg

production.

Time of Lay

Under natural lighting the hen lays only during
daylight hours. The eggs constituting a sequence are
not laid at the same time on consecutive days. The first
egg may be laid in the early hours, the last may be
laid in mid or late afternoon (Withrow, 1959).

One role of photoperiodicity in the hen's ovulation
cycle is to time the appearance of a period of low
thresholds to ovarian hormones in the neural component
of the mechanism controlling the release of ovulation-
lnducing hormone from the pituitary. The period of low
thresholds has a duration of not over 8 or 9 hours, and
its onset is thought to follow rather closely (l to 3
hours) upon the onset of darkness.

Fraps (l95h) proposed an hypothesis to explain the
meéhanlsm of the time of ovulation with regards to photo-

periods. He suggests that the nervous component of the

36
ovulation-inducing release mechanism exhibits a diurnally
recurrent rythmicity. The blood concentrations of ova-
rian hormones "exciting" the neural component of the
ovulation-inducing hormone release apparatus increase by
substantially the same course after each release of
ovulation-inducing hormone in cycles of given length.
Each curve of increasing excitation hormone concentra-
tion beyond that associated with the first excitation of
a sequence is retarded, in time of day, by the extent
of lag at the preceding ovulation-inducing hormone
release.

Bastian and Zarrow (1955) proposed a slightly dif-
ferent hypothesis than Fraps to account for the asyn-
chronous ovulatory cycle of the domestic hen. They
recognize two separate and independent cycles which
interact to produce the ovulatory cycle. (1) The
release of an ovulation-inducing hormone is assumed to
be continuous over a relatively long period (e.g., 8
hours) during the same hours every night. (2) The matu-
ration of ovarian follicles is assumed to be gradually

<:ompleted at more or less regular intervals.

37

Physiology of the Eye

In general, eyes vary only slightly in structure
from one animal to another. Basically, the eye resem-
bles a camera in structure. The retina is similar to
film in that it is the photosensitive part of the eye.
The cornea plus crystalline lens simulates the lens on
a camera. The lid is similar to a shutter. The pupil
resembles the diaphragm aperature. The interior of the
eye is darkened by a chorioid pigment just as the interior
of the camera is painted with a dead black paint. Some
parts of the eye are automatically adjusted for changes
in environment. The eye has accomodation; a way of
automatically varying the distance between lens and
film by changing from one lens shape to another.

The visual angle for a single eye of a vertebrate is
rarely much greater or much less than 1700 according to
Walls (19h2) in his book, The Vertebrate Eye. A.hen has
eyes which are at a divergence angle of lhho from the
optic axis of the eyes. This causes a very slight
'convergence of overlapping of the visual angle of each

eye of around 13°.

38

Retina Light waves coming to the eye are absorbed in
the retina. The retina is a relatively transparent mem-
brane containing millions of energy-sensitive nerve
endings. These nerve endings are attached individually
or in groups to fibers of the Optic nerve.

Cones and rods are the two kinds of nerve endings
and are named after their shapes. The cones are concen-
trated in the fovea, a slight depression in the retina
slightly off the optical axis of the eye. They also
exist throughout the retina but in lesser density. Cone
vision is called photoplc vision and is used for dis-
crimination of fine detail and hues of color. The
cones function only at higher levels of radiant-energy
stimuli.

The rods exist only in the retina outside of the
fovea. Rod vision is called scotopic vision. The
details are neither sharp nor are hues of color discrimi-
nated with this type of vision. Vision is fuzzy and
gray.

in general, the relative number of cones-per-rod

are high in diurnal forms and low in nocturnal forms

39
of vertebrates (Wall, l9h2). ln.many birds, only a few
rods can be found and these may be present over only a
part of the whole retina area. Cones greatly outnumber
rods in all diurnal birds which have any rods at all.
The adoption of diurnality entails a sacrifice of sensi-
tivity. .At the same time diurnality is an adaptation
for sharp vision.

There is a difference in the spectral response curve
of the eye between scotopic vision (rods) and photoplc
vision (cones). The curve tends to shift to the shorter
wavelengths for scotopic vision. This is called the
Purkinje Effect. Scotopic vision is effective below the
threshold of seeing for photoplc vision.

in vertebrates the area of the brain which receives
the impulses from the retina is called the hypothalmus.
This region of the brain also influences temperature
regulation, sugar and fat metabolism, the states of
sleeping and waking, and sexual activities. it is
generally believed that the hypothalmus stimulates the
pituitary gland in chickens. The pituitary then induces

ovulation in the hen.

no
Photochemistry of Vision if the retina were removed in
the presence of red light greater than 650 millimicrons
wavelength it would be magenta in color. This is due to
the light-sensitive pigment, the visual purple (rhodopsin),
which is contained in the rods. The cones do not contain
this pigment. The rhodopsin is largely responsible for
the ability of the rod to "dark-adapt" or lower its
threshold until the amount of light needed to stimulate
it is a tiny part of that required to arouse a cone.
Under ordinary daylight, the rhodopsin breaks down or in
essence its synthesis and breakdown are in equilibrium.
Under dim light the higher concentration of rhodopsin
makes the light appear brighter. in the presence of
light it bleaches to a pale yellow substance named
retinene.

The hypothetical pigment in the cones has been named
iodopsin because of the nature of the absorption spec-
trum attributed to it. Studnitz (1930) calls the photo-
chemical: zapfensubstanz, i.e., cone-substance. The
absorption spectrum of zapfensubstanz is similar to the

electrical responsitivity of the photoplc retina.

hl

Earlier experimenters said that human vision was
trichromatic. The Young-Helmholtz theory calls for
three "somethings" in color vision. Young said that
there were three sets of receptors in the retina.
Helmholtz said that there were three photochemical sub-
stances or processes in each cone. Studnitz recognized
the possibility that what he had called one substance
might really be a group of three which his solvents
cannot separate from each other.

Polyak's (l9ul) painstaking studies of the micro-
scopic structure of the retina led him to the conclusion
that all cones are essentially alike. This does not
rule out the possibility of triply differentiated pat-
terns of nerve impulses. He mentions that a host of
other structures in the retina may give clues to the
visual process since they are interconnected and must
be there for a purpose.

A color vision theory was advanced by Krause (1863).‘
His theory is called the oil-droplet function. 011
droplets are located just inside the cone layer. This

theory proposes that each color of oil droplet makes

”2 .
possible the independent sensation of the corresponding
color in the spectrum. The supposition was that the

bird has but one (not three) photochemical substances

in its cone outer segments, and that this undifferen-
tiated substance would be affected equally by any and

all visible wavelengths of light. Color vision would

be possible only by a certain wavelength, others by
another wavelength, and so on.

Only red, orange, and yellow droplets occur in
birds, along with some colorless droplets. The pigments
in a chicken's retina are the carotenoids; astacin, sar-
cinene, and xanthophyll. The cones of a birds fovea
contain only yellow droplets, the red ones stopping at
the margin of the retinal pit.

Most birds are such early risers that they expose
themselves to Rayleigh scattering of light by molecules
of water and gases in the atmosphere on even the clearest
of sunrises. it seems that the shorter wavelengths are
scattered the most and red the least. This is one
reason for the red colored sunrises and sunsets.

The bird, aided by red droplets, gets in most of the

h3
day's work at dawn and shortly after. As the day wears
on the yellow droplets (colorless ones on dull days)
take over. The orange ones give a smooth transition.
Primarily the oil droplets act as colored filters. The
yellow filter reduces the effects of chromatic aber-
ration and reduces glare and dazzle.

Hecht (1937) developed a chemical basis of vision.

He discusses the process with the aid of simple sta-
tionary state photochemical reactions. By using the
basic equation:

H1 = xn/(a - x)m

Where:
x = concentration of photoproducts
a = concentration of photosensitive substance

1 = intensity of light

m = order of primary chemical reaction

n order of primary dark regenerating reaction
K = constant
he developed equations for (1) intensity discrimination

and photo reaction rates and concentration, (2) visual

acuity, and (3) flicker or intermittent light stimulation

uh

which closely approximated experimental data. Many of
his relationships involved reaction rates. Hecht's
chemical theory considers only the concentration of the
photoproducts of visual purple (rhodopsin) in the rods.
Hecht(l9h2) determined the threshold vision of the
rods to require between 2.1 and 5.7 x 10"10 ergs at the
cornea. This amounts to between 5k and lh8 quanta of
blue-green light. He states that the corneal reflection
is approximately h percent, the ocular media absorption
50 percent, and the retinal transmission 80 percent.
Therefore, 5h to lh8 quanta becomes 5 to 1h quanta by
the retinal rods. He further states that one quantum
must be absorbed by each of 5 tolh rods in the retina
since a large number of rods (500) is involved in order
to produce a visual effect in a 10 minute circular field.
Hugo de Vries (l9h3) states that the threshold of
vision can be defined as the smallest number of quanta
giving rise to a sensation of light. He assumes that
rods and cones act like counters of light quanta. He
says that the sensitivity of rods at 510 millimicrons

10

is approximately 7.5 x 10' erg/sec based upon several

us
experimenters' results plus his own results. The energy

of one quantum at 510 millimicrons is h.3 x 10’12 erg.

The smallest amount of energy for vision is 3.0 x 10-10
erg if supplied in less than 0.1 seconds. At 510 milli-

10 represents 70 quanta. The threshold

microns 3.0 x 10'
of vision is then at 70 quanta. HOwever, only 50 percent
of the quanta passing through.the pupil reach the retina.
At full dark adaptation approximately 15 percent of the
light is absorbed by the visual purple (rhodopsin). if
only about 1h percent of the visual purple is active then
one can assume a sensation with one quantum of light and
it follows that 69 quanta are lost for every quantum
hitting a rod. Also, it follows that 5 molecules of
visual purple are decomposed by 70 quanta passing through
the pupil. These 5 molecules generally lie on different
rods. The minimum number of rods to see in the human
equals approximately 1600 rods in the retina. Sensi-
tivity for different wavelengths is proportional to

the absorption coefficient of visual purple. According

to Reeves (1918) the angle at which the light spot is

seen may be increased to about 30 minutes before the

M6
minimum visible energy increases. This corresponds to
about 1600 rods in the human retina. The number of

quanta observed at the retina for rod vision is given

by the expression:

N = rip/7o

R

Where Np = the number of quanta passing through
the pupil per second

N = quanta observed at the retina

R
The ratio of cone sensitivity to rod sensitivity
is 1:60. The cones react on one quantum out of u200

passing throuoh the pupil. The expression for cone

vision is:

N1. = Np/h200

An expression for the number of quanta observed
per second was formulated by deVries. .A surface of
S cm2 with L millllambert brightness (1 ml = lO/n
candles/m2) emits LS/lOs; lumens per unit solid angle.
At 510 millimicrons wavelength, 1 lumen equals 1.33

15

x 10“ erg/sec equals 3.2 x 10 quanta/sec. The total

12

number of quanta emitted equals 1.0 x 10 LS/sec.

With Np = number quanta passing through the pupil with

M7

surface Sp then

Np = (1.0 x 1012) SLSp i/a2 cos b
Where:

a 8 distance of object to eye

b = angle between normal to surface and line to eye
When L = candles/m2 a Sp in mmz, then Lsp is called the
"retinal illumination," P. Therefore; Np =;: x 109
(SP) cos b/az. When an object is seen as a circular
spot at an angle of c, then Np = 250 P c2.

it follows that the number of observed quanta per
second in half of a circular field of 31 minutes with

a retinal illumination of 10 photons is:

Nr 8 (l/2)Np/h200

(1/2) (250) (P) c2/uzoo

(1/2) 2500/u200 (31)2
= 300 quanta/sec
The effective number is (0.2)(300) = 60 quanta, since
the effective time of observation is approximately
0.2 seconds.
For an intensity discrimination of 10 photons, the

number of quanta to be found on one cone is

h8
2500/h200 (1.5)2 = 1.3/sec. (One cone equals approxi-
mately a 1.5 minute angle.)
The maxima of visual acuity and intensity discrimi-
nations are reached between 3,000 and 10,000 photons.
For one cone (about 1.5 minutes) this is 500 to 1600

quanta per second with no adaptation.

A9
DISCUSSION or LITERATURE REVIEW

Summaries of the articles on the effect of light on
rate of lay, total annual egg production, age at matu-
rity, activity, and molting are presented respectively
in Tables 11, iii, 1V, V and Vi. Factors of light
listed in the first column are day length, light inten-
sity, frequency of lighting periods, and wavelength.
The headings of the other columns give the effect of
the light treatment factor on the particular response
of the chickens as listed in the title of the table.

The following discussions attempt to analyze the
literature. Some possible fallacies in past research
are discussed. .Also, analytical comparisons are made
of experiments where differences are reported for the
same general type of experiment. The discussions are
divided into the following sections: General Discus-
sion; Daylength; Light Intensity; Wavelength of Light;

and Frequency of Lighting Periods.

made use
some: a.3a-o> com seam camcoaosaz

Ado mac ~m -
ma camcog Ame mums:
xooB poo .cmE mg

messed cone and .mxz

 

mason mm “macs .mcn 0 mo
am as samba oooooaaoum .n
mwmwmwm .oum ON a» m mo
g couwam monomflm mamas .m
A~co>o o acouuuecmoca .~
mmocxcmu an Add
cwo was: meow .N
.o.u on ou
.o.u n Scum momumm
icoucq mcnzum> .a .o.e ~ .o.u a co>o .o.m g case who; Auumcoacu
Samoa
coda caubusc
nonvoaa moo oboe loan moo cameo»
lungs m.uo-=a co 1—5 co mao-sa co
unmuu msoscabcou acmqu nsoscuucoo .n
, nomads zoo co
acauosooua omcmno ocmzczoa .N
.uac n~ moon :6 a:m~:t-<. mason nu spasm .~ camcoa zen
sooecm oz eaeaoao au>ocasH oooaaacca assume

and mo mama so suspense“; on» on mo~o~au<.mo mauswum mo heuEEsm um ufimah

51

buoumo beau
inuucmqn o:

 

 

can Samoa
msoscuucou .~ cameo“ Ann
uouocm oz sssoooo cusocoeo _ seasoned” taboos
coquosooum mam ~os¢¢< moves :0
ocsuauouaa us» ca mo~o~uk< Ho mumswum mo Aguassw Ham smash

52

zqmsoacua
icoo com: cmg3
oo>ouaed unmud
Ho zuuqaso zc<_ :umcmflo>o3

have as as
A commode magmas
adauaeaouo co on: .m

 

Aoouoanaaucoo
camco— mason Nu onus baby i hon
has ousuomn< .~ can» one: .~ .c: :N usoscnocou .u camco~ Asa
suscem oz assaeao essences cuaaoacca sconce

1'1

hamasuoz as oa<.co
anaconda"; on» c“ no~oqaa<.uo nausuom ho Auaessm .>~ u~omh

53

 

mcmcoom
com cocoa:
meson 0“ .~ nausea man
camouoom
new use am can
as m.:co .n 16900» com
15 mémm .n
acum~> oua
touoca 15.:N: oaaouoca :vzoam
on as 20w .N caucus 30m .N new: mcnnwouo
1:" .amococuun
Escaooaa mo concave dado “smegma .N
smash :8 mo: unmnu can
0 man a» as some such on
i . . «a use
map 00» a sec 12 coo a ou~o~> do acaam .2 camcoao>a3
mauooou A
non .o.m g .u camMMwflfl
Edens“: madam Essuxmz oouunucen uouoom

 

1|

xuu>uuo<_co oasaoauunu on» Ca wo~uuue<_uo mu~snom mo Auusesm > munch

odds
mo mmucmoaa
«comma ac: one

unmmci-¢..m

 

 

«oedema unmuu camcoa man
no cameo“ ho omcaco cash “so
coauococu .u oamzcaon .~ sausage» mesa: mg .~ caucus Ann
383 oz 3282: 5520 3:25: cocoon
H> muons

mena~oz :o oasaucouuq us» ca uououuh< ho muusuom Ho hassssm

55
General Discussion

it is difficult to compare experimental results of
poultry lighting of several years ago with experimental
results of today. For instance, egg production has
improved through better breeding. Also, better feeding
practices have played a major role in obtaining higher
egg production. Some of the experiments a few'years
ago were concerned mainly with maintaining a high rate
of egg production during the winter months. Today, the
yearly egg production is considerably higher than it was
a few'years ago. Therefore, we are not as seriously con-
cerned with boosting peak production during the winter
months as previously, as we are interested in obtaining
a higher rate of lay and a higher annual egg production.
Research is needed to establish lighting recommendations
for present day chickens.

Generally speaking, many of the experiments on the
effects of light on chickens were not a basic research
type of experiment. instead, most experiments were an
applied type of research with little precision in the

control of their source of light or in their measurement

56
of light intensity. The intensity and spectral charac-
teristics of light varied considerably from one experi-
ment to the next depending upon the following conditions:
wattage of the electric light source, the size and
location of windows, the spectral transmission charac-
teristics of the windows, the reflectance of the envi-
ronment in both energy and wavelength, time of day,
size of pen, and season of the year.

Many articles mention the lamp wattage used in the
pens, and frequently state the size of the pens. The
light intensity, in footcandles, is often given in
the more recent articles. However, the reflectance of
the environment should be included. .A chicken (or any
other vertebrate with an eye) does not see light. He
sees only objects from which the light is reflected.
Therefore, the reflectance of the environment is impor-
tant since it is the reflected light that a chicken
generally sees, and not the emitted light which most
researchers have tried to measure. ,Actually, results
should not be measured in terms of footcandles since the

footcandle is based upon the spectral sensitivity curve

57

of the human eye. .A unit of light intensity or reflect-
ance based upon the spectral sensitivity curve of the
chicken eye should be the basis for making light
measurements. ’
221122321

it appears that 13 to 1h.hOurs of light per day are
needed to maintain a good rate of egg production. Pri-
marily, this recommendation is based on the hours of
day light received during the months of March and
.Aprll when the hens lay the best under normal conditions.
During the first six months of the year the days become
progressively longer. This positive rate of change of
daylength tends to promote or maintain rate of lay. .A
negative rate of change of daylength appears to cause a
'decrease in egg production and an increase in molting.

Any additional daylength over a normal 1h hour day.
delays sexual maturity. Callenbach (l9hh) and Carson
(1958) obtained different results on the rate of lay
after sexual maturity of pullets by using continuous
light. Callenbach found that constant 2h hours per day

illumination during the growing period and thereafter

58
appeared to inhibit the expression of sexual maturity
and prevented a high rate of ovulation during the entire
laying period. However, there are differences between
their experiments. Callenbach used June-hatched White
Leghorn pullets; Carson used unrelated strains of a
Columbian-patterned bird of a September hatch. No
information is given on the intensity of light under
the natural daylight condition for either experiment.
Different results might be attributed to this factor,
since the light intensity may have varied considerably
in each instance. The length of day and the natural
outdoor light intensity would have been different in
each case since Callenbach's experiment started in June
and Carson's started in September. Probably more over-
cast weather prevailed during Carson's experiment, so
it is possible that low outdoor light intensities pre-
vailed.

Callenbach used a lower level of artificial illu-
mination than Carson. He used a no watt incandescent
filment lamp in a 10 x 12 foot (120 sq. ft.) pen, whereas

Carson used a 60 watt incandescent filament lamp in a

59
6 x 13% foot (ill sq. ft.) pen. Therefore, Carson's pen
had higher light intensity.

Callenbach moved his pullets to a lower light inten-
sity pen (12 x 20 foot or 2&0 sq. ft.) which may have
affected their age at sexual maturity. Carson separated
his pullets at 102 weeks into different pens. The pens
were of the same size before and after separation. The
light intensity probably remained the same for all of

Carson's pens.

Light Intensigy

 

The commonly recommended minimum light intensity is
one footcandle. This recommendation is based upon
research conducted in l92u by Fairbanks and Rice. Com-
mon measuring instruments used at that time were prob-
ably not very accurate, at least the researchers did
not report the accuracy of the light intensity readings.
They did not mention the breed of chickens used in the
experiment. A difference probably existed between the
various breeds of chickens in their response to light.
Some breeds of hens can produce eggs when subjected to

continuous darkness as evidenced by Wilson (1958).

60

Light intensity investigations on chickens have been
limited primarily to light intensities below no foot-
candles. Perhaps higher intensities would have a more
pronounced effect on the chickens than the lower inten-
sities which have been used for many years. Chickens
live outdoors quite successfully even in brilliant sun-
shine when the light intensity approaChes 10,000 foot-
candles. The effect on chickens of light intensities from O
footcandles to 10,000 footcandles has not been thoroughly
investigated.

The combinations of various light intensities with
various time periods have not been investigated. Both
Roberts, et al., and Nicholas, et al., investigated the
effects of light intensity on the egg production of
hens and found no significant difference between dif-
ferent light intensities. However, the experiments
were below forty footcandles maximum light intensity.
Each experiment used a nearly constant day length of
13 to in hours. Different combinations of light inten-
sities and day lengths were not tried. Possibly the

effect of the total light energy received by the chickens

61
would be a more meaningful way of exploring the effects

of light on chickens.

Wavelength of Light

 

The spectral limits of a chick's eye have been
established with fairly good experimental techniques.

‘A chick sees from approximately h000 Angstroms to 7000
Angstroms, or Just about the same as the human eye.

The spectral sensitivity curve of the chick peaks at
nearly the same place as man's. However, certain
articles in the literature indicate that birds tend to
respond to red light better than other wavelengths of
light. Blue light appears to be the least desirable for
chickens. 'lt appears as if the chicken's eye becomes
less sensitive to blue light with increasing age.

In general, the experiments on the effect of wave-
length of light on egg production or age at maturity
were not very precise. None of the experiments balanced
the energy in different parts of the chicken's visible
spectrum. Incandescent filament lamps were used pre-
dominately, therefore the energy in the red end of the

spectrum was the highest. A.few experimenters tried to

62
isolate the various wavelengths by means of filters, but
they failed to balance the energy transmitted through
the filters.

Some experiments consisted of using different colors
of fluorescent lighting. Fluorescent tubes generally
emit more light in the greens and blues than the fila-
ment lamps, and less in the reds. Therefore, compari-
sons between filament and fluorescent lamps may be
fallacious unless the spectral characteristics of the
two light sources are considered.

Frequency of LightPeriods

Higher egg production of hens is apparently obtained
by breaking up the day into several light periods.

There are many types of lighting plans for the rearing
of puliets and for laying hens. Most plans are pri-
marily interested in the duration of the light period.
With the exception of flash lighting (or shock lighting),
little mention is made of the light intensity. Flash
lighting is accomplished by high intensity light for a
duration of a few seconds. Some of the other inter-

mittent lighting plans apparently follow the normal

63
recommended light intensity of at least one footcandle.
However, little mention is made of the intensity or
dominant wavelength of light. Perhaps, the total energy
of light received per day by the chicken is the impor-
tant factor and not just the duration, intensity, or
wavelength of the light.

The darkness cycles are probably nearly as effective
in stimulating egg production as the corresponding light
cycles. At least the onset of darkness supposedly ini-
tiates the ovulation process. Information on the dark
cycle is lacking, especially the intensity of light
during the dark periods. One experimenter found that
some hens lay in total darkness. From this information
one might be led to believe that even a few photons of
light might be enough to stimulate hens to lay. It is
difficult to compare results from the different studies,
since each is conducted under different environmental
conditions. Buildings are difficult to seal from light
so different degrees of darkness likely prevail between

the various experiments.

6h

PRELIMINARY STUDIES OF LIGHT INTENSITIES
.AT ROOSTING.AND RISING

The motive behind this preliminary study was to
explore various facets of the effect of light on poul-
try. This study was confined to the effect of natural
daylight on chickens. .A conspicuous point to investi-
gate was the light intensity at roosting1 and rising2
of chickens at dusk and dawn respectively, because of
chickens' apparent reaction to light intensity changes

at those times.

Location and Apparatus
The investigations were conducted with 20 White
Rock hens in pen 205 of the Commercial House of the
Poultry Science Department, Michigan State University.
This pen is 20' x 2h'. The walls are a medium gray
color. Two standard windows are located on the east

side of the pen with a small window located in the door

 

lRoasting, as defined in this study, is the act
of a chicken hopping onto a roost.

2Rising is defined as the act of a chicken hop-
ping off a roost.

65
on the west side of the pen (See Fig. l).

A phototube was mounted in a box on the roosts near
the south wall. Light passed through a three inch square
hole in the box and then through a two and one-half inch
square opening hi a disk inside the box before it reached
the phototube. Car window weatherstripping was fastened
to the inside of the box between the box and the disk to
inhibit light leaks into the interior. The inside of
the box was painted with a flat black paint to increase
the absorption of light and reduce reflection of light.

A disk contained a series of eight openings, six of
which were covered with Kodak Wratten Filters. The
seventh opening was covered to permit measurements of
the phototube dark current. The eighth opening allowed
all available wavelengths of light to reach the phototube.
A pipe extended from the center of the disk through the
south wall to the adjoining feed room. A.handle on the
end of the pipe aided in positioning the various open-
ings on the disk. Also, copper lead wires from the
phototube passed through the wall near the pipe and

connected to the microammeter and the voltage supply

FlG.

HALLWAY

 

PEN 204

PEN 205

 

 

M'CR o -- D D VOLTAGE
AMMETER 39PM”
FEEDROOM

LOCATION OF APPARATUS IN PEN 205
OF COMMERCIAL POULTRY HOUSE

67
located in the adjoining feed room.

The height of the phototube was just slightly above
the height of a head of a chicken standing on the roost.
The phototube has a visual field of 1120 horizontally
and 129° vertically. This angle includes the windows
along the east side and the window in the door.

Light SensingrApparatus

The basic electrical circuit consists of three com-
ponents as shown in Fig. 2: microammeter, d-c power
supply, and phototube.

The microammeter is a Keithly Vacuum Tube Electro-
meter Model 210, with a Keithly Decade Shunt Model 2008,
which permits accurate measurements as low as.5 x 10'1“
ampere. With very high shunt resistances small currents
representing levels of illumination in the order of hun-
dreths of a footcandle can be measured.

The d-c voltage for the circuit was supplied by a
Heathkit variable voltage regulated power supply. A
constant d-c voltage of 250 volts was supplied to the
phototube since that is the maximum anode voltage rating

of the tube.

 

68

 

FIG. 2. LIGHT MEASURING APPARATUS CONSISTING
0F MICROAMMETER, D-C POWER SUPPLY

AND PH 0TOT UBE

 

69

A RCA vacuum cartridge type phototube was used. This
tube is used primarily for colorimetric applications.
The cathode has a silver-rubidium oxide-rubidium surface
with a maximum response near h200.Angstroms. The spec-
tral response curve of this cathode shown in Fig. 3 is
called an S-3 curve. The curve approximates relatively
close the response of the human eye. The absolute lumi-
nous sensitivity is given in microamperes per lumen with
an incandescent tungsten filament at a color temperature

of 28700K serving as a light source.

Phototube Characteristics

Type RCA 926
Surface Area 0.h in2
Spectral ResponSe 8-3
WaVelength of Maximum Spectral Response h2009A
Sensitivity

uafl1 watt at response peak 0.0016

ua/lumen, 2870°K 6.5
.Anode Voltage 250 d-c

Maximum Ratings

Anode Supply Voltage
dc or peak ac volts 500

I00

80

 

60

4O

RELATIVE SENSITIVITY

20

0
0.3 0.4 0.5 0.6 0.7 0.8 0.9

WAVELENGTH, MICRONS

FIG. 3. SPECTRAL RESPONSE CURVE FOR RCA~ 926
PHOTOTUBE

71

Average Cathode - Current Density Ila/in2 30

Average Cathode Current pa 5
Ambient Temperature C0 100
Maximum Anode Dark Current at 25°C pa 0.005

The response of a vacuum phototube to incident light
signals is exceedingly rapid due to: (l) The time which
elapses between the incidence of a light quantum and
the ejection of a photoelectron has been found to be
too brief for measurement; (2) The time of transit of
the electron between cathode and anode is exceedingly
short due to the fact that the electron has a large
ratio of charge to mass. A vacuum phototube has
essentially a linear response compared to a gas-filled
phototube. However, the amplification is several times
higher in a gas-filled tube than in a vacuum tube.

.Any phototube to which voltage is applied will pass
a certain amount of current even if the photocathode
is unilluminated. Sources of dark current in an elec-
tron tube are:

(l) Ohmic leakage between electrodes, both inside

and on the outside of the tube envelope.

72
(2) Thermionic emission from the photocathode.
(3) Current generated by positive ion impact on

the photocathode.

Calibration of Phototube

Facilities of the Michigan Highway Research Photo-
metric Laboratory were used to calibrate the phototube.
.A l2h.3 candlepower 100 watt 120 volt standard lamp was
used at a voltage of 105 volts as recommended by the
Bureau of Standards. The lamp was used as a point source
of light by allowing the light to pass through a small
slit in the container holding the standard lamp.

The intensity of light received by the phototube
was calibrated against the calculated footcandles from
the standard lamp by using the inverse square law for
the distance. The distance was measured from the
filament of the lamp to the photocathode of the photo-
tube.

The calibration curve is linear in response (See
Fig. u). The equation for the calibration curve is

X = 63.7 Y - 0.32

73
Where:
Y = microamperes reading of microammeter

X = footcandles calculated from standard lamp
and distance

At the time of calibration the dark current was 0.005
microamperes.

Infrared Sensing Equipment

 

A U}S. Army Corps of Engineers Metascope, Image
Model T-6 was used to detect the movement of chickens
on the roost at night. it contains a if volt dry
battery as a power source. This metascope is a near
infrared viewer.

.An infrared light source has to supply the needed
infrared energy at night. The metascope will not pick
up the natural long wave infrared radiations emitted
by the surroundings. .A 75 watt lamp in a medium bowl
reflector was used as the infrared source to illuminate
the roosting area. Filter paper was placed over the
reflector so that all visible light was filtered out

allowing only infrared energy to illuminate the room.

 

0.20

0J0

MICROAMPERES

CURRENT,

0.0 0

FIG. 4.

74

 

Y=0.0I57 X 4- 0.005
orX= 63.7 Y - 0.32

2 4 6 8 I0 l2 I4 I6 I8 20
LIGHT INTENSITY, FOOTCANDLES

CALIBRATION CURVE FOR RCA 926
PHOTOTUBE AND MICROAMMETER

75

Results of Roosting_lnvestigations
Roosting light intensities of the pen of 20 White
Rock hens were investigated during two different periods:
from April in to 25, 1960 and from.April 30 to May 6,
1960. Data collected for roosting times and light in-
tensities under natural conditions is presented in

Table VII.

Analysis of RoostingTTime vs Sunset Time A plot of
sunset time and roosting time vs day of the month is
presented in Fig. 5. The slope of sunset time is 0.863
minutes per day for this period of the year.

The slopes of the time of roosting were determined
statistically for the first, median, and last chicken
on the roost. A sample calculation of the slope is

given as follows for the median chicken on the roost:

X number of the day beginning with.Aprii in
as daynumber l and ending May 6 as day
number 23

Y = number of minutes from 6:00 p.m.

W

 

 

 

eeeau - «eases» 0~.~ 00.0 05.0 00“» 00“0 0mum 0:“~ 0-m
succee>o 200005 00.0 00.0 00.~ was» mane mono Nana mum
aweoeo>o 000.. 0~.0 00.“ 00.~ 0su~ mane 0mum "0“» sum
seneso saseae 00.0 0~.m 0m.: owns m0ne mmnm onus 0am
seen - geese 00.0 00. 04.: mane 00”0 0mum 00"~ mum
enema - muse—o 00.. 0:.m 0m.: 00“» 0:“0 onuo m0u~ ~-m
sauce .euuuee>o 00.0 00.0 00.0 mane "nee mdum 00.5 00-:
suuuee>o 0m.0 0:.0 00.m m0.» 00ue osum ~0ua mNI:
sea: . eae_o 00.0 00.“ 0~.0 nous emue mono 0mup 0m-:
sea: . eeeao 0m.0 0m.m 00.0 an» mane asum mmnp NNIJ
eaeao 00.0 0:.a 0~.0 own» smxo onue awn» _m-:
sue: . eeoso m0.0 00.~ 0~.m hone 0:“0 amnm mmuh 0NI:
eaoao mh.0 00.0 0m.0 moua onue 0mum sane 0b-:
eueau 0~.0 00.“ 0 .0 man» 0mue oeue 0muu can:
eeoso . 3000.0 00.0 0~.~ 00.0 mun» mmue 00“0 «we» anus
oneoeu>o m_.0 mm.0 mm.0 ooua 0:"0 0a” awn» 0a-:
s0=0_o m~.0 m:.0 00.0 m_"~ mmne mono 0mua ma-:
secuee>o mm.0 00.0 mo.“ ~0ue cone ocum 0a.» 0a-:
9 JD .40.... 13
m 00m... mum mum mum 0mm mm... m“ m
1 J!“ am“ J!“ 803 :33 :33 as a
u. 0!... 03.... 081. 1H. 1”. 1”0 W
“ WWI WWI “3.... mm: um. U!»
10W TWW. 1WW 0!. 0m OI
\IU.3 \l 3 )IO U2 U3 US
JIU Jan Jan 8 P 1
.0" .mn man 1 u
“a”? “403 .qu u
U
00004 satesoz_ns«3 queasaassno>ca museuoom 00 museums 00> eases

 

 

 

 

 

8:00
' ‘ b
‘ _: LAST .e
700 x x .CHICKEN ‘ . .
x x X
X
x x MEDIAN ‘ x "
xcHIcKEN " x
2' x x x x
a:
u: 0
2 , . o O
I: o 0 °
510' FIRST
° ° CHICKEN . ° ° °

0

5:00
I4 I6 I8 2022 2426 28 30 2 4 6 8 I0
DAY OF MONTH

FIG. 5. ROOSTING TIME VERSUS DAY OF MONTH
UNDER NATURAL LIGHT CONDITIONS FOR
PERIODS FROM APRIL I4-25,AND APRIL 30—-
MAY 6.

78

2x = 207 X = 11.5

2x2 = 3,357 V = 111.9

ZY = 75'4

2Y2 = 3h,209

:XY = 8,332

2 - ZXZY/N 8,332 - 156,078/18 _ -339

 

- —— = -O.3LI7
z 2 - (mg/N 3.357 - Imam/18 976

 

then:

T? + b(X - '55) = I11.9 - 0.3LI7(x -11.5)

.<
II

Two of the three slopes for roosting time vs day
are negative. Only the slope of the first chicken on
the roost is positive and that one is only slightly
positive.

From this investigation it would appear that no
correlation exists between time of roosting and sunset
time. Therefore, the act of roosting must be the result

of some other factor than time of day.

79
Maia of Roasting Light Intensity Plots of light
intensity and number of chickens on roost vs time of day
are presented for two different days in Figs. 6 and 7.
Figure 6 is for a clear day at roosting time and Fig. 7
is for an overcast day. The rate of change of light
intensity is constant for the two days represented.
Differences in light intensities during roosting exist
between the two representative days.

.‘ The results of the preliminary investigation indi-
cate that chickens roost at a different light intensity
on a clear day as compared to an overcast day. The
light intensity of roosting for clear days and for cloudy
days is presented in Table‘VlIl. This is an arbitrary
division of clear and cloudy days with a considerable
variation of light intensity present in each category.
This investigation indicates only that a chicken roasts
at a light intensity dependent upon the average light
intensity to which he has become adapted during the day.
However, it does not establish whether the act of roosting
is the result of’a rate of change of light intensity or

the differential change in levels of illumination.

 

 

 

 

3’, 6 _ MAY 2, |960
é SUNSET—7:39
“ CLEAR
8
p-
): ”Vr I5 0
*- ~3Ir x °
(75 )r 005 m
E 3 — o“ 9 2
p. O
E a '0
«*6 g
3 0? x
3 9"“ - 5 93.:
| n— “\I“ U
0 l 1 l l l l l .
5:40 5:50 6:00 640 6:20 6:30 6:40 6:50 7:00 7:IO 7:20
TIME, P. M.

FIG. 6. LIGHT INTENSITY AND NUMBER OF CHCKENS 0N ROOST DURING
ROOSTING TIME FOR A CLEAR DAY

 

 

 

 

 

 

 

m 6 _. APRIL I6, I960 -
IL!
5' SUNSET-7:2I
z
4 5 — OVERCAST ’\ -- 20
o ‘J
'—
o
8 4 I;

- I5 0
,- 8
I:
s 3 s
:2 —l0 2
Z 2 In
5; :3
:2 ' 5 5
.1 I

I
O 1 :30
5:40 5:50 6:00 6:!0 6:20 6:30 6:40 6:50 7:00 7:10 7:20

TIME, RM.
FIG. 7. LIGHT INTENSITY AND NUMBER OF CHICKENS 0N ROOST DURING
ROOSTING TIME FOR AN OVERCAST DAY

81

 

 

 

 

 

Table V111 Comparison of Roosting Light Intensities
for Clear and Cloudy Days
Median First Last
Weather Date chicken chicken chicken
on roost on roost on roost
Clear h-18 1.3 f.c. 3.u f.c. 0.13 f.c.

h-l9 3.0 3.8 0.75

h-20 1.0 2.7 0.35

h-Zl l.h 3.2 0.30

h-22 2.2 3.6 0.20

h-23 1.3 3.7 0.80

5-1 2.h h.2 1.h0

5-2 2.7 h.h 0.90

5-3 2.7 LI.S 0.60

Sou 1.3 2.9 0.70

Average 1.9 3.6 0.61
Cloudy h-lh 0.80 1.05 0.25
h-lS 0.h5 1.30 0.25

h-l6 0.25 0.55 0.15

h-17 1.10 0.70 0.30

h-25 0.h0 2.60 0.20

h-30 0.h0 0.90 0.30

5-5 0.80 1.80 0.30

5-6 0.h0 0.70 1.10

.Average 0.58 1.20 0.36

 

 

82
Results of Risingfiinvestiggtiggg_
Investigation of the light intensity required by 20
White Rock hens to rise was conducted from.April 15 to
23, 1960 and April 30 to May 6, 1960. Data for this

investigation is presented in Table 1X.

.Analysis of Rising_Time vs Sunrise Time .A plot of sun-
rise time and rising time for the median chicken to
roost vs day of month is presented in Fig. 8. The slope
of the sunrise time vs day is -l.h3 for this period of
the year.

The slope of the time of the median chicken off the
roost vs day is -1.33. This slope is 7 percent less
than.the sunrise slope of -1.h3. Thus, the rising time
of the median chicken correlates quite closely
‘with the sunrise time. The calculation of the slape
of the rising time was determined from the same rela-
tionships as the slope of the roosting time diacussed
previously.

One of the possible reasons for the high correlation
between sunrise time and time of the median chicken to

rise is that the light intensity during darkness is

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85
fairly uniform regardless of the prevailing weather con-
ditions. The chickens become adjusted to approximately
the same level of light intensity each night and there-
fore rise at approximately the same light intensity every
day. The rising light intensitnyr the first few
chickens off the roost remains fairly constant. However,
there is still a considerable difference in the rising
light intensity for the last chicken off the roost. This
appears to be an effect of the degree of cloudiness.
Apparently, some chickens do not respond to a change
in light intensity from low levels of illumination to

high levels as quickly as other chickens.

:EEELXP‘S of Rising Light Intensity' Plots of the light
intensity and number of chickens off the roost are pre-
sented for two different days. Figure 9 is for April 17,
1960 which was an overcast morning, and Fig. 10 is for5
May h, 1960 which was a clear morning. There is only a
slight difference in rising intensities for the first
chicken off the roost for the two days, 0.05 footcandles
on April 17 and 0.03 footcandles on May 5. There is

considerably more difference in the light intensity for

 

 

 

 

 

 

 

 

 

 

 

 

 

2.0
APRIL I7, I960
_
3 I”; SUNRISE-5:54
-J I—
0
C2) 0 OVERCAST 20
q a:
Q I-
I- Li.
C Ii. I—
o - ° 8
u. g '58
,:I.O- g u.
g 2 ‘6
- 1:
E t: '03
i. :5 e
I - m '15:
o z 0151‘“ 0
:1 b a LIGHT mTE
00 i I I I I l I I O
5330 5:40 5350 6:00 6=IO 6:20 6330 6:40 6150 7:00 7:I0
TIME, A.M.
FIG. 9. LIGHT INTENSITY AND NUMBER OF CHICKENS OFF ROOST
DURING RISING TIME FOR AN OVERCAST DAY
2.0
_ MAY 4, I960 ‘
In SUNRISE-5:29
3 —
0 CLEAR —20
3 _.
o
.—
8 —
,L - I5
,, I.O -—
).
I:
3 - -1 I0
1.1.1
I- —
'2’
I- — -I 5
1'3 —
5:00 530 5120 5:30 5:40 5150 6:00 6=I0 6:20 6130 62

FIG. IO.

TIME, A. M.

LIGHT INTENSITY AND NUMBER OF- CHICKENS OFF ROOST

DURING RISING TIME FOR A

CLEAR DAY

CHICKENS OFF ROOST

87
the median chicken off the roost, 0.05 footcandles on
.April 17 and 0.125 on May h. On.April 17 a reading of
0.08 footcandles was recorded for_the last chicken off
the roost as compared to 1.70 footcandles on May k.
.Apparently the last chickens to rise are affected more

by the degree of cloudiness than the earlier ones.

Comparison of Rising;vs goosting;lntensigy

There is a difference between roosting and rising
light intensities for chickens. In general, chickens
rise at a much lower light intensity than the light
intensity at roosting. The lowest recorded light inten-
sity for the median chicken roosting was 0.h0 footcandles
as compared to the highest rising light intensity of 0.16
footcandles. The lowest light intensity for the last
chicken on the roost was 0.13 footcandles as compared

to the highest for rising of 0.05 footcandles for the

first chicken off the roost.

variation of Light Intensity in Pen 205
A weston footcandle meter was used to determine the

light intensity in various parts of the pen shown in

88
Fig. 11 on a uniformly overcast_day. The readings taken
at the east window at 3:00 p.m. were much higher than the
rest of the pen. The phototube detected an average light
intensity of 3.0 footcandles for the pen. The visual
angle of the tube did not include the darkest area of
the pen (the nesting area). This area of the pen had
less than 0.1 footcandle. The chickens tended to con-

gregate in the areas of higher light intensity.

Conclusion
.Apparently, chickens respond to a lower light inten-
sity after becoming adapted to a low level of illumina-

tion than if they had become adapted to a higher level

of illumination. This is evidenced by the difference
between light intensities of rising and roosting. .Also,
the differences of roosting light intensities between
overcast weather and clear weather tend to substantiate
this hypothesis.

This investigation indicates that the act of roosting

. t

i
(I

or rising is not directly correlated with the ime of *

., 5'0... ,
V '0‘f‘Afi-I.

sunset 0r sunrise. .The effects of changes in light in-

'I
A ' ’.

tensity appear to be more important in determining when

when a chicken is activated to roost or rise.

89

 

 

 

 

N
' D I 3 4
20 0.2FZC.
220 l
2 l
\ 230. I
0' \\ z
3.0 //
5
FIG. II. VARIATION OF LIGHT INTENSITY IN PEN

205 FOR A'. UNIFORMLY OVERCAST DAY
(APRIL 26, I960) WITH THE PHOTOTUBE

READING 3.0 FOOTCANDLES

9i

INVESTIGATION OF RISING.AND ROOSTING
LIGHT INTENSITY

The results of preliminary tests indicated that there
were differences in roosting light intensity between
cloudy days and bright days under the natural daylight
conditions existing at the commercial house. However,
the light intensity varied considerably. The degree of
cloudiness changed from day to day and hour to hour,
thereby causing changes of light intensity in the pen.
Also, the rate of change of light intensity at roosting
time was dependent upon the degree of cloudiness.

.A different experiment with more precisely control-
led dependent variables was developed. The objective
of this experiment was to test the hypothesis that a
chicken roosts at a light intensity dependent upon the
light intensity to which he has become adapted.

The requirements for this experiment were:"'
(1) Pens sealed from exterior sources of light,
(2) Pens where light intensities could be adjusted

at any intensity between one and thirty foot-

candles.

92
(3) Method of observing roosting and rising of
chickens,
(h) Constant length of light period,
(5) Constant rate of change of light intensity

at roosting and again at rising.

Design of the Experiment

Location The experiment was conducted in five pens of
the Experimental House of the Poultry Science Depart-
ment as shown in Fig. 12. Ten White Rock hens of the
same strain as the ones used in the preliminary tests
were used in each pen.

The Experimental House has a straw loft and windows
facing south. Five pens were sealed from outside light
by tacking roofing paper over the cracks. Two sheets
of black plastic were placed over the windows to pre-
Vent outside light from reaching the pens. The plastic
sheets were lapped so that observations could be made
by pulling open one of the sheets.

.Artificial Lights One hundred twenty volt incandes-

 

cent filament lamps were used to provide artificial

93
light for each of the five pens. Table X shows the

wattage of lamp used in each pen during each three day

test.

 

Table X Wattage of Lamp Used in Each Pen for Tests

 

 

 

lest £22_l Pen 2 Pen 3 £22_& .222_§
No.1 25 W 150 W 200 W 60 W 100 W
2 200 60 25 100 150
3 100 200 60 150 25
u 150 25 100 200 60
5 60 100 150 25 200

 

The duration of the full intensity light period was
13 hours per day, 8:30 a.m. to 9:30 p.m. .At rising time
the light intensity increased frOm 0.0 footcandles at
7:55 a.m. to full light intensity for each pen at 8:30
a.m. During roosting the light intensity changed from
full intensity at 9:30 p.m. to 0.0 footcandles at
10:00 p.m.
.Apparatus The light intensity in the pens was lowered

by reducing the line voltage to the lamps by means of

 

94

 

EXPERILENTAL POULTRY HOUSE WITH
BLACK PLASTIC OVER WINDOWS OF TEST
PENS

 

VOLTAGE CONTROL APPARATUS USED
AT ROOSTING AND RISING TIMES

 

95

a Variac. The rotor of the‘Variac was turned at a con-
stant rate by a series of gears driven by an electric
motor shown in Fig. 13. A Graham transmission was used
to switch the direction of rotation of the rotor, and
to control the rate of increase or decrease in voltage.
Footcandle readings were made with a Weston Foot-
candle Meter Model 6ih. Brightness measurements were
made with a Spectra Brightness Spot Meter with readings

in footlamberts.

Calibration of Lightlntensity vs Volts
Footcandle readings were obtained in several areas
of each pen for different voltages under the five
treatments. in Fig. 1b are footcandle values measured
at the height of a chicken directly under the lamp for

each pen treatment.

Procedure

 

The standard procedure for each test period was:
(1) Start stop watch shortly before each test
started (checked with Western Union time).

(2) Record line voltage and stop watch time.

(3)
(II)

(5)

(6)

96

Record time at which motor was turned on.
Record both number of chickens on or off
roost and stop watch time for each pen.
Repeat N0. 2 and No. u until all chickens
are on or off roost.

Determine light intensity at which each
chicken gets on or off roost from Fig. 1h.

Daily Results

 

An example of the data for the hens roosting in

Pen Number 2 with 150 watt lamps is presented in Table

XI. First, the light intensity in footcandles for each

time of change in number of chickens on the roost was

 

Table X1 Sample of Daily Results for Chickens Roost-

ing in Pen No. 2 With 150 Watt Lamps

 

 

 

 

Time, Light Intensity, Number on SIOpe
Min Footcandles Roost
T I N b

15.1 3.6 3

18.1 2.0 6

21.5 101 8

23.3 0.7 10

Average 1.9 6.8 . -0.h36

 

 

97

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98

obtained with the aid of the curves in Fig. lb. Second,
the average light intensity at roosting was determined.
Next, the average number of chickens on the roost (off
the roost for rising) was determined. The slope of the
number of chickens on the roost vs light intensity was
determined from the same formula as used in the prelimi-
nary results.

Results

The results of the experiment for roosting are pre-
sented in Table X11. Average light intensity (in foot-
candles), average number of chickens on the roost, and
slope of roosting are represented for each day of the
experiment.

.An analysis of variance showed that there were sig-
nificant differences at the 5 percent level between
treatments for all three factors: light intensity,
number on roost, and slope. No significant difference
was found between pens. A summary of the significance
between treatments is given in Fig. 15. The line over
the values indicates no significant differences between

treatments.

99

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25 W 60 W IOO W I50 W 200 W

I.25 2.26 3.57 5.25 7.20
O I 2 3 4 5 6 7 8

AVERAGE ROOSTING LIGHT INTENSITY, FOOTCANDLES

 

200 W
’ I00 W I50 W 60W 25 W
6.0 6.5 6.8 SJ
5 6 7 8 9

AVERAGE NUMBER 0N ROOST

 

 

200 w I50 w Ioow ’60 w 25 w

-0.77 -0.62 -I.22 -I.84 -2.96
0 -I.0 02.0 - -3.0

SLOPE 0F ROOSTING

FIG. I5. SUMMARY OF SIGNIFICANT DIFFERENCES
BETWEEN LIGHT TREATMENTS FOR ROOSTING.
LINES OVER VALUES. INDICATE N0 SIGNIFICANT
DIFFERENCES BETWEEN TREATMENTS.

101

For light intensity treatments, no significant dif-
ference was found between the 25 watt - 2 footcandle
and 60 watt - 5.5 footcandle treatments and between
the 60 watt - 5.5 footcandle and 100 watt - 12 footcandle
treatments. There were significant differences between
all other treatments.

For the average number of chickens on the roost,
there are significant differences between the 25 watt -
2 footcandle treatment and the other four treatments.

No significant differences exist between any of the
four higher light intensity treatments.

The slope for the 25 watt - 2 footcandle treatment
is significantly different than the 100 watt - 12 foot-
candle, 150 watt - 20 footcandle and 200 watt - 30
footcandle treatments, but not significantly different
from the 60 watt - 5.5 footcandle treatment. There are
no significant differences between the other treatments.

The results for the rising experiments are presented
in Table X111. No significant differences were found
between any of the light treatments for either the

average light intensity, average number off the roost,

102

or average slope. Only pen number one was significantly
different from other pens for number of chickens off the
roost.
Discussion of Results

The results indicate that the following hypothesis
is correct: .A chicken roosts at a light intensity
dependent upon the light intensity to which he has
become adapted. The proof of this hypothesis comes
from the fact that there is a significant difference
between most of the light treatments.

The analysis of variance of average roosting
light intensity showed that the 20 footcandle and 30
footcandle treatments were significantly different from
all other treatments. Daily average light intensity for
each treatment varies too much to be significantly dif-
ferent for the treatments at the lower light intensities
of 2 and 5.5 footcandles and 5.5 and 12 footcandles.
However, the means of the average light intensity for
each treatment are distinctly different and indicate
that chickens roosted at a light intensity dependent

upon the light intensity treatment.

103

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The analysis of variance for average number of chickens
on the roost showed that only the 2 footcandle treat-
ment was significantly different from the other treatments.
lfNo significant difference was found between the other
treatments. .Actually, several chickens in the 2 foot-
candle treatments were consistently on the roost before
9:30 p.m. when the light intensity started to change.
This caused the average number on the roost to be higher
for the 2 footcandle treatment than for.the.other treat-
ments. The other treatments had only a few (zero, one,
or two) chickens on the roost at 9:30 p.m. .Apparently
the chickens in the 2 footcandle treatment were antici-
pating the onset of darkness. .At least they were tired
of struggling in the dark environment. Observations of
activity in the two footcandle treatment pens showed
that the hens were sluggish as compared to the hens in
the higher light intensity pens.

The results indicate that the slope of roosting is
not affected significantly by the different light treat-
ments. Only the 2 footcandle treatment is significant

from the 12, 20, and 30 footcandle treatments. 'The

105
averages of the slopes are distinctly different from
each other. However, the variation of the slopes within
the treatments is high, causing the average slopes of
four of the five treatments to be not significantly
different from each other. The above is probably an
indication that a chicken acts as an individual and is
not dependent entirely on the action of the group.

The results of the rising experiments showed no
significant difference between any of the treatments
for either average rising light intensity, average
number off the roost, or average slope. For rising,

' the chickens reacted similarly, regardless of treatment,
since each pen of chickens had been subjected to the
same light intensity (total darkness). .Apparently,

the act of rising took place shortly after the time
when the chickens first could distinguish other objects
in the room, such as a feed trough or even another

chicken off the roost.

106

CCMPARISON 0F INCIDENT LIGHT AND REFLECTED LIGHT

The footcandle meter is a common instrument for
measuring light intensity in a chicken pen. This meter
measures the incident light in footcandles. However,

a chicken, or even a person, does not see the incident
light, but the reflected light. Objects, such as
feeders, nests, roosts, and other chickens, reflect the
incident light. Objects vary in their ability to
reflect light. Light colored objects reflect more
incident light than the dark objects. Thus, a discrep-
ancy exists between what a chicken sees and what is
commonly measured in a poultry house wdth a footcandle
meter.

The reflectance of the surroundings in a poultry
house should be measured instead of the incident light.
Some interesting results were obtained when reflectance
readings in footlamberts were made. (See Table XV).
A.footlambert is a unit of reflected light egual to a
footcandle. White chickens within a pen reflected more
footlamberts than any other object in the room. The

light sources are the brightest objects in the room

 

107
ranging from 3,300 footlamberts for the 25 watt lamp to
2h,000 footlamberts for the 200 watt lamp. The reflect-
ance from.the chickens at the center of the floor under-
neath the lamps was l.h footlamberts in the 25 watt pen
and approximately 15 footlamberts in the 200 watt pen.
Other objects in the room had low reflectances from 0.1
footlamberts to 0.6 footlamberts in the 25 watt pen,
and from 1.3 footlamberts to 8.0 footlamberts in the
200 watt pen. 2

Table XIV gives the footcandle readings in the
various psns.as taken at the points shownuin Fig. 16.
The footcandle readings can be compared with the foot-
lambert readings in Table XV. The footcandle readings,
are higher than the footlambert readings due to the

low reflectance of the surroundings.

108

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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FIG. I6. LOCATION OF FOOTOANOLE READINGS IN PENS OF EXPERIMENTAL
HOUSE
Table XIV Footcandle Readings at Looatieao shown in Fig. 16 for
the Verieao Leap Hattaooe. footcandle Motor Hes Held
Perpendicular to Light Source at Level of Litter and
nun-uninPUh
LII, Location of headings
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110

CONCLUSIONS
As a result of the investigations of-roosting and
rising light intensities, the following conclusions
can be made:

(1) under natural light conditions roosting time
does not correlate with sunset time for periods
of less than one month.

(2) Chickens roost at a lower light intensity on
a cloudy day than on a clear day.

(3) The rising light intensity is.much lower
than the roosting light intensity.

(h)IA correlation exists between sunrise time
and rising time under natural light condi-
tions.-

(5) The hypothesis is correct that chickens roost
at a light intensity dependent upon a light
intensity to which they have become adapted.

(6) The rising light intensity is not significantly
different for the various treatments due to
chickens becoming adapted to the.same light

intensity (absence of light) for each treatment.

5

 

111

(7) Measuring the surroundings in terms of reflected
"light (footlamberts) is a more realistic approach
to studying poultry house lighting, than by

measuring the surroundings in terms of incident

light (footcandles).

112-
FUTURE lNVESTiGATlONS
More fundamental facts on the effects of light on
chickens are needed. The underlying reasons of why and
how chickens react to light need to be investigated.

Further investigations are needed on the effect of

light intensities on the roosting of chickens.

(l) The effect of different rates of change of
light intensity on the roosting of chickens
should be investigated.

(2) The investigation of the effect of higher
light intensities on the roosting light
intensity of chickens, perhaps up to 10,000
footcandles, is needed. .Also, the effect of
higher light intensities on some of the
performance factors such as egg production,
feed conversion, and growth should be inves-
tigated.

(3) A.study of certain responses to light of the
different breeds of chickens is needed. The
lighter breeds, such as White Leghorns, may

respond to a light change differently than

 

113

the heavier breeds.

(u) The threshold light intensity for the cones
in the retina is needed. Perhaps, this is
the point, the transition between rod and
cone vision, which causes chickens to rise. r
This same point may be higher for roosting
and causes the chickens to roost at a higher
light intensity than the light intensity at
rising.

(S) The length of time for a chicken to adapt
to an environmental change in light inten-
sity should be investigated.

(6) Determine whether incident light or reflected
light is the better criteria for measuring

light intensity for poultry lighting.

2.

10.

11.

12.

11h
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