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Clutch Length in Relation to Period of Illumination in the Domestic Fowl
POULTRY S C I E N C E September, 194.1, Vol. XX, N o . 5
T.
C.
BYERLY AND 0 .
K.
MOORE
University of Maryland (Received for publication January 8, 1941)
I
T IS well known that the rate of egg production in the domestic fowl may be stimulated temporarily during seasons of normally short daylight periods by increasing the length of the daylight period with artificial light. Such stimulation is usually followed by a decline in egg production below the normal rate. Payne and Simmons (1934) presented an excellent paper on this subject and reviewed the literature to that date. Whetham (1933) showed that rate of egg production increases during seasons of increasing daylight in widely separated latitudes. Decline in rate of production begins before maximum daylight period is reached, however. . The relationship of light to the ovulation cycle in the fowl is less well understood. Atwood (1929) showed that successive eggs in a clutch are usually laid at successively later hours in the day. An egg laid after 2 p.m. under natural day and night conditions is usually followed by a day during which no egg is laid, thus terminating the clutch. Warren and Scott (1936) reported that the onset of darkness seems to be a factor in termination of the clutch of eggs and the consequent restriction of egg laying in
the hen to the daylight period. These workers showed that hens would lay at any hour of the day under continuous artificial light and only at night under reversal of daylight and darkness. Some clutch terminations occurred independently of the light factor, however. Warren and Scott found evidence that the effect of light on laying reaction was psychological. The present paper presents the results of experiments undertaken to determine the effects on clutch length of reducing the daily lighted period to the minimum sufficient for adequate feed intake, reported by Burmester and Card (1939) 6 hours in each 24 for mash feeding, and to determine whether clutch length may be lengthened by subjecting birds to alternate light and dark periods totaling 26 hours. The 26hour day was chosen because this is about the average period elapsing between successive eggs in clutches during periods of normal rapid production. It was postulated that a 26-hour day should produce an increase in clutch length if darkness is a purely limiting factor while the 24-hour day with only six hours of light should reduce clutch length if absolute light period is also a limiting factor.
[387]
Downloaded from http://ps.oxfordjournals.org/ at University of Alberta on April 26, 2015
Clutch Length in Relation to Period of Illumination in the Domestic Fowl
388
T. C. BYERLY AND O. K. MOORE TABLE 1.—Clutch length and rale of production in relation to period of illumination {experiment 1)
Measure of egg production Maximum clutch length Average clutch length Percent production per 24-hour period
6 hours light= 18 hours darkness
Natural JulyAugust day and night periods
Continuous light.
14 hours light= 12 hours darkness
16 2.16±0.149
11 2.25±0.166
9 2.60 + 0.100
31 4.50 + 0.536
38.8
48.3
58.3
71.6
MATERIAL AND METHODS
of the first experiment were used in the 14 hours light-10 hours darkness and 14 hours light-12 hours darkness groups, respectively, of the second experiment. The birds placed in each second experiment group had approximately equal egg production during the first experimental period. The natural day-night group were birds in this same group in the first experiment. All artificially lighted birds received 14 hours light-10 hours darkness in the interval between first and second experiments. The 14 hours light-12 hours darkness group of the second experiment occupied the dark room occupied by the 6 hours light-18 hours darkness group during the first experiment. The 14 hours light-10 hours darkness group occupied the dark room occupied by the 14 hours light-12 hours darkness group during the first experiment. RESULTS
Data obtained in the first experiment are summarized in Table 1. It will be noted that maximum clutch length was very much greater in the 14 hours light-12 hours darkness group than in any of the others. Aver-
TABLE 2.—Clutch length and rate of production in relation to period of illumination {experiment 2)
Measure of egg production
Natural Sept.-Nov. day and night periods
10 Maximum clutch length Average clutch length 2.10 + 0.147 Percent production per 2444.6
14 hours light= 10 hours darkness
14 hours light = 12 hours darkness
Yearlings
Pullets
Yearlings
Pullets
8 1.83 + 0.093
5 2.04 + 0.300
42 5.14 + 0.893
17 5.42 + 1.12
43.5
64.8
63.6
83.6
Downloaded from http://ps.oxfordjournals.org/ at University of Alberta on April 26, 2015
Most of the data were obtained from yearling fowl from the sex-linked cross New Hampshire male X Barred Plymouth Rock females. The remainder of the data were obtained from pullets of the same breeding. The first experiment began on July 3, and terminated August 25, 1940. The second experiment began September 18 and terminated on November 10, 1940. For the first experiment, three lots of 17 yearling females each were subjected to normal day and night periods, six hours light and 18 hours darkness, and continuous lighting, respectively. A fourth lot of 11 yearling females was subjected to alternate periods of 14 hours light and 12 hours of darkness. The birds which received normal day and night periods were housed in an ordinary laying house while the other lots were confined to cages. All were given the Maryland Agricultural Experiment Station laying mash. During lighted periods, the intensity of illumination which the caged birds received was about 11 foot candles. Five yearlings which received 14 hours light-12 hours darkness and nine yearlings which received continuous light during the period
CLUTCH LENGTH IN RELATION TO ILLUMINATION IN THE DOMESTIC FOWL
DISCUSSION These data show conclusively that it was possible to lengthen the clutch by synchonizing dark and light periods with the hen's natural ovulation cycle. Rate of production was materially increased in the 14 hours light-12 hours darkness groups in both experiments over production with continuous light, with 14 hours darkness-10 hours light, or under natural summer and fall day and night periods. This increase in length of clutch with its secondary increase in rate of production was apparently brought about in two ways. First, the limiting effect of the onset of darkness soon after the laying of an egg, shown by Warren and Scott (1936) to be a factor in terminating a rlntrh ma» at least partially removed-This thesis might be better stated conversely; egg laying and ovulation usually were followed shortly by a lighted period of sufficient length for stimulation, indirectly through the eye and the pituitary, of ovarian development. Slightly over 60 percent of the eggs laid by > the 14 hours light-12 hours darkness groups were laid in the dark, usually, however,
within two hours of the end of the dark period. On the other hand, about 75 percent A of the final eggs in the various clutches were laid during the lighted period. Obviously, this limiting effect of darkness must be upon either the growth of ova or on some stage of their maturation prior to ovulation, since laying in thp HarV -mac regularly followed by ovulation.. This is in accord with the observations of Warren and Scott (1936) who found that reversal of day and night required a minimum of 60 hours to reverse the time of egg laying. These workers suggested that the beginning nf the rapid phase of yolk growth might be the critical stage. In the present experiments, most of the eggs were followed by the maximum lighted period and when laying occurred toward the end of the lighted period, the clutch was usually terminated.
-
The birds which received 6 hours light-18 hours darkness usually laid before the lighted period so that in their case, too, laying was usually followed by maximum lighted period. This may account for the fact that their clutches were no shorter than those of normally lighted birds. The 6 hours light-18 hours darkness birds be- J^ gan to molt heavily and most of them ceased to lay before the end of the first experiment. Second, the rhythmic use of 14 hours light and 12 hours darkness apparently prolonged cycles without producing refractori-_ ness to light, stimulation. I t is common experience that stimulating egg production £? by use of artificial light is usually followed by decline in later egg production. In experiment 1, the continuously lighted birds laid at a rate of 76 percent during the first 'in davs ot the experiment but had fallea. t_r> .SO percent during the final 10-dav period. The 14 hours light-12 hours darkness group laid 68 percent per 24 hours during the first ten 26-hour periods and at an iden-
Downloaded from http://ps.oxfordjournals.org/ at University of Alberta on April 26, 2015
age clutch length was significantly greater in this group than in any other group. The average clutch length for the continuously lighted group was slightly longer than that for the six hours light or the natural daylight group. These differences were of border line significance. The data obtained in the second experiment are summarized in Table 2. Maximum clutch length and rate of production were much greater for the 14 hours light-12 hours darkness groups than for the other comparable groups in the second experiment. Average clutch length was significantly greater for both yearlings and pullets in the 14 hours light-12 hours darkness groups than for any of the other groups.
389
390
T. C. BYERLY AND 0. K. MOORE
length to maintain pituitary and consequently ovarian activity shortly after ovulation. 2. By permitting the birds adequate rest periods and thus delaying the onset of refractoriness. LITERATURE CITED
Atwood, H., 1929. A study of the time factor in egg production. W.Va. Agr. Exp. Sta. Bui. 223:1-11. Burmester, B. R., and L. E. Card, 1939. The effect of restricted feeding time on food intake, body weight, and egg production. Poult. Sci. 18:402. Card, L. E., B. R. Burmester, and H. M. Scott, 1937. Some effects of artificial light on time of laying. (Abstract) Poult. Sci. 16:353. Payne, L. F., and L. J. Simmons, 1934. Management of Leghorn hens and pullets with and without artifical lights. Poult. Sci. 13:323-332. Warren, D. C , and H. M. Scott, 1936. Influence of light on ovulation in the fowl. J. Exp. Zool. 74:137-156. Whetham, E. O., 1933. Factors modifying egg production with special reference to seasonal changes. Jour. Agri. Sci. 23:383-411.
Downloaded from http://ps.oxfordjournals.org/ at University of Alberta on April 26, 2015
tical rate during the final ten 26-hour periods. During the second experiment, the 14 hours light-10 hours darkness group of yearlings laid at a rate of 60 percent during the first 10 days of the experiment but fell to 36 percent during the last 10 days. The yearling group which received 14 hours light and 12 hours darkness laid at the rate of 60 percent per 24 hours during the first 10 periods and 64 percent during the final 10 periods. The naturally lighted controls laid 54 percent during the first 10-day period of the first experiment and had dropped to 40 percent during the final 10-day period of the second experiment, a normal seasonal decline. CONCLUSION It is therefore concluded that the use of 14 hours light and 12 hours dark periods lengthened clutches by, 1. Assuring a lighted period of sufficient
T.
C.
BYERLY AND 0 .
K.
MOORE
University of Maryland (Received for publication January 8, 1941)
I
T IS well known that the rate of egg production in the domestic fowl may be stimulated temporarily during seasons of normally short daylight periods by increasing the length of the daylight period with artificial light. Such stimulation is usually followed by a decline in egg production below the normal rate. Payne and Simmons (1934) presented an excellent paper on this subject and reviewed the literature to that date. Whetham (1933) showed that rate of egg production increases during seasons of increasing daylight in widely separated latitudes. Decline in rate of production begins before maximum daylight period is reached, however. . The relationship of light to the ovulation cycle in the fowl is less well understood. Atwood (1929) showed that successive eggs in a clutch are usually laid at successively later hours in the day. An egg laid after 2 p.m. under natural day and night conditions is usually followed by a day during which no egg is laid, thus terminating the clutch. Warren and Scott (1936) reported that the onset of darkness seems to be a factor in termination of the clutch of eggs and the consequent restriction of egg laying in
the hen to the daylight period. These workers showed that hens would lay at any hour of the day under continuous artificial light and only at night under reversal of daylight and darkness. Some clutch terminations occurred independently of the light factor, however. Warren and Scott found evidence that the effect of light on laying reaction was psychological. The present paper presents the results of experiments undertaken to determine the effects on clutch length of reducing the daily lighted period to the minimum sufficient for adequate feed intake, reported by Burmester and Card (1939) 6 hours in each 24 for mash feeding, and to determine whether clutch length may be lengthened by subjecting birds to alternate light and dark periods totaling 26 hours. The 26hour day was chosen because this is about the average period elapsing between successive eggs in clutches during periods of normal rapid production. It was postulated that a 26-hour day should produce an increase in clutch length if darkness is a purely limiting factor while the 24-hour day with only six hours of light should reduce clutch length if absolute light period is also a limiting factor.
[387]
Downloaded from http://ps.oxfordjournals.org/ at University of Alberta on April 26, 2015
Clutch Length in Relation to Period of Illumination in the Domestic Fowl
388
T. C. BYERLY AND O. K. MOORE TABLE 1.—Clutch length and rale of production in relation to period of illumination {experiment 1)
Measure of egg production Maximum clutch length Average clutch length Percent production per 24-hour period
6 hours light= 18 hours darkness
Natural JulyAugust day and night periods
Continuous light.
14 hours light= 12 hours darkness
16 2.16±0.149
11 2.25±0.166
9 2.60 + 0.100
31 4.50 + 0.536
38.8
48.3
58.3
71.6
MATERIAL AND METHODS
of the first experiment were used in the 14 hours light-10 hours darkness and 14 hours light-12 hours darkness groups, respectively, of the second experiment. The birds placed in each second experiment group had approximately equal egg production during the first experimental period. The natural day-night group were birds in this same group in the first experiment. All artificially lighted birds received 14 hours light-10 hours darkness in the interval between first and second experiments. The 14 hours light-12 hours darkness group of the second experiment occupied the dark room occupied by the 6 hours light-18 hours darkness group during the first experiment. The 14 hours light-10 hours darkness group occupied the dark room occupied by the 14 hours light-12 hours darkness group during the first experiment. RESULTS
Data obtained in the first experiment are summarized in Table 1. It will be noted that maximum clutch length was very much greater in the 14 hours light-12 hours darkness group than in any of the others. Aver-
TABLE 2.—Clutch length and rate of production in relation to period of illumination {experiment 2)
Measure of egg production
Natural Sept.-Nov. day and night periods
10 Maximum clutch length Average clutch length 2.10 + 0.147 Percent production per 2444.6
14 hours light= 10 hours darkness
14 hours light = 12 hours darkness
Yearlings
Pullets
Yearlings
Pullets
8 1.83 + 0.093
5 2.04 + 0.300
42 5.14 + 0.893
17 5.42 + 1.12
43.5
64.8
63.6
83.6
Downloaded from http://ps.oxfordjournals.org/ at University of Alberta on April 26, 2015
Most of the data were obtained from yearling fowl from the sex-linked cross New Hampshire male X Barred Plymouth Rock females. The remainder of the data were obtained from pullets of the same breeding. The first experiment began on July 3, and terminated August 25, 1940. The second experiment began September 18 and terminated on November 10, 1940. For the first experiment, three lots of 17 yearling females each were subjected to normal day and night periods, six hours light and 18 hours darkness, and continuous lighting, respectively. A fourth lot of 11 yearling females was subjected to alternate periods of 14 hours light and 12 hours of darkness. The birds which received normal day and night periods were housed in an ordinary laying house while the other lots were confined to cages. All were given the Maryland Agricultural Experiment Station laying mash. During lighted periods, the intensity of illumination which the caged birds received was about 11 foot candles. Five yearlings which received 14 hours light-12 hours darkness and nine yearlings which received continuous light during the period
CLUTCH LENGTH IN RELATION TO ILLUMINATION IN THE DOMESTIC FOWL
DISCUSSION These data show conclusively that it was possible to lengthen the clutch by synchonizing dark and light periods with the hen's natural ovulation cycle. Rate of production was materially increased in the 14 hours light-12 hours darkness groups in both experiments over production with continuous light, with 14 hours darkness-10 hours light, or under natural summer and fall day and night periods. This increase in length of clutch with its secondary increase in rate of production was apparently brought about in two ways. First, the limiting effect of the onset of darkness soon after the laying of an egg, shown by Warren and Scott (1936) to be a factor in terminating a rlntrh ma» at least partially removed-This thesis might be better stated conversely; egg laying and ovulation usually were followed shortly by a lighted period of sufficient length for stimulation, indirectly through the eye and the pituitary, of ovarian development. Slightly over 60 percent of the eggs laid by > the 14 hours light-12 hours darkness groups were laid in the dark, usually, however,
within two hours of the end of the dark period. On the other hand, about 75 percent A of the final eggs in the various clutches were laid during the lighted period. Obviously, this limiting effect of darkness must be upon either the growth of ova or on some stage of their maturation prior to ovulation, since laying in thp HarV -mac regularly followed by ovulation.. This is in accord with the observations of Warren and Scott (1936) who found that reversal of day and night required a minimum of 60 hours to reverse the time of egg laying. These workers suggested that the beginning nf the rapid phase of yolk growth might be the critical stage. In the present experiments, most of the eggs were followed by the maximum lighted period and when laying occurred toward the end of the lighted period, the clutch was usually terminated.
-
The birds which received 6 hours light-18 hours darkness usually laid before the lighted period so that in their case, too, laying was usually followed by maximum lighted period. This may account for the fact that their clutches were no shorter than those of normally lighted birds. The 6 hours light-18 hours darkness birds be- J^ gan to molt heavily and most of them ceased to lay before the end of the first experiment. Second, the rhythmic use of 14 hours light and 12 hours darkness apparently prolonged cycles without producing refractori-_ ness to light, stimulation. I t is common experience that stimulating egg production £? by use of artificial light is usually followed by decline in later egg production. In experiment 1, the continuously lighted birds laid at a rate of 76 percent during the first 'in davs ot the experiment but had fallea. t_r> .SO percent during the final 10-dav period. The 14 hours light-12 hours darkness group laid 68 percent per 24 hours during the first ten 26-hour periods and at an iden-
Downloaded from http://ps.oxfordjournals.org/ at University of Alberta on April 26, 2015
age clutch length was significantly greater in this group than in any other group. The average clutch length for the continuously lighted group was slightly longer than that for the six hours light or the natural daylight group. These differences were of border line significance. The data obtained in the second experiment are summarized in Table 2. Maximum clutch length and rate of production were much greater for the 14 hours light-12 hours darkness groups than for the other comparable groups in the second experiment. Average clutch length was significantly greater for both yearlings and pullets in the 14 hours light-12 hours darkness groups than for any of the other groups.
389
390
T. C. BYERLY AND 0. K. MOORE
length to maintain pituitary and consequently ovarian activity shortly after ovulation. 2. By permitting the birds adequate rest periods and thus delaying the onset of refractoriness. LITERATURE CITED
Atwood, H., 1929. A study of the time factor in egg production. W.Va. Agr. Exp. Sta. Bui. 223:1-11. Burmester, B. R., and L. E. Card, 1939. The effect of restricted feeding time on food intake, body weight, and egg production. Poult. Sci. 18:402. Card, L. E., B. R. Burmester, and H. M. Scott, 1937. Some effects of artificial light on time of laying. (Abstract) Poult. Sci. 16:353. Payne, L. F., and L. J. Simmons, 1934. Management of Leghorn hens and pullets with and without artifical lights. Poult. Sci. 13:323-332. Warren, D. C , and H. M. Scott, 1936. Influence of light on ovulation in the fowl. J. Exp. Zool. 74:137-156. Whetham, E. O., 1933. Factors modifying egg production with special reference to seasonal changes. Jour. Agri. Sci. 23:383-411.
Downloaded from http://ps.oxfordjournals.org/ at University of Alberta on April 26, 2015
tical rate during the final ten 26-hour periods. During the second experiment, the 14 hours light-10 hours darkness group of yearlings laid at a rate of 60 percent during the first 10 days of the experiment but fell to 36 percent during the last 10 days. The yearling group which received 14 hours light and 12 hours darkness laid at the rate of 60 percent per 24 hours during the first 10 periods and 64 percent during the final 10 periods. The naturally lighted controls laid 54 percent during the first 10-day period of the first experiment and had dropped to 40 percent during the final 10-day period of the second experiment, a normal seasonal decline. CONCLUSION It is therefore concluded that the use of 14 hours light and 12 hours dark periods lengthened clutches by, 1. Assuring a lighted period of sufficient