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Diurnal Activity Patterns of Broilers in a Controlled Environment
Diurnal Activity Patterns of Broilers in a Controlled Environment D. P. FOSHEE, D. M. CENTA, G. R. MCDANIEL AND C. A. ROLLO
Department of Psychology and Departments of Poultry Science and Agricultural Engineering, Auburn University, Auburn, Alabama 36830 (Received for publication May 8, 1970)
T
mination and two schedules of light change which have been demonstrated effective in increasing broiler growth under our laboratory conditions. METHOD AND PROCEDURE
Twelve hundred day-old broilers (600 males, 600 females) were randomly assigned by sex to twelve test chambers in the Avian Environmental Research facility on April 21, 1969. Attrition during the early phase of the experiment was equally distributed within chambers. The experiment was terminated June 17,1969. Environmental chambers provided 80 square feet of floor space, or approximately .8 square feet per bird. Temperature was set at 28°C. at beginning of experiment and lowered 3° per week until 21°C. ( ± 1°C.) was achieved. Noise was reduced significantly so that outside noises did not affect activity level of birds within the chamber. Relative humidity was maintained at 60 percent. Lighting (when used) was provided by a 25-watt overhead bulb and yielded a light level of 1^ foot candles measured 18 inches from floor. Four chambers were assigned to each of three experimental conditions. The "continuous" group had light for the entire experiment. The "IS minutes on—45 minutes off" group had light in recurring cycles of 15 minutes on and 45 minutes off. The "10 minutes on—70 minutes off" group had light in recurring cycles of 10 minutes on and 70 minutes off. Birds were weighed in bulk by chamber at termination of the experiment. Total weight of birds per cham514
Downloaded from http://ps.oxfordjournals.org/ at RMIT Central Library on July 1, 2015
HE objective of this study was to determine the patterning of diurnal activity of broilers in a controlled environment. Previous studies (Moore, 1957; Centa et al., 1969; Gore et al., 1969) have indicated that manipulation of background illumination and alternating periods of light and dark may effectively alter activity patterns and growth rates. Indications are that (1) relatively low levels of light are superior and (2) that activity may be synchronized by the use of a "change" cue. Centa et al. (1969) restricted both light and access to feed and found that light control alone was the significant variable. This was interpreted as the result of a direct effect upon activity of the birds. Cumulative sound level recordings of activity (and by inference feeding) patterns demonstrated that behavior was minimal during the no-light periods and maximal during light periods. Weaver and Siegel (1968) had previously reported findings similar to Centa et al. (1969) 14 hours light—10 hours dark control group. They commented that their continuous light provided at two intensities (8 hours high—16 hours low) yields a diurnal rhythm having peaks "less dramatic than those observed for broilers exposed to light and darkness." Weaver and Siegel interpreted these findings to suggest "that efforts should be made to minimize fluctuations of light intensity as they have a large influence on feeding rhythms which in turn effect growth." The paradigm of the present study provides contrasts of low-level continuous illu-
DIURNAL ACTIVITY OF BROILERS
RESULTS AND DISCUSSION Body Weight and Feed Efficiency. Means of body weight and feed efficiency by groups are presented in Table 1. Except for the very obvious sex effect, there were no significant differences between groups as indicated by an analysis of variance. As would be expected under the ideal conditions provided by the environment chambers both weight gain and feed efficiency were unusually good (Weaver and Siegel, 1968; Beane etal., 196S). Previous studies (Gore et al., 1969; Centa et al., 1969) had led the experimenters to predict that the weight gains would T A B L E 1.—Means for body weight (grams), feed efficiency, and testes weights (mg./lOO g.) for all groups at termination of experiment Testes Weight Light
Regime
Continuous 15-45 10-70 Pooled
Male Female r_ Mmc Grams
*£»*g£S Gain/Feed Grams
Mean
Standard Deviation
2,037
1,618
.518
55.3
7.26
2,044 2,077 2,053
1,610 1,608 1,612
.512 .530 .520
47.7 50.0 51.0
6.65 6.07
be ordered with the "10 minutes on—70 minutes off" group heaviest, "IS minutes on—45 minutes off" group intermediate, and the "continuous" group lightest. If one uses the Mann-Whitney U test (Mosteller and Bush, 1954) to evaluate these results, this order is significant for the males, but no difference exists for females. The lack of any more significant differences between groups is at variance with other studies from this laboratory. The only observation that can be offered at this point is that the rigid control of extraneous variables in this situation provides ideal conditions where differences would be extremely difficult to demonstrate. The exceptionally good gains would tend to support this interpretation. Endocrine Response. Mean testes weights are presented in Table 1. These data are calculated from a random sample of 10 birds from each chamber. Although the trend is in the expected direction, no statistical difference exists. As indicated by the standard deviations, testes weight is a very unstable indicant of maturity. It may be that the developmental process of birds at this particular age accounts for much of this variability. It can be seen that variability is greatest in the "continuous" group and least in the "10 minutes on—70 minutes off" group. Activity Patterns. Activity for all groups is presented in Figures 1 and 2. It should be noted that consideration is directed to the relative proportionality of the distribution over clock time. The method of recording utilized does not permit an assessment of absolute levels of activity. Figure 1 indicates that the distribution of total activity for the three groups in this study was fairly evenly distributed with no significant differences between groups. Peaks occur between 7-10 a.m. and between 3-8 p.m. Data from Centa et al. (1969) are presented as a reference to indi-
Downloaded from http://ps.oxfordjournals.org/ at RMIT Central Library on July 1, 2015
ber (grams) was divided by total weight of feed used (grams) in that chamber to determine feed efficiency. Continuous 24-hour recordings of sound level were obtained from each chamber on a random-day sampling schedule. Sound records of activity in each chamber were recorded by placing a Grason-Stadler microphone (Model #E7300A-1) against one wall of the chamber six inches above floor level. Impulses from the microphone operated a Grason-Stadler Voice Operated Relay (Model #E7300A-1), and the output counted. Each data point on the graphs represents an average of 12-24 recordings. Feed and water were supplied ad libitum, with caretaker services between 8-9 a.m. and 3-5 p.m.
ISIS
1516
D. P. FOSHEE, D. M. CENTA, G. R. MCDANIEL AND C. A. ROLLO
3-4
6-7 AM
9-10
12-1
3-4
CLOCK TIME SESSIONS
6-7
9-10
PM.
FIG. 1. Relative proportionality of activity distribution over time for groups (14 hour on—10 hour off group from Centa et al. (1969) is included for comparison purposes).
cate the distribution for a "14 hour on—10 hour off" control group typically used in this laboratory. These peaks correspond to times at which caretaker services were performed and were to some extent influenced by this intervention. However, direct observations indicate that these birds were extremely passive and no major change occurred when the caretaker entered the chambers. These peaks were also relatively long in duration to be accounted for on this basis. Figure 2 presents a breakdown for the "15 minutes on—45 minutes off" and "10 minutes on—70 minutes off" groups into proportions occurring in "on" and "off" periods. It can be seen that the stimulation change was very effective in controlling the
distribution with 3-4 times as much activity occurring in the short "on" periods (10 minutes or IS minutes) as in the longer "off" periods (45 minutes or 70 minutes). It will be noted that control is probably better in the "IS minutes on—45 minutes off" group than in the "10 minutes on—70 minutes off" group. The overall distribution of activity seems generally to support other diurnal findings (Siegel and Guhl, 1956; Weaver and Siegel, 1968). Similarly, it supports the results demonstrated by Meier (1969) for monkeys on a self-feeding cafeteria arrangement. These findings suggest that maximum broiler growth occurred when activity periods (and by inference feeding) were distrib-
Downloaded from http://ps.oxfordjournals.org/ at RMIT Central Library on July 1, 2015
12-1
1517
DIURNAL ACTIVITY OF BROILERS
o i
ce w Q.
> o < u. o
6
i-
5 Light on" Periods
cc o CL CL UJ
> £
fee
2
-I5min. on-45min.off
10 min. o n - 7 0 min. off "Light off" Periods
UJ
ce
12-1
3-4
6-7
9-10
12-1
3-4
6-7
9-10
PM.
AM CLOCK TIME SESSIONS
FIG. 2. Relative proportionality of activity distribution over time for groups plotted for "light on" and "light off" periods.
uted fairly uniformly over time. This should not imply that activity and feeding are uniformly distributed on a minute-byminute basis, but rather that maximally efficient short periods of feeding and inactivity are relatively uniformly distributed throughout the 24-hour day. This interpretation contradicts the suggestion of Weaver and Siegel (1968) that light fluctuations per se are detrimental. From our study it would appear that light fluctuations are of no consequence except in the manner in which they affect the distribution pattern of activity. SUMMARY
An experiment was conducted in a highly controlled environment to compare a lowlevel "continuous" light group and two
schedules of light change which had been demonstrated effective in increasing broiler growth. Diurnal activity patterns indicated that all three groups achieved relatively uniform distribution of activity periods over clock time. No significant differences were present in either body weight or feed efficiency, although both indices were exceptionally high indicating superior performance. Testes weight was utilized as an endocrine function indicant and yielded no significant differences. Trends may be cautiously interpreted as demonstrating anticipated effects of the schedules being utilized. These results were interpreted to support the suggestion that the primary factor affecting superior growth rates was the uni-
Downloaded from http://ps.oxfordjournals.org/ at RMIT Central Library on July 1, 2015
o cc
1518
D. P. FOSHEE, D. M. CENTA, G. R. MCDANIEL AND C. A. ROLLO
form distribution of activity throughout the 24-hour day.
periods
REFERENCES
Further Studies on the Nutritive Value of Opaque-2 Corn for the Chick1 J. B. FONSECA,2 J. C. ROGLER, W. R. FEATHERSTON AND T. R. CLINE Department of Animal Sciences, Purdue University, West Lafayette, Indiana 47907 (Received for publication May 11, 1970)
C
ROMWELL et al. (1967, 1968), working with young chicks, reported only slight differences in growth rate and feed conversion by the isonitrogenous substitution of opaque-2 corn for normal corn in corn-soybean meal diets of suboptimal protein content. However, when a deficiency of the first limiting amino acid in this type of diet, methionine, was corrected by supplementation, significantly better gains and feed conversions were observed with opaque-2 corn as compared with normal corn. Since supplementation of normal corn diets with lysine up to the level in opaque-2 corn diets resulted in equal performance, it was concluded that the beneficial effects of opaque-2 over normal corn is mediated 1 Journal Paper No. 4055 of the Purdue University Agricultural Experiment Station. 2 Present address: Institute de Zootechnia, Universidade Federal de Vicosa, Vicosa, Minas Gerais, Brazil.
solely through the higher lysine content of opaque-2 corn. Analyses of plasma amino acids revealed higher lysine levels in chicks fed opaque-2 corn as compared with chicks fed normal com. In the current studies, the nutritive value of opaque-2 and high protein opaque-2 corn, obtained by the introduction of the opaque-2 gene into an Illinois high protein strain, was studied in corn-soybean meal and corn-safflower meal diets. It was deemed advisable to use a supplemental protein source which is low in lysine (safflower meal) to circumvent using suboptimal protein levels in evaluating the corn. The work of several investigators (Young and Halloran, 1962; Valadez et al., 1965; Kuzmicky and Kohler, 1968a) has shown that the poor growth observed in chicks fed corn-safflower meal diets can be completely corrected by lysine supplementation, although feed conversion is usually slightly poorer as compared with a corn-soybean
Downloaded from http://ps.oxfordjournals.org/ at RMIT Central Library on July 1, 2015
Beane, W. L., P. B. Siegel and H. S. Siegel, 1965. Light environment as a factor in growth and feed efficiency of meat-type chickens. Poultry Sci. 44: 1009-1012. Centa, D. M., D. P. Foshee and J. R. Howes, 1969. Control of feeding behavior in poultry. Psychological Reports, 24: 153-154. Gore, W. E., D. P. Foshee and J. R. Howes, 1969. Effects of background illumination and lightdark period on weight gain in broilers. Poultry Sci. 48: 1282-1287.
Meier, G. W., 1969. Operant cycles and imitational learning in a social setting. Paper read to AAAS, Boston, December 26-31. Moore, C. H., 1957. The effect of light on growth of broiler chickens. Poultry Sci. 36: 1142-1143. Mosteller, F., and R. R. Bush, 1954. Selected Quantitative Techniques, in G. Lindzey (Ed.) : Handbook of Social Psychology, Volume I, Addison-Wesley, Cambridge, Massachusetts. Siegel, P. B., and A. M. Guhl, 1966. The measurement of some diurnal rhythms in the activity of White Leghorn cockerels. Poultry Sci. 45: 1340-1345. Weaver, W. D., and P. B. Siegel, 1968. Photoperiodism as a factor in feeding rhythms of broiler chickens. Poultry Sci. 47: 1148-1154.
Department of Psychology and Departments of Poultry Science and Agricultural Engineering, Auburn University, Auburn, Alabama 36830 (Received for publication May 8, 1970)
T
mination and two schedules of light change which have been demonstrated effective in increasing broiler growth under our laboratory conditions. METHOD AND PROCEDURE
Twelve hundred day-old broilers (600 males, 600 females) were randomly assigned by sex to twelve test chambers in the Avian Environmental Research facility on April 21, 1969. Attrition during the early phase of the experiment was equally distributed within chambers. The experiment was terminated June 17,1969. Environmental chambers provided 80 square feet of floor space, or approximately .8 square feet per bird. Temperature was set at 28°C. at beginning of experiment and lowered 3° per week until 21°C. ( ± 1°C.) was achieved. Noise was reduced significantly so that outside noises did not affect activity level of birds within the chamber. Relative humidity was maintained at 60 percent. Lighting (when used) was provided by a 25-watt overhead bulb and yielded a light level of 1^ foot candles measured 18 inches from floor. Four chambers were assigned to each of three experimental conditions. The "continuous" group had light for the entire experiment. The "IS minutes on—45 minutes off" group had light in recurring cycles of 15 minutes on and 45 minutes off. The "10 minutes on—70 minutes off" group had light in recurring cycles of 10 minutes on and 70 minutes off. Birds were weighed in bulk by chamber at termination of the experiment. Total weight of birds per cham514
Downloaded from http://ps.oxfordjournals.org/ at RMIT Central Library on July 1, 2015
HE objective of this study was to determine the patterning of diurnal activity of broilers in a controlled environment. Previous studies (Moore, 1957; Centa et al., 1969; Gore et al., 1969) have indicated that manipulation of background illumination and alternating periods of light and dark may effectively alter activity patterns and growth rates. Indications are that (1) relatively low levels of light are superior and (2) that activity may be synchronized by the use of a "change" cue. Centa et al. (1969) restricted both light and access to feed and found that light control alone was the significant variable. This was interpreted as the result of a direct effect upon activity of the birds. Cumulative sound level recordings of activity (and by inference feeding) patterns demonstrated that behavior was minimal during the no-light periods and maximal during light periods. Weaver and Siegel (1968) had previously reported findings similar to Centa et al. (1969) 14 hours light—10 hours dark control group. They commented that their continuous light provided at two intensities (8 hours high—16 hours low) yields a diurnal rhythm having peaks "less dramatic than those observed for broilers exposed to light and darkness." Weaver and Siegel interpreted these findings to suggest "that efforts should be made to minimize fluctuations of light intensity as they have a large influence on feeding rhythms which in turn effect growth." The paradigm of the present study provides contrasts of low-level continuous illu-
DIURNAL ACTIVITY OF BROILERS
RESULTS AND DISCUSSION Body Weight and Feed Efficiency. Means of body weight and feed efficiency by groups are presented in Table 1. Except for the very obvious sex effect, there were no significant differences between groups as indicated by an analysis of variance. As would be expected under the ideal conditions provided by the environment chambers both weight gain and feed efficiency were unusually good (Weaver and Siegel, 1968; Beane etal., 196S). Previous studies (Gore et al., 1969; Centa et al., 1969) had led the experimenters to predict that the weight gains would T A B L E 1.—Means for body weight (grams), feed efficiency, and testes weights (mg./lOO g.) for all groups at termination of experiment Testes Weight Light
Regime
Continuous 15-45 10-70 Pooled
Male Female r_ Mmc Grams
*£»*g£S Gain/Feed Grams
Mean
Standard Deviation
2,037
1,618
.518
55.3
7.26
2,044 2,077 2,053
1,610 1,608 1,612
.512 .530 .520
47.7 50.0 51.0
6.65 6.07
be ordered with the "10 minutes on—70 minutes off" group heaviest, "IS minutes on—45 minutes off" group intermediate, and the "continuous" group lightest. If one uses the Mann-Whitney U test (Mosteller and Bush, 1954) to evaluate these results, this order is significant for the males, but no difference exists for females. The lack of any more significant differences between groups is at variance with other studies from this laboratory. The only observation that can be offered at this point is that the rigid control of extraneous variables in this situation provides ideal conditions where differences would be extremely difficult to demonstrate. The exceptionally good gains would tend to support this interpretation. Endocrine Response. Mean testes weights are presented in Table 1. These data are calculated from a random sample of 10 birds from each chamber. Although the trend is in the expected direction, no statistical difference exists. As indicated by the standard deviations, testes weight is a very unstable indicant of maturity. It may be that the developmental process of birds at this particular age accounts for much of this variability. It can be seen that variability is greatest in the "continuous" group and least in the "10 minutes on—70 minutes off" group. Activity Patterns. Activity for all groups is presented in Figures 1 and 2. It should be noted that consideration is directed to the relative proportionality of the distribution over clock time. The method of recording utilized does not permit an assessment of absolute levels of activity. Figure 1 indicates that the distribution of total activity for the three groups in this study was fairly evenly distributed with no significant differences between groups. Peaks occur between 7-10 a.m. and between 3-8 p.m. Data from Centa et al. (1969) are presented as a reference to indi-
Downloaded from http://ps.oxfordjournals.org/ at RMIT Central Library on July 1, 2015
ber (grams) was divided by total weight of feed used (grams) in that chamber to determine feed efficiency. Continuous 24-hour recordings of sound level were obtained from each chamber on a random-day sampling schedule. Sound records of activity in each chamber were recorded by placing a Grason-Stadler microphone (Model #E7300A-1) against one wall of the chamber six inches above floor level. Impulses from the microphone operated a Grason-Stadler Voice Operated Relay (Model #E7300A-1), and the output counted. Each data point on the graphs represents an average of 12-24 recordings. Feed and water were supplied ad libitum, with caretaker services between 8-9 a.m. and 3-5 p.m.
ISIS
1516
D. P. FOSHEE, D. M. CENTA, G. R. MCDANIEL AND C. A. ROLLO
3-4
6-7 AM
9-10
12-1
3-4
CLOCK TIME SESSIONS
6-7
9-10
PM.
FIG. 1. Relative proportionality of activity distribution over time for groups (14 hour on—10 hour off group from Centa et al. (1969) is included for comparison purposes).
cate the distribution for a "14 hour on—10 hour off" control group typically used in this laboratory. These peaks correspond to times at which caretaker services were performed and were to some extent influenced by this intervention. However, direct observations indicate that these birds were extremely passive and no major change occurred when the caretaker entered the chambers. These peaks were also relatively long in duration to be accounted for on this basis. Figure 2 presents a breakdown for the "15 minutes on—45 minutes off" and "10 minutes on—70 minutes off" groups into proportions occurring in "on" and "off" periods. It can be seen that the stimulation change was very effective in controlling the
distribution with 3-4 times as much activity occurring in the short "on" periods (10 minutes or IS minutes) as in the longer "off" periods (45 minutes or 70 minutes). It will be noted that control is probably better in the "IS minutes on—45 minutes off" group than in the "10 minutes on—70 minutes off" group. The overall distribution of activity seems generally to support other diurnal findings (Siegel and Guhl, 1956; Weaver and Siegel, 1968). Similarly, it supports the results demonstrated by Meier (1969) for monkeys on a self-feeding cafeteria arrangement. These findings suggest that maximum broiler growth occurred when activity periods (and by inference feeding) were distrib-
Downloaded from http://ps.oxfordjournals.org/ at RMIT Central Library on July 1, 2015
12-1
1517
DIURNAL ACTIVITY OF BROILERS
o i
ce w Q.
> o < u. o
6
i-
5 Light on" Periods
cc o CL CL UJ
> £
fee
2
-I5min. on-45min.off
10 min. o n - 7 0 min. off "Light off" Periods
UJ
ce
12-1
3-4
6-7
9-10
12-1
3-4
6-7
9-10
PM.
AM CLOCK TIME SESSIONS
FIG. 2. Relative proportionality of activity distribution over time for groups plotted for "light on" and "light off" periods.
uted fairly uniformly over time. This should not imply that activity and feeding are uniformly distributed on a minute-byminute basis, but rather that maximally efficient short periods of feeding and inactivity are relatively uniformly distributed throughout the 24-hour day. This interpretation contradicts the suggestion of Weaver and Siegel (1968) that light fluctuations per se are detrimental. From our study it would appear that light fluctuations are of no consequence except in the manner in which they affect the distribution pattern of activity. SUMMARY
An experiment was conducted in a highly controlled environment to compare a lowlevel "continuous" light group and two
schedules of light change which had been demonstrated effective in increasing broiler growth. Diurnal activity patterns indicated that all three groups achieved relatively uniform distribution of activity periods over clock time. No significant differences were present in either body weight or feed efficiency, although both indices were exceptionally high indicating superior performance. Testes weight was utilized as an endocrine function indicant and yielded no significant differences. Trends may be cautiously interpreted as demonstrating anticipated effects of the schedules being utilized. These results were interpreted to support the suggestion that the primary factor affecting superior growth rates was the uni-
Downloaded from http://ps.oxfordjournals.org/ at RMIT Central Library on July 1, 2015
o cc
1518
D. P. FOSHEE, D. M. CENTA, G. R. MCDANIEL AND C. A. ROLLO
form distribution of activity throughout the 24-hour day.
periods
REFERENCES
Further Studies on the Nutritive Value of Opaque-2 Corn for the Chick1 J. B. FONSECA,2 J. C. ROGLER, W. R. FEATHERSTON AND T. R. CLINE Department of Animal Sciences, Purdue University, West Lafayette, Indiana 47907 (Received for publication May 11, 1970)
C
ROMWELL et al. (1967, 1968), working with young chicks, reported only slight differences in growth rate and feed conversion by the isonitrogenous substitution of opaque-2 corn for normal corn in corn-soybean meal diets of suboptimal protein content. However, when a deficiency of the first limiting amino acid in this type of diet, methionine, was corrected by supplementation, significantly better gains and feed conversions were observed with opaque-2 corn as compared with normal corn. Since supplementation of normal corn diets with lysine up to the level in opaque-2 corn diets resulted in equal performance, it was concluded that the beneficial effects of opaque-2 over normal corn is mediated 1 Journal Paper No. 4055 of the Purdue University Agricultural Experiment Station. 2 Present address: Institute de Zootechnia, Universidade Federal de Vicosa, Vicosa, Minas Gerais, Brazil.
solely through the higher lysine content of opaque-2 corn. Analyses of plasma amino acids revealed higher lysine levels in chicks fed opaque-2 corn as compared with chicks fed normal com. In the current studies, the nutritive value of opaque-2 and high protein opaque-2 corn, obtained by the introduction of the opaque-2 gene into an Illinois high protein strain, was studied in corn-soybean meal and corn-safflower meal diets. It was deemed advisable to use a supplemental protein source which is low in lysine (safflower meal) to circumvent using suboptimal protein levels in evaluating the corn. The work of several investigators (Young and Halloran, 1962; Valadez et al., 1965; Kuzmicky and Kohler, 1968a) has shown that the poor growth observed in chicks fed corn-safflower meal diets can be completely corrected by lysine supplementation, although feed conversion is usually slightly poorer as compared with a corn-soybean
Downloaded from http://ps.oxfordjournals.org/ at RMIT Central Library on July 1, 2015
Beane, W. L., P. B. Siegel and H. S. Siegel, 1965. Light environment as a factor in growth and feed efficiency of meat-type chickens. Poultry Sci. 44: 1009-1012. Centa, D. M., D. P. Foshee and J. R. Howes, 1969. Control of feeding behavior in poultry. Psychological Reports, 24: 153-154. Gore, W. E., D. P. Foshee and J. R. Howes, 1969. Effects of background illumination and lightdark period on weight gain in broilers. Poultry Sci. 48: 1282-1287.
Meier, G. W., 1969. Operant cycles and imitational learning in a social setting. Paper read to AAAS, Boston, December 26-31. Moore, C. H., 1957. The effect of light on growth of broiler chickens. Poultry Sci. 36: 1142-1143. Mosteller, F., and R. R. Bush, 1954. Selected Quantitative Techniques, in G. Lindzey (Ed.) : Handbook of Social Psychology, Volume I, Addison-Wesley, Cambridge, Massachusetts. Siegel, P. B., and A. M. Guhl, 1966. The measurement of some diurnal rhythms in the activity of White Leghorn cockerels. Poultry Sci. 45: 1340-1345. Weaver, W. D., and P. B. Siegel, 1968. Photoperiodism as a factor in feeding rhythms of broiler chickens. Poultry Sci. 47: 1148-1154.