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Significance of Growing Photoperiod and Light Stimulation at Various Ages for Leghorn Pullets Subjected to Regular or Ahemeral Photoperiods
Significance of Growing Photoperiod and Light Stimulation at Various Ages for Leghorn Pullets Subjected to Regular or Ahemeral Photoperiods S. LEESON and J. D. SUMMERS Department of Animal and Poultry Science, University of Guelph Guelph, Ontario, Canada NIG 2W1 (Received for publication May 26, 1987)
1988 Poultry Science 67:391-398 INTRODUCTION
It is well known that the growing Leghorn pullet is light sensitive and that a response to changes in available light is manifested in a number of observable parameters. Classical data suggest a curvilinear relationship between hours of light during rearing and age at first egg, with earliest maturity corresponding to 12 to 14 h light (Morris, 1967). As commercial birds are maturing at earlier ages than previously (Leeson and Summers, 1981), the key to successful rearing programs is attainment of desired weight for age. Leeson and Summers (1985a) indicated that birds reared under constant 14-h photoperiods were significantly heavier than birds reared under 8 h light. Although long day lengths may promote growth during rearing, apparently in response to stimulation of feed intake, a problem arises at maturity, as there is less potential for effect of longer photoperiods for adults. There is some research evidence to support industry reports that increasing the photoperiod at maturity is unnecessary for modern strains of Leghorn and brown-egg producing birds. Sauveur and Mongin (1983) showed identical egg mass output for birds on continuous light from 4 wk of age, relative to those receiving 391
light stimulation at 18 wk. With continuous light, birds produced fewer eggs, although eggs produced were larger. Namai and Iwashita (1982) moved birds from an ahemeral 15.75L:5.25D to a 15.75L:8.25D photoperiod, and recorded no differences in egg output or age at 50% egg production, even though birds received proportionally less light in the adult house. Morris (1978) also recorded earlier maturity with birds changed from a normal 6L:18D day to a 6L:21D-ahemeral photoperiod. As suggested by Morris (1978), such apparent stimulation indicates that ahemeral photoperiods are effectively larger than 24-h photoperiods and that presumably birds are responding to the extra ' 'daylength.'' The present trials were conducted to test the effectiveness of light stimulation around the time of maturity when birds are subsequently exposed to conventional 24-h or ahemeral adult photoperiods. MATERIALS AND METHODS
Experiment 1. Day-old Leghorn pullets of a commercial strain were wing-banded, weighed, and randomly distributed to rearing cages maintained in two rooms with total environmental
Downloaded from http://ps.oxfordjournals.org/ at D H Hill Library - Acquis S on April 23, 2015
ABSTRACT Leghorn pullets were cage reared to 15 or 19 wk of age in environmentally controlled rooms that provided either 8 h or 14 h of light per day. In Experiment 1, birds were moved to laying cages at 15 wk of age and subjected to either 14 h light (L):10 h (D) dark or ahemeral 14L:14D photoperiods. Feed intake, egg weight, shell quality, and egg production were monitored to 67 wk of age. In Experiment 2, pullets were moved at 19 wk of age and subjected to 14L:10D or 17L:7D light programs. Production parameters were measured as previously described. No significant (P>.05) interactions were observed between rearing and laying photoperiods, suggesting that increase in the length of photoperiod around time of maturity is not essential for adequate performance. In Experiment 1, ahemeral lighting resulting in reduced egg production, whereas egg shell quality and egg weight were improved (P<.05). In both experiments, the 14-h rearing program resulted in improved egg size together with improved eggshell quality (P<.05). Whereas increased egg size may relate to body weight, no explanation is apparent for the consistent pattern with respect to shell quality. In Experiment 2, poorer shell quality was observed with 17 vs. 14 h light per day. It is concluded that light stimulation at maturity has little effect on overall egg production. Improved shell quality observed with birds reared under 14 h light vs. those reared under 8 h per day may relate to a less rapid attainment of peak egg production. (Key words: rearing photoperiod, laying photoperiod, egg production, shell quality, ahemeral photoperiod)
392
LEESON AND SUMMERS
RESULTS
Egg Production. In Experiment 1, no significant interactions (P>.05) were observed between rearing and adult photoperiod (Table 1). During the initial period of production from 19
to 22 wk of age (Period 1) birds reared on 8 h light produced significantly more eggs than did birds reared on 14 h; however after this time, rearing photoperiod had no effect on egg production (P>.05). Adult lighting programs had a significant effect on egg production in virtually all periods of the trial. Birds exposed to 14-h regular light periods laid some 9% more eggs than did birds subjected to the ahemeral program. In Experiment 2, rearing treatment had a significant effect during most of the early periods of production and this resulted in a significant overall effect (P<.01). Birds reared on 8 h light produced 4.2% more eggs over the 19 to 67-wk period relative to birds reared on 14 h light. Adult photoperiod had a sporadic effect on egg production and where significance occurred, egg production was higher with 17 h of light. A significant interaction was observed in Period 6, where lower production was noted with birds exposed to 14 h light in both rearing and adult environments. Egg Weight. In Experiment 1, both rearing and adult light programs influenced egg weight, although no interaction was observed (Table 2). Birds reared on 14 h light consistently produced larger eggs than did birds reared on 8 h; an ahemeral program in the adult environment also significantly stimulated egg size. A similar result of increased egg size produced by 14 vs. 8-h rearing photoperiod was seen in Experiment 2. In Experiment 2, adult photoperiod had the greatest effect during the latter part of production, where birds exposed to 17 h light produced larger eggs than did birds receiving 14 h constant light. No interaction was observed (P>.05). Feed Intake. In Experiment 1, rearing treatment influenced feed intake during Periods 7, 9, and 10, and for the overall 15 to 67-wk mean (Table 3). During these time periods, birds reared on 14 h light consumed more feed than did birds reared on 8 h light. Adult photoperiod affected feed intake only during Periods 5 and 6. The data are difficult to interpret, as increased intake is noted for birds on regular light treatment in Period 5 and for ahemeral lighting in Period 6. No significant (P>.05) effects were observed at any time during Experiment 2. Eggshell Deformation. Both rearing and adult photoperiods influenced eggshell quality, as assessed by deformation, during both experiments, although again no interactions were observed (Table 4). In Experiment 1, ahemeral adult treatment improved shell quality, as did
Downloaded from http://ps.oxfordjournals.org/ at D H Hill Library - Acquis S on April 23, 2015
control. All birds were exposed to constant light for 3 days, after which time birds in one room were subjected to 8 h light/day at 10 lx intensity, whereas birds in the alternate room received 14 h light/day at 10 lx intensity. All birds received a conventional (corn-soybean) rearing diet containing 16% CP and 2,750 kcal ME/kg as crumbles throughout the rearing period. Water was available ad libitum. Each room contained 1,040 birds, housed at 10 birds/2,930-cm2 cage. After brooding, room temperature was maintained at 22 ± 1 C. At 15 wk of age, birds were selected at random, weighed, and allocated to laying cages maintained in two identical rooms with environmental control. After weighing all birds, body weight was standardized for each room. Birds in one room were immediately subjected to 14L: 10D photoperiod, whereas birds in the alternate room received an ahemeral photoperiod of 14L:14D. All birds received a conventional corn-soybean laying diet as crumbles (17.5% CP, 2,750 kcal ME/kg) together with water ad libitum. Each rearing treatment was represented by 24 replicate groups of four adjacently and individually caged birds (960 cm2). Egg production was monitored daily. Eggs collected on the last 2 days of each 28-day period were weighed, and shell deformation recorded (Summers etal., 1976). Birds were weighed periodically and feed intake per bird was calculated for each 28-day period. The experiment was terminated after 13 28-day periods of observation. Experiment 2. Pullets were reared to 19 wk of age, in rooms as described in Experiment 1. At this time, birds were moved to one of two environmentally controlled rooms that provided either 14 or 17 h light/day. Each rearing treatment (8 vs. 14 h light) was represented by 30 replicate groups of four individually and adjacently arranged cages (960 cm2). Diet, management, and measurement parameters were as described in Experiment 1. Data from each experiment were analyzed as a 2 x 2 factorial ANOVA (Steel and Torrie, 1980). The factors tested were growing-period photoperiod and laying-period photoperiod.
Starting at 19 wk of age.
14
8
14
8
(h>
""•Significant difference P<.01.
•Significant difference P<.05.
1
SD
Statistical analysis Rearing Adult Rearing X adult
2 ( 1 9 to 67 wk age)
SD
Statistical analysis Rearing Adult Rearing X adult
1 (15 to 67 wk age)
Experiment
Rearing
14 17 14 17
14 14 14 14
Adult
Photoperiod
Regular Ahemeral Regular Ahemeral
Photoperiod type
**
NS NS 9.8
24.4 22.8 17.2 20.5
10.8
NS
** **
52.2 43.7 27.4 24.3
l1
**
NS NS 9.4
90.9 86.4 81.8 83.3
NS NS NS 6.7
93.6 92.8 91.0 92.0
NS 7.4
**
NS 8.7
NS
**
91.6 77.8 92.3 79.1
3
NS
90.1 76.3 86.9 74.2
2
*
NS NS 7.4
93.5 92.7 87.9 91.7
NS 8.4
**
NS
90.8 75.2 91.2 76.9
4
8.9
*» * •
92.4 92.4 83.4 90.0
NS 8.8
•*
NS
88.5 86.1 91.5 84.7
5
NS 9.2
** **
88.3 90.1 81.2 88.4
NS 9.2
**
NS
87.3 81.9 88.2 83.3
6
**
NS 7.6
NS
86.6 90.7 83.1 88.8
NS 9.3
**
NS
86.3 83.8 89.1 82.1
7
28-Day perio
TABLE 1. Effect of rearing and adult photoperiod on percentage hen-day egg produ
d from http://ps.oxfordjournals.org/ at D H Hill Library - Acquis S on April 23, 2015
Starting at 19 wk of age.
* 'Significant difference P<.01.
14 17 14 17
14 14 14 14
8 8 14 14
8 8 14 14
Adult
•Significant difference P<.05.
1
Statistical analysis Rearing Adult Rearing X adult SD
2 (19 to 67 wk age)
Statistical analysis Rearing Adult Rearing X adult SD
1 (15 to 67 wk age)
Experiment
Rearing
Photoperiod (h)
Regular Ahemeral Regular Ahemeral
Photoperiod type
NS NS NS 3.5
45.9 46.3 46.9 46.8
NS NS NS 4.4
43.9 44.6 44.5 46.2
1'
**
NS NS 2.7
52.6 53.2 53.8 54.8
•* *•
NS 3.0
50.6 53.1 51.7 55.4
2
NS NS 3.3
**
54.6 56.3 57.0 57.6
*• •*
NS 2.4
53.0 57.9 55.3 58.8
3
**
NS NS 2.7
57.3 57.6 59.0 59.5
•* •*
NS 2.4
55.4 58.7 57.1 61.2
4
«•
NS NS 2.6
58.3 58.9 60.2 60.4
**
NS NS 2.5
56.4 56.2 58.2 59.0
5
**
NS NS 3.0
59.0 59.2 61.0 61.5
•*
NS NS 2.5
56.7 57.6 59.1 59.9
6
**
NS NS 3.0
59.6 59.2 61.4 61.1
*•
NS NS 2.3
57.5 58.4 60.0 60.7
7
28-Day peri
TABLE 2. Effect of rearing and adult photoperiod on egg weight
from http://ps.oxfordjournals.org/ at D H Hill Library - Acquis S on April 23, 2015
Starting at 15 wk of age.
(h)
'•Significant difference P<.01.
•Significant difference P<.05.
1
SD
Statistical analysis Rearing Adult Rearing X adult
2 (19 to 67 wk age)
SD
8 8 14 14
8 8 14 14
1 (15 to 67 wk age)
Statistical analysis Rearing Adult Rearing X adult
ing
Experiment
Rear-
14 17 14 17
14 14 14 14
Adult
Photoperiod
Regular Ahemeral Regular Ahemeral
Photoperiod type
NS NS NS 8.7
74.0 72.1 73.3 71.1
1'
NS 8.2
*NS*
71.1 72.3 73.7 78.3
12.4
NS NS NS
85.2 84.7 79.8 83.4
2
*NS
NS NS NS
12.8
18.5
12.6
109.2 107.5 109.9 109.5
12.2
NS NS NS
11.1
14.0 18.2
116.0 112.8 117.0 115.7
11.2
NS NS NS
112.8 110.8 117.3 113.9
NS NS NS
107.0 106.0 107.0 109.0
10.8
*
NS NS
106.7 110.5 111.2 114.1
8
28-Day period 7
NS NS NS
110.5 104.7 107.1 109.8
16.5
NS
•
NS
105.0 108.5 102.4 113.2
6
NS
108.8 104.8 112.4 106.9
5
NS NS NS
102.2 102.4 99.0 104.0
15.0
NS NS NS
107.2 101.0 106.2 106.5
4
NS NS NS
95.0 90.4 93.1 94.6
13.3
NS NS NS
98.1 97.2 100.7 98.7
3
TABLE 3. Effect of rearing and adult photoperiod on feed intake
d from http://ps.oxfordjournals.org/ at D H Hill Library - Acquis S on April 23, 2015
Starting at 19 wk of age.
(h)
"Significant difference P<.01.
•Significant difference P<,05.
1
SD
Statistical analysis Rearing Adult Rearing X adult
2 (19 to 67 wk age)
SD
8 8 14 14
8 8 14 14
1 (15 to 67 wkage)
Statistical analysis Rearing Adult Rearing X adult
ing
Experiment
Rear-
14 17 14 17
14 14 14 14
Adult
Photoperiod
NS NS NS 2.9
23.9 25.3 24.6 24.4
NS 4.0
28.0 23.8 23.8 22.3
Regular Ahemeral Regular Ahemeral
** **
1'
Photoperiod type
NS 2.3
**
NS
25.1 27.1 25.1 26.1
1.8
* ** NS
25.3 21.9 24.0 21.8
2
NS NS NS 2.2
26.2 25.4 25.4 25.5
NS 2.0
**
NS
25.7 27.7 25.0 21.9
3
NS NS NS 2.2
26.0 26.2 25.6 25.4
NS 2.2
* **
26.9 21.6 25.4 21.3
4
** **
NS 1.9
25.6 26.6 24.2 25.6
26.2 26.6 24.8 25.1
**
2.4
NS NS 2.0
**
*
NS
24.2 23.7 23.2 22.8
6
NS 2.4
* *
26.1 25.3 25.4 24.0
5
* *
NS 2.4
25.2 25.9 24.0 25.2
** *«
NS 2.6
25.4 2.3.7 24.2 22.5
(/jm)
7
28-Day perio
TABLE 4. Effect of rearing and adult photoperiod on eggshell deformation
d from http://ps.oxfordjournals.org/ at D H Hill Library - Acquis S on April 23, 2015
REARING AND LAYING PHOTOPERIODS
14 v*. 8-h lighting during rearing. In Experiment 2, 14-h lighting during rearing again improved shell quality, whereas the longer 17-h day during the adult period reduced shell quality relative to that of birds exposed to 14 h light.
DISCUSSION
trial. For both trials this weight differential was around 6% and is likely responsible for the increased egg size produced by these birds (Table 2). These results confirm observations of Summers and Leeson (1983) of a relationship between body weight and egg size. It is also interesting to note that birds subjected to 17 vs. 14 h light during lay also produced larger eggs, although this was not correlated with increased feed intake or body weight. In fact, mean body weight of birds receiving 17 vs. 14 h light was significantly less (1,674 vs. 1,721 g, respectively). The effect of rearing program on body weight and maturity is, however, contrary to observations of Leeson and Summers (1985b), which indicate that smaller birds invariably produce fewer eggs during the first few months of production. This apparent contradiction likely relates to a differential effect of body weight caused by genetics (Summers and Leeson 1983) or light stimulation (Table 1). Similar observations with broiler breeder pullets were made by Payne (1975). These results indicate that Leghorn pullets reared on long photoperiods can perform adequately without the need for light stimulation at maturity. Although such pullets are slower to mature and reach peak production, overall performance is little affected. Birds reared on 14-h daylengths produce fewer eggs than do birds reared on 8 h, although such eggs are heavier and consistently of improved shell quality. Data confirm the premise that rearing management can have a major influence on laying performance (Leeson and Summers, 1987). ACKNOWLEDGMENTS
This work was supported by the Ontario Egg Producers' Marketing Board and the Ontario Ministry of Agriculture and Food. REFERENCES Leeson, S., and J. D. Summers, 1981. Effect of rearing diet on performance of early maturity pullets. Can. J. Anim. Sci. 61:743-749. Leeson, S., and J. D. Summers, 1985a. Response of growing Leghorn pullets to long or increasing photoperiods. Poultry Sci. 64:1617-1622. Leeson, S., and J. D. Summers, 1985b. Early application of conventional or ahemeral photoperiods in an attempt to improve egg size. Poultry Sci. 64:2020-2026. Leeson, S., and J. D. Summers, 1987. Effect of immature body weight on laying performance. Poultry Sci. 66:1924-1928. Morris, T. R., 1967. Lighting programs for growing and laying pullets. World's Poult. Sci. J. 23:326-335. Morris, T. R., 1978. The photoperiodic effect of ahemeral
Downloaded from http://ps.oxfordjournals.org/ at D H Hill Library - Acquis S on April 23, 2015
Results of the present study confirm previous observations on the effect of ahemeral photoperiods during the entire laying period (Leeson and Summers, 1985b). Thus, decreased egg output is associated with increased egg weight and improved eggshell quality. Calculation of overall egg mass production favors the regular lighting schedule during the laying period by some 5%. The economics of these lighting programs will obviously depend on market requirements and price differentials for various egg grades. Although only significant (P<.01) in Experiment 2, data from both experiments indicate superior overall egg production for birds reared on 8 rather than 14 h of light. Substantial differences in shell quality in favor of the 14-h rearing treatment were seen in both experiments. This apparently was not due to increased nutrient intake (Table 3). The improved shell quality may relate to initial lower egg production, as in both trials birds reared on 14 h of light were somewhat slower in attaining peak egg output. It is suggested that improved shell quality is therefore related to reduced egg production (Experiment 2) or slower onset of production (Experiments 1 and 2). As no significant interactions were observed between growing and laying treatments, it would appear that little benefit is to be gained from light stimulation at maturity. These data confirm observations of Siegel etal. (1963), and Sauveur and Mongin (1983) of the nonstimulatory effect of light at maturity on subsequent egg mass output. However, results fail to support those of Morris (1978), which indicated earlier maturity of birds moved to 6L:21D compared with that of birds remaining on a program of 6L:18D. Thus, in Experiment 1 (Table 1), birds moved from 14L:10D to 14L:14D showed no increase in early egg output relative to that of birds maintained on 14L:10D. Rearing birds on the longer 14-h day length did delay rise to peak egg output, as previously mentioned. In both experiments, pullets reared on 14 h vs. 8 h light were heavier during the entire laying
397
398
LEESON AND SUMMERS
light-dark cycles which entrain circadian rhythms. Br. Poult. Sci. 19:207-212. Namai, K., and E. Iwashita, 1982. Effect of short light-dark cycles on egg production in the fowl. Jpn. Poult. Sci. 19:251-256. Payne, C. G., 1975. Day-length during rearing and the subsequent egg production of meat-strain pullets. Br. Poult. Sci. 16:559-563. Sauveur, B., and P. Mongin, 1983. Performance of layers reared and/or kept under different 6-hour light-dark cycles. Br. Poult. Sci. 24:405^116.
Siegel, H. S., W. L. Beane, and C. E. Howes, 1963. Lighting regimes as an influence on maturity and productivity of Leghom-type layers. Poultry Sci. 42:1064-1071. Steel, R.G.D., and J. H. Torrie, 1980. Principles and Procedures of Statistics. A Biometrical Approach. 2nd ed. McGraw-Hill Book Co., New York, NY. Summers, J. D., R. Grandhi, andS. Leeson, 1976. Calcium and phosphorus requirements of the laying hen. Poultry Sci. 55:402-413. Summers, J. D., and S. Leeson, 1983. Factors influencing early egg size. Poultry Sci. 62:1155-1159.
Downloaded from http://ps.oxfordjournals.org/ at D H Hill Library - Acquis S on April 23, 2015
1988 Poultry Science 67:391-398 INTRODUCTION
It is well known that the growing Leghorn pullet is light sensitive and that a response to changes in available light is manifested in a number of observable parameters. Classical data suggest a curvilinear relationship between hours of light during rearing and age at first egg, with earliest maturity corresponding to 12 to 14 h light (Morris, 1967). As commercial birds are maturing at earlier ages than previously (Leeson and Summers, 1981), the key to successful rearing programs is attainment of desired weight for age. Leeson and Summers (1985a) indicated that birds reared under constant 14-h photoperiods were significantly heavier than birds reared under 8 h light. Although long day lengths may promote growth during rearing, apparently in response to stimulation of feed intake, a problem arises at maturity, as there is less potential for effect of longer photoperiods for adults. There is some research evidence to support industry reports that increasing the photoperiod at maturity is unnecessary for modern strains of Leghorn and brown-egg producing birds. Sauveur and Mongin (1983) showed identical egg mass output for birds on continuous light from 4 wk of age, relative to those receiving 391
light stimulation at 18 wk. With continuous light, birds produced fewer eggs, although eggs produced were larger. Namai and Iwashita (1982) moved birds from an ahemeral 15.75L:5.25D to a 15.75L:8.25D photoperiod, and recorded no differences in egg output or age at 50% egg production, even though birds received proportionally less light in the adult house. Morris (1978) also recorded earlier maturity with birds changed from a normal 6L:18D day to a 6L:21D-ahemeral photoperiod. As suggested by Morris (1978), such apparent stimulation indicates that ahemeral photoperiods are effectively larger than 24-h photoperiods and that presumably birds are responding to the extra ' 'daylength.'' The present trials were conducted to test the effectiveness of light stimulation around the time of maturity when birds are subsequently exposed to conventional 24-h or ahemeral adult photoperiods. MATERIALS AND METHODS
Experiment 1. Day-old Leghorn pullets of a commercial strain were wing-banded, weighed, and randomly distributed to rearing cages maintained in two rooms with total environmental
Downloaded from http://ps.oxfordjournals.org/ at D H Hill Library - Acquis S on April 23, 2015
ABSTRACT Leghorn pullets were cage reared to 15 or 19 wk of age in environmentally controlled rooms that provided either 8 h or 14 h of light per day. In Experiment 1, birds were moved to laying cages at 15 wk of age and subjected to either 14 h light (L):10 h (D) dark or ahemeral 14L:14D photoperiods. Feed intake, egg weight, shell quality, and egg production were monitored to 67 wk of age. In Experiment 2, pullets were moved at 19 wk of age and subjected to 14L:10D or 17L:7D light programs. Production parameters were measured as previously described. No significant (P>.05) interactions were observed between rearing and laying photoperiods, suggesting that increase in the length of photoperiod around time of maturity is not essential for adequate performance. In Experiment 1, ahemeral lighting resulting in reduced egg production, whereas egg shell quality and egg weight were improved (P<.05). In both experiments, the 14-h rearing program resulted in improved egg size together with improved eggshell quality (P<.05). Whereas increased egg size may relate to body weight, no explanation is apparent for the consistent pattern with respect to shell quality. In Experiment 2, poorer shell quality was observed with 17 vs. 14 h light per day. It is concluded that light stimulation at maturity has little effect on overall egg production. Improved shell quality observed with birds reared under 14 h light vs. those reared under 8 h per day may relate to a less rapid attainment of peak egg production. (Key words: rearing photoperiod, laying photoperiod, egg production, shell quality, ahemeral photoperiod)
392
LEESON AND SUMMERS
RESULTS
Egg Production. In Experiment 1, no significant interactions (P>.05) were observed between rearing and adult photoperiod (Table 1). During the initial period of production from 19
to 22 wk of age (Period 1) birds reared on 8 h light produced significantly more eggs than did birds reared on 14 h; however after this time, rearing photoperiod had no effect on egg production (P>.05). Adult lighting programs had a significant effect on egg production in virtually all periods of the trial. Birds exposed to 14-h regular light periods laid some 9% more eggs than did birds subjected to the ahemeral program. In Experiment 2, rearing treatment had a significant effect during most of the early periods of production and this resulted in a significant overall effect (P<.01). Birds reared on 8 h light produced 4.2% more eggs over the 19 to 67-wk period relative to birds reared on 14 h light. Adult photoperiod had a sporadic effect on egg production and where significance occurred, egg production was higher with 17 h of light. A significant interaction was observed in Period 6, where lower production was noted with birds exposed to 14 h light in both rearing and adult environments. Egg Weight. In Experiment 1, both rearing and adult light programs influenced egg weight, although no interaction was observed (Table 2). Birds reared on 14 h light consistently produced larger eggs than did birds reared on 8 h; an ahemeral program in the adult environment also significantly stimulated egg size. A similar result of increased egg size produced by 14 vs. 8-h rearing photoperiod was seen in Experiment 2. In Experiment 2, adult photoperiod had the greatest effect during the latter part of production, where birds exposed to 17 h light produced larger eggs than did birds receiving 14 h constant light. No interaction was observed (P>.05). Feed Intake. In Experiment 1, rearing treatment influenced feed intake during Periods 7, 9, and 10, and for the overall 15 to 67-wk mean (Table 3). During these time periods, birds reared on 14 h light consumed more feed than did birds reared on 8 h light. Adult photoperiod affected feed intake only during Periods 5 and 6. The data are difficult to interpret, as increased intake is noted for birds on regular light treatment in Period 5 and for ahemeral lighting in Period 6. No significant (P>.05) effects were observed at any time during Experiment 2. Eggshell Deformation. Both rearing and adult photoperiods influenced eggshell quality, as assessed by deformation, during both experiments, although again no interactions were observed (Table 4). In Experiment 1, ahemeral adult treatment improved shell quality, as did
Downloaded from http://ps.oxfordjournals.org/ at D H Hill Library - Acquis S on April 23, 2015
control. All birds were exposed to constant light for 3 days, after which time birds in one room were subjected to 8 h light/day at 10 lx intensity, whereas birds in the alternate room received 14 h light/day at 10 lx intensity. All birds received a conventional (corn-soybean) rearing diet containing 16% CP and 2,750 kcal ME/kg as crumbles throughout the rearing period. Water was available ad libitum. Each room contained 1,040 birds, housed at 10 birds/2,930-cm2 cage. After brooding, room temperature was maintained at 22 ± 1 C. At 15 wk of age, birds were selected at random, weighed, and allocated to laying cages maintained in two identical rooms with environmental control. After weighing all birds, body weight was standardized for each room. Birds in one room were immediately subjected to 14L: 10D photoperiod, whereas birds in the alternate room received an ahemeral photoperiod of 14L:14D. All birds received a conventional corn-soybean laying diet as crumbles (17.5% CP, 2,750 kcal ME/kg) together with water ad libitum. Each rearing treatment was represented by 24 replicate groups of four adjacently and individually caged birds (960 cm2). Egg production was monitored daily. Eggs collected on the last 2 days of each 28-day period were weighed, and shell deformation recorded (Summers etal., 1976). Birds were weighed periodically and feed intake per bird was calculated for each 28-day period. The experiment was terminated after 13 28-day periods of observation. Experiment 2. Pullets were reared to 19 wk of age, in rooms as described in Experiment 1. At this time, birds were moved to one of two environmentally controlled rooms that provided either 14 or 17 h light/day. Each rearing treatment (8 vs. 14 h light) was represented by 30 replicate groups of four individually and adjacently arranged cages (960 cm2). Diet, management, and measurement parameters were as described in Experiment 1. Data from each experiment were analyzed as a 2 x 2 factorial ANOVA (Steel and Torrie, 1980). The factors tested were growing-period photoperiod and laying-period photoperiod.
Starting at 19 wk of age.
14
8
14
8
(h>
""•Significant difference P<.01.
•Significant difference P<.05.
1
SD
Statistical analysis Rearing Adult Rearing X adult
2 ( 1 9 to 67 wk age)
SD
Statistical analysis Rearing Adult Rearing X adult
1 (15 to 67 wk age)
Experiment
Rearing
14 17 14 17
14 14 14 14
Adult
Photoperiod
Regular Ahemeral Regular Ahemeral
Photoperiod type
**
NS NS 9.8
24.4 22.8 17.2 20.5
10.8
NS
** **
52.2 43.7 27.4 24.3
l1
**
NS NS 9.4
90.9 86.4 81.8 83.3
NS NS NS 6.7
93.6 92.8 91.0 92.0
NS 7.4
**
NS 8.7
NS
**
91.6 77.8 92.3 79.1
3
NS
90.1 76.3 86.9 74.2
2
*
NS NS 7.4
93.5 92.7 87.9 91.7
NS 8.4
**
NS
90.8 75.2 91.2 76.9
4
8.9
*» * •
92.4 92.4 83.4 90.0
NS 8.8
•*
NS
88.5 86.1 91.5 84.7
5
NS 9.2
** **
88.3 90.1 81.2 88.4
NS 9.2
**
NS
87.3 81.9 88.2 83.3
6
**
NS 7.6
NS
86.6 90.7 83.1 88.8
NS 9.3
**
NS
86.3 83.8 89.1 82.1
7
28-Day perio
TABLE 1. Effect of rearing and adult photoperiod on percentage hen-day egg produ
d from http://ps.oxfordjournals.org/ at D H Hill Library - Acquis S on April 23, 2015
Starting at 19 wk of age.
* 'Significant difference P<.01.
14 17 14 17
14 14 14 14
8 8 14 14
8 8 14 14
Adult
•Significant difference P<.05.
1
Statistical analysis Rearing Adult Rearing X adult SD
2 (19 to 67 wk age)
Statistical analysis Rearing Adult Rearing X adult SD
1 (15 to 67 wk age)
Experiment
Rearing
Photoperiod (h)
Regular Ahemeral Regular Ahemeral
Photoperiod type
NS NS NS 3.5
45.9 46.3 46.9 46.8
NS NS NS 4.4
43.9 44.6 44.5 46.2
1'
**
NS NS 2.7
52.6 53.2 53.8 54.8
•* *•
NS 3.0
50.6 53.1 51.7 55.4
2
NS NS 3.3
**
54.6 56.3 57.0 57.6
*• •*
NS 2.4
53.0 57.9 55.3 58.8
3
**
NS NS 2.7
57.3 57.6 59.0 59.5
•* •*
NS 2.4
55.4 58.7 57.1 61.2
4
«•
NS NS 2.6
58.3 58.9 60.2 60.4
**
NS NS 2.5
56.4 56.2 58.2 59.0
5
**
NS NS 3.0
59.0 59.2 61.0 61.5
•*
NS NS 2.5
56.7 57.6 59.1 59.9
6
**
NS NS 3.0
59.6 59.2 61.4 61.1
*•
NS NS 2.3
57.5 58.4 60.0 60.7
7
28-Day peri
TABLE 2. Effect of rearing and adult photoperiod on egg weight
from http://ps.oxfordjournals.org/ at D H Hill Library - Acquis S on April 23, 2015
Starting at 15 wk of age.
(h)
'•Significant difference P<.01.
•Significant difference P<.05.
1
SD
Statistical analysis Rearing Adult Rearing X adult
2 (19 to 67 wk age)
SD
8 8 14 14
8 8 14 14
1 (15 to 67 wk age)
Statistical analysis Rearing Adult Rearing X adult
ing
Experiment
Rear-
14 17 14 17
14 14 14 14
Adult
Photoperiod
Regular Ahemeral Regular Ahemeral
Photoperiod type
NS NS NS 8.7
74.0 72.1 73.3 71.1
1'
NS 8.2
*NS*
71.1 72.3 73.7 78.3
12.4
NS NS NS
85.2 84.7 79.8 83.4
2
*NS
NS NS NS
12.8
18.5
12.6
109.2 107.5 109.9 109.5
12.2
NS NS NS
11.1
14.0 18.2
116.0 112.8 117.0 115.7
11.2
NS NS NS
112.8 110.8 117.3 113.9
NS NS NS
107.0 106.0 107.0 109.0
10.8
*
NS NS
106.7 110.5 111.2 114.1
8
28-Day period 7
NS NS NS
110.5 104.7 107.1 109.8
16.5
NS
•
NS
105.0 108.5 102.4 113.2
6
NS
108.8 104.8 112.4 106.9
5
NS NS NS
102.2 102.4 99.0 104.0
15.0
NS NS NS
107.2 101.0 106.2 106.5
4
NS NS NS
95.0 90.4 93.1 94.6
13.3
NS NS NS
98.1 97.2 100.7 98.7
3
TABLE 3. Effect of rearing and adult photoperiod on feed intake
d from http://ps.oxfordjournals.org/ at D H Hill Library - Acquis S on April 23, 2015
Starting at 19 wk of age.
(h)
"Significant difference P<.01.
•Significant difference P<,05.
1
SD
Statistical analysis Rearing Adult Rearing X adult
2 (19 to 67 wk age)
SD
8 8 14 14
8 8 14 14
1 (15 to 67 wkage)
Statistical analysis Rearing Adult Rearing X adult
ing
Experiment
Rear-
14 17 14 17
14 14 14 14
Adult
Photoperiod
NS NS NS 2.9
23.9 25.3 24.6 24.4
NS 4.0
28.0 23.8 23.8 22.3
Regular Ahemeral Regular Ahemeral
** **
1'
Photoperiod type
NS 2.3
**
NS
25.1 27.1 25.1 26.1
1.8
* ** NS
25.3 21.9 24.0 21.8
2
NS NS NS 2.2
26.2 25.4 25.4 25.5
NS 2.0
**
NS
25.7 27.7 25.0 21.9
3
NS NS NS 2.2
26.0 26.2 25.6 25.4
NS 2.2
* **
26.9 21.6 25.4 21.3
4
** **
NS 1.9
25.6 26.6 24.2 25.6
26.2 26.6 24.8 25.1
**
2.4
NS NS 2.0
**
*
NS
24.2 23.7 23.2 22.8
6
NS 2.4
* *
26.1 25.3 25.4 24.0
5
* *
NS 2.4
25.2 25.9 24.0 25.2
** *«
NS 2.6
25.4 2.3.7 24.2 22.5
(/jm)
7
28-Day perio
TABLE 4. Effect of rearing and adult photoperiod on eggshell deformation
d from http://ps.oxfordjournals.org/ at D H Hill Library - Acquis S on April 23, 2015
REARING AND LAYING PHOTOPERIODS
14 v*. 8-h lighting during rearing. In Experiment 2, 14-h lighting during rearing again improved shell quality, whereas the longer 17-h day during the adult period reduced shell quality relative to that of birds exposed to 14 h light.
DISCUSSION
trial. For both trials this weight differential was around 6% and is likely responsible for the increased egg size produced by these birds (Table 2). These results confirm observations of Summers and Leeson (1983) of a relationship between body weight and egg size. It is also interesting to note that birds subjected to 17 vs. 14 h light during lay also produced larger eggs, although this was not correlated with increased feed intake or body weight. In fact, mean body weight of birds receiving 17 vs. 14 h light was significantly less (1,674 vs. 1,721 g, respectively). The effect of rearing program on body weight and maturity is, however, contrary to observations of Leeson and Summers (1985b), which indicate that smaller birds invariably produce fewer eggs during the first few months of production. This apparent contradiction likely relates to a differential effect of body weight caused by genetics (Summers and Leeson 1983) or light stimulation (Table 1). Similar observations with broiler breeder pullets were made by Payne (1975). These results indicate that Leghorn pullets reared on long photoperiods can perform adequately without the need for light stimulation at maturity. Although such pullets are slower to mature and reach peak production, overall performance is little affected. Birds reared on 14-h daylengths produce fewer eggs than do birds reared on 8 h, although such eggs are heavier and consistently of improved shell quality. Data confirm the premise that rearing management can have a major influence on laying performance (Leeson and Summers, 1987). ACKNOWLEDGMENTS
This work was supported by the Ontario Egg Producers' Marketing Board and the Ontario Ministry of Agriculture and Food. REFERENCES Leeson, S., and J. D. Summers, 1981. Effect of rearing diet on performance of early maturity pullets. Can. J. Anim. Sci. 61:743-749. Leeson, S., and J. D. Summers, 1985a. Response of growing Leghorn pullets to long or increasing photoperiods. Poultry Sci. 64:1617-1622. Leeson, S., and J. D. Summers, 1985b. Early application of conventional or ahemeral photoperiods in an attempt to improve egg size. Poultry Sci. 64:2020-2026. Leeson, S., and J. D. Summers, 1987. Effect of immature body weight on laying performance. Poultry Sci. 66:1924-1928. Morris, T. R., 1967. Lighting programs for growing and laying pullets. World's Poult. Sci. J. 23:326-335. Morris, T. R., 1978. The photoperiodic effect of ahemeral
Downloaded from http://ps.oxfordjournals.org/ at D H Hill Library - Acquis S on April 23, 2015
Results of the present study confirm previous observations on the effect of ahemeral photoperiods during the entire laying period (Leeson and Summers, 1985b). Thus, decreased egg output is associated with increased egg weight and improved eggshell quality. Calculation of overall egg mass production favors the regular lighting schedule during the laying period by some 5%. The economics of these lighting programs will obviously depend on market requirements and price differentials for various egg grades. Although only significant (P<.01) in Experiment 2, data from both experiments indicate superior overall egg production for birds reared on 8 rather than 14 h of light. Substantial differences in shell quality in favor of the 14-h rearing treatment were seen in both experiments. This apparently was not due to increased nutrient intake (Table 3). The improved shell quality may relate to initial lower egg production, as in both trials birds reared on 14 h of light were somewhat slower in attaining peak egg output. It is suggested that improved shell quality is therefore related to reduced egg production (Experiment 2) or slower onset of production (Experiments 1 and 2). As no significant interactions were observed between growing and laying treatments, it would appear that little benefit is to be gained from light stimulation at maturity. These data confirm observations of Siegel etal. (1963), and Sauveur and Mongin (1983) of the nonstimulatory effect of light at maturity on subsequent egg mass output. However, results fail to support those of Morris (1978), which indicated earlier maturity of birds moved to 6L:21D compared with that of birds remaining on a program of 6L:18D. Thus, in Experiment 1 (Table 1), birds moved from 14L:10D to 14L:14D showed no increase in early egg output relative to that of birds maintained on 14L:10D. Rearing birds on the longer 14-h day length did delay rise to peak egg output, as previously mentioned. In both experiments, pullets reared on 14 h vs. 8 h light were heavier during the entire laying
397
398
LEESON AND SUMMERS
light-dark cycles which entrain circadian rhythms. Br. Poult. Sci. 19:207-212. Namai, K., and E. Iwashita, 1982. Effect of short light-dark cycles on egg production in the fowl. Jpn. Poult. Sci. 19:251-256. Payne, C. G., 1975. Day-length during rearing and the subsequent egg production of meat-strain pullets. Br. Poult. Sci. 16:559-563. Sauveur, B., and P. Mongin, 1983. Performance of layers reared and/or kept under different 6-hour light-dark cycles. Br. Poult. Sci. 24:405^116.
Siegel, H. S., W. L. Beane, and C. E. Howes, 1963. Lighting regimes as an influence on maturity and productivity of Leghom-type layers. Poultry Sci. 42:1064-1071. Steel, R.G.D., and J. H. Torrie, 1980. Principles and Procedures of Statistics. A Biometrical Approach. 2nd ed. McGraw-Hill Book Co., New York, NY. Summers, J. D., R. Grandhi, andS. Leeson, 1976. Calcium and phosphorus requirements of the laying hen. Poultry Sci. 55:402-413. Summers, J. D., and S. Leeson, 1983. Factors influencing early egg size. Poultry Sci. 62:1155-1159.
Downloaded from http://ps.oxfordjournals.org/ at D H Hill Library - Acquis S on April 23, 2015