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Research Note: Influence of Ahemeral Light:Dark Cycles on Egg Traits in Brown Egg Pullets1
RESEARCH NOTES Research Note: Influence of Ahemeral Light:Dark Cycles on Egg Traits in Brown Egg Pullets1 N. LAKSHMANAN,2 R. O. HAWES,3 and L. J. KLING Department of Animal, Veterinary, and Aquatic Sciences, University of Maine, Orono, Maine 04469 (Received for publication May 6, 1991)
1992 Poultry Science 71S65-569
INTRODUCTION Previous research aimed at inducing early sexual maturity with white egg pullets resulted in reduced egg size and birds taking a longer time to reach their expected egg size (Morris and Fox, 1958; Harrison et ah, 1969). Lightrdark cycles longer than 24 h (ahemeral cycles) have been studied in an attempt to increase egg size (Fox et ah, 1971; Morris, 1973; Shanawany, 1982), but the reduction in egg numbers associated with these treatments was an undesirable effect. It has been demonstrated, however, that the increase in egg weight and reduction in egg number due to ahemeral cycles are
1 Maine Agricultural Experiment Station, Publication Number 1608. 2 Present address: Department of Animal and Veterinary Sciences, University of Massachusetts, Amherst, MA 01002. •To whom correspondence should be addressed.
completely reversible once the pullets are returned to a 24-h cycle. Moreover, egg production has been shown to be equal to that of pullets that were maintained continuously under 24-h light:dark cycles (Shanawany, 1982). Previous work at the University of Maine (Hawes et al., 1991) compared hemeral (24 h) with ahemeral (26 h) lighting schedules for early (16 wk) lightstimulated pullets. Egg weight was significantly improved during the ahemeral schedule (27 to 30 wk); however, egg numbers were significantly reduced for this period, as well as for the entire period of production (19 to 59 wk). Shanawany (1982) reported that with cycle lengths between 26 and 28 h, the reduction in rate of lay was not as great as the increase in egg weight. By combining the results of egg numbers and egg weights, the total egg mass under these cycles was slightly higher than that under 24-h cycles. The 26-h cycle does not comply with a conven-
565
Downloaded from http://ps.oxfordjournals.org/ at New York University on May 22, 2015
ABSTRACT Brown egg pullets (DeKalb Sex-Sal) were subjected to an ahemeral lighting program to determine their response in terms of egg traits. All birds were reared on a conventional lighting program of 10 h light (L):14 h dark (D) to 16 wk. At 16 wk, all birds received a schedule of 11L:13D followed by a weekly 1-h increase in photoperiod to 14L:10D at 19 wk. Control treatment (CON) birds were continued on this schedule. Ahemeral treatment (AHM) birds were given a 28-h schedule 14L:14D at 23 wk that was continued to 28 wk, then returned to a 24-h cycle of 14L:10D. Shell weight responded quickly to the ahemeral treatment and showed a significant (P<.05) increase during the 2nd 28-h cycle. Shell thickness and total egg weight showed significant increases on the 3rd cycle; albumen weight showed an increase on Cycle 4, and yolk weight increased significantly only on the 8th cycle. When AHM treatment birds were returned to a conventional cycle (14L:10D) at 28 wk, the total weight remained significantly higher (P<.05) as late as Cycle 6. (Key words: ahemeral lightdark cycles, early photostimulation, brown egg pullets, shell quality, egg weight)
566
LAKSHMANAN ET AL.
published results indicating the number of cycles required to produce changes in egg components. The following experiment was designed and carried out to determine the number of cycles required to produce a significant effect on egg weight and egg components following an abrupt change from a hemeral to an ahemeral lighfcdark cycle, and to determine the effect on egg weight following the termination of an ahemeral cycle. MATERIALS AND METHODS Day-old DeKalb Sex-Sal pullets were vaccinated for Marek's disease and brooded in battery units for Weeks 1 to 4, then transferred to conventional floor pens for Weeks 5 to 16. They received 24 h of light/day [24 h light (L):0 h dark (D)] to 3 days of age followed by 8 h of light daily (8L:16D) to 8 wk. From 8 to 16 wk the birds received a schedule of 10L:14D. All birds were fed a starter ration (20% CP) up to 8 wk. A grower mash (14% CP) was fed from 8 to 19 wk, followed by a 17% CP layer ration for the remainder of the trial. Pullets were vaccinated for avian encephalomyelitis at 10 wk; for Newcastle disease at 16 days, 36 days, and 16 wk; and for infectious bursal disease at 14 days, 34 days, and 16 wk of age. Flock
TABLE 1. The effect of ahemeral lighfcdark cycles1 on egg weight
Cycle
Treatment period Conventional Ahemeral (14L:10D) (14L:14D)
02 1 2 3 4 5 6 7 8 9 10
49.2 50.9 50.6 51.1 51.3 51.9 52.8 52.2 52.2 53.1 53.3
Posttreatment period Conventional Ahemeral (14L:10D) (14L:10D) fr>
± 7.6a ± 4.1a ± 4.0* ± 4.1b ± 4.0b ± 4.0b ± 4.7b ± 4.4b ± 4.3b ± 4.8b ± 4.4b
50.4 ± 4.0s 523 ±4.7 a 52.4 ± 5.0* 53.1 ± 4.3a 53.7 ± 4.8a 54.6 ± 4.8a 552 ± 4.4a 55.8 ± 5.4a 56.8 ± 5.4a 573. ± 4.4a 56.4 ± 4.3a
*>
58.0 ± 3.8a 57.4 ± 4 5 b 60.0 ± 5.0s 57.7 ± 4.6b 592 ± 4 ! a 572. ± 4.8b 57.8 ± 4.2* 57.8 ± 5.6a 59.1 ± 5.0" 572 ± 4.3a 58.1 ± 4.6a
59.9 60.5 60.0 60.4 58.7 60.1 58.7 572 57.6 582 58.0
± 5.4a ± 5.6a ± 4.0s ± 3.8* ± 4.6a ± 4.0s ± 3.1a ± 4.6a ± 4.4a ± 4.7* ± 3.7*
ab ' Means (± SD) with no common superscripts within the same row and within either the Treatment or Posttreatment columns are significantly different (P<.05). 1 14L:10D = 14 h lighfclO h dark; 14L:14D = 14 h light:14 h dark. ^Treatment period = 23 wk; posttreatment period = 28 wk.
Downloaded from http://ps.oxfordjournals.org/ at New York University on May 22, 2015
tional working day. The use of 28-h cycles has interesting possibilities, as six cycles occur during seven 24-h periods and therefore routine management is easier to organize (Morris, 1973). Water is a major component of albumen. Fifteen to 16 g of water is added to the developing egg while it remains in the uterus (Gilbert, 1972). Burmester et al. (1940) reported that the amount of water intake was proportional to the amount of time the developing egg spent in the oviduct and that increasing the light:dark cycle length would increase the amount of time the developing egg spends in the oviduct. Low Haugh unit values associated with eggs collected from birds exposed to ahemeral cycles were reported by Cooper and Barnett (1976). No differences in the dry matter content of eggs obtained from hens exposed to a 28-h light:dark cycle were observed by Leeson et al. (1979). The above reports suggest that the increase in albumen weight reported by earlier researchers might be due to an increased deposition of water resulting from longer retention time in the uterus. Birds subjected to lighfcdark cycles longer than 24 h usually laid eggs during the dark period and the pattern of lay could be changed within three to four cycles (Ibaraki et al., 1985). There are no
RESEARCH NOTE
567
TABLE 2. The effect of ahemeral lighfcdark cycles1 on shell thickness and weight Shell thickness
O2 1 2 3 4 5 6 7 8 9 10
.35 35 .35 .35 .36 .35 .35 .33 .35 .33 .34
Shell weight Ahemeral (14L:14D)
Conventional (14L:10D)
.34 ± .03* 35 ± .03* .36 ± .03a .37 ± .04" 37 ± ,04a .38 ± ,04a .37 ± .04a 37 ± .03a 37 ± .03a .37 ± .03a .36 ± .04a
53 ± 5 a 5 3 ± .6a 53 ± .6b 5.4 ± .6 b 55 ± .6b 55 ± 5 b 55±5b 5.4 ± 5 b 5.6 ± 5 b 55 ± .6 b 5.6 ± 5 b
(mm) — ± .02s ± .03a ± .03a ± .03b ± .03b ± .03b ± .03b ± .03b ± .03b ± .03b ± .02b
Ahemeral (14L:10D) ftr> HS'
53 55 5.7 5.8 5.9 6.1 6.1 62 63 63 6.1
± 5a ±.7" ± .6a ± .6a ± .7* ± .7 s ± .7 s ±.7" ± .7" ± .6a ± .7*
ab ' Means (± SD) with no common superscripts within the same row and within either the Shell thickness or Shell weight columns are significantly different (P<.05). h4L:10D = 14 h light:10 h dark; 14L:14D = 14 h light:14 h dark. 223 wk.
health was monitored throughout the trial and all dead birds were necropsied. At 16 wk, pullets were housed two per laying cage (25.4 x 45.7 cm) in four semienvironmentally controlled, lightproof rooms. There were two treatments with eight replicates per treatment, consisting of 21 cages (42 birds) each, divided between each of two rooms. Thus each room held 168 (four replicates) and each treatment consisted of 336 birds. All birds received a conventional 24-h lighting program of 11L:13D at 16 wk. A 1-h increase in photoperiod was provided weekly until the total photoperiod reached 14 h (14L:10D) at 19 wk. This schedule was maintained throughout the trial for Treatment 1 (CON). Birds on Treatment 2 were continued on the schedule of 14L:10D to 23 wk, when egg production was approximately 50% (henday). At 23 wk, birds in two of the rooms were switched to a 28-h cycle of 14L:14D (AHM), which was continued until 28 wk then returned to a 24-h schedule (14L: 10D). To determine cycle effects, 50 eggs were collected on each "cycle day" for each treatment. Eggs were also collected the
4
B. C. Ames Co., Waltham, MA 02154.
cycle prior to the day on which birds were 23 wk and this is termed "Cycle 0" in Tables 1 through 3. The AHM treatment (14L-.14D) was then applied and eggs were collected on each of the 10 following cycledays. Eggs were collected the cycle prior to the day on which birds were 28 wk and this is termed "Cycle 0" (postfareatment period) in Table 1. Birds were then returned to a hemeral cycle (14L:10D) and eggs were collected for the 10 following cycle-days. The effect of a return to the conventional lighting was determined for egg weight only. Total egg weight was individually recorded; eggs were then broken out and shell weights were determined after the inner surface had been wiped dry with tissue. Yolk weight was recorded after carefully rolling the yolk on a paper towel to remove adherent chalazae; albumen weight was determined by difference. Shells were air-dried for 48 h and thickness plus membranes determined to an accuracy of .01 mm using an Ames™ micrometer.4 All data were analyzed with General Linear Models (GLM) procedures (SAS Institute, 1982). Means were calculated by replicate for each treatment for all dependent variables. The GLM procedure (SAS Institute, 1982) was employed using a nested model statement: dependent vari-
Downloaded from http://ps.oxfordjournals.org/ at New York University on May 22, 2015
Cycle
Conventional (14L:10D)
568
LAKSHMANAN ET AL. TABLE 3. The effect of ahemeral lighfcdark cycles1 on yolk and albumen weight Yolk weight
Cycle
Conventional (14L:10D)
Ahemeral (14L:14D)
02 1 2 3 4 5 6 7 8 9 10
11.1 ± 1.3a 11.3 ± 1.3a 11.3 ± 1.2a 115 ± 1.2a 11.5 ± 1.3a 12.1 ± 1.8a 11.9 ± 1.2a 11.7 ± 1.0* 11.7 ± l.l b 125 ± l.l a 12.1 ± l.l b
11.1 ± 115 ± 115 ± 11.8 ± 12.0 ± 1Z1 ± 11.9 ± 122 ± 125 ± 12.7 ± 12.9 ±
Albumen weight Conventional Ahemeral (14L:10D) (14L:10D) (g) 3X8 343 34.0 342 34.3 34.3 35.4 35.4 35.0 35.4 35.6
± 7.0a ± 35 a ± 3.1a ± 3.1a ± 32h ± 35 b ± 4.0b ± 3.7b ± 3.6b ± 3.8b ± 35 b
34.0 ± 2.9* 355 ± 3.6a 352 ± 3.7* 355 ± 32* 35.9 ± 3.8a 365 ± 3.8a 372 ± 3.7* 37.4 ± 4.1a 38.0 ± 4.4a 38.3 ± 3.7* 37.4 ± 35 a
ab ' Means (± SD) with no common superscripts within the same row and within either the Yolk weight or Albumen weight column are significantly different (P<.05). 1 14L:10D = 14 h lighfclO h dark; 14L:14D = 14 h light:14 h dark. 223 wk.
able = treatment + room (treatment) + replicate (room). Mean square for treatment and room (treatment) was used as the hypothesis effect (numerator) and the mean square for room (treatment) and replicate (room) as error team (denominator), respectively. Replicates (42 birds per replicate, four replicates per room) were used as an experimental unit only if there were no significant interaction among the replicates within the rooms. Significance was determined at P<.05 unless otherwise noted. RESULTS AND DISCUSSION The effect of light cycle on egg weight is shown in Table 1. There was a significant increase in egg weight during the third AHM cycle. Ibaraki et ah (1985) reported that complete entrainment of oviposition to a change in light occurred after three to four cycles. Results presented here showed a significant difference in egg weight following the entrainment to the new cycles, and egg weight continued to be significantly larger for the entire 10 cycles. Returning birds to a conventional schedule (posttreatment period, Table 1), the larger egg size persisted as late as Cycle 5 before it became insignificantly different from eggs
produced under the conventional schedule. Both shell thickness and shell weight responded to an AHM cycle at the same time period as total egg weight (Table 2). Shell thickness for AHM birds was significantly greater on the 3rd cycle but shell weight increased significantly on the 2nd cycle. Both traits remained significantly greater for the remaining cycles. The quick response of these two traits to the longer cycles could result from a shift in ovulation towards onset of the dark period and thereby a greater portion of the calcification process during the photoperiod, or increased egg retention time in the oviduct (Morris, 1973). It was also noted that egg numbers decreased from those of birds on the AHM treatment, thus reducing the total calcium demand. The increased length of time in the oviduct resulted in an increase in albumen weight after the fourth cycle (Table 3) and the difference persisted through the 10-cycle test period. Yolk weight, however, did not show a great response to the AHM treatment and increased significantly only for the 8th and 10 cycles. The increase in yolk weight is the one egg trait not related to increased oviduct retention time; however, the accumulation of yolk material continues until ovulation (Gilbert,
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l.l a 1.2* 1.2a 12* 1.1" l.l a 1.2* 15 a 1.2* 1.2* .9*
RESEARCH NOTE
1972) or at least until 2 or 3 h prior to ovulation (Etches et at, 1984). As the oviposition-ovulation interval increases with increased cycle length, it is presumed that the preovulatory follicle is retained in the ovary for an extended period. ACKNOWLEDGMENTS
REFERENCES Buimester, B. R., H. M. Scott, and L. E. Card, 1940. The rate of plumping of eggs immersed in an artificial uterine solution. Poultry Sci. 19: 299-302. Cooper, J. B., and B. D. Barnett, 1976. Ahemeral photoperiod for chicken hens. Poultry Sci. 55: 1183-1187. Etches, R. J., J. N. Petitte, and C. E. AndersonLangmuir, 1984. Interrelationship between the
hypothalamus, pituitary gland, ovary, adrenal gland and open period for LH release in the hen (Gallus domesticus). J. Exp. ZooL 232:501-511. Fox, S., T. R. Morris, and R. C. Jeniung, 1971. The use of non-24 hour cycles to manipulate egg weight in pullets. World's Poult. Sci. J. 27:159.(Abstr.) Gilbert, A. B., 1972. The activity of the ovary in relation to egg production. Pages 3-21 in: Egg Formation and Production. B. M. Freeman and P. E. Lake, ed. British Poultry Science Ltd., Edinburgh, Scotland. Harrison, P. C., G. Schmaier, and J. McGinnis, 1969. Reproductive development and response of White Leghorn pullets subjected to increasing day length at different ages. Poultry Sci. 48: 1021-1026. Hawes, R. O., N. Lakshmanan, and L. J. Ming, 1991. Effect of ahemeral light:dark cycles on egg production in early photostimulated brown-egg type pullets. Poultry Sci. 70:1481-1486. Ibaraki, K., S. Yoshida, Y. Kunimatsu, and Y. Kojima, 1985. The effect of 28-h ahemeral light-dark cycle on egg production and egg shell qualities of laying hens. Jpn. Poult. Sou 22:181-189. Leeson, S., J. D. Summers, and R. J. Etches, 1979. Effect of a 28-hour light:dark cycle on egg shell quality of end-of-lay birds. Poultry Sd. 58: 285-287. Morris, T. R., 1973. The effect of ahemeral light and dark cycles on egg production in the domestic fowl. Poultry Sci. 52:423-445. Morris, T. R., and S. Fox, 1958. Light and sexual maturity in the domestic fowl. Nature 181: 1453-1454. SAS Institute, 1982. SAS® User's Guide: Statistics. 1983 Edition. SAS Institute Inc., Cary, NC. Shanawany, M. M., 1982. The effect of ahemeral light and dark cycles on the performance of laying hens. World's Poult. Sci. J. 38:120-126.
Downloaded from http://ps.oxfordjournals.org/ at New York University on May 22, 2015
The present research was supported by state and Hatch funds allocated to the Maine Agricultural Experiment Station of the University of Maine and grants from Agway, Inc., Syracuse, NY 13221 and Arbor Acres Farm, Inc., Glastonbury, CT 06033. Vaccines were kindly donated by the Maine Biological Laboratories, Waterville, ME 04901. The authors are indebted to H. Michael Opitz for outlining the health program and to William Halteman and Lorraine Whitmore King for assistance in analysis of data.
569
1992 Poultry Science 71S65-569
INTRODUCTION Previous research aimed at inducing early sexual maturity with white egg pullets resulted in reduced egg size and birds taking a longer time to reach their expected egg size (Morris and Fox, 1958; Harrison et ah, 1969). Lightrdark cycles longer than 24 h (ahemeral cycles) have been studied in an attempt to increase egg size (Fox et ah, 1971; Morris, 1973; Shanawany, 1982), but the reduction in egg numbers associated with these treatments was an undesirable effect. It has been demonstrated, however, that the increase in egg weight and reduction in egg number due to ahemeral cycles are
1 Maine Agricultural Experiment Station, Publication Number 1608. 2 Present address: Department of Animal and Veterinary Sciences, University of Massachusetts, Amherst, MA 01002. •To whom correspondence should be addressed.
completely reversible once the pullets are returned to a 24-h cycle. Moreover, egg production has been shown to be equal to that of pullets that were maintained continuously under 24-h light:dark cycles (Shanawany, 1982). Previous work at the University of Maine (Hawes et al., 1991) compared hemeral (24 h) with ahemeral (26 h) lighting schedules for early (16 wk) lightstimulated pullets. Egg weight was significantly improved during the ahemeral schedule (27 to 30 wk); however, egg numbers were significantly reduced for this period, as well as for the entire period of production (19 to 59 wk). Shanawany (1982) reported that with cycle lengths between 26 and 28 h, the reduction in rate of lay was not as great as the increase in egg weight. By combining the results of egg numbers and egg weights, the total egg mass under these cycles was slightly higher than that under 24-h cycles. The 26-h cycle does not comply with a conven-
565
Downloaded from http://ps.oxfordjournals.org/ at New York University on May 22, 2015
ABSTRACT Brown egg pullets (DeKalb Sex-Sal) were subjected to an ahemeral lighting program to determine their response in terms of egg traits. All birds were reared on a conventional lighting program of 10 h light (L):14 h dark (D) to 16 wk. At 16 wk, all birds received a schedule of 11L:13D followed by a weekly 1-h increase in photoperiod to 14L:10D at 19 wk. Control treatment (CON) birds were continued on this schedule. Ahemeral treatment (AHM) birds were given a 28-h schedule 14L:14D at 23 wk that was continued to 28 wk, then returned to a 24-h cycle of 14L:10D. Shell weight responded quickly to the ahemeral treatment and showed a significant (P<.05) increase during the 2nd 28-h cycle. Shell thickness and total egg weight showed significant increases on the 3rd cycle; albumen weight showed an increase on Cycle 4, and yolk weight increased significantly only on the 8th cycle. When AHM treatment birds were returned to a conventional cycle (14L:10D) at 28 wk, the total weight remained significantly higher (P<.05) as late as Cycle 6. (Key words: ahemeral lightdark cycles, early photostimulation, brown egg pullets, shell quality, egg weight)
566
LAKSHMANAN ET AL.
published results indicating the number of cycles required to produce changes in egg components. The following experiment was designed and carried out to determine the number of cycles required to produce a significant effect on egg weight and egg components following an abrupt change from a hemeral to an ahemeral lighfcdark cycle, and to determine the effect on egg weight following the termination of an ahemeral cycle. MATERIALS AND METHODS Day-old DeKalb Sex-Sal pullets were vaccinated for Marek's disease and brooded in battery units for Weeks 1 to 4, then transferred to conventional floor pens for Weeks 5 to 16. They received 24 h of light/day [24 h light (L):0 h dark (D)] to 3 days of age followed by 8 h of light daily (8L:16D) to 8 wk. From 8 to 16 wk the birds received a schedule of 10L:14D. All birds were fed a starter ration (20% CP) up to 8 wk. A grower mash (14% CP) was fed from 8 to 19 wk, followed by a 17% CP layer ration for the remainder of the trial. Pullets were vaccinated for avian encephalomyelitis at 10 wk; for Newcastle disease at 16 days, 36 days, and 16 wk; and for infectious bursal disease at 14 days, 34 days, and 16 wk of age. Flock
TABLE 1. The effect of ahemeral lighfcdark cycles1 on egg weight
Cycle
Treatment period Conventional Ahemeral (14L:10D) (14L:14D)
02 1 2 3 4 5 6 7 8 9 10
49.2 50.9 50.6 51.1 51.3 51.9 52.8 52.2 52.2 53.1 53.3
Posttreatment period Conventional Ahemeral (14L:10D) (14L:10D) fr>
± 7.6a ± 4.1a ± 4.0* ± 4.1b ± 4.0b ± 4.0b ± 4.7b ± 4.4b ± 4.3b ± 4.8b ± 4.4b
50.4 ± 4.0s 523 ±4.7 a 52.4 ± 5.0* 53.1 ± 4.3a 53.7 ± 4.8a 54.6 ± 4.8a 552 ± 4.4a 55.8 ± 5.4a 56.8 ± 5.4a 573. ± 4.4a 56.4 ± 4.3a
*>
58.0 ± 3.8a 57.4 ± 4 5 b 60.0 ± 5.0s 57.7 ± 4.6b 592 ± 4 ! a 572. ± 4.8b 57.8 ± 4.2* 57.8 ± 5.6a 59.1 ± 5.0" 572 ± 4.3a 58.1 ± 4.6a
59.9 60.5 60.0 60.4 58.7 60.1 58.7 572 57.6 582 58.0
± 5.4a ± 5.6a ± 4.0s ± 3.8* ± 4.6a ± 4.0s ± 3.1a ± 4.6a ± 4.4a ± 4.7* ± 3.7*
ab ' Means (± SD) with no common superscripts within the same row and within either the Treatment or Posttreatment columns are significantly different (P<.05). 1 14L:10D = 14 h lighfclO h dark; 14L:14D = 14 h light:14 h dark. ^Treatment period = 23 wk; posttreatment period = 28 wk.
Downloaded from http://ps.oxfordjournals.org/ at New York University on May 22, 2015
tional working day. The use of 28-h cycles has interesting possibilities, as six cycles occur during seven 24-h periods and therefore routine management is easier to organize (Morris, 1973). Water is a major component of albumen. Fifteen to 16 g of water is added to the developing egg while it remains in the uterus (Gilbert, 1972). Burmester et al. (1940) reported that the amount of water intake was proportional to the amount of time the developing egg spent in the oviduct and that increasing the light:dark cycle length would increase the amount of time the developing egg spends in the oviduct. Low Haugh unit values associated with eggs collected from birds exposed to ahemeral cycles were reported by Cooper and Barnett (1976). No differences in the dry matter content of eggs obtained from hens exposed to a 28-h light:dark cycle were observed by Leeson et al. (1979). The above reports suggest that the increase in albumen weight reported by earlier researchers might be due to an increased deposition of water resulting from longer retention time in the uterus. Birds subjected to lighfcdark cycles longer than 24 h usually laid eggs during the dark period and the pattern of lay could be changed within three to four cycles (Ibaraki et al., 1985). There are no
RESEARCH NOTE
567
TABLE 2. The effect of ahemeral lighfcdark cycles1 on shell thickness and weight Shell thickness
O2 1 2 3 4 5 6 7 8 9 10
.35 35 .35 .35 .36 .35 .35 .33 .35 .33 .34
Shell weight Ahemeral (14L:14D)
Conventional (14L:10D)
.34 ± .03* 35 ± .03* .36 ± .03a .37 ± .04" 37 ± ,04a .38 ± ,04a .37 ± .04a 37 ± .03a 37 ± .03a .37 ± .03a .36 ± .04a
53 ± 5 a 5 3 ± .6a 53 ± .6b 5.4 ± .6 b 55 ± .6b 55 ± 5 b 55±5b 5.4 ± 5 b 5.6 ± 5 b 55 ± .6 b 5.6 ± 5 b
(mm) — ± .02s ± .03a ± .03a ± .03b ± .03b ± .03b ± .03b ± .03b ± .03b ± .03b ± .02b
Ahemeral (14L:10D) ftr> HS'
53 55 5.7 5.8 5.9 6.1 6.1 62 63 63 6.1
± 5a ±.7" ± .6a ± .6a ± .7* ± .7 s ± .7 s ±.7" ± .7" ± .6a ± .7*
ab ' Means (± SD) with no common superscripts within the same row and within either the Shell thickness or Shell weight columns are significantly different (P<.05). h4L:10D = 14 h light:10 h dark; 14L:14D = 14 h light:14 h dark. 223 wk.
health was monitored throughout the trial and all dead birds were necropsied. At 16 wk, pullets were housed two per laying cage (25.4 x 45.7 cm) in four semienvironmentally controlled, lightproof rooms. There were two treatments with eight replicates per treatment, consisting of 21 cages (42 birds) each, divided between each of two rooms. Thus each room held 168 (four replicates) and each treatment consisted of 336 birds. All birds received a conventional 24-h lighting program of 11L:13D at 16 wk. A 1-h increase in photoperiod was provided weekly until the total photoperiod reached 14 h (14L:10D) at 19 wk. This schedule was maintained throughout the trial for Treatment 1 (CON). Birds on Treatment 2 were continued on the schedule of 14L:10D to 23 wk, when egg production was approximately 50% (henday). At 23 wk, birds in two of the rooms were switched to a 28-h cycle of 14L:14D (AHM), which was continued until 28 wk then returned to a 24-h schedule (14L: 10D). To determine cycle effects, 50 eggs were collected on each "cycle day" for each treatment. Eggs were also collected the
4
B. C. Ames Co., Waltham, MA 02154.
cycle prior to the day on which birds were 23 wk and this is termed "Cycle 0" in Tables 1 through 3. The AHM treatment (14L-.14D) was then applied and eggs were collected on each of the 10 following cycledays. Eggs were collected the cycle prior to the day on which birds were 28 wk and this is termed "Cycle 0" (postfareatment period) in Table 1. Birds were then returned to a hemeral cycle (14L:10D) and eggs were collected for the 10 following cycle-days. The effect of a return to the conventional lighting was determined for egg weight only. Total egg weight was individually recorded; eggs were then broken out and shell weights were determined after the inner surface had been wiped dry with tissue. Yolk weight was recorded after carefully rolling the yolk on a paper towel to remove adherent chalazae; albumen weight was determined by difference. Shells were air-dried for 48 h and thickness plus membranes determined to an accuracy of .01 mm using an Ames™ micrometer.4 All data were analyzed with General Linear Models (GLM) procedures (SAS Institute, 1982). Means were calculated by replicate for each treatment for all dependent variables. The GLM procedure (SAS Institute, 1982) was employed using a nested model statement: dependent vari-
Downloaded from http://ps.oxfordjournals.org/ at New York University on May 22, 2015
Cycle
Conventional (14L:10D)
568
LAKSHMANAN ET AL. TABLE 3. The effect of ahemeral lighfcdark cycles1 on yolk and albumen weight Yolk weight
Cycle
Conventional (14L:10D)
Ahemeral (14L:14D)
02 1 2 3 4 5 6 7 8 9 10
11.1 ± 1.3a 11.3 ± 1.3a 11.3 ± 1.2a 115 ± 1.2a 11.5 ± 1.3a 12.1 ± 1.8a 11.9 ± 1.2a 11.7 ± 1.0* 11.7 ± l.l b 125 ± l.l a 12.1 ± l.l b
11.1 ± 115 ± 115 ± 11.8 ± 12.0 ± 1Z1 ± 11.9 ± 122 ± 125 ± 12.7 ± 12.9 ±
Albumen weight Conventional Ahemeral (14L:10D) (14L:10D) (g) 3X8 343 34.0 342 34.3 34.3 35.4 35.4 35.0 35.4 35.6
± 7.0a ± 35 a ± 3.1a ± 3.1a ± 32h ± 35 b ± 4.0b ± 3.7b ± 3.6b ± 3.8b ± 35 b
34.0 ± 2.9* 355 ± 3.6a 352 ± 3.7* 355 ± 32* 35.9 ± 3.8a 365 ± 3.8a 372 ± 3.7* 37.4 ± 4.1a 38.0 ± 4.4a 38.3 ± 3.7* 37.4 ± 35 a
ab ' Means (± SD) with no common superscripts within the same row and within either the Yolk weight or Albumen weight column are significantly different (P<.05). 1 14L:10D = 14 h lighfclO h dark; 14L:14D = 14 h light:14 h dark. 223 wk.
able = treatment + room (treatment) + replicate (room). Mean square for treatment and room (treatment) was used as the hypothesis effect (numerator) and the mean square for room (treatment) and replicate (room) as error team (denominator), respectively. Replicates (42 birds per replicate, four replicates per room) were used as an experimental unit only if there were no significant interaction among the replicates within the rooms. Significance was determined at P<.05 unless otherwise noted. RESULTS AND DISCUSSION The effect of light cycle on egg weight is shown in Table 1. There was a significant increase in egg weight during the third AHM cycle. Ibaraki et ah (1985) reported that complete entrainment of oviposition to a change in light occurred after three to four cycles. Results presented here showed a significant difference in egg weight following the entrainment to the new cycles, and egg weight continued to be significantly larger for the entire 10 cycles. Returning birds to a conventional schedule (posttreatment period, Table 1), the larger egg size persisted as late as Cycle 5 before it became insignificantly different from eggs
produced under the conventional schedule. Both shell thickness and shell weight responded to an AHM cycle at the same time period as total egg weight (Table 2). Shell thickness for AHM birds was significantly greater on the 3rd cycle but shell weight increased significantly on the 2nd cycle. Both traits remained significantly greater for the remaining cycles. The quick response of these two traits to the longer cycles could result from a shift in ovulation towards onset of the dark period and thereby a greater portion of the calcification process during the photoperiod, or increased egg retention time in the oviduct (Morris, 1973). It was also noted that egg numbers decreased from those of birds on the AHM treatment, thus reducing the total calcium demand. The increased length of time in the oviduct resulted in an increase in albumen weight after the fourth cycle (Table 3) and the difference persisted through the 10-cycle test period. Yolk weight, however, did not show a great response to the AHM treatment and increased significantly only for the 8th and 10 cycles. The increase in yolk weight is the one egg trait not related to increased oviduct retention time; however, the accumulation of yolk material continues until ovulation (Gilbert,
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l.l a 1.2* 1.2a 12* 1.1" l.l a 1.2* 15 a 1.2* 1.2* .9*
RESEARCH NOTE
1972) or at least until 2 or 3 h prior to ovulation (Etches et at, 1984). As the oviposition-ovulation interval increases with increased cycle length, it is presumed that the preovulatory follicle is retained in the ovary for an extended period. ACKNOWLEDGMENTS
REFERENCES Buimester, B. R., H. M. Scott, and L. E. Card, 1940. The rate of plumping of eggs immersed in an artificial uterine solution. Poultry Sci. 19: 299-302. Cooper, J. B., and B. D. Barnett, 1976. Ahemeral photoperiod for chicken hens. Poultry Sci. 55: 1183-1187. Etches, R. J., J. N. Petitte, and C. E. AndersonLangmuir, 1984. Interrelationship between the
hypothalamus, pituitary gland, ovary, adrenal gland and open period for LH release in the hen (Gallus domesticus). J. Exp. ZooL 232:501-511. Fox, S., T. R. Morris, and R. C. Jeniung, 1971. The use of non-24 hour cycles to manipulate egg weight in pullets. World's Poult. Sci. J. 27:159.(Abstr.) Gilbert, A. B., 1972. The activity of the ovary in relation to egg production. Pages 3-21 in: Egg Formation and Production. B. M. Freeman and P. E. Lake, ed. British Poultry Science Ltd., Edinburgh, Scotland. Harrison, P. C., G. Schmaier, and J. McGinnis, 1969. Reproductive development and response of White Leghorn pullets subjected to increasing day length at different ages. Poultry Sci. 48: 1021-1026. Hawes, R. O., N. Lakshmanan, and L. J. Ming, 1991. Effect of ahemeral light:dark cycles on egg production in early photostimulated brown-egg type pullets. Poultry Sci. 70:1481-1486. Ibaraki, K., S. Yoshida, Y. Kunimatsu, and Y. Kojima, 1985. The effect of 28-h ahemeral light-dark cycle on egg production and egg shell qualities of laying hens. Jpn. Poult. Sou 22:181-189. Leeson, S., J. D. Summers, and R. J. Etches, 1979. Effect of a 28-hour light:dark cycle on egg shell quality of end-of-lay birds. Poultry Sd. 58: 285-287. Morris, T. R., 1973. The effect of ahemeral light and dark cycles on egg production in the domestic fowl. Poultry Sci. 52:423-445. Morris, T. R., and S. Fox, 1958. Light and sexual maturity in the domestic fowl. Nature 181: 1453-1454. SAS Institute, 1982. SAS® User's Guide: Statistics. 1983 Edition. SAS Institute Inc., Cary, NC. Shanawany, M. M., 1982. The effect of ahemeral light and dark cycles on the performance of laying hens. World's Poult. Sci. J. 38:120-126.
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The present research was supported by state and Hatch funds allocated to the Maine Agricultural Experiment Station of the University of Maine and grants from Agway, Inc., Syracuse, NY 13221 and Arbor Acres Farm, Inc., Glastonbury, CT 06033. Vaccines were kindly donated by the Maine Biological Laboratories, Waterville, ME 04901. The authors are indebted to H. Michael Opitz for outlining the health program and to William Halteman and Lorraine Whitmore King for assistance in analysis of data.
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