Ahemeral Cycles Research Articles

Zebrafish Temperature Selection and Synchronization of Locomotor Activity Circadian Rhythm to Ahemeral Cycles of Light and Temperature

In addition to light cycles, temperature cycles are among the most important synchronizers in nature. Indeed, both clock gene expression and circadian activity rhythms entrain to thermocycles. This study aimed to extend our knowledge of the relative strength of light and temperature as zeitgebers for zebrafish locomotor activity rhythms. When the capacity of a 24∶20°C (thermophase∶cryophase, referred to as TC) thermocycle to synchronize activity rhythms under LL was evaluated, it was found that most groups (78%) synchronized to these conditions. Under LD, when zebrafish were allowed to select the water temperature (24°C vs. 20°C), most fish selected the higher temperature and showed diurnal activity, while a small (25%) percentage of fish that preferred the lower temperature displayed nocturnal activity. Under conflicting LD and TC cycles, fish showed diurnal activity when the zeitgebers were in phase or in antiphase, with a high percentage of activity displayed around dawn and dusk (22% and 34% of the total activity for LD/TC and LD/CT, respectively). Finally, to test the relative strength of each zeitgeber, fish were subjected to ahemeral cycles of light (T=25 h) and temperature (T=23 h). Zebrafish synchronized mostly to the light cycle, although they displayed relative coordination, as their locomotor activity increased when light and thermophase coincided. These findings show that although light is a stronger synchronizer than temperature, TC cycles alone can entrain circadian rhythms and interfere in their light synchronization, suggesting the existence of both light‐ and temperature‐entrainable oscillators that are weakly coupled.

Delay of Ovarian Development in Japanese Quail Reared under Short or Long Ahemeral Cycles.

This study was designed to investigate the influence of day length on sexual maturity in female Japanese quail (Coturnix coturnix japonica). At 10 days of age, chicks were divided into four groups; 21H (14L:7D), 24H (16L:8D), 27H (18L:9D) and 30H (20L:10D). At 20, 30, 40 and 50 days of age, 9-10 birds from each group were selected randomly, weighed, and slaughtered to determine ovary weight and the number of ovarian follicles. The age at the first egg and the egg production rate were recorded until 70 days of age. Overy weights in 21H, 27H and 30H at 40 days of age were significantly less than that of birds in 24H (P<.01). At 50 days of age, however, no significant differences were found among groups in ovary weight. The egg production rate was also highest in 24H and the difference between 24H and 30H was statistically significant (P<.01). It was suggested that the female quail exposed to ahemeral light/dark cycle might be influenced only in the early stage of ovary growth, but thereafter, compensatory growth might occur and restore the delay of growth.

Feeding duration in young rats exposed to ahemeral LD cycles

(1994). Feeding duration in young rats exposed to ahemeral LD cycles. Biological Rhythm Research: Vol. 25, No. 2, pp. 185-190.

Influence of sequence length on the response to ahemeral lighting late in lay

1. An experiment is described in which 96 individually-caged SCWL hens in two rooms were used to investigate the response to changing to a 28-h cycle using a reverse treatment design. 2. The application of the 28-h cycle did not affect mean rate of lay but increased mean egg weight and egg output. 3. Grouping the birds according to their preliminary sequence length yielded an interesting outcome. In both rooms, birds with short sequences (< or = 6 eggs) produced significantly more eggs under the 28-h cycle, while those with long sequences (> 6 eggs) produced marginally fewer eggs. The same trend was also evident with egg output. 4. Changing from 24-h to 28-h increased yolk and albumen weights as well as shell quality. However, relative to egg weight, no measurable effect was detected due to light cycle, age or sequence length on yolk and albumen weights. 5. The paper provides new evidence suggesting that long ahemeral cycles could be used to improve egg production as well as shell thickness in flocks with modest rates of lay.

Ahemeral lighting and reproductive efficiency in breeding flocks

The paper addresses all feasible applications of long ahemeral light cycles in breeding flocks and reviews the limited published studies. Long cycles are likely to be most beneficial towards the en...

Response of layers to ahemeral light cycles incorporating age at application and changes in effective photoperiod

The possible influence of age at change in cycle length and differences in effective photoperiod (Δp) on the response of layers to ahemeral light cycles have been examined. A brief account of the physiology of pattern of lay in the hen is given.When an ahemeral light cycle is applied, mean rate of lay in relation to a normal 24-h cycle changes. The change in mean rate of lay depends upon the rate of ovarian follicular maturation of the individuals in the flock at the time of change to an ahemeral cycle. Early in lay, when rate of follicular maturation is rapid, changing to a long light cycle reduces rate of lay, whereas changing to a short cycle could increase rate of lay. As rate of follicular maturation declines with age, changing to a long cycle late in lay leads to an improvement in rate of lay. Based on published reports, a theoretical curve of the response to a 28-h cycle is given showing the significance of age at which application is made. From the available literature it appears that, provided Δp ≥ 0, response to ahemeral light cycles is not affected.

The Effects of Ahemeral Light-Dark Cycles Early in the Laying Cycle on Egg Production in White Leghorn Hens

Studies were conducted to compare the effects of two ahemeral (AH) light-dark cycles of 26 and 28 h (AH26 and AH28) with a 24-h hemeral (H) cycle early in the lay cycle on egg production and size. Nine rooms, three per treatment, each holding 264 hens, were maintained with identical photoperiods. The scotoperiod was increased to provide (he desired AH “day length” at 20 wk of age. Later decreases of the AH cycles back to the H cycle were accomplished by decreasing the scotoperiod only.There were no significant differences in egg production in Experiment 1 for both AH26 and AH28 compared with the H control. However, egg size as percentage of large (56 g) and above was significantly improved at 28 wk of age for both AH treatments.In Experiment 2, egg size was again significantly higher for AH28. This was accompanied by a significant increase in egg production for 28-day Periods 1 and 2 and a decrease in Periods 3, 7, and 10 versus H.A new AH26 lighting program was then tested in Experiments 3 and 4. This resulted in significant increases in egg production for Periods 2 (Experiment 3) and 1 (Experiment 4). Within experiment, annual egg production was similar for H and AH26 birds. Egg size, as percentage of large and above, was also significantly increased for AH26 at 25, 26, 27, and 29 wk of age (Experiment 3) and 26 wk (Experiment 4).A tested AH26 lighting program leading to increased pullet egg size with no loss in egg numbers for 20-wk-old pullets is outlined.

Ahemeral light cycles and egg quality

The literature concerning the influence of ahemeral light cycles on the quality of eggs is reviewed. Results pooled from published reports were used to arrive at a quantitative relationship between...

Production responses of laying hens to 28 h bright:dim light cycles using different light intensity ratios and a 24 h temperature regimen.

Seven hundred and twenty laying hens housed in 8 environmentally-controlled rooms were changed from a 24 h light:dark cycle to a 28 h ahemeral bright:dim cycle. The ahemeral cycles consisted of periods of bright and dim light in ratios of intensity: 5:1, 10:1 and 30:1. The last regimen was applied either at a constant 21 degrees C or with a 24 h alternating temperature varying between 21 and 31 degrees C. Eggs were collected hourly from each bird for 5 d immediately before the introduction of ahemeral cycles and then over the same period 2 weeks after introduction. The interval between successive eggs within sequences lengthened with increasing bright:dim ratios. The increase in egg weight and decrease in deformation score were not significant. Total egg mass output was not altered. The cycling temperature regimen did not alter the entrainment of the birds, although intra-sequence interval decreased. The decrease in egg weight and increase in deformation score were not significant.

Changes in Ring-Necked Pheasants’ (Phasianus colchicus) Egg Formation Time, Oviposition Lag Time, and Egg Sequence Length Due to Ahemeral Light-Dark Cycles

A total of 108 pheasant hens was exposed to either a conventional 24-hr (14L:10D), an ahemeral 22-hr (14L:8D), or an ahemeral 26-hr (14L:12D) light-dark (L:D) cycle. Total lag time for each egg sequence was greater in the ahemeral cycles than in the conventional L:D cycle, resulting in significant (P<.05) differences in egg formation times (EFT) or intraclutch intervals of 26.4, 25.8, and 27.5 hr, respectively. The EFT under the ahemeral 26-hr L:D cycle was synchronized (within 1.5 hr) with the length of the L:D cycle. This light cycle resulted in the longest egg sequences (average 8.5 eggs per sequence) produced under any of the three L:D cycle treatments due to a shorter pause in oviposition. Values were significantly (P<.05) different from the average values obtained under the conventional 24 hr L:D cycle (4.9 egg per sequence) and ahemeral 22 hr L:D cycle (3.5 eggs per sequence).

External factors affecting the duration of broody behavior in the ring dove ( Streptopelia risoria)

The object of this study was to investigate factors which determine the duration of sitting in ring doves. This normally lasts ca. 19 days from laying, with very small variation. The period is made up of 15 days incubating eggs and 4–5 days brooding squabs. The duration of sitting is unaffected by substituting fresh or sterile eggs, and can only be slightly influenced by substituting foster squabs or new eggs just before or after hatching. The sitting period appears to be predetermined to run for 19 days following laying. The maintenance of sitting, however, requires the presence of the nest and eggs, and can be drastically varied by keeping subjects in continuous daylight or on a day of 6 hr light:6 hr dark (6 L:6 D). Birds kept on ahemeral cycles (11 L: 10 D; 13 L:14 D) displayed significantly different periods of incubation on infertile eggs and recycling, indicative of an endogenous circadian basis to the timing mechanism.

Effect of Ahemeral Light-Dark Cycles on Production and Egg Quality of Laying Hens

Abstract To compare the effects of a long but decreasing light-dark cycle (LDLDC) on egg weight and shell quality and a short light-dark cycle (SLDC) on egg production, 264 University of Missouri-Columbia (UMC) Single Comb White Leghorn (SCWL) pullets and 96 SCWL pullets from a leading commercial (C) strain were individually caged in light-controlled rooms. Treatments were: 1) 26-hr light-dark cycle (LDC) reduced to 23 hr, 2) 24-hr LDC (controls), and 3) 23-hr LDC applied at 22 weeks of age with photoperiods of 14 hr gradually increased to 18 hr. Data were obtained on hen-day egg production (HDP), egg weight, egg mass, egg specific gravity, and yolk weight. The LDC effect was significant (P .05) on initial egg specific gravity for the C strain.

Early Application of Conventional or Ahemeral Photoperiods in an Attempt to Improve Egg Size

Treatments were arranged as a 2 × 2 × 3 × 2 factorial representing 2 housing ages, 2 17% crude protein diets with and without added methionine and corn oil, 3 weight groups, and 2 light treatments 14L:10D and 14L:14D. Leghorn pullets were classified as heavy, medium, or light weight at either 15 or 19 weeks of age, and at those times, moved to individual laying cages maintained in rooms with either a 14L:10D or 14L:14D photoperiod. Birds were fed a conventional 17% CP corn-soybean diet or one containing additional methionine and corn oil. Each factorial treatment was represented by four replicate groups of seven consecutive individually caged birds. The trial was terminated at 71 weeks of age. Ahemeral lighting resulted in increased egg weight, body weight, and inferior shell quality, whereas egg production and feed intake were reduced (P<.01). Early transfer at 15 weeks resulted in loss of egg numbers (P<.01), while body weight at transfer was positively correlated with egg production, feed intake, and egg weight. Diet had no effect on production.In a second and third trial Leghorn pullets were reared on constant photoperiods of 8 or 14 hr. At 15 or 19 weeks of age, pullets were transferred to environments providing regular or ahemeral cycles as described for Trial 1. Again, pullets were classified according to weight and fed diets of low or high nutrient density. Both trials were terminated at 31 weeks of age. The effects of ahemeral lighting in Trial 2 on food intake, egg weight, egg production, and body weight were as described in Experiment 1, although in this situation eggshell quality was improved. Rearing birds on 14 vs. 8 hr photoperiods, in both trials, resulted in loss in egg numbers (P<.01), although egg weight was increased (P<.01). A final trial also involved rearing on photoperiods of 8 vs. 14 hr for weight-segregated pullets fed regular or high nutrient density diets. Adult photoperiod was a constant 14 or 17 hr, and again the trial was terminated at 31 weeks of age. Heavier pullets, at transfer time of 19 weeks, produced the greatest amount of eggs that were also larger (P<.01) while consuming more feed (P<.01). A rearing photoperiod of 14 vs. 8 hr reduced egg numbers (P<.01) while increasing egg size (P<.05) and body weight (P<.01).It is concluded that ahemeral lighting can be used to stimulate early egg size, although this is at the expense of egg numbers. While increasing the rearing photoperiod from 8 to 14 hr stimulates pullet growth, subsequent egg production is reduced, possibly due to the insufficient photostimulation at time of transfer.

Ahemeral Light Cycles and Protein Levels for Older Laying Hens

Variations in light:dark ratios and timing schedules of 26- and 28-hr ahemeral cycles were examined for their effects on shell quality and egg weight. In two experiments utilizing 2578 White Leghorn Laying hens, 16-week long ahemeral treatments were instituted abruptly late in the pullet laying season and again following a forced-molt production cycle.Ahemeral light-dark cycles of 28-hr length resulted in significantly heavier shell and egg weights as compared to 26-hr ahemeral cycles or the control 24-hr cycle. Ahemeral 26-hr cycles did not significantly increase egg weight compared to the 24-hr controls but did increase shell weight. Varying total light in 28-hr cycles from 20 to 10 hr with the light given in either one continuous period or interrupted by two intermediate dark periods and as either 18 or 16 hr of continuous light in the 26-hr cycles did not result in significant differences in shell or egg weight compared to the other treatments of the same cycle length. Rate of lay was lower for the hens given only 10 hr of interrupted light in a 28-hr cycle but was not otherwise affected by light treatment.Dietary protein levels of 15% (as compared to 17%) and 14% (as compared to 16 and 18%) consistently reduced egg weights (P<.10 or <.05) and tended to improve shell quality.These experiments further demonstrated the effectiveness of 26- and 28-hr ahemeral light-dark cycles in increasing shell weight as a method of extending the economic laying period of either older pullets or force-molted hens without a sacrifice in the number of eggs produced.

The Effect of Ahemeral Light and Dark cycles on the Performance of Laying Hens—(A Review)

The Effect of Ahemeral Light and Dark cycles on the Performance of Laying Hens—<i>(A Review)</i>

Shell Quality of Eggs from Hens Exposed to 26- and 27-Hour Light-Dark Cycles from 56 to 76 Weeks of Age

The effect of ahemeral light-dark cycles on shell quality and laying hen performance near the end of the laying year was measured using 1342 Single Comb White Leghorn laying hens. The hens were housed in multiple-bird cages in 18 separate, windowless, fan-ventilated rooms. Hens were exposed abruptly to either a 26-hr cycle (16L:10D) or a 27-hr cycle (16L:11D) at either 56 or 60 weeks of age; a 26-hr cycle at 56 weeks, which was increased t o 27-hrs at 60 weeks of age; or remained on a 24-hr cycle (16L:8D) until the experiment was terminated at 76 weeks of age.Shell weight, and consequently shell quality, expressed as shell weight (mg) per square centimeter egg surface area (SWUSA), were significantly increased after 1 week exposure to either ahemeral cycle. The increase in shell weight was greatest for the hens on the 27-hr cycle, but because egg weight also was significantly increased by this treatment, there was no difference in SWUSA between the two ahemeral cycles. The magnitude of increase in shell weight and SWUSA, but not egg weight, was less in the hens exposed to the ahemeral cycles at 60 weeks of age. This was due to shell weight progressively decreasing with increasing age of the hens on all three light cycles. But SWUSA, irrespective of when the ahemeral cycles were initiated, was as great or greater through 72 weeks of age than SWUSA measured in these hens at 53 weeks of age prior to the experiment.The ahemeral cycles had no significant effect on albumen quality, rate of lay adjusted to a 24-hr basis, hen body weight, or mortality. There was a significant improvement in feed efficiency for the hens on the 27-hr cycle.

The photoperiodic effect of ahemeral light-dark cycles which entrain circadian rhythms.

1. A 27-h cycle of light and dark provides a greater gonadotrophic stimulus to the laying fowl, as judged by sexual maturity and rate of lay, than a 24-h cycle incorporating the same photoperiod. 2. An hypothesis put forward to account for these effects states that Effective Photoperiod equal p + c - b, where p = actual photoperiod, c = cycle length and b = the period of the endogenous biological clock. 3. Two experiments designed to test this hypothesis have yielded results which are consistent with it. 4. A poultryman who use an ahemeral cycle to alter egg weight or shell thickness and then whishes to transfer his flock back to a 24-h cycle should calculate the difference between the two cycle lengths and then add this quantity to the prevailing photoperiod to find the appropriate amount of light to be used in the 24-h cycle.

The Effects of Ahemeral Light and Dark Cycles on Growth and Sexual Maturity in Chickens

Replacement pullets were reared in environmentally controlled chambers in which the lighting schedule was 14L:7D, 14L:10D or 14L:14D. Both temperature and humidity were constant throughout the experiment. Neither body weight nor age at sexual maturity were altered by these lighting schedules. It was concluded that a unifying hypothesis to explain the various effects of photoperiods on growth and sexual maturity would probably not involve circadian rhythms.

The Effects of Ahemeral Light and Dark Cycles on Egg Production in the Fowl

This review deals first with theoretical aspects of the subject and discusses a model which attempts to predict rates of lay for hens kept under non-24-hour (ahemeral) light-dark cycles. It is concluded that the model is unsatisfactory, chiefly because the intra-clutch interval for an individual hen does not remain stable under different light-dark cycles. It is suggested that the average interval between all ovipositions may be a more characteristic feature of a hen than the mean intra-clutch interval.New evidence is presented concerning the effect of ahemeral cycles on rate of lay, egg weight, yolk weight, albumen weight, shell weight, time of ovulation and time of peak luteinising hormone release. Hens exposed to 27 h. and 30 h. light-dark cycles lay larger eggs but fewer eggs than 24 h. controls. These effects are achieved rapidly and are readily reversible, so that ahemeral cycles may be used to manipulate egg-weight in practical situations. Eggs formed by hens under a 27 h. light-dark cycle remain, on average, 1 h. longer in the shell gland than those of 24 h. controls. There is also a 10% improvement in shell thickness associated with a 27 h. cycle but this may arise partly because eggs are laid during the dark period and only partly because of the longer oviducal term. The mechanism responsible for the timing of ovulation, which results in eggs being laid during darkness, is considered in detail. It is shown that oviposition times can be controlled by alternating bright light with dim light and the critical intensities needed to achieve phase-setting are described. Finally, it is argued that the mechanisms controlling rate of egg output and timing of oviposition are separate and, though both are influenced by light, the systems are clearly distinguishable so that the photoperiodic and the phase-setting properties of a light pattern should always be considered separately. Egg production can be modified by employing either the photoperiodic properties or the phase-setting properties of light, but the end results are not the same.

Photoperiodic control of diapause in the codling moth

For a southern California strain of the codling moth, Carpocapsa pomonella, the ‘critical day length’ is 13·5 hr. Light regimens of 24 hr with interrupted nights produced diapause response curves with a single mid-point depression. The time of maximal inhibition of diapause did not markedly shift relative to dawn when the duration of the main light period was shortened or lengthened. Photocycles of 48 hr, with 8 hr photophases and interrupted nights, produced two significant depressions of the diapause response curve at 16 and at 40 hr. Ahemeral cycles also produced data consistent with the hypothesis that diapause is timed by a circadian mechanism. Both long days and chilling can terminate diapause. The necessity for adequate experimental replication and the need for large numbers of insects in photoperiodic investigations is stressed.