Gamma-Irradiation Reduces Survivorship, Feeding Behavior, and Oviposition of Female Aedes aegypti

Aedes aegypti is a prominent disease vector that is difficult to control through traditional integrated vector management due to its cryptic peridomestic immature-stage habitat and adult resting behavior, increasing resistance to pesticide formulations approved by the US Environmental Protection Agency, escalating deregistration of approved pesticides, and slow development of new effective chemical control measures. One novel method to control Ae. aegypti is the sterile insect technique (SIT) that leverages the mass release of irradiated (sterilized) males to overwhelm mate choice of natural populations of females. However, one potential liability of SIT is sex sorting errors prior to irradiation, resulting in accidental release of females. Our goal in this study was to test the extent to which irradiation affects female life-history parameters to assess the potential impacts of releasing irradiated females accidentally sorted with males. In this study, we determined that a radiation dose ≥30 Gy-a dose sufficient to sterilize males while preserving their mating competitiveness-may substantially impact longevity, bloodfeeding, oviposition, and egg hatch rate of female Ae. aegypti after being irradiated as pupae. These findings could reduce public concern for accidental release of females alongside irradiated males in an operational Ae. aegypti SIT control program.

Meta-analysis: Supplementary artificial light and goose reproduction

Photoperiod affects poultry reproduction, and in birds, photoperiod regulation is a complex physiological process. In modern poultry production, lighting management has become an important and effective management approach for increasing egg production. Geese are domesticated fowl and in many goose production enterprises animals are allowed to roam in outside pens during the day and are housed indoors at night, so the animals can be exposed to artificial lighting during the night periods. Supplementary artificial lighting resulted in improved reproduction in some studies, but reports have been inconsistent. To evaluate the results from previous studies of supplementary lighting on goose egg production, a meta-analysis was conducted to determine optimal supplementary artificial lighting regimens for geese egg production. Results indicated supplementary artificial light increases mean egg production, the length of the period of egg production before there is cessation of egg production capacity, and fertility. In summary, there were evaluations of data from five studies focused on White Roman geese in the meta-analysis conducted in the present study, however, examination of more breeds is necessary to make more definitive assessments of the findings from this meta-analysis.

Darkness increases the population growth rate of the poultry red mite Dermanyssus gallinae

BACKGROUND

The poultry red mite (PRM), Dermanyssus gallinae, is one of the most economically deleterious ectoparasites affecting egg-laying hens worldwide. It may be possible to control D. gallinae populations by manipulating lighting regimes within poultry units. However, no studies have clearly shown the effects of darkness on the population growth rate of D. gallinae.

METHODS

The effect of darkness on the population growth rate of D. gallinae was investigated, together with the first description of the molecular identity of the mite from China. Mite variables under two lighting regimens (1:23 h L:D and 12:12 h L:D) were compared, including number of mites and eggs, survival and feeding rates, engorgement, oviposition, hatchability and the life-cycle of D. gallinae.

RESULTS

The results showed that the number of mites (13,763 ± 956) and eggs (5424 ± 317) in the rearing system with prolonged darkness of 1:23 h L:D at 4th week were 2.4- and 3.6-fold higher than those under a conventional lighting regimen of 12:12 h L:D, respectively. The feeding rates of mites under prolonged darkness ranged from 36.7 ± 1.1% to 52.0 ± 7.0%, which were significantly higher than those under conventional lighting regimen (ranging from 22.6 ± 1.9% to 37.3 ± 1.6%). The mean weight of engorged females (0.26 ± 0.01 mg) and the mean number of eggs per female (on average 5.87 ± 0.36) under prolonged darkness were significantly higher than those under conventional lighting regimen (0.22 ± 0.01 mg and 3.62 ± 0.31, respectively). However, the survival rate ranging from 98.07 ± 0.10% to 98.93 ± 0.19%, hatchability of 97.93 ± 0.01% and the life-cycle of D. gallinae (9 days) was not affected by the lighting period.

CONCLUSIONS

Our findings demonstrated that prolonged darkness significantly promoted the proliferation levels of D. gallinae, resulting in increased number of mites and eggs in the rearing system. The promoted population growth of D. gallinae was found to be related to the increased feeding rate, engorgement level and oviposition level of mites under prolonged darkness. The egg hatchability, the survival rates and the duration of life-cycle of D. gallinae were not affected by the light regimes.

Influence of Light on Reproductive Rates of Asian Citrus Psyllid (Hemiptera: Liviidae)

The impact of light on reproductive rates of Asian citrus psyllid (Diaphorina citri Kuwayama) was assessed in an air-conditioned, polycarbonate greenhouse. This psyllid is an important pest because it transmits a bacterium presumed responsible for a serious citrus disease known as Asiatic huanglongbing. Numbers of psyllids produced were compared among rearing cages subjected to different amounts of light provided by natural sunlight and light-emitting diode floodlights. Light to some rearing cages was purposely reduced by shading. The cages received a daily mean of 12 h of light (range 7 to 14 h) during immature development. Irradiance during daylight hours in the cages during a 24-h oviposition period varied from 2 to 145 (mean 66) W/m2 and during immature development to the adult stage from 3 to 169 (mean 71) W/m2. Estimates of illuminance during immature development ranged from 354 to 73,500 (mean 22,409) lumens/m2. Oviposition rates were not correlated with these light variables. Numbers of adults produced were positively correlated with daily hours of light (r = 0.57, P = 0.002), irradiance (r = 0.39, P = 0.05), and illuminance (r = 0.59, P = 0.001). For producing large numbers of adults, optimal targets for these light variables as measured in this study were projected to be 14 or more hours of daylight, 60 or more W/m2, and 20,000 or more lumens/m2. Comparisons of oviposition rates and resulting numbers of adults produced in a cage indicated that increasing these light variables increased survival of immatures to the adult stage, possibly because the quality of host plants increased as these light variables increased.

Influence of three artificial light sources on oviposition and half-life of the Black Soldier Fly, Hermetia illucens (Diptera: Stratiomyidae): Improving small-scale indoor rearing

Hermetia illucens (L.), the Black Soldier Fly, has received increased scientific attention for its potential in circular waste management where larvae can serve as feedstuff for livestock and for biodiesel production. The flies occur naturally in (sub)-tropical and warm-temperate climates, and their mating depends on space and sunlight. Small-scale indoor rearing of Black Soldier Flies has been challenging because they react sensitive to artificial light sources and cage sizes, but recent studies have shown that small-scale rearing under artificial light is feasible. Here, we test the influence of three artificial light sources (light-emitting diodes, fluorescent lamps, and halogen lamps) on small-scale indoor rearing. Three experiments were conducted to compare oviposition traits (pre-oviposition period, total oviposition-period, and egg mass per female) and half-life among the three light sources. Oviposition did not differ among the three light sources, but male and female half-life did. Based on the performance of the light-emitting diodes and their outstanding energy efficiency, we recommend this light source for small-scale indoor rearing of Black Soldier Flies.

Effect of UV-A radiation as an environmental stress on the development, longevity, and reproduction of the oriental armyworm, Mythimna separata (Lepidoptera: Noctuidae)

The ultraviolet light (UV-A) range of 320-400 nm is widely used as light trap for insect pests. Present investigation was aimed to determine the effect of UV light-A radiation on development, adult longevity, reproduction, and development of F1 generation of Mythimna separata. Our results revealed that the mortality of the second instar larvae was higher than the third and fourth instar larvae after UV-A radiation. As the time of UV-A irradiation for pupae prolonged, the rate of adult emergence reduced. Along with the extension of radiation time decreased the longevity of adult females and males. However, the radiation exposure of 1 and 4 h/day increased fecundity of female adults, and a significant difference was observed in a 1 h/day group. The oviposition rates of female adults in all the treatments were significantly higher than the control. In addition, UV-A radiation treatments resulted in declined cumulative survival of F1 immature stages (eggs, larvae, and pupae). After exposure time of 4 and 7 h/day, the developmental periods of F1 larvae increased significantly, but no significant effects on F1 pupal period were recorded.

Male irradiation affects female remating behavior in Anastrepha serpentina (Diptera: Tephritidae)

Female remating in target pest species can affect the efficacy of control methods such as the Sterile Insect Technique (SIT) but very little is known about the postcopulatory mating behavior of these pests. In this study, we investigated the remating behavior of female Anastrepha serpentina (Diptera: Tephritidae), an oligophagous pest of Sapotaceae. First, we tested how long the sexual refractory period of females lasted after an initial mating. Second, we tested the effect of male and female sterility, female ovipositing opportunities and male density on female propensity to remate. Lastly, we tested if the amount of sperm stored by females was correlated to the likelihood of females to remate. We found that receptivity of mass-reared A. serpentina females had a bimodal response, with up to 16% of mass-reared A. serpentina females remating five days after the initial copulation, decreasing to 2% at 10 and 15 days and increasing to 13% after 20 days. Compared to fertile males, sterile males were less likely to mate and less likely to inhibit females from remating. Copula duration of sterile males was shorter compared to fertile males. Remating females were less likely to mate with a sterile male as a second mate. Sterile females were less likely to mate or remate compared to fertile females. Opportunity to oviposit and male density had no effect on female remating probability. Sperm numbers were not correlated with female likelihood to remate. Information on the post-copulatory behavior of mass-reared A. serpentina will aid fruit fly managers in improving the quality of sterile males. We discuss our results in terms of the differences this species presents in female remating behavior compared to other tephritids.

The Effect of Ultraviolet-A Radiation Exposure on the Reproductive Ability, Longevity, and Development of the Dialeurodes citri (Homoptera: Aleyrodidae) F1 Generation

Ultraviolet (UV) light has been used worldwide to monitor and trap insect pests. Whitefly adults show conspicuous positive phototactic behavior toward UV light stimuli; however, knowledge of the effect of UV light exposure on various life-history parameters of Dialeurodes citri remains limited. The present research aimed to investigate the effect of ultraviolet radiation (UV-A; long-wave) exposure on the reproduction and longevity of D. citri adults as well as the development of immature (eggs, larvae, and pupae) flies in the F1 generation. Paired D. citri adults were exposed to UV-A radiation for different periods (0, 1, 4, and 7 h/d) until the end of their life. The results of the experiment revealed that fecundity and oviposition rates increased when adults were irradiated for 1 and 4 h/d, but interestingly, both were significantly decreased compared with those of the controls after the longest exposure time (7 h/d). The longevity of adults of both sexes and the cumulative survival of F1 immatures were decreased with increased exposure time. Exposure to UV-A radiation prolonged the developmental time of immature stages, and a positive correlation was observed with exposure time. Exposure to UV light significantly inhibited egg hatching, larval development, pupation, and adult emergence. To the best of our knowledge, this is the first study describing the effect of UV radiation on a homopteran insect pest. This research may provide a foundation for the scientific community to use UV light in the field as an integrated pest management strategy to control this devastating agricultural pest.

Effects of radiation on inherited sterility in the European grapevine moth (Lobesia botrana)

BACKGROUND

The sterile insect technique (SIT) is an alternative, environmentally friendly method for controlling insect pests. In the Lepidoptera, a low dose of gamma irradiation causes inherited sterility (SIT-IS), leading to full sterility in females but only partial sterility in males, which successfully compete with wild males for mates. This study examined the effect of a low radiation dose (150 Gy) on the fitness parameters of male and female Lobesia botrana, a polyphagous and major pest of vineyards found in the Middle East, Europe and the Americas.

RESULTS

Irradiation of the pupae did not affect their emergence rate, flight ability out of a cylinder, male response to sex pheromone in a field cage or male or female mating success. A major effect of irradiation was observed in the significantly reduced number of irradiated females' offspring reaching pupation, and as a consequence a limited number of F2 offspring. The effect of irradiation on male partial sterility (also called inherited sterility) was reflected in the male-biased sex ratio of F1 offspring of irradiated males, the reduced number of F1 offspring and the very low number of F2 descendants.

CONCLUSION

This study demonstrates the feasibility of controlling L. botrana using SIT-IS. Adding this method to the arsenal of environmentally friendly tools to control this pest may assist in further reducing the use of insecticides on edible crops.

Polarotaxis in egg-laying yellow fever mosquitoes Aedes (Stegomyia) aegypti is masked due to infochemicals

Aquatic and water-associated insects need to locate suitable bodies of water to lay their eggs in and allow their aquatic larvae to develop. More than 300 species are known to solve this task by positive polarotaxis, relying primarily on the horizontally polarized light reflected from the water surface. The yellow fever mosquito Aedes (Stegomyia) aegypti has been thought to be an exception, locating its breeding habitats by chemical cues like odour of conspecifics, their eggs, or water vapour. We now demonstrate through dual-choice experiments that horizontally polarized light can also attract ovipositing Ae. aegypti females when the latter are deprived of chemical cues: water-filled transparent egg-trays illuminated by horizontally polarized light from below gained a 94.2% higher total number of eggs than trays exposed to unpolarized light, but only when no chemical substances capable of functioning as cues were present. Ae. aegypti is the first known water-associated insect in which polarotaxis exists, but does not play a dominant role in locating water bodies and can be constrained in the presence of chemical cues.

Effects of ultraviolet radiation on predatory mites and the role of refuges in plant structures

Most studies on ecological impact of solar ultraviolet (UV) radiation generally focus on plants. However, UV radiation can also affect organisms at other trophic levels. Protection against mortality induced by solar UV has, therefore, been hypothesized as one of the reasons why Typhlodromalus aripo hides in the apex of cassava plants during the day and comes out at night to prey on spider mites on leaves. In laboratory experiments using UV lamps, we determined the impact of UVA and UVB radiation on survival and oviposition of two leaf-inhabiting mites (Amblydromalus manihoti, Euseius fustis) and the apex-inhabiting mite (T. aripo), all three species being predators used for controlling the cassava green mite Mononychellus tanajoa in Africa. Whereas on leaf discs UVA has no negative impact on survival of the three predators, UVB is lethal to all of them. In contrast, nearly 85% of T. aripo survived after exposure to UVB inside apex of cassava plants. Exposure of A. manihoti and E. fustis to UVB radiation on the lower surface of a cassava leaf resulted in 36% survival. Oviposition and hatching of eggs laid after exposure to UVB were not affected, but eggs directly exposed to UVB did not hatch. Although caution should be exercised to extrapolate laboratory studies to the field, our results support the hypothesis that lower side of leaves, but especially plant apices, represent refuges that protect predatory mites from UVB. This might explain why T. aripo moves out of the apex to forage on leaves only during the night.

An artificial light source influences mating and oviposition of black soldier flies, Hermetia illucens

Current methods for mass-rearing black soldier flies, Hermetia illucens (L.) (Diptera: Stratiomyidae), in the laboratory are dependent on sunlight. Quartz-iodine lamps and rare earth lamps were examined as artificial light sources for stimulating H. illucens to mate and lay eggs. Sunlight was used as the control. Adults in the quartz-iodine lamp treatment had a mating rate of 61% of those in the sunlight control. No mating occurred when the rare earth lamp was used as a substitute. Egg hatch for the quartz-iodine lamp and sunlight treatments occurred in approximately 4 days, and the hatch rate was similar between these two treatments. Larval and pupal development under these treatments required approximately 18 and 15 days at 28°C, respectively. Development of methods for mass rearing of H. illucens using artificial light will enable production of this fly throughout the year without investing in greenhouse space or requiring sunlight.

Effect of Light Intensity on the Oviposition Rhythm of the Altitudinal Strains ofDrosophila Ananassae

The sensitivity of the circadian photoreceptors mediating entrainment of the eclosion rhythm and phase shifts of oviposition rhythm of the high altitude (HA) strain of Drosophila ananassae originating from Badrinath (5123 m above sea level) in the Himalayas was compared with the low altitude (LA) strain from Firozpur (179 m above sea level). Reduced photic sensitivity of the HA strain is regarded as the result of natural selection, which led to the weakening of the coupling mechanism between the circadian pacemaker and light at the high altitude of origin. The present study was designed to determine whether or not the photic entrainment of the oviposition rhythm of the HA strain of D. ananassae is also altered by the high altitude of its origin, and the results are compared with those of the LA strain. The effects of light intensity on the phase angle difference (Psi), degree of rhythmicity (R), the percent oviposition in photophase, the threshold light intensity (i.e., the intensity at which stable entrainment occurred), and the saturation light intensity (i.e., the intensity beyond which the values of Psi or amplitude of rhythm remained unaltered) were determined. Entrainment was studied in light-dark cycles in which the light intensity of 12 h of photophase varied from 1 to 1000 lux, and complete darkness prevailed in all scotophases. The oviposition rhythm of the HA strain was arrhythmic from 1 to 90 lux, weakly rhythmic at 95 lux, but rhythmic at or above 100 lux, while that of the LA strain was weakly rhythmic at 1 lux but rhythmic at or above 2 lux. Oviposition of the HA strain occurred mostly in the photophase, while that of the LA strain occurred in the scotophase; as a result, the oviposition medians of the HA strain were around the subjective forenoons while those of the LA strain were around the subjective evenings. The percent of oviposition in photophase increased from 68 to 98 in the HA strain and from 5 to 33 in the LA strain as light intensity increased from 1 to 1000 lux. In the HA strain, the Psi values were significantly less and values of R and percent oviposition in photophase were significantly more than those of the LA strain at each level of light intensity. Threshold and saturation intensities for Psi were 100 and 700 lux, respectively, for the HA strain, but just 2 and 45 lux, respectively, for the LA strain. The saturation intensity for R was 650 and 700 lux for the HA and LA strains, respectively. These results extend the confirmation that the reduced photic sensitivity of the HA strain might have been acquired through natural selection in response to environmental conditions at the high altitude of its origin.

Effects of Photophase and Altitude on Oviposition Rhythm of the Himalayan Strains ofDrosophila Ananassae

The effects of varying photophase and altitude of origin on the phase angle difference (Psi) of the circadian rhythm of oviposition during entrainment to light-dark (LD) cycles and the aftereffects of such photophases on the period of the free-running rhythm (tau) in constant darkness (DD) were evaluated in two Himalayan strains of Drosophila ananassae, the high-altitude (HA) strain from Badrinath (5,123 m above sea level=ASL) and the low-altitude (LA) strain from Firozpur (179 m ASL). The Psi (i.e., the hours from lights-on of the LD cycle to oviposition median) of both strains was determined in LD cycles in which the photophase at 100 lux varied from 6 to 18 h/24 h. The HA strain was entrained by all LD cycles except the one with 6 h photophase in which it was weakly rhythmic, but the LA strain was entrained by only three LD cycles with photophases of 10, 12, and 14 h, but photophases of 6, 8, 16, and 18 h rendered it arrhythmic. Lights-off transition of LD cycles was the phase-determining signal for both strains as oviposition medians of the HA strain occurred approximately 6 h prior to lights-off, while those of the LA strain occurred approximately 1 h after lights-off. The Psi of the HA strain increased from approximately 2 h in 8 h photophase to approximately 11 h in 18 h photophase, while that of the LA strain increased from approximately 11 h in 10 h photophase to approximately 15 h in 14 h photophase. The aftereffects of photophase of the prior entraining LD cycles on tau in DD were determined by transferring flies from LD cycles to DD. The tau of the HA strain increased from approximately 19 to approximately 25 h when transferred to DD from LD 8:16 and LD 18:6 cycles, respectively, whereas the tau of the LA strain increased from approximately 26 to approximately 28 h when transferred to DD from LD 10:14 and LD 14:10 cycles, respectively. Thus, these results demonstrate that the photophases of entraining LD cycles and the altitude of origin affected several parameters of entrainment and the period of the free-running rhythm of these strains.

Effects of acute gamma irradiation on Folsomia candida (Collembola) in a standard test

An understanding of the effects of ionizing radiation on non-human biota is required by the International Commission on Radiological Protection for the radiological protection of the environment. We examined dose-effect relationships for gamma radiation on survival, growth, and reproduction in the soil invertebrate Folsomia candida (Collembola) in a standard laboratory test. F. candida were acutely irradiated at increasing doses of gamma radiation, and subsequent survival, growth in body length, and number of neonates produced by irradiated specimens were examined. The 50% lethal dose was at 1356 Gy, and the 10% and 50% effective doses (ED10 and ED50) for growth were at 32 and 144 Gy, respectively. The ED10 and ED50 values for reproduction were at 7.1 and 21.9 Gy, respectively. These data establish important baselines for the radiological protection of terrestrial ecosystems based on scientific principles.

Tri-trophic consequences of UV-B exposure: plants, herbivores and parasitoids

In this paper we demonstrate a UV-B-mediated link between host plants, herbivores and their parasitoids, using a model system consisting of a host plant Brassica oleracea, a herbivore Plutella xylostella and its parasitoid Cotesia plutellae. Ultraviolet-B radiation (UV-B) is a potent elicitor of a variety of changes in the chemistry, morphology and physiology of plants and animals. Recent studies have demonstrated that common signals, such as jasmonic acid (JA), play important roles in the mechanisms by which plants respond to UV-B and to damage by herbivores. Plant responses elicited by UV-B radiation can affect the choices of ovipositing female insects and the fitness of their offspring. This leads to the prediction that, in plants, the changes induced as a consequence of UV damage will be similar to those elicited in response to insect damage, including knock-on effects upon the next trophic level, predators. In our trials female P. xylostella oviposited preferentially on host plants grown in depleted UV-B conditions, while their larvae preferred to feed on tissues from UV-depleted regimes over those from UV-supplemented ones. Larval feeding patterns on UV-supplemented tissues met the predictions of models which propose that induced defences in plants should disperse herbivory; feeding scars were significantly smaller and more numerous--though not significantly so--than those on host plant leaves grown in UV-depleted conditions. Most importantly, female parasitoids also showed a clear pattern of preference when given the choice between host plants and attendant larvae from the different UV regimes; however, in the case of the female parasitoids, the choice was in favour of potential hosts foraging on UV-supplemented tissues. This study demonstrates the potential for UV-B to elicit a variety of interactions between trophic levels, most likely mediated through effects upon host plant chemistry.

Effect of moving dawn, dusk, or both on oviposition time in domestic laying hens

1. Lohmann Brown pullets were reared on 8-h photoperiods and transferred to 12 h at 15 weeks by either advancing dawn or delaying dusk by 4 h. At 25 weeks, half of each group was transferred to 16 h by advancing dawn or delaying dusk and, 10 d later, each photoperiod-group was advanced or delayed 4 h by moving both dawn and dusk. Individual oviposition times were recorded over 48 h at 25 weeks and 8-10 d after each lighting change. 2. At 25 weeks, there were no differences in mean time of oviposition, eggs laid in the modal 8 h, or in the proportion of eggs laid before dawn between pullets that had been given a 4-h increase in daylength at 15 weeks by advancing dawn and those photostimulated by delaying dusk. 3. Extensions of the daylength from 12 to 16 h at 25 weeks, whether by advancing dawn or by delaying dusk, delayed mean oviposition time by 2 h and virtually eliminated egg-laying before dawn. All groups laid > or = 94% of eggs in the modal 8 h. 4. Moving the complete 12- or 16-h photoperiod forwards by 4 h delayed egg-laying by 0.5 h (relative to dawn), whilst moving them backwards advanced it by 0.7 h. Pullets given 16 h of light laid very few eggs before lights-on, but the divergent movements in oviposition time, relative to dawn, resulted in more eggs being laid before lights-on when the 12-h photoperiod was moved backwards and fewer eggs when it was moved forwards. However, a slower adjustment to the new times of dawn and dusk by the pullets whose day had been moved forward, as indicated by fewer eggs being laid in the modal 8 h and poorer rates of lay compared with pullets that had their photoperiod moved backwards, may explain these differences. It is doubtful that the differences would have persisted after all birds had adjusted their ovulatory cycle, and so any reduction in pre-dawn egg-laying is likely to have been transitory. 5. The only permanent way to minimise pre-dawn egg-laying in brown-egg hybrids is to provide a photoperiod of at least 16 h, though 14-15 h may be long enough for white-egg hybrids and 12-13 h sufficient for broiler breeders.

Broiler breeders do not respond positively to photoperiodic increments given during the laying period

1. Broiler breeders were given a 3-h increase in photoperiod to 11 h at 20 week and then a series of increases to reach 16 or 17 h either immediately after the initial increment or in 30-min, 1- or 2-h increments starting at various ages after peak rate of lay. Controls were maintained on 11 h from 20 weeks. Changes in plasma LH concentration (after 7 d) were measured in birds that had been transferred to 11 or 16 h at 20 weeks and given further increases in photoperiod at 41 or 61 weeks of age. 2. Birds that were transferred to 16- or 17-h photoperiods, irrespective of when and how the maximum photoperiod was reached, had inferior rates of lay between 52 and 60 weeks of age to birds maintained on 11 h from 20 weeks. However, the 11-h birds laid more eggs on the floor and produced a larger number of cracked and dirty eggs, resulting in similar numbers of settable eggs. 3. Although transferring birds from 11- to 16-h photoperiods at 41 weeks of age significantly increased plasma LH concentration, there was no effect on egg production during the ensuing 12 d. None of the other increases in photoperiod significantly increased plasma LH, whether given at 41 or 61 weeks. 4. It is concluded in broiler breeders, that increases in photoperiod applied during the laying period, from 11 or 16 h, have little or no effect on LH secretion, do not compensate for age-related declines in egg production, and adversely affect rate of lay.

Influence of temperature, photoperiod and humidity on oviposition and egg hatch of the root-feeding flea beetle Longitarsus bethae (Chrysomelidae: Alticinae), a natural enemy of the weed Lantana camara (Verbenaceae)

The root-feeding flea beetle Longitarsus bethae Savini & Escalona, was introduced into South Africa as a candidate biological control agent for the noxious and invasive weed, Lantana camara L. As part of the study to predict the beetles' survival in its new range, the influence of climatic conditions on its egg development and reproductive performance were investigated in the laboratory. The threshold temperature (T degrees) and degree-days (DD) required for egg hatch were determined after exposing the eggs to various constant temperatures (12, 17, 22, 27 and 32 degrees C) in separate growth chambers. The DD required for egg hatch was 178.6, and the temperature threshold required for egg hatch was 11.3 degrees C. Survival of eggs varied from 27 to 56% at 32 and 17 degrees C, respectively, and was optimum between 17 and 25 degrees C. Oviposition was examined under high and low relative humidity (RH) regimes while egg hatch was determined at six RH levels, each maintained in a separate controlled growth chamber set at a constant temperature (25 degrees C). Whilst RH had no influence on oviposition, eggs were highly susceptible to aridity, and continuous exposure to relative humidity below 63% for more than three days was wholly lethal at 25 degrees C. Optimum egg hatch occurred at RH between 85 and 95% for up to 12 days. The effect of day length on oviposition and subsequent egg hatch was investigated under two photoperiod regimes. Neither oviposition nor subsequent egg hatch was influenced by photoperiod. The knowledge obtained will be useful for mass rearing as well as field release programmes for L. bethae.

Effect of temporary transfers to 14 h on age at first egg in domestic pullets reared on 8-h photoperiods

1. Brown-egg pullets were reared on 8-h photoperiods and temporarily transferred at 80 d of age to 14-h photoperiods for 2, 4, 6, 8, 10 or 12 d. Controls were either maintained on 8 h or permanently transferred to 14 h at 80 d. 2. Pullets given 8 or 12 long days matured 8-9 d earlier than constant 8-h controls, but 22-23 d later than pullets transferred permanently to long days. Mean age at first egg for the groups given 2, 4, 6 or 10 d of 14-h days were not significantly different from the 8-h controls. The mean weight of first egg and body weight at first egg for the temporarily-photostimulated groups were not significantly different from constant 8-h controls, but egg weights were > or = 5.1 g and body weights at first egg > or = 200 g heavier than the birds transferred permanently to 14 h. 3. It is concluded that up to 6 temporary long days may be given (from 80 d of age) without affecting the timing of sexual maturity, but that the provision of 8 or more long days will accelerate sexual development, thought not to the extent of a permanent transfer, in most birds within a flock. A regression analysis of the ages at which the first and last birds in the groups given 6, 8, 10 or 12 long days matured suggested that about 20 d of photostimulation are required to achieve a mean age at first egg similar to that of birds permanently transferred to long days.

Effect of strain of layer and age at photostimulation on egg production, egg quality, and bone strength

Bone strength in layers is a concern for economic reasons and animal welfare concerns. Bone characteristics were investigated in 3 strains of hens: Babcock B-300, a small-bodied commercial white-egg layer; ISA-Brown, a commercial brown-egg layer; and an unselected Brown Leghorn line (BL). After being reared together in a single pen with 8 h of light per day, hens were caged with 14 h of light per day. Half of the hens were caged at 18 wk of age and the other half at 20 wk of age, resulting in a 2-wk difference in the age at photostimulation. Body weights, egg production, feed efficiency, and egg quality were measured throughout production. At 15, 25, 50, and 74 wk of age, hens were euthanized for sampling of the radius and the humerus. Breaking strength of the radius and humerus was measured, and the area and density of trabecular (largely medullary bone) and cortical bone were measured using quantitative computed tomography. Egg production and feed conversion of ISA-Brown hens was as good as or better than that of Babcock B-300 hens, and both commercial strains had higher production than the BL. Photostimulation late delayed sexual maturity and improved albumen and shell characteristics but had only minor effects on egg production and did not affect the yolk weight. The delayed photostimulation resulting from caging 2 wk later affected the radius by increasing the area of the trabecular space at 50 wk of age and the density of the bone in the trabecular space at 74 wk of age. Breaking strength of the humerus at 25 wk of age was greater for the birds that were photostimulated late but was not different later in the trial. The humerus, but not the radius, of the BL had a greater breaking strength than that of the commercial strains, suggesting that selection has decreased humeral breaking strength.

Effects of artificial supplemental light on the reproductive season of geese kept in open houses

1. New lighting programmes were designed to change the pattern of goose reproduction, based on the response of predictable avian photoperiodic stimulation. The objective of this study was to evaluate the efficiency of a long photoperiod of 20L on shifting goose reproduction to the non-breeding season in an open housing system. 2. Eighty mature White Roman geese were randomly allocated into 4 groups (male:female = 1:4). The supplemental lighting programmes with a daily photoperiod of 20 h were initiated on 22 November and withdrawn when 90% of geese were moulting in the treatment groups. Artificial light intensities of 220, 120 and 20 lux were provided to experimental groups A, B and C, respectively. In contrast, the geese in control group D were kept under natural lighting conditions throughout this study. 3. The annual reproductive curves of all the experimental groups consisted of two separate laying periods. The first period was induced by the supplemental lighting programme while the second was induced by the naturally increasing photoperiod in this subtropical region. The first laying period of the experimental groups occurred in the breeding season, and the second was relocated to the non-breeding season. 4. The supplemental lighting could shift the laying periods of geese to the non-breeding season and had no significant effect on annual reproductive performance. The supplemental light programmes described here were able to manipulate the reproductive season of geese reared in open houses, which would be of practical value.

Solar ultraviolet-B radiation alters the attractiveness of Arabidopsis plants to diamondback moths (Plutella xylostella L.): impacts on oviposition and involvement of the jasmonic acid pathway

Solar ultraviolet-B radiation (UV-B) can have large impacts on the interactions between plants and herbivorous insects. Several studies have documented effects of UV-B-induced changes in plant tissue quality on the feeding performance of insect larvae. In contrast, the effects of UV-B-induced plant responses on the behavior of adult insects have received little attention. We carried out a series of field and glasshouse experiments using the model plant Arabidopsis thaliana L. and the crucifer-specialist insect Plutella xylostella L. (diamondback moth) to investigate the effects of UV-B on natural herbivory and plant-insect interactions. Natural herbivory under field conditions was less severe on plants exposed to ambient UV-B than on plants grown under filters that attenuated the UV-B component of solar radiation. This reduced herbivory could not be accounted for by effects of UV-B on larval feeding preference and performance, as P. xylostella caterpillars did not respond to changes in plant quality induced by UV-B. In contrast, at the adult stage, the insects presented clear behavioral responses: P. xylostella moths deposited significantly more eggs on plants grown under attenuated UV-B levels than on plants exposed to ambient UV-B. The deterring effect of UV-B exposure on insect oviposition was absent in jar1-1, a mutant with impaired jasmonic acid (JA) sensitivity, but it was conserved in mutants with altered ethylene signaling. The jar1-1 mutant also presented reduced levels of UV-absorbing phenolic compounds than the other genotypes that we tested. Our results suggest that variations in UV-B exposure under natural conditions can have significant effects on insect herbivory by altering plant traits that female adults use as sources of information during the process of host selection for oviposition. These effects of natural UV-B on plant quality appear to be mediated by activation of signaling circuits in which the defense-related hormone JA plays a functional role.

Assessment of the effects of electromagnetic field modification on egg-laying hens in commercial flocks as indicated by production measures

OBJECTIVE

To assess the effects of electromagnetic (EM) field modification by use of Nufield EM field modification (NEFM) units on egg-laying hens in commercial flocks as indicated by production measures, including hen-day mortality rate (HDMR) and eggs per hen housed (EHH).

ANIMALS

16 commercial flocks of egg-laying hens.

PROCEDURE

5 caged commercial table egg layer flocks (Single Comb White Leghorns) successively housed at the same location during a 6-year period were exposed to NEFM. There were 7 hens/cage (317 cm2 of floor space/bird). At the same site, 11 concurrent non-NEFM-exposed flocks (4 genetically different strains) were sequentially housed. All 16 flocks underwent the same feed and management practices. For each NEFM- and non-NEFM-exposed flock, HDMR and EHH were compared with their respective national breeder goals (BG), defined as the reasonable genetic potential expressed under optimal management and environmental conditions. Furthermore, the HDMRs and EHHs of the NEFM- and non-NEFM-exposed flocks were compared.

RESULTS

Mean HDMR and EHH of the NEFM-exposed flocks was 36.9% less and 4.96% greater than the relevant BG, respectively. Mean HDMR and EHH of the non-NEFM-exposed flocks was 12.6% and 0.49% greater than the relevant BG, respectively. Compared with the 11 non-NEFM-exposed flocks, the NEFM-exposed flocks collectively had a 47.6% decrease in HDMR and 1.33% increase in EHH.

CONCLUSIONS AND CLINICAL RELEVANCE

Results strongly suggest that application of NEFM in commercial egg-layer flocks improves production measures, which has important welfare implications as well as gross economic advantage.

Spontaneous recovery of photosensitivity by turkey breeder hens given prolonged exposure to long day lengths

Three experiments were done to examine spontaneous photosensitivity (SP) and the associated renewal of egg production in Large White turkey breeder hens. In experiment 1, hens were photostimulated with 16 h of light:8 h of dark in December for 54 wk. In experiment 2, SP was examined in a different season than experiment 1. One group of hens was recycled and then photostimulated with 16 h of light:8 h of dark for 23wk. Another group of hens was not recycled and received 16 h of light:8 h of dark throughout the experiment. Egg production was used to assess SP in both experiments 1 and 2. Experiment 3 was designed to produce SP and renewed egg production during prolonged exposure (64 wk) to constant, long day lengths and to evaluate circulating thyroid hormones immediately prior to the renewal of egg production. Egg production was recorded daily to assess SP, and blood samples were taken weekly for radioimmunoassay for thyroid hormones. In both experiments 1 and 2, there was SP and renewed egg production, and this occurred in the fall season. Egg production increased gradually from less than 5% to a peak of 67% (experiment 1) and 38% (experiment 2) in November. In experiment 3, SP occurred in the fall, and egg production increased gradually and was similar to control hens from 8 wk of lay to the end of the experiment. Both groups also had similar declines in egg production following a decrease in photoperiod at wk 24 of the experiment. In the 8-wk period preceding the onset of laying, there were no significant differences between control and SP hens in plasma thyroid hormone levels. In both groups, there was a significant time effect for plasma triiodothyronine, expressed as a parabolic pattern of change. It was concluded that for turkey hens maintained in prolonged and constant long day lengths that SP and renewal of egg production occurs in the fall season. This response was independent of season of photostimulation, did not alter photoresponsiveness to shorten day lengths, and was preceded by a parabolic increase in plasma triiodothyronine.

Impact of UV-B exposure on amphibian embryos: linking species physiology and oviposition behaviour

Increasing ultraviolet-B radiation (UV-B) has recently captured the attention of ecologists as a key environmental stressor. Certain species may be particularly vulnerable as a result of either high natural exposure to UV-B or limited physiological capacity to withstand it. UV-B sensitivity has been examined at the cellular and individual level for a wide variety of taxa, but estimates of exposure to UV-B in natural systems are lacking and predictions of large-scale impacts are therefore limited. Here, we combine data on the physiological sensitivity to UV-B and patterns of field exposure across sites for embryos of several well-studied US Pacific Northwest amphibian species. We find substantial differences among species' physiological abilities to withstand UV-B and in the level of UV-B exposure of embryos in the field. More specifically, we find that species with the highest physiological sensitivity to UV-B are those with the lowest field exposures as a function of the location of embryos and the UV-B attenuation properties of water at each site. These results also suggest that conclusions made about species' vulnerability to UV-B in the absence of information on field exposures may often be misleading.

Effect of a single short-term reduction in photoperiod on photorefractoriness in turkey hens

In a prior study, we reported that a high proportion of hens in a winter-laying flock became relatively photorefractory (rPR) early in the reproductive cyand that successive short-term reductions in photoperiod in such hens each initially depressed egg production but then caused a rebound in rate of lay to briefly exceed that of hens that did not exhibit rPR. The present study was conducted to assess rPR in a summer-laying flock and to determine whether a single short-term reduction in day length early in the reproductive cycle might enhance egg production and delay the onset of absolute photorefractoriness (aPR). Control hens received a photoperiod of 16L:8D throughout the experiment. Experimental hens were photostimulated with 16L:8D, received a reduced (but still stimulatory) photoperiod of 11.5L:12.5D for 2 wk beginning 8 wk after photostimulation, and then were returned to 16L:8D for the remainder of the 23-wk test period. Results showed that a single 2-wk reduction in day length shortly after the hens reached peak egg production did not significantly reduce overall flock egg production, but it also did not improve late-season egg production or retard the onset or incidence of aPR. The incidence of rPR was substantially less in this study than we had observed with a winter-laying flock (32.9 vs. 67.1%), but similar proportions of treated hens exhibited the most severe rPR response (a brief but complete cessation of egg production) in both studies (21.1 vs. 24.0%), and all treated hens that subsequently became aPR had shown this severe rPR response to the test photoperiod. We concluded that a core proportion of hens (approximately one-fifth) exhibited a strong rPR response when presented with a reduced photoperiod early in the reproductive cycle, regardless of season of the year, and that such hens were more likely to subsequently exhibit poor egg production or become aPR than flockmates that did not exhibit rPR. Therefore, some indication of the incidence of rPR early in the lay period may have a predictive value for the overall egg production of the flock.

Effect of lighted incubation on embryonic growth and hatchability performance of two strains of layer breeder eggs

1. Eggs from two layer-type breeder flocks (ISA-W vs Leghorn) between 30 and 45 weeks of age were used in 4 trials to study the effects of lighted incubation on embryonic growth from 5 to 18 d of age and hatchability per cent (HP). The physical dimensions, eggshell characteristics and conductance (EC) of eggs of the two strains were compared. 2. Eggs were set in an incubator on trays either in the dark-control or under two tubes of 20-watt white fluorescent light during the first 18 d of incubation. The light intensity ranged from 1230 to 1790 lux at the surface of the eggs. Eggs were transferred to dark hatching compartments at d 19 of incubation. 3. The genetic make-up of birds influenced the physical dimensions and eggshell characteristics of eggs. ISA-W eggs had higher weight, surface area (ESA), volume (EV), width, EC, shell volume and HP, and lower ESA:EV ratio, per cent shell, shell density and dead embryos than those of Leghorn eggs. 4. Lighted incubation increased daily embryonic growth (mg/d) and HP by 3.9 and 5.9%, respectively, when compared with the dark-control incubation. 5. The physical dimensions and eggshell characteristics of eggs influenced the effects of lighted incubation on embryonic growth and HP. Lighted incubation increased embryonic growth and HP of ISA-W eggs. The increase in embryonic growth and HP of the Leghorn eggs was not significant. 6. The genetic make-up of birds influenced the physical dimensions and eggshell characteristics of their eggs and these differences in the characteristics of hatching eggs influenced embryonic growth and HP when incubated under light.

Immune function in turkey breeder hens during the short day prelighting period and renewal of photosensitivity for egg production

Photorefractoriness (PR) in the turkey breeder hen is characterized by a lack of responsiveness to photoperiods that previously induced or maintained egg production. The consequence of PR is spontaneous regression of ovarian function and cessation of lay. Photosensitivity (PS) may be regained by giving at least 8 wk of short photoperiod (8L:16D) (light restriction). Following the transition from PR to PS, the birds may be photostimulated with long photoperiods, which allows for the recrudescence of ovarian function and normal egg production. Although the return of reproductive viability is the parameter for determining the successful recycle of ovarian function, there are no known reports of the physiological costs of this transition on immune function in the turkey breeder hen. We conducted an experiment to determine the immune responsiveness at various stages of recycle in the turkey breeder hen. Fifty photorefractory birds were selected and distributed equally among five treatment groups (time points). All birds were given an 8-wk period of light restriction (8L:16D) followed by a 12-wk period of photostimulation (16L:8D). The cellular (cutaneous basophil hypersensitivity CBH) and humoral (antibody titer) immune responses were determined in each treatment group (sequential time points): prelight restriction, 2-wk light restriction, 7-wk light restriction, 2-wk photostimulation, and 12-wk photostimulation. After 2-wk light restriction, there was a reduction in the cellular (64.1%) and humoral (59.5%) immune responses from that of the PR hens at the start. After 7-wk light restriction, the humoral responses increased (33.5%) as compared to the 2-wk light restriction time point Upon photostimulation, both the cellular (23.3%) and humoral (52.4%) immune responses were reduced at 2 wk of photostimulation as compared to the prior 7-wk light restriction time point. Finally, there was a rise in cellular (45.7%) and humoral (72.3%) immune responses after 12 wk of photostimulation as compared to the prior 2-wk photostimulation time point. We concluded that recycling of PR turkey hens was associated with altered cellular and humoral immune responses characterized by initial decline then recovery in both the light restriction and the postphotostimulation periods.

Circulating thyroid hormone levels in recycled turkey breeder hens during a short day prelighting period and renewal of photosensitivity for egg production

Two experiments were conducted with yearling turkey hens at the end of their first season of egg laying. The purpose was to examine changes in plasma thyroid hormone levels during recycling and renewal of photosensitivity for egg production. Plasma concentrations of thyroid hormones were determined weekly or biweekly for 8 wk following a change from existing photoperiods of long days (LD) to short days (SD) and during the associated complete renewal (recycling) of photosensitivity for egg production. In both experiments, neither thyroxine (T4) nor triiodothyronine (T3) declined from starting values during the SD exposure but plasma T3 increased significantly from LD controls. There were no significant treatment effects (SD vs. LD) for T4 in either experiment. The increase in T3 was 101 and 145% in Experiments 1 and 2, respectively, and extended over the 8-wk SD treatment period in a parabolic fashion. The T3/T4 ratio was also significantly increased in the SD treatments of both experiments as compared to LD controls. Plasma concentrations of T3, but not T4, clearly changed during recycling and renewal of photosensitivity for egg production in breeder hens. These results were consistent with a participation of plasma T3 in promoting photosensitivity and diminishing photorefractoriness in turkey hens during SD-induced recycling.

The effects of age at photostimulation and dietary protein intake on reproductive efficiency in three strains of broiler breeders varying in breast yield

The effects of strain, age at photostimulation, and dietary CP intake during the early lay period on sexual maturation and egg production parameters in broiler breeder hens were determined. Three Arbor Acres strains, Classic, Feather Sexable Yield (FSY), and an experimental line (EXP), were reared in floor pens. At 19 wk of age, pullets were moved into individual cages. At 20 wk of age one-half of the birds were photostimulated by increasing the day length from 8L:16D to 15L:9D. The remaining birds were photostimulated at 23 wk of age. The birds were fed 16 or 18% CP diets from 19 to 32 wk of age. The Classic hens achieved sexual maturity 4 d before the EXP hens. Delaying photostimulation to 23 wk of age delayed sexual maturity but the rate of sexual maturation was accelerated after photostimulation occurred. Egg weight at sexual maturity was higher for the later photostimulated birds. The FSY and EXP hens, selected for more white-meat yield than the Classic hens, were heavier in BW but had lower settable egg production than the latter. Feeding 18% CP resulted in a higher BW throughout the trial, as compared to the 16% CP diet. There was a response to dietary CP and photostimulation age on initial egg weight and the number of double-yolked eggs. Early photostimulation was not advantageous because egg production parameters were not affected. Both Classic and FSY strains performed well when fed 18% CP; however, EXP hens benefited from 16% CP intake.

Effect of exogenous oestradiol and lighting regime on age at first egg in domestic pullets

1. Groups of ISA Brown pullets were transferred from 8- to 16-h photoperiods at 34, 44 or 54 d. In each group, 12 birds were injected on alternate days over a 12-d period starting 6 d before the change in photoperiod with beta-oestradiol-3-benzoate (1 mg/kg body weight) or with arachis oil vehicle (controls). Short-day controls were similarly injected from 28 to 40 d. Long-day (16 h) controls were also included in the trial but were not injected. Age at first egg (AFE) was recorded and plasma luteinising hormone (LH) concentrations were measured around the time of oestradiol treatment. 2. Mean AFE for birds photostimulated at 34 d was not significantly different from short-day controls. Birds photostimulated at 44 and 54 d matured at similar ages but 3 weeks earlier than short-day controls (P<0.05). 3. There was a tendency for oestradiol to advance AFE for birds photostimulated at 34 d (P=0.15) but to delay AFE following photostimulation at 44 d (P=0.23). Oestradiol significantly delayed AFE for the birds photostimulated at 54 d (P=0.01). 4. Plasma LH levels during 6 d of oestradiol injection but before transfer from 8- to 16-h photoperiods tended to fall between 28 and 34 d, were relatively constant between 38 and 44 d, but declined significantly between 48 and 54 d. Following photostimulation at 34 d, increases in plasma LH levels for oestradiol-injected birds were significantly greater than for controls. Oestradiol treatment had no significant effect on changes in plasma LH concentrations after photostimulation at 44 or 54 d. 5. This trial confirms previous work showing that pullets are unresponsive to photostimulation before 6 weeks of age. It also demonstrates that raising circulating oestrogen levels by injecting 0.5 mg/kg oestradiol benzoate on alternate days enhances the LH response to photostimulation at 34-d, but only very slightly sensitises a 34-d old bird to an increase in photoperiod which, 10 d later, is capable of advancing AFE in control birds by 24 d. Increased circulating oestrogen might be a factor which allows pullets to advance AFE in response to an increase in daylength.

Effects of light intensity from photostimulation in four strains of commercial egg layers: 2. Egg production parameters

The effects of light intensity (LI) from photostimulation to 45 wk of age on egg production parameters and egg size characteristics were examined in four layer strains. Floor housed pullets were raised in a light-tight facility from 1 d of age until housing in individually illuminated cages at 17 wk of age. At 17 wk of age, two white egg strains, ISA-White (ISA-W) and Shaver 2000 (S2000), and two brown egg strains, ISA-Brown (ISA-B) and Shaver 579 (S579), were assigned to a processing group [Group 1 was killed at sexual maturity (first oviposition); Group 2 was kept to 45 wk] and were photostimulated at 18 wk of age using a LI of 1, 5, 50, or 500 lx (4 x 4 factorial design). One bird from Group 1 and one bird Group 2 were caged together in individually lit cages (one brown and one white egg layer). Cages were equipped with hardware to monitor egg laying time. Data of individual egg weight and time of lay were kept on Group 2 birds until 45 wk of age. Egg production data were analyzed for hen-day production, laying sequence length, egg and egg component weights, time of lay, and egg interval time as related to strain or LI. Hen-day production was greater in brown egg strains (ISA-B = 86.7%, S579 = 88.1%) than in white egg strains (ISA-W = 83.4%, S2000 = 82.3%) and was reduced in birds under 1 lx compared to 5 or 50 lx. A LI of 1 lx resulted in reduced egg production and laying sequence length compared to birds with a 50 or 500 lx. The effects of LI were strain dependant, however. Postpeak sequence length and egg production declined at more rapidly under 500 lx compared to other LI in brown egg strains, indicating possible development of a photorefractory condition. Mean settable egg weight was lower in 500 lx birds (56.1 g) compared to other groups (mean = 57.9 g), reducing total egg mass produced. Mean interval between successive eggs in a sequence was lengthened in 1 lx birds compared to other LI groups. Mean time of lay was earlier in brown egg strains than in white egg strains by 48 min. Mean time of lay was shifted to occur later by an increasing LI. Light intensity affected sexual maturation and egg production, as layers had differential responses to lighting. LI of 1 lx and 500 lx were found to be limiting to the egg production efficiency of layers. Whereas the birds receiving 1 lx had a reduced rate of egg production, those receiving 500 lx had reduced egg size later in the production period in combination with reduced shell quality, which indicated that inadequate feed intake under high LI conditions may be a factor affecting layer stocks. Exposure to high LI reduced egg size and total egg mass produced. Ultimately, the brown egg strains appeared to be more susceptible to the negative effects of low or high LI, indicating the importance of matching management practices to the particular hen genotype.

Ultraviolet radiation and laying pullets

1. Responses to ultraviolet (UV) radiation were studied in two trials. In one trial, sexually mature pullets, that had been maintained on an 8L:16D regimen from 2 d of age, were exposed sequentially, for periods of 9 to 12 d, to a further 8 h of very dim visible light (VDV), to 8 h of UV radiation and, finally, to an extra 8 h of normal light (conventional 16L:8D). Individual ovipositions were recorded during the last 48 h of each treatment. In the second trial, sexually mature pullets which had been allowed to 'free-run' for 14 d under continuous normal illumination (LL), were given, in addition to the normal light, a 12-h period of UV radiation commencing at midday or midnight for a further 15 d. During the final 48 h oviposition times were recorded and 4 food intakes for each 12-h period were determined. 2. In trial 1, mean oviposition time under VDV and UV supplementation was not significantly different from that under the 8L:16D regimen. Transfer to a 16L:8D regimen altered mean time of oviposition by about 4 h. In trial 2, eggs continued to be laid almost at random in all groups. 3. Food intake was suppressed during the 12-h period of UV supplementation compared with that when the birds were not receiving UV. 4. It is concluded that the addition of 8 h of UV radiation (at the intensity used in these studies) to 8 h of normal light does not cause a phase shift in the timing of the 'open-period' for pre-ovulatory luteinising hormone release which determines the time of oviposition. Furthermore, the insertion of 12-h periods of UV into continuous illumination does not entrain egg laying. 5. The suppressing effect of UV on food intake but lack of influence on the timing of the ovulatory cycle suggests that UV (at the intensity used in this study) acts principally at the retinal level and, as a result, stimulates only behavioural responses in laying birds.

Intermittent lighting increases egg weight and facilitates early photostimulation of turkey breeder hens

A major limitation to reducing the age at photostimulation of turkey breeder hens has been small egg size, especially at the start of lay. The present study was designed to determine whether intermittent lighting (IL) could be used to photostimulate hens at an early age (26 wk) and enhance the typical small egg size at the start of lay. Control hens were photostimulated with standard [16 h light (L):8 h dark (D)] lighting at 26 or 30 wk of age. An additional group of hens was photostimulated with IL (2L:12D:2L:8D) from 26 to 32 wk of age and then switched to 16L:8D thereafter. Data were collected for BW, onset of lay, egg production, and egg weight to 54 wk of age. Although IL delayed onset of lay there was no adverse effect on rate of lay because numbers of eggs per hen in 24 wk of photostimulation (30 to 54 wk of age) were similar to that of controls. However, because hens in the IL treatment were photostimulated at 26 wk of age they produced about 10 more eggs per hen (P = 0.18) to 54 wk of age than control hens photostimulated at 30 wk of age. In addition, IL increased egg weight during the first 7 d of lay by about 5% as compared to those of controls also photostimulated at 26 wk of age. Interestingly, the increased egg weight in the IL treatment persisted to the end of lay, well after IL had been switched to 16L:8D. Thus, IL lighting facilitated successful early lighting of hens.

Effect of constant and of changing photoperiod on plasma LH and FSH concentrations and age at first egg in layer strains of domestic pullets

1. ISA Brown pullets were transferred from 8 to 14 h or from 14 to 8 h photoperiods at 35 or 56 d of age. Controls were maintained on constant 8 or 14 h photoperiods from day 1. 2. Blood samples were obtained immediately before each daylength change and subsequently at 7 d intervals until 1st egg in the treated groups and at 70 d of age and then at 14 d intervals until 1st egg in the constant photoperiod controls. Plasma luteinising hormone (LH) and follicle stimulating hormone (FSH) concentrations were determined using homologous radioimmunoassays. 3. Prior to 16 weeks, LH was consistently higher in birds on constant 14 h photoperiods than in those on constant 8 h, but was down-regulated as birds approached maturity so that LH concentrations in the 2 groups were similar during the final 10 d before the first egg was laid. FISH concentrations rose steadily with age but with a tendency for concentrations to be higher in the 8 h than in the 14 h treatment. Birds on constant 8 h daylengths matured 18.3 d later than those on constant 14 h photoperiods. 4. A 6 h increment in photoperiod given at 35 d or 56 d, resulted in an increase in LH within 7 d in both cases. FSH concentration did not respond to an increase in photoperiod at 35 d but rose following the same increase at 56 d. This was associated with a 3-week advance in sexual maturity, whilst age at 1st egg in birds photostimulated at 35 d was similar to the age with a constant 14 h photoperiod. 5. LH concentration fell when photoperiod was reduced from 14 to 8 h at either 35 or 56 d and remained below the constant 8 h controls for many weeks before rising to a concentration not significantly different from other groups in the final 10 d before 1st egg. FSH concentrations in birds exposed to a decreased daylength at 35 d, although more oscillatory, were similar to the constant 8 h photoperiod controls. In birds exposed to the same decrease at 56 d, FSH concentration initially tumbled but was similar in the 2 groups during the latter stages of rearing; neither differed significantly from the constant daylength controls during the 60 d before 1st egg. Sexual maturity in both groups given a reduction in photoperiod was delayed by about 2 weeks compared with constant 8 h controls. 6. Change in FSH concentration following an increase in daylength was a better predictor of age at 1st egg than change in LH. However, FSH concentrations after 14 weeks of age were rather similar in short day and long day controls and in the 2 groups given reductions in photoperiod at 35 d and 56 d, despite differences of nearly 5 weeks in mean age at 1st egg amongst these 4 treatments.

Oviposition patterns and plasma melatonin rhythms in response to manipulations of the light:dark cycle

1. In 2 experiments with Single Comb White Leghorn hens, the effects of different light:dark cycles (LD-cycles) upon oviposition patterns and plasma melatonin rhythms were studied. In experiment 1, a 28-h ahemeral LD-cycle (12L:16D) was used. In experiment 2, a normal 24-h LD-cycle (16L:8D) was applied and the effects of a sudden 8-h forward or backward shift of the 8-h dark period (that is phase-advanced or phase-delayed LD-cycle) were studied. 2. The oviposition patterns as well as the plasma melatonin rhythms were fully synchronised with both LD-cycles (24-h or 28-h). The 2 rhythms were gradually re-synchronised after phase shifts, and the melatonin response phase-led the oviposition response by 2 cycles. Thus, the change of the melatonin rhythm coincided with the change of the (presumed) open period for LH-release. 3. In the unchanged 24-h LD-cycle, ovipositions occurred almost exclusively (98.9%) during light hours, whereas in the 28-h LD-cycle, ovipositions occurred primarily (84.5%) during the last 9 h of the dark period. 4. In both LD-cycles and after changes of the LD-cycle, light always suppressed plasma melatonin, regardless of previous light history. During dark periods, concentrations were elevated but, interestingly, only if darkness had also been experienced during the same time period 24 h earlier. This indicates that light has a direct inhibiting effect upon pineal melatonin release, while actual melatonin release during darkness is controlled by an endogenous clock.

Effects on white Leghorn hens of constant exposure to ultraviolet light from insect traps

Constant exposure of Hy-Line W-36 White Leghorn hens to ultraviolet light from insect traps resulted in no significant differences in egg production, fertility, hatchability of fertile eggs, or total hatchability. Also, there were no apparent effects on the eyes of the birds. Results were the same when either blacklight or blacklight blue tubes were used. The need for additional testing of light traps for nuisance fly control in commercial caged layer houses is discussed.

Photoperiodic response in the soft tick, Ornithodoros turicata

The effects of photoperiod on the feeding, development and quiescent behavior of the burrow-dwelling soft tick, Ornithodoros turicata (Dugès) were investigated. Ticks were assigned randomly to either continuous darkness (DD), a short-day photoperiod (L:D 10:14), a long-day photoperiod (L:D 14:10) or constant light (LL). Ticks reared under constant light succumbed to much higher mortality than those reared under the other conditions. However, photoperiod did not induce quiescent behavior in O. turicata; the ticks were active and fed regularly throughout the study. Also, ticks reared in continuous darkness developed more slowly than those reared under short-day or long-day conditions. In contrast, pre-oviposition period was significantly longer for ticks reared in long-day conditions. Egg-hatch success was significantly higher for ticks reared in continuous darkness than for those reared under the photoperiods. The stage-specific effects of photoperiod on O. turicata are adaptive; these ticks very likely utilize photoperiod information to predict seasonal conditions.

Evidence for an inducible repair-recombination system in the female germ line of Drosophila melanogaster. I. Induction by inhibitors of nucleotide synthesis and by gamma rays

In the I-R system of hybrid dysgenesis in Drosophila melanogaster, the transposition frequency of I factor, a LINE element-like retrotransposon, is regulated by the reactivity level of the R mother. This reactivity is a cellular state maternally inherited but chromosomally determined, which has been shown to undergo heritable, cumulative and reversible changes with aging and some environmental conditions. We propose the hypothesis that this reactivity level is one manifestation of an inducible repair-recombination system whose biological role might be analogous to the SOS response in bacteria. In this paper, we show that inhibitors of DNA synthesis and gamma rays enhance the reactivity level in a very similar way. This enhancement is heritable, cumulative and reversible.

Turkey breeder hen performance by strain during consecutive lay periods

The results of this study provide information about reproductive performance among commercially available strains of Large White Turkey breeder hens, Nicholas (N), British United (B), and Hybrid (H). The hens were managed identically through two consecutive lay periods, summer-fall (1st-yr) followed by winter-spring (recycled). Effects of the intensity (351 vs 24 lx) of supplemental light were evaluated during the 1st-yr lay period. Data were collected for onset of oviposition, egg production, BW, feed consumption, livability, egg weight, and egg components. Light intensity had similar effects on all variables measured. There were neither strain differences nor genetic interactions with light intensity treatment. There was no difference in livability among strains (P = .20) or between year of lay (P = .08), and there was no strain by year interaction. Body weight differed by strains and year and there was a significant strain by year interaction. In general, N were heavier than H or B in the 1st-yr and early recycle lay period, whereas H and B were similar in BW in both lay periods. Recycled hens of all strains were heavier than 1st-yr hens. The onset of lay was earlier in H than B or N in both lay periods and all three strains had a delay in onset of lay after recycling. Through 23 wk photostimulation the B hens produced more eggs per hen than N or H hens (B > N > H) and recycled hens produced more eggs per hen than 1st-yr hens. Strain, year, and strain by year interaction effects were significant for egg weight. The first eggs laid, as well as subsequent eggs in both lay periods, were heaviest in N hens. In all strains, percentage yolk increased and albumen decreased with time in lay. However, N hens had a smaller percentage yolk and greater albumen than H or B hens. The mean percentage shell was greatest in H hens.

Effects of gamma irradiation on the reproductive capacity and the longevity of Panstrongylus megistus (Hemiptera: Reduviidae)

The effects of radiation on the reproductive capacity and the longevity of Panstrongylus megistus were studied. An indirect correlation between longevity and radiation doses was observed. Males were more affected than females. Longevity of females submitted to 10 Gy was not different when compared to controls. Some of the irradiated males copulated and in these cases semen was transferred to females, but only few eggs were laid. Fertility was seriously affected in all irradiated groups, decreasing with increasing intensity of dose. The dose of 80 Gy induced sterility in males and females. Gelatinous spermatophores that were expelled by females irradiated with 20 and 40 Gy, may be a consequence of irradiation that induced modification in the bursa copulatrix pH.

The effect of photoperiodic history on egg laying in dwarf broiler hens

An experiment was conducted in dwarf broiler breeders to determine whether the decrease in egg production towards the end of a laying year is due to the development of photorefractoriness or to age per se. The birds were reared on short days (8 h light/day) and subjected to dietary restriction to prevent BW exceeding the minimum required to support egg production. They were transferred at 22 wk of age to long days (20 h light/day) while controls were maintained on short days for a further 2, 14, or 30 wk. At the end of these periods, dietary restriction was relaxed to stimulate egg production, and the control short-day birds were transferred to long days. The number of days to the onset of egg laying after lifting dietary restriction was less in short-day controls than in hens exposed to long days for 14 wk [19.5 +/- .5 (SE) versus 24.0 +/- 1.1 days, P < .01] or 30 wk (26.4 +/- 1.3 versus 41.2 +/- 1.1 days, P < .001). The number of eggs laid during the 12 wk after first oviposition in hens exposed to long days for 2, 14, or 30 wk before relaxing dietary restriction was not significantly different from that of the short-day controls. The numbers of eggs laid during the 12 wk after first oviposition decreased (P < .001) as the hens became older irrespective of photoperiodic history. These observations indicate that in dwarf broiler breeders, photoperiodic history, and therefore the development of photorefractoriness, is less important than age per se in maintaining intensity of egg laying in the 1st laying yr.

Effects of age at lighting on reproduction of turkey hens

Two experiments were conducted to evaluate age at photostimulation on subsequent reproductive performance of Large White turkey hens. All hens were exposed to short daylengths [8 h light (L):16 h dark (D)] for a minimum of 8 wk immediately prior to photostimulation with long day-lengths (16L:8D). Photostimulation started at either 24, 26, 28, or 30 wk of age during January and February (Experiment 1) or July and August (Experiment 2). Data were collected for body weight, time to onset of lay, egg production, and livability in both experiments. In addition, egg quality, broodiness, floor egg production, and poult weight data were obtained in Experiment 2. An inverse relationship occurred between initiation of egg production and the age at lighting up to 30 wk of age. However, peak egg production level and the number of eggs produced per hen during the first 20 wk of egg laying were similar among treatment groups in both experiments. The number of soft-shelled or shell-less eggs produced was also similar among treatment groups. Hens photostimulated at 30 wk of age in Experiment 2 laid the heaviest eggs throughout 20 wk of egg production. Poult weight was reduced when hens were photostimulated at 24 or 26 wk of age, but this only occurred in the first 11 wk of lay. Even though Large White hens responded to photostimulation at 24 wk of age, the results do not support advancing the age at photostimulation to 28 wk or earlier.

Effects of genetic strain and light management on the reproductive performance of turkeys

The laying performance of six genetic strains of turkeys, which have been bred and maintained at the Ohio Agricultural Research and Development Center, Wooster, OH, was compared under three laying house lighting regimens over a period of 3 yr. Light Treatment 1 (L1) consisted of 14 h of continuous light (L) and 10 h of dark (D; 14L:10D) throughout the laying period. Treatment 2 (L2) consisted of 14 h of intermittent light (IL, 15 min L and 45 min D/h) followed by 10 h of continuous dark. The IL treatment was started following a period (6 wk) in which the hens were trained to use the trapnests. Thus, during the first 6 wk of their laying period, L2 hens were also provided 14L:10D. Treatment 3 (L3) hens were provided the same program as L1 for the first 14 wk of the laying period. They were then moved to a continuous period of 19L:5D for the remainder of the laying period. All eggs produced were recorded through 180 days after the first egg was laid. Traits studied included: the number of days to first egg after light stimulation; the number of eggs produced through 84, 120, and 180 days after the first egg was laid; the average clutch length; the maximum clutch length; the total days lost to broodiness; the rate of lay; and the effective length of the laying period. Highly significant differences (P less than or equal to .01) were observed among the strains used for all traits measured. Light treatments showed no significant effects on any trait measured. Thus, from the present studies, the delayed IL program provides an economically attractive management program for environmentally controlled turkey breeder houses.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of light intensity level during prelay light restriction on subsequent reproductive performance of turkey breeder hens

Two trials were conducted to determine whether light intensity levels during the prelay (light restriction) and the lay (egg production) periods influenced subsequent photoinduced reproductive performance of turkey breeder hens. The light intensity levels were 22 and 270 lx and each was provided during the prelay and lay periods in a factorial arrangement. Each of the period light intensity levels were applied to half of the hens from each prelay treatment group. Data were collected for BW, rate of reproductive development, egg production, fertility, hatchability, egg weight, and poult weight. There were no interactions between the prelay and lay period treatments, nor a consistent prelay light intensity effect on rate of initiation of lay or duration of time to achieve 50% production. In addition, prelay and lay light intensity levels had no consistent effects on rate of lay, percentage of fertility and hatchability, egg weight, and poult weight. It was concluded that there was no advantage to the use of high-intensity light during short-day light restriction of the prelay period on subsequent reproductive performance.

Effects of photostimulation at 18, 24 and 30 weeks of age on the productivity of female turkeys fed ad libitum or restricted until point of lay

1. Turkey females were fed ad libitum or restricted from 6 weeks of age to achieve mean body weights of 0.6 of ad libitum fed birds on photostimulation at 18, 24 or 30 weeks of age. Body weight, food intake, egg production and hatchability were recorded to 54 weeks of age. 2. Restricted turkeys were fed ad libitum after first egg or 36 weeks of age. Food intake after 30 weeks of age averaged 170 g/bird/d and was similar for all treatments. At 54 weeks of age, restricted turkeys photostimulated at 24 and 30 weeks were not as heavy as turkeys photostimulated at 18 weeks and ad libitum fed turkeys. 3. A large proportion of restricted turkeys photostimulated at 18 weeks of age did not commence lay until 30 to 40 weeks and a significant number of restricted birds photostimulated at 24 weeks had short laying cycles. Restricted birds photostimulated at 30 weeks came into lay and showed similar persistency of lay to ad libitum fed turkeys. 4. Ad libitum fed turkeys laid 115.0, 122.0 and 101.0 and restricted turkeys 92.4, 99.5 and 103.4 eggs when photostimulated at 18, 24 and 30 weeks, respectively. The number of non-settable eggs was lower in restricted compared with ad libitum fed turkeys and declined with age at photostimulation. 5. Egg size at the end of the experiment was similar for ad libitum fed turkeys and restricted birds photostimulated at 18 weeks but was 2.3 g lower for restricted birds photostimulated at 24 and 30 weeks of age. 6. Hatchability was higher, and the proportion of second quality poults was lower with eggs from restricted turkeys. The mean numbers of poults hatched were 59.9, 75.1 and 66.0 for ad libitum fed and 71.7, 65.7 and 79.4 for restricted turkeys photostimulated at 18, 24 and 30 weeks of age.

Light intensity effects on reproductive performance of turkey breeder hens

Two trials were conducted to evaluate the reproductive performance of turkey hens to different light intensity during the lay period. In Trial 1 the hens were exposed to 16 h of light (L) and 8 h dark (D) per day (16L:8D) at 54, 108, or 216 lx and in Trial 2 a 2 x 2 factorial arrangement of treatments was used with main treatment factors being intensity level (54 versus 324 lx) and photoperiod (16L:8D versus 14L:10D). Data were collected for time to onset of lay, rate of lay, fertility, hatchability, and egg and poult weight in both trials, and feed intake in Trial 1. In both trials the light intensity treatments were similarly effective in the photoinduction of reproductive performance in Large White turkey hens. This occurred with daily photoperiods of both 14L:10D and 16L:8D in Trial 2 and there was no photoperiod by intensity interaction. There were no significant differences in feed intake or feed efficiency among the 54-, 108-, and 216-lx treatments of Trial 1. It may be concluded that reproductive performance of turkey hens in closed confinement is equivalent within an intensity range of 54 to 324 lx.

Effect of ahemeral light:dark cycles on egg production in early photostimulated brown-egg pullets

A laying trial was conducted to determine the effect of an ahemeral lighting program on early photostimulated brown-egg pullets (DeKalb Sex-Sal). All birds received 24 h of light/day (24L:0D) to 3 days of age followed by 8 h of light (8L:16D) to 8 wk of age. From 8 to 16 wk the birds received 10 h of light daily. At 16 wk, the control group (CON) received 11 h of light and 13 h of darkness (11L:13D) followed by a weekly 1-h increase in photoperiod to 14L:10D at 19 wk, which was maintained for the duration of the trial (59 wk of age). Birds on the ahemeral (AHM) schedule were exposed to a 26-h schedule of 11L:15D at 16 wk with a weekly 1-h increase in the photoperiod to 14L:12D at 19 wk. The AHM schedule (14L:12D) was maintained from Weeks 19 to 30 at which time birds were returned to a 24-h cycle of 14L:10D and kept on this schedule for the remainder of the trial. Egg weight was significantly increased by the AHM treatment for 27 to 30 wk; however, there was no cumulative (Weeks 19 to 59) effect on egg weight. Percentages of eggs per hen per day (%HDP) were significantly reduced by the AHM treatment for the periods 23 to 26 wk and 31 to 34 wk. This reduction caused a significant cumulative effect on %HDP (68.9 for CON versus 66.2 for AHM).(ABSTRACT TRUNCATED AT 250 WORDS)