Showing papers on "Incubation published in 2008"
TL;DR: Data suggest that the consumption of flavanol-rich foods may support gut health through their ability to exert prebiotic actions, as both ( − )-epicatechin and (+)-catechin were converted to the same metabolites.
Abstract: We have investigated the bacterial-dependent metabolism of ( - )-epicatechin and (+)-catechin using a pH-controlled, stirred, batch-culture fermentation system reflective of the distal region of the human large intestine. Incubation of ( - )-epicatechin or (+)-catechin (150 mg/l or 1000 mg/l) with faecal bacteria, led to the generation of 5-(3',4'-dihydroxyphenyl)-gamma-valerolactone, 5-phenyl-gamma-valerolactone and phenylpropionic acid. However, the formation of these metabolites from (+)-catechin required its initial conversion to (+)-epicatechin. The metabolism of both flavanols occurred in the presence of favourable carbon sources, notably sucrose and the prebiotic fructo-oligosaccharides, indicating that bacterial utilisation of flavanols also occurs when preferential energy sources are available. (+)-Catechin incubation affected the growth of select microflora, resulting in a statistically significant increase in the growth of the Clostridium coccoides-Eubacterium rectale group, Bifidobacterium spp. and Escherichia coli, as well as a significant inhibitory effect on the growth of the C. histolyticum group. In contrast, the effect of ( - )-epicatechin was less profound, only significantly increasing the growth of the C. coccoides-Eubacterium rectale group. These potential prebiotic effects for both (+)-catechin and ( - )-epicatechin were most notable at the lower concentration of 150 mg/l. As both ( - )-epicatechin and (+)-catechin were converted to the same metabolites, the more dramatic change in the growth of distinct microfloral populations produced by (+)-catechin incubation may be linked to the bacterial conversion of (+)-catechin to (+)-epicatechin. Together these data suggest that the consumption of flavanol-rich foods may support gut health through their ability to exert prebiotic actions.
391 citations
TL;DR: It is shown that the basic reproduction number is a decreasing function of both time delays, and prolonging the incubation periods in either humans or mosquitos (via medicine or control measures) could reduce the prevalence of infection.
164 citations
TL;DR: New, validated scales for measuring the process of incubating new ventures, empirically-based refinements to a theoretical model of the incubation process, and data on business incubation outcomes that are very useful for incubator planning and benchmarking purposes are offered.
Abstract: Due to a lack of valid and reliable scales, few studies have sought to describe and measure the business incubation process. After rigorously developing and pre-testing scales intended to measure the incubation process (Study A), we collected data from 53 incubators operating in the US in order to (a) systematically examine the incubation process, and (b) validate the scales. Accordingly, this study offers (1) new, validated scales for measuring the process of incubating new ventures, (2) empirically-based refinements to a theoretical model of the incubation process, and (3) data on business incubation outcomes that are very useful for incubator planning and benchmarking purposes.
160 citations
TL;DR: Results indicate that exposure of larvae to mild thermal shock conditions induces a protective cellular and humoral immune response mediated by increased numbers of haemocytes and elevated expression of antimicrobial peptides.
Abstract: The use of insects for evaluating the virulence of microbial pathogens and for determining the efficacy of antimicrobial drugs is increasing. When larvae of the greater wax moth Galleria mellonella were incubated at 4 or 37°C for 24 h. prior to infection, they manifested increased resistance to infection by the yeast Candida albicans compared to larvae that had been pre-incubated for 24 h at 30°C. Incubation at 4 or 37°C led to an increase in haemocyte density and the expression of genes coding for gallerimycin, transferrin, an inducible metalloproteinase inhibitor (IMPI) and galiomicin. Peak expression of these genes was recorded at approximately 24 h after the commencement of the 4 or 37°C incubation. These results indicate that exposure of larvae to mild thermal shock conditions induces a protective cellular and humoral immune response mediated by increased numbers of haemocytes and elevated expression of antimicrobial peptides.
108 citations
TL;DR: It is suggested that incubation by both sexes was the primitive method among birds, and many modifications in the incubation pattern, especially those involving the participation of the sexes, appear to be non-adaptive, and to persist because they do not decrease reproductive efficiency.
Abstract: Summary.
A classification of the known methods of incubation of the birds of the world, on the basis of the division of labour between the sexes and the apportionment of time on the eggs, shows that practically every feasible pattern has been adopted by one species or another.
A review of the evidence suggests that incubation by both sexes was the primitive method among birds.
Among passerines, there appears to be little correlation between incubation by the male and his possession of a brood-patch. Some males which regularly incubate lack it, whereas others which fail to incubate develop it.
There is also poor correlation between the form of the nest (whether open or covered), the coloration of the two sexes, and their participation in incubation.
Participation of the sexes is not generally correlated with the environment. The non-incubation by the female Emperor Penguin and the sharing of incubation by the male Gould's Hummingbird, seem to be instances of response to rigorous climates.
Except possibly in migratory birds whose breeding season is short, incubation by the male seems compatible with efficient territorial defence. Some males and even females sing loudly from the nest, apparently without betraying it to predators.
When the sex-ratio is strongly unbalanced, the failure of the less numerous sex to incubate makes it possible for a larger proportion of the adults to reproduce. But in a number of species in which polygamy or polyandry occurs, the sex-ratio is not known to be unbalanced.
Many modifications in the incubation pattern, especially those involving the participation of the sexes, appear to be non-adaptive, and to persist because they do not decrease reproductive efficiency.
103 citations
TL;DR: It is inferred that chemical treatments enhance the nutritive value of RS through improving rumen fermentation and fibrolytic enzyme activities that are mainly resultant from more available substrate, and has great influences on rumen microbial distribution and populations, but their fluctuating pattern with incubation time is slightly different between two treated straws.
95 citations
TL;DR: Initial data is provided to show that yolks of tropical birds contain substantially lower concentrations of growth-promoting androgens than north temperate relatives, which may enhance offspring quality through physiological trade-offs that may be particularly beneficial in longer-lived species, as in the tropics and subtropics.
Abstract: Embryonic development rates are reflected by the length of incubation period in birds, and these vary substantially among species within and among geographical regions. The incubation periods are consistently shorter in North America (Arizona study site) than in tropical (Venezuela) and subtropical (Argentina) South America based on the study of 83 passerine species in 17 clades. Parents, mothers in particular, may influence incubation periods and resulting offspring quality through proximate pathways, while variation in maternal strategies among species can result from selection by adult and offspring mortality. Parents of long-lived species, as is common in the tropics and subtropics, may be under selection to minimize costs to themselves during incubation. Indeed, time spent incubating is often lower in the tropical and subtropical species than the related north temperate species, causing cooler average egg temperatures in the southern regions. Decreased egg temperatures result in longer incubation periods and reflect a cost imposed on offspring by parents because energy cost to the embryo and risk of offspring predation are both increased. Mothers may adjust egg size and constituents as a means to partially offset such costs. For example, reduced androgen concentrations in egg yolks may slow development rates, but may enhance offspring quality through physiological trade-offs that may be particularly beneficial in longer-lived species, as in the tropics and subtropics. We provide initial data to show that yolks of tropical birds contain substantially lower concentrations of growth-promoting androgens than north temperate relatives. Thus, maternal (and parental) effects on embryonic development rates may include contrasting and complementary proximate influences on offspring quality and deserve further field study among species.
86 citations
TL;DR: The role of the sexes in incubation, their changes in body weight and associated energy costs were studied in the Wandering Albatross at South Georgia and on average both sexes are able at least to maintain body weight during the incubation period.
Abstract: The role of the sexes in incubation, their changes in body weight and associated energy costs were studied in the Wandering Albatross at South Georgia. Males incubate significantly more than females (54%, range 36–68%) and lose weight during incubation shifts at a greater absolute, but smaller proportional, rate. On average this results in both sexes losing equal proportions of body weight during typical shifts. Energy costs of incubation are calculated to lie between 1.2 and 2.0 times basal metabolism, and probably much closer to the former.
All males and most females gained weight while at sea between shifts, most males doing so faster than females. On average both sexes are able at least to maintain body weight during the incubation period. More extreme individuals, however, may end incubation in poor condition and can probably redress this only by neglecting their chick. Chicks that died were more likely to have had parents with a less equal division of incubation duties.
77 citations
TL;DR: To determine whether the diversity of pyrene-degrading bacteria in an aged polycyclic aromatic hydrocarbon-contaminated soil is affected by the addition of inorganic nutrients or by slurrying the soil, various incubation conditions were examined by mineralization studies and stable-isotope probing.
Abstract: To determine whether the diversity of pyrene-degrading bacteria in an aged polycyclic aromatic hydrocarbon-contaminated soil is affected by the addition of inorganic nutrients or by slurrying the soil, various incubation conditions (all including phosphate buffer) were examined by mineralization studies and stable-isotope probing (SIP). The addition of nitrogen to either continuously mixed slurry or static field-wet soil incubations increased the rate and extent of mineralization of [14C]pyrene, with the most rapid mineralization observed in slurried, nitrogen-amended soil. Microcosms of slurry and static field-wet soil amended with nitrogen were also examined by SIP with [U-13C]pyrene. Recovered 13C-enriched deoxyribonucleic acid (DNA) was analyzed by denaturing-gradient gel electrophoresis (DGGE) and 16S ribosomal ribonucleic acid (rRNA) gene clone libraries. DGGE profiles of 13C-enriched DNA fractions from both incubation conditions were similar, suggesting that pyrene-degrading bacterial community diversity may be independent of treatment method. The vast majority (67 of 71) of the partial sequences recovered from clone libraries were greater than or equal to 97% similar to one another, 98% similar to sequences of pyrene-degrading bacteria previously detected by SIP with pyrene in different soil, and only 89% similar to the closest cultivated genus. All of the sequences recovered from the field-wet incubation and most of the sequences recovered from the slurry incubation were in this clade. Of the four sequences from slurry incubations not within this clade, three possessed greater than 99% similarity to the 16S rRNA gene sequences of phylogenetically dissimilar Caulobacter spp.
61 citations
TL;DR: The experiment shows that food and temperature both affect avian incubation behaviour, but that different trade-offs apply to each environmental factor.
58 citations
TL;DR: It was concluded that lower blood pCO(2), HCO(3)-, K(+), and higher pO(2) at IP stage, plus increased plasma triglyceride concentrations at hatch, indicate adaptive responses of embryos.
TL;DR: Temperature, relative humidity and electromagnetic fields in the experimental chamber were permanently monitored over the entire experiment and a causal relationship between the intensity of the electric field and embryo mortality could not be established.
TL;DR: The seasonal reproductive activities in Magang geese is directly inhibited by long photoperiod and directly stimulated by shortPhotoperiod via PRL and LH secretions, whose interplays also cause occurrences of four to five lay and incubation cycles in the breeding season.
TL;DR: Agarwal et al. as discussed by the authors examined potentially available nitrogen (PAN) from poultry manure using two contrasting Iowa agricultural soils, a Clarion loam (fine-loamy, mixed, superactive, mesic Typic Hapludolls) and Canisteo clay loam, and two consecutive incubation experiments were conducted, each using the same soils and treatments.
Abstract: Poultry production is an important and growing livestock industry in Iowa and use of poultry manure as a crop N resource is increasing. Aerobic incubation studies were used to examine potentially available nitrogen (PAN) from poultry manure using two contrasting Iowa agricultural soils, a Clarion loam (fine-loamy, mixed, superactive, mesic Typic Hapludolls) and Canisteo clay loam (fine-loamy, mixed, superactive, calcareous, mesic Typic Endoaquolls). Two consecutive incubation experiments were conducted, each using the same soils and treatments. Incubation 1 used an approximate rate of 86 mg total N kg -1 incubated for 112 d, and Incubation 2 used an approximate rate of 200 mg total N kg -1 incubated for 84 d. Incubation 2 included more frequent initial sampling. Nitrogen sources included urea, uric acid, and two sources of poultry manure, chicken (Gallus domesticus) and turkey (Melleagris gallopavo) obtained from local production facilities. Soil samples were collected at multiple times during incubation and inorganic NH 4 + -N and NO 3 - -N concentrations measured. The accumulation of NO 3 - -N was used to estimate PAN. The poultry manure sources provided high levels of PAN, 66% of total manure N for chicken and 55% for turkey. These values were lower than those found for urea and uric acid. The majority of the NO 3 - -N accumulation occurred within 7 d of incubation, with no increase after 14 d. This indicates that considerable NO 3 - -N used to estimate PAN originated from the combined NH 4 + -N and uric acid-N components of the poultry manures. However, water soluble nitrogen (WSN) represented approximately 66 and 58% of total N for the chicken and turkey manure, respectively, which are higher than the NH 4 + -N plus uric acid-N fractions. These WSN levels are close to the estimated PAN values for each manure source. This indicates that poultry manure analysis for WSN could improve the estimation of crop available-N compared to NH 4 + -N or a fraction of total N.
TL;DR: It is concluded that incubation is a costly period, with the potential to affect both the trade-off between current and future reproduction and the one between parental effort and offspring quality within the current breeding attempt.
Abstract: Incubation was for a long time considered to be a period of decreased activity and low cost for parents. It was therefore ignored as a potential factor affecting life-history trade-offs in birds. Lately this view has started to change, and studies now show that there might be considerable costs connected to incubation. We experimentally reduced the nest temperature during incubation in blue tits Cyanistes caeruleus, thus increasing the energetic cost of incubation, to test the importance of incubation as a component of reproductive costs and for nestling quality. While most other studies use brood size manipulation to manipulate reproductive costs, we were able to separate treatment effects acting during the incubation period from those acting on later reproductive performance by applying a cross-foster design. We were also able to isolate the effects of decreased incubation temperature on the nestlings from treatment effects acting on incubating females. We found no experimental effect on the length of the incubation period or on hatching success. The lower temperature during incubation, however, caused lower growth rates in nestlings and reduced chick rearing capacity in adults. We conclude that incubation is a costly period, with the potential to affect both the trade-off between current and future reproduction and the one between parental effort and offspring quality within the current breeding attempt.
TL;DR: This article modifies a theoretical model originally developed by Brookmeyer and others for the inhalational anthrax incubation period distribution in humans by using a more accurate distribution to represent the in vivo bacterial growth phase and by extending the model to represents the time from exposure to death, thereby allowing it to be fit to nonhuman primate time-to-death data.
Abstract: Ever since the pioneering work of Philip Sartwell, the incubation period distribution for infectious diseases is most often modeled using a lognormal distribution. Theoretical models based on underlying disease mechanisms in the host are less well developed. This article modifies a theoretical model originally developed by Brookmeyer and others for the inhalational anthrax incubation period distribution in humans by using a more accurate distribution to represent the in vivo bacterial growth phase and by extending the model to represent the time from exposure to death, thereby allowing the model to be fit to nonhuman primate time-to-death data. The resulting incubation period distribution and the dose dependence of the median incubation period are in good agreement with human data from the 1979 accidental atmospheric anthrax release in Sverdlovsk, Russia, and limited nonhuman primate data. The median incubation period for the Sverdlovsk victims is 9.05 (95% confidence interval = 8.0-10.3) days, shorter than previous estimates, and it is predicted to drop to less than 2.5 days at doses above 10(6) spores. The incubation period distribution is important because the left tail determines the time at which clinical diagnosis or syndromic surveillance systems might first detect an anthrax outbreak based on early symptomatic cases, the entire distribution determines the efficacy of medical intervention-which is determined by the speed of the prophylaxis campaign relative to the incubation period-and the right tail of the distribution influences the recommended duration for antibiotic treatment.
TL;DR: It is concluded that nonventilation during the first 10 d of incubation had a stimulatory effect on embryonic development of the 2 broiler strains with no effect of heart weights but with effects on hormone levels, air cell pressures, and hatching parameters.
TL;DR: The length of the chilling period and the stage of development at which it occurs have little effect on the proportion surviving, and many well-developed eggs hatched after being chilled in the burrow for up to 7 days.
Abstract: Summary.
1. Large-scale excavations and observations during homing experiments provided incidental data on incubation.
2. The main period (median 90%) of egg-laying is from 25 April to 20 May, of hatching from 17 June to 12 July. The median dates for these processes are 6 May and 28 June. The average incubation period is 53 days.
3. Incubation shifts are long (average 5 days) and variable, 2 to 16 days if unrelieved. Temporarily deserted eggs were only found in about 1% of undisturbed nests.
4. Nevertheless many well-developed eggs hatched after being chilled in the burrow for up to 7 days. Others remained viable for up to 13 days in the laboratory. The length of the chilling period and the stage of development at which it occurs have little effect on the proportion surviving.
5. The ecological and evolutionary significance of the faculty is considered, with a brief survey of chilling resistance in the embryos of other birds.
TL;DR: The tremendous buckling caused by Iopromide and Iomeprol, coinciding with an echinocyte formation of erythrocytes, might be the reason why a bolus injection of IOPromide in vivo into the left coronary artery was followed by a 50% decrease of oxygen partial pressure in the supplied tissue.
TL;DR: In this article, it was shown that assimilatory reduction of 15N2O plays only a negligible role in the consumption of N2O in soil organic matter in one sample and on average, 15N enrichment of organic matter during the incubation may have corresponded to a retention of 0.019% (s.e. ± 0.19%) of consumed 15N 2O in organic matter.
Abstract: . Soils are capable to consume N2O. It is generally assumed that consumption occurs exclusively via respiratory reduction to N2 by denitrifying organisms (i.e. complete denitrification). Yet, we are not aware of any verification of this assumption. Some N2O may be assimilatorily reduced to NH3. Reduction of N2O to NH3 is thermodynamically advantageous compared to the reduction of N2. Is this an ecologically relevant process? To find out, we treated four contrasting soil samples in a flow-through incubation experiment with a mixture of labelled (98%) 15N2O (0.5–4 ppm) and O2 (0.2–0.4%) in He. We measured N2O consumption by GC-ECD continuously and δ15N of soil organic matter before and after an 11 to 29 day incubation period. Any 15N2O assimilatorily reduced would have resulted in the enrichment of soil organic matter with 15N, whereas dissimilatorily reduced 15N2O would not have left a trace. None of the soils showed a change in δ15N that was statistically different from zero. A maximum of 0.27% (s.e. ±0.19%) of consumed 15N2O may have been retained as 15N in soil organic matter in one sample. On average, 15N enrichment of soil organic matter during the incubation may have corresponded to a retention of 0.019% (s.e. ±0.14%; n=4) of the 15N2O consumed by the soils. We conclude that assimilatory reduction of N2O plays, if at all, only a negligible role in the consumption of N2O in soils.
TL;DR: Temperature-dependent sex-biased embryo mortality represents a novel mechanism of altering sex ratios in birds and offers a potentially unparalleled opportunity in which to investigate sex allocation theory in birds.
Abstract: Sex ratios have important evolutionary consequences and are often biased by environmental factors. The effect of developmental temperature on offspring sex ratios has been widely documented across a diverse range of taxa but has rarely been investigated in birds and mammals. However, recent field observations and artificial incubation experiments have demonstrated that the hatching sex ratio of a megapode, the Australian brush-turkey (Alectura lathami), varied with incubation temperature; more females hatched at high incubation temperatures and more males hatched at low temperatures. Here, we investigated the causes of this temperature-dependent sex-biasing system. Molecular sexing of chicks and embryos confirmed that male embryo mortality was greater at high temperatures while female embryo mortality is greater at low temperatures, with mortality in both sexes similar at intermediate incubation temperatures. Temperature-dependent sex-biased embryo mortality represents a novel mechanism of altering sex ratios in birds. This novel mechanism, coupled with the unique breeding biology of the brush-turkey, offers a potentially unparalleled opportunity in which to investigate sex allocation theory in birds.
TL;DR: Both males and females gained weight at a higher rate when at sea than they lost it during incubation, and it is suggested that factors unrelated to food availability or individual feeding skills may be important in regulating the duration of the incubation shifts and the stay at sea.
Abstract: Antarctic Petrel Thalassoica antarctica incubation and brooding effort was studied at Svarthamaren, Dronning Maud Land, during the austral summer of 1991–1992. The females probably left the nest site shortly after egg laying. The duration of incubation and brooding shifts as well as the daily weight loss (absolute and proportionate) were comparable with those of other similar-sized procellariform species. Males spent more time incubating and brooding than did females, suggesting higher female energy stress due to egg laying. Incubating birds which were below average weight were likely to desert the nests before their mates returned from feeding trips. Both males and females lost approximately one-fifth of their body-weight during their first incubation shifts. Nevertheless, they increased their initial weights from egg laying to hatching and had their highest initial weights when they returned to start the shift during which the egg hatched. No factors related to adult body-weight explained the duration of the incubation shifts. Both males and females gained weight at a higher rate when at sea than they lost it during incubation, and it is suggested that factors unrelated to food availability or individual feeding skills may be important in regulating the duration of the incubation shifts and the stay at sea.
TL;DR: It is concluded that parental attendance patterns do not account for latitudinal differences in incubation period but that some other as yet unmeasured factor intrinsic to the egg or embryo, or both, extends development time in the tropics.
Abstract: Incubation periods of Neotropical birds are often longer than those of related species at temperate latitudes. We conducted a common-garden experiment to test the hypothesis that longer tropical incubation periods result from longer embryo development times rather than from different patterns of parental incubation behavior. House wrens, one of few species whose geographic range includes tropical equatorial and temperate high latitudes, have incubation periods averaging 1.2 days longer at tropical latitudes. We incubated eggs of house wrens in Illinois and Panama under identical conditions in mechanical incubators. Even after factoring out differences in egg size, tropical house wrens still required 1.33 days longer, on average, to hatch. We conclude that parental attendance patterns do not account for latitudinal differences in incubation period but that some other as yet unmeasured factor intrinsic to the egg or embryo, or both, extends development time in the tropics.
TL;DR: In A. carolinensis, egg incubation temperature had latent effects on juvenile growth despite the absence of any detected immediate effects on hatchling phenotype, suggesting the total impact and evolutionary importance of developmental environment should not be assessed or assumed based solely on the phenotype of reptiles at birth or hatching.
Abstract: Varied egg incubation temperatures can result in immediate effects on the phenotype of reptiles, and also latent effects that can augment or contradict effects evident at egg hatching. I examined the effects of incubation temperature on embryonic development, hatching morphology, and subsequent growth in multiple populations of the lizard Anolis carolinensis. Eggs from wild-caught females in four populations were incubated at up to three temperatures, 23.5, 27, and 301C. Measures of body size were collected immediately after hatching and weekly thereafter, while juveniles were maintained in a common laboratory environment for 8 weeks. Cooler incubation temperatures resulted in longer incubation periods but did not affect conversion of egg mass to hatchling mass. Incubation temperature did not affect hatchling mass or snout vent length (SVL), but did affect subsequent growth in both mass and SVL, which varied by population. Cooler incubation temperatures generally resulted in greater overall growth over 8 weeks of housing all juveniles in a common environment. In A. carolinensis, egg incubation temperature had latent effects on juvenile growth despite the absence of any detected immediate effects on hatchling phenotype. Therefore, the total impact and evolutionary importance of developmental environment should not be assessed or assumed based solely on the phenotype of reptiles at birth or hatching. J. Exp. Zool. 309A, 2008. r 2008 Wiley-Liss, Inc.
TL;DR: Evidence is found that incubation constancy increased with greater visual obstruction, usually from vegetation, of nests, and an understanding of how incubation patterns relate to environmental factors will help managers make decisions aimed at increasing productivity through successful incubation.
Abstract: Birds in which only one sex incubates the eggs are often faced with a direct conflict between foraging to meet metabolic needs and incubation. Knowledge of environmental and ecological factors that shape life-history strategies of incubation is limited. We used continuous videography to make precise measurements of female Greater Sage-Grouse (Centrocercus urophasianus) incubation constancy (percentage of time spent at the nest in a 24-hour period) and recess duration. We used an information-theoretic approach to evaluate incubation patterns in relation to grouse age, timing of incubation, raven abundance, microhabitat, weather, and food availability. Overall, sage-grouse females showed an incubation constancy of 96% and a distinctive bimodal distribution of brief incubation recesses that peaked at sunset and 30 min prior to sunrise. Grouse typically returned to their nests during low light conditions. Incubation constancy of yearlings was lower than that of adults, particularly in the later stage...
TL;DR: A retrospective descriptive study of 24 of 30 influenza virus (H5N1) cases in China to estimate and compare incubation periods for different exposure settings, including case-patients exposed only to sick or dead poultry versus those exposedonly to a wet poultry market, where small animals and poultry may be purchased live or slaughtered.
Abstract: To the Editor: Since 1997, more than 400 human cases of highly pathogenic influenza A virus (H5N1) infection have been reported worldwide, including 30 from mainland China. Ascertainment of the incubation period for influenza virus (H5N1) is important to define exposure periods for surveillance of patients with suspected influenza virus (H5N1) infection. Limited data on the incubation period suggest that illness onset occurs <7 days after the last exposure to sick or dead poultry (1–4). For clusters in which limited human-to-human virus transmission likely occurred, the incubation period appeared to be 3–5 days (5–7) but was estimated to be 8–9 days in 1 cluster (5). In China, exposure to sick or dead poultry in rural areas and visiting a live poultry market in urban areas were identified as sources of influenza A virus (H5N1) exposures (8), but the incubation period after such exposures has not been well described.
We conducted a retrospective descriptive study of 24 of 30 influenza virus (H5N1) cases in China to estimate and compare incubation periods for different exposure settings, including case-patients exposed only to sick or dead poultry versus those exposed only to a wet poultry market, where small animals and poultry may be purchased live or slaughtered (www.searo.who.int/en/Section23/Section1001/Section1110_11528.htm). Exposures may be direct (e.g., touching poultry) or indirect (e.g., no physical contact, but in close proximity to poultry, poultry products, or poultry feces). We excluded 6 cases, including 2 with unavailable epidemiologic data, 1 without an identified exposure source, 2 in a cluster with limited person-to-person transmission (6), and 1 in which the patient was exposed to both a wet poultry market and to sick or dead poultry. Epidemiologic data were collected through patients and family interviews and a review of case-patients’ medical records.
The incubation period was defined as the time from exposure to symptom onset. The maximum time from first exposure to illness onset was limited to 14 days for biological plausibility. For case-patients with exposures on multiple days, we calculated each case-patient’s median incubation period and then calculated the overall median and range of the distribution of these median incubation periods. Similarly, the minimum and maximum incubation periods for case-patients with exposures on multiple days was estimated by using the last or first known exposure day, respectively. The overall incubation period among these case-patients was estimated by determining the median of the distribution of case-patients’ median incubation periods. Incubation periods were compared by using the Wilcoxon rank-sum test. All statistical tests were 2-sided with a significance level of α = 0.05.
Of the 24 case-patients, 16 (67%) had exposure to sick or dead poultry only (median age = 25 years [range 6–44]; 25% male; 100% lived in rural areas). Eight (33%) had visited a wet poultry market only (median age = 30 years [range 16–41]; 63% male; 88% [7/8] lived in urban areas) (Table). For case-patients with >2 exposure days (n = 18), and for case-patients with a single exposure day (n = 6), the overall median incubation period was longer for those who had visited a wet poultry market than for those who were exposed to sick or dead poultry, but the difference was not significant. When data for single and multiple exposure days were combined, the overall median incubation period for case-patients exposed to a wet poultry market (n = 8) was significantly longer than for case-patients (n = 16) exposed to sick or dead poultry (7 days [range 3.5–9] vs. 4.3 days [range 2–9]; p = 0.045).
Table
Estimated incubation period of 24 human cases of infection with avian influenza A virus (H5N1), China*
Our findings are subject to limitations. Proxies for deceased case-patients may not have known all of the case-patient’s exposures. Surviving case-patients may not have recalled or identified all exposures that occurred, including environmental exposures. It was impossible to ascertain when infection occurred for case-patients with multiple days of exposures. Our limited data did not permit the use of other methods such as survival analysis to better define incubation periods. We did not quantify exposure duration and could not determine whether repeated exposures (dose-response) or a threshold of exposure to influenza virus (H5N1) exists to initiate infection of the respiratory tract. Laboratory testing was not performed to confirm that the exposure sources contained influenza virus (H5N1) or to quantify exposures.
Despite exposures of many persons in China to sick or dead poultry or to wet poultry markets, human influenza A (H5N1) disease remains very rare. Our findings suggest that the incubation period may be longer after exposure to a wet poultry market than after exposure to sick or dead poultry, and, therefore, a longer incubation period than the 7 days that is used widely (4,9) could be considered for surveillance purposes. However, because of the small number of influenza virus (H5N1) case-patients, our study was too underpowered to draw any firm conclusions; results should be interpreted cautiously. In a study of influenza virus (H5N1) cases in Vietnam, 5 case-patients did not have any identified exposure <7 days of illness onset (10). In China, the exposure period for surveillance of suspected influenza virus (H5N1) cases now includes exposure to a wet poultry market <14 days before illness onset. Although data on person-to-person virus transmission are limited, close contacts of patients infected with influenza virus (H5N1) in China are monitored daily for 10 days after the last known exposure. Further studies are needed to quantify the incubation period after exposure to sick or dead infected poultry, a wet poultry market, or to an influenza A virus (H5N1) case-patient and to investigate the basis for any differences.
TL;DR: It may be concluded that this process observed during the high incubation temperature may be related to a protective strategy and thus contributes to postnatal heat adaptation.
TL;DR: It is concluded that changes in blood acid-base balance reflected adaptive responses to heat stress, and incubating eggs at IT(HA) improved thermotolerance of fast-growing broilers.
TL;DR: The total period required to hatch all incubated fertile eggs was not influenced by breeder age, which, however, affected hatching distribution, and eggs laid by old breeders presented higher infertility and total embryo mortality, resulting in lower hatching percentage.
Abstract: This study investigated the hatching distribution of eggs from broiler breeders of different ages in distinct periods of incubation. Eggs were incubated in a single-stage experimental incubator. A number of 3.510 eggs were distributed into 3 treatments with 13 replicates of 90 eggs each. Treatments corresponded to breeder age: young (34 weeks), intermediate-age (44 weeks) and old (72 weeks) breeders. Eggs were transferred to the hatcher at 432 incubation hours, hatching was first checked at 449 hours, after which the number of hatched chicks was counted every 6 hours up to 515 incubation hours. After each count, hatched chicks were removed from the hatcher. Data were submitted to analysis of variance using measures repeated. A significant interaction between breeder age and incubation time was found. The total period required to hatch all incubated fertile eggs was not influenced by breeder age, which, however, affected hatching distribution. Eggs from old breeders hatched later as compared to young and intermediate-age breeders. More than 71% of the eggs had already hatched at 485 incubation hours, and 94% at 491 hours. Eggs laid by old breeders presented higher infertility and total embryo mortality, resulting in lower hatching percentage.
TL;DR: Incubation at moderate temperatures provided the best conditions for both embryonic and post-hatching development, and changes in temperature during incubation increased the among-clutch variance in incubation length relative to that of constant temperature treatments.
Abstract: I evaluated the effect of incubation temperature on phenotypes of the veiled chameleon, Chamaeleo calyptratus. I chose this species for study because its large clutch size (30-40 eggs or more) allows replication within clutches both within and among experimental treatments. The major research objectives were (1) to assess the effect of constant low, moderate, and high temperatures on embryonic development, (2) to determine whether the best incubation temperature for embryonic development also produced the "best" hatchlings, and (3) to determine how a change in incubation temperature during mid-development would affect phenotype. To meet these objectives, I established five experimental temperature regimes and determined egg survival and incubation length and measured body size and shape, selected body temperatures, and locomotory performance of lizards at regular intervals from hatching to 90 d, or just before sexual maturity. Incubation temperature affected the length of incubation, egg survival, and body mass, but did not affect sprint speed or selected body temperature although selected body temperature affected growth in mass independently of treatment and clutch. Incubation at moderate temperatures provided the best conditions for both embryonic and post-hatching development. The highest incubation temperatures were disruptive to development; eggs had high mortality, developmental rate was low, and hatchlings grew slowly. Changes in temperature during incubation increased the among-clutch variance in incubation length relative to that of constant temperature treatments.