Post Molt Research Articles

Egg Production and Biological Activities in Laying Hens are Affected By Different Molting Programs

This study was conducted to compare two molting methods by using aluminum sulfate (2.5 g/kg) and diet withdrawal on productivity, eggs quality, and lipid profile of laying hens. A total of 180 Hy-line Brown hens 80 weeks of age were randomly assigned to three replicates of three treatments of 30 hens/treatment from 70–87 weeks of age; hens were exposed to one of the following two molt groups: T1, aluminum sulfate (2.5 g/kg) and T2, feed withdrawal(14 days). Egg production was recorded daily/hen in each cage and weekly for each treatment. Following the forced molting, feed consumption was recorded and calculated weekly. Feed conversion rate as a feed/g egg mass was calculated weekly for each treatment. Haugh unit was determined by [11]. At the end of the experiment blood samples were collected from nine laying hens/treatment from the extrinsic vein using a 5mL sterilized syringe with heparin for biochemical determination parameters. Blood samples were centrifuged at 4000rpm for ten minutes. Plasma and serum were separated and stored (- 20°C) until the biochemical measurement. Cholesterol, Triglycerides, Total Protein, Albumin, Globulin, ALT, and AST were determined in this study. The data were analyzed using (ANOVA) to analyze the difference between treatments. A significant difference was identified between treatments, by using Duncan’s test for multiple comparisons. The results of this study indicated that hens subject to feed withdrawal treatment showed a significant (p < 0.05) percentage of body weight loss compared to those in the feed with aluminum (2.5g/kg). We did not find significant (p>0.05) differences in hens performance for all treatments in the post molt for 56 days. Our data showed hens had significantly lower (p < 0.05) in hen day egg production when compared with other treatments after molting, also, the egg weight showed no significant differences between treatments. The results showed a significant (p<0.05) difference in albumin and globulin between molt methods. Our experiment indicated that aluminum sulfate (2.5 g/kg) and feed withdrawal represent a viable alternative to the molting method for the successful induction of molting and retention of post molt performance.

Comprehensive analysis of metabolomics and transcriptomics provides insights into growth difference of juvenile Eriocheir sinensis during the molting cycle

Considerable differences in weight gain rates (WGRs) after molting is a puzzling phenomenon exhibited by individuals of the Chinese mitten crab Eriocheir sinensis even under the same environmental conditions. However, the mechanisms underlying the control of growth difference during the molting cycle have not been illustrated. In the present study, juvenile E. sinensis individuals were cultured in the same environment during one molting cycle. After molting, the E. sinensis individuals were classified into the high- and low-WGR groups on the basis of WGRs. Hemolymph samples were collected at the intermolt (InM), premolt (PrM) and postmolt (PoM) stages of the molting cycle for metabolomic and transcriptomic analyses. Differential metabolites (DMs) and differentially expressed genes (DEGs) at the InM, PrM, and PoM stages were identified and mapped to Kyoto Encyclopedia of Genes and Genomes pathways. Integrated metabolomic and transcriptomic analyses revealed significantly varied metabolic pathways between different WGR groups at the three molting stages. These pathways involved amino acid metabolism, nucleotide metabolism, and energy metabolism. Results showed that the high-WGR group exhibited more active cellular protein biosynthesis, a robust neuroendocrine system, and higher antioxidant and detoxifying capabilities than the low-WGR group, which may promote weight gain during the molting cycle. This study provided novel insights into the molecular and metabolic mechanisms in controlling the growth of E. sinensis during the molting cycle, and afforded the theoretical basis for further aquaculture and selective breeding practices of crustacean species.

Transcriptomic analysis of gills provides insights into the molecular basis of molting in Chinese mitten crab (Eriocheir sinensis).

Chinese mitten crab (Eriocheir sinensis) is an economically important freshwater aquaculture species and is a model species for research on the mechanism of molting. This study aimed to identify important candidate genes associated with the molting process and to determine the role of gills in the regulation of molting with the help of transcriptomic analysis. The transcriptomes of crabs at different molting stages—postmolt (PoM), intermolt (InM), premolt (PrM) and ecdysis (E)—were de novo assembled to generate 246,232 unigenes with a mean length of 851 bp. A total of 86,634 unigenes (35.18% of the total unigenes) were annotated against reference databases. Significantly upregulated genes were identified in postmolt compared to intermolt (1,475), intermolt compared to premolt (65), premolt compared to ecdysis (1,352), and ecdysis compared to postmolt (153), and the corresponding numbers of downregulated genes were 1,276, 32, 1,573 and 171, respectively. Chitin synthase, endochitinase, chitinase A, chitinase 3, chitinase 6 and chitin deacetylase 1 were upregulated during the postmolt and ecdysis stages, while phosphoglucomutase 3 (PGM3), glucosamine 6-phosphate deaminase (GNPDA) and glucosamine glycoside hydrolase (nagZ) were upregulated during the intermolt and premolt stages compared to the other stages. The upregulated genes were enriched in several lipid-related metabolic pathways, such as “fatty acid elongation”, “glycerophospholipid metabolism” and “sulfur metabolism”. Meanwhile, three signaling pathways, including the “phosphatidylinositol signaling system”, the “calcium signaling pathway” and the “GnRH signaling pathway” were also enriched. Tetraspanin-18, an important effector gene in the lysosomal pathway involved in cell apoptosis, up-regulate with the beginning of molting (in premolt stage) and reach the top in the ecdysis stage, and barely expressed in the intermolt stage. The expression variations in the tetraspanin-18 gene indicated that it may play an important role in the beginning of molting cycle, which might be regulated by the stress of salinity. This study revealed that the gills could participate in chitin degradation, in reestablishment of the exoskeleton and the signaling process. Based on transcriptomic analysis of the gills, we not only explored novel molecular mechanisms of molting in E. sinensis but also acquired foundational genetic data for E. sinensis.

Identification and comparative analysis of Eriocheir sinensis microRNA transcriptome from claw muscles related molting

Molting is a critical developmental process for crustaceans, during which the claw muscles undergo periodic atrophy and restoration. The regulatory mechanism of this special muscle reshuffle around ecdysis was not clear. To investigate the molecular mechanism underlying the muscle changes in crustaceans, we used Illumina/Solexa deep sequencing technology to sequence small RNA libraries prepared from claw muscles of Eriocheir sinensis in three molting stages (inter-molt C stage, later pre-molt D3–4 stage and post molt A–B stage). The sequencing resulted in 8,054,808, 9,944,487 and 10,202,589 high-quality clean reads, corresponding to 2767, 2676, and 2891 unique miRNAs for the A–B, C and D3–4 stage samples, respectively. Bioinformatic analyses identified 1485 mature miRNAs, among which 1392 miRNAs belong to 218 miRNA families and 93 miRNAs belong to unknown families. Altogether, 115 miRNAs were differentially expressed among the three molting stages, and they were clustered into 5 subclusters according to their expression patterns. GO and KEGG analysis revealed that the predicted targets of the differentially expressed miRNAs are particularly associated with gene expression, protein degradation and synthesis, muscle atrophy and development, post-embryonic morphogenesis, and anatomical structure development. Our findings suggest that the differentially expressed miRNAs and their target genes play important roles in growth and development of crab muscles induced by molting.

Transcriptomic analysis of differentially expressed genes in the molting gland (Y-organ) of the blackback land crab, Gecarcinus lateralis, during molt-cycle stage transitions

A transcriptome of the Gecarcinus lateralis molting gland (Y-organ or YO) contained 48,590 contiguous sequences (contigs) from intermolt (IM), early premolt (EP), mid premolt (MP), late premolt (LP), and postmolt (PM) stages. The YO is kept in the basal state in IM by molt-inhibiting hormone (MIH)/cyclic nucleotide-dependent signaling. YO activation in EP requires down-regulation of MIH signaling and activation of mechanistic target of rapamycin (mTOR)-dependent protein synthesis. Transition of the YO to the committed state in MP requires activin/transforming growth factor-beta (TGFβ) signaling. YO repression occurs at the end of LP. A total of 28,179 contigs (58%) showed molt stage-specific changes in gene expression. The largest number of differentially-expressed genes (DEGs) were at the IM/EP (16,142 contigs), LP/PM (18,161 contigs), and PM/IM (8290 contigs) transitions. By contrast, the numbers of DEGs were 372 and 1502 contigs for the EP/MP and MP/LP transitions, respectively. DEG analysis of 23 signal transduction pathways showed significant changes in MIH, mTOR, activin/TGFβ, Notch, MAP kinase, and Wnt signaling. Down-regulation of MIH signaling genes in premolt is consistent with reduced MIH sensitivity in MP and LP. Up-regulation of mTOR signaling genes in IM and premolt stages is consistent with its role in YO activation and sustained ecdysteroidogenesis. Up-regulation of activin/TGFβ signaling genes in EP and MP is consistent with the role of a myostatin/activin-like factor in YO commitment. Notch, MAP kinase, and Wnt DEG analysis may indicate possible crosstalk with the MIH, mTOR, and activin/TGFβ pathways to integrate other inputs to control YO ecdysteroidogenesis.

Alternative induced molting methods for feed withdrawal and their effect on post molt egg quality parameters of White Leghorn hens

Forced molting were practiced using the flock of hens by promoting a second laying cycle. In the present study, the effectiveness of induced molting method was studied in comparison to conventional feed withdrawal in terms of egg quality parameters. Layer chicken (160), 72–week-old were divided into 4 groups and were subjected to induce molting for a period of 14 days. The first group that received ad lib. water with complete feed withdrawal served as a control. The birds of the second group received ad lib. layer ration without calcium fortified with organic zinc (20,000 ppm) along with organic copper (600 ppm/kg of feed). The third group was provided with organic zinc (20,000 ppm) along with organic cobalt (150 ppm/kg of feed). The fourth group was provided with organic zinc (20,000 ppm) with organic chromium (500 ppm/kg of feed). Egg and shell weight were significantly different among different treatments; whereas, in shell thickness, egg production and body weight reduction, no significant difference was observed. The feed withdrawal treatment resulted in lower egg weight than other treatments. In conclusion, mineral supplemented methods could be substituted for conventional feed withdrawal method of induced molting.

Climbing ability of teneral and sclerotized adult bed bugs and assessment of adhesive properties of the exoskeletal fluid using atomic force microscopy.

We observed that teneral adults (<1 h post-molt) of Cimex lectularius L. appeared more adept at climbing a smooth surface compared to sclerotized adults. Differences in climbing ability on a smooth surface based on sclerotization status were quantified by measuring the height to which bed bugs climbed when confined within a glass vial. The average maximum height climbed by teneral (T) bed bugs (n = 30, height climbed = 4.69 cm) differed significantly (P< 0.01) from recently sclerotized (RS) bed bugs (n = 30, height climbed = 1.73 cm at ~48 h post molt), sclerotized group 1 (S1) bed bugs (n = 30, S1 = 2.42 cm at >72 h), and sclerotized group 2 (S2) bed bugs (n = 30, height climbed = 2.64 cm at >72 h post molt). When heights from all climbing events were summed, teneral bed bugs (650.8 cm climbed) differed significantly (P< 0.01) from recently sclerotized (82 cm climbed) and sclerotized (group 1 = 104.6 cm climbed, group 2 = 107.8 cm climbed) bed bugs. These findings suggested that the external surface of teneral bed bug exoskeletons possess an adhesive property. Using atomic force microscopy (AFM), we found that adhesion force of an exoskeletal (presumably molting) fluid decreased almost five-fold from 88 to 17 nN within an hour of molting. Our findings may have implications for laboratory safety and the effectiveness of bed bug traps, barriers, and biomimetic-based adhesives.

Transcriptomic variation of eyestalk reveals the genes and biological processes associated with molting in Portunus trituberculatus.

BackgroundMolting is an essential biological process throughout the life history of crustaceans, which is regulated by many neuropeptide hormones expressed in the eyestalk. To better understand the molting mechanism in Portunus trituberculatus, we used digital gene expression (DGE) to analyze single eyestalk samples during the molting cycle by high-throughput sequencing.ResultsWe obtained 14,387,942, 12,631,508 and 13,060,062 clean sequence reads from inter-molt (InM), pre-molt (PrM) and post-molt (PoM) cDNA libraries, respectively. A total of 1,394 molt-related differentially expressed genes (DEGs) were identified. GO and KEGG enrichment analysis identified some important processes and pathways with key roles in molting regulation, such as chitin metabolism, peptidase inhibitor activity, and the ribosome. We first observed a pattern associated with the neuromodulator-related pathways during the molting cycle, which were up-regulated in PrM and down-regulated in PoM. Four categories of important molting-related transcripts were clustered and most of them had similar expression patterns, which suggests that there is a connection between these genes throughout the molt cycle.ConclusionOur work is the first molt-related investigation of P. trituberculatus focusing on the eyestalk at the whole transcriptome level. Together, our results, including DEGs, identification of molting-related biological processes and pathways, and observed expression patterns of important genes, provide a novel insight into the function of the eyestalk in molting regulation.

Assessing the feasibility of dietary soybean meal replacement for fishmeal to the swimming crab, Portunus pelagicus, juveniles

The feasibility of dietary soybean meal (SBM) replacement for fishmeal was evaluated to the swimming crab Portunus pelagicus juveniles over six consecutive molts by measuring their growth, development, hemolymph cholesterol, triglycerides, phosphate, whole-body crude protein and cholesterol as well as hepatopancreatic trypsin activity, histopathology and glycogen reserves. A total of six isonitrogenous, isolipidic and isoenergetic diets were formulated with SBM replacing fishmeal at 0 (control), 20, 40, 60, 80 or 100% of total dietary protein. Each treatment consisted of 30 replicate crabs starting from the first juvenile stage and after the crabs molted to the seventh stage, three-day post molt crabs were sampled. Results showed that crabs fed the 20% SBM diet had the best growth, which was significantly higher than the control diet (0% SBM). Growth became significantly lower in the 60% dietary SBM treatment and above, while hemolymph cholesterol, triglycerides and phosphate significantly decreased with increasing dietary SBM. The whole-body moisture, crude protein and cholesterol were unaffected by dietary SBM. Meanwhile, hepatopancreatic trypsin activity significantly decreased in the 20 to 60% SBM treatments, with a further significant decrease in the 80 and 100% SBM treatments. Hepatopancreatic damage, significantly fewer epithelial cells and glycogen reserves occurred at 60% SBM and above. Results indicate that dietary SBM can replace up to 40% of fishmeal in the diets of P. pelagicus juveniles without reducing their growth or hepatopancreatic condition. Statement of relevanceSBM at 40% can be used in the diets of P. pelagicus without affecting survival or growth.

Intensity, rate, and outcome of agonistic interactions in harbor seals (Phoca vitulina concolor) vary with density on haul-out ledges

Due to successful conservation efforts, several marine mammal populations have increased in the past 40 years, leading to the possibility of increased competition for resources. We evaluated competition for haul-out space in western Atlantic harbor seals ( Phoca vitulina concolor ) by assessing agonistic interactions at 2 haul-out sites in Casco Bay, Maine. We predicted that intensity and rate of interactions increase as density increases, larger seals win more interactions than smaller seals do, seals already occupying a space win more interactions than arriving seals, and intensity of interactions is higher during molt but rates are higher during post molt. During molt at Gunpoint Ledge, 1 of the 2 sites, intensity of interactions decreased as density increased, but the pattern reversed during post molt. Rate of interactions peaked at intermediate density. Size and age class did not affect outcomes of interactions, but seals that already occupied space won more interactions than expected by chance. Interaction rate was higher during molt versus post-molt seasons. Harbor seals may experience increased competition for limited haul-out space as populations continue to grow, with seals occupying space outcompeting intruders.

Efficacy of protein, symbiotic and probiotic supplementation on production performance and egg quality characteristics in molted layers

Two hundred white leg horn layers at 70weeks of age were induced to molt with high dietary zinc (3g/kg of feed); thereafter, birds were equally and randomly divided (n = 50 each) into four groups keeping G1 as control (CP 16% diet, no other supplement), G2 (CP 18% diet), G3 (CP 16% diet + symbiotic; Perfectin® at 85mg/L in drinking water daily), and G4 (CP 16% diet + probiotic; Protexin® at 85mg/L in drinking water daily). The egg production record was maintained throughout the experiment period, and egg quality parameters were performed at 5%, peak, and end of post molt production stage. The overall egg production was highest in G2 (74.51%) followed by G3 (64.95%) and G4 (65.03%) and lowest in G1 (58.51%). The overall egg weight, length, diameter, weight and diameter of albumin and yolk, egg shell thickness as well as egg shell breaking strength increased (P ≤ 0.01) in G2 and G3 as compared to G1. The albumin height, yolk height, yolk index, and haugh unit score decreased (P ≤ 0.01) in G2 and G3 as compared to G1. FCR/12 eggs improved in all the supplemented groups as compared to control (G1). The bacterial contamination of eggs was seen in G1. Conclusively, it was observed in the current experiment that the supplementation with protein, probiotic, and symbiotic did improve the production quality and potential in molted layers.

Natural and Induced (Eyestalk Ablation) Molt Cycle in Freshwater Rice Field Crab Oziothelphusa Senex Senex

In crustaceans, molting is the process of shedding old exoskeleton and is required for the somatic growth of new exoskeleton for its growth. The molting processes in crustaceans vary from one species to other and also vary with the environmental conditions. In the present study the molt cycle of freshwater crab Oziothelphusa senex senex was studied. The size of crabs selected for the study is 30 ± 2 g. The natural molt cycle is consisting of intermolt (C1, C2, C3 and C4), premolt (D1, D2, D3 and D4), ecdysis (E) and post molt (A1, A2, B1 and B2) stages were measured and the percentage of each stage in the molt cycle was calculated. The biggest stage in the O. senex senex molt cycle is intermolt stage (90.0%) and shortest one is ecdysis (0.01%). Induced molt cycle was studied by eyestalk extirpation (ESX) and observed that 60.71% of male crabs and 52.0% female crabs were molted after 28th day of extirpation suggesting the role of eyestalk principle in regulating the molting process.

Immunohistochemical localization and morphometry of somatotrophs and lactotrophs in protein, probiotic and symbiotic supplemented molted layers

Two hundred Single Comb White Leg-Horn spent hens at the age of 70 weeks were purchased from a commercial layer farm. The birds were shifted to the Poultry Research Station, Department of Physiology and Pharmacology, University of Agriculture, Faisalabad, Pakistan. High dietary zinc (3 g/kg feed/day) was used to induce molting in all the birds after one week of acclimatization. Thereafter, birds were divided in groups of 50 birds each, with the following treatments: G1 [control; crude protein (CP)16%, no other supplement], G2 (CP18%, no other supplement), G3 (CP16%, Symbiotic, 85 mg/L drinking water) and G4 (CP16%, Probiotic, 85 mg/L in drinking water). Fifteen birds were slaughtered at 5% of peak of production for each group to collect their pituitary glands. Better egg production was seen in all the supplemented groups as compared to the control. Especially an earlier post molt production recovery and delayed decline was seen in G2 as compared to all other groups. The immunohistochemistry of the pituitary gland reveals the decrease (P≤0.01) in the cell and nucleus size as well as area of somatotrophs in G2 and G4 as compared to G1. The cell and nucleus size as well as area of lactotrophs decreased (P≤0.01) in G2, G3 and G4 as compared to G1. The better and earlier post molt production in G2 highlights the potential role of protein supplementation in connection with the decreased lactotroph size and area in molted birds.

Lipid composition and fatty acid profiles of wild caught and fattened mud crab, &lt;i&gt;Scylla serrata&lt;/i&gt;, in Sri Lanka

There is a huge demand for mud crab ( Scylla serrata ) in overseas markets. The mud crabs available to the market are mainly wild caught crabs and cage fattened crabs. Crab fattening is used to fatten the thin crab or post molt crab to fill up their meat in a shorter period. In the present study, lipid levels and fatty acid profiles of wild caught and fattened mud crabs at the harvested stage as well as at the stocking and harvesting stages of the fattening process were analyzed using gas chromatography. The total lipid content of wild caught (fattened) S. serrata (0.65±0.1%) was significantly higher than that of cage fattened individuals (0.56±1%). Polyunsaturated fatty acids were the predominant group of fatty acids found in S. serrata (39%-43%) and Oleic acid (C 18:1 n-9) was the most abundant fatty acid (16%-21%). Oleic acid (C 18:1 n-9), Gondoic acid (C 20:1), Eicosapentaenoic acid (C20: 5 n-3), Docosatetraenoic acid (C22: 4 n-6) and Docosahexanoic acid (C22: 6 n-3) contents varied significantly between crabs at stocking and harvested stages of fattening process. The contents of Oleic acid (C 18:1 n-9), Gondoic acid (C 20:1) and Docosatetraenoic acid (C 22:4 n-6) were significantly different in wild caught crabs in comparison to fattened crabs. The differences in fatty acid composition among wild caught crabs (fattened stage) and cage fattened crabs (fattened stage) might be a reason for flavour difference between the two types. DOI: 10.4038/sljas.v14i0.2201 Sri Lanka J. Aquat. Sci. 14 (2009): 75-85

Molting of megalopae of the Asian shore crab Hemigrapsus sanguineus in intertidal habitats of Northeastern North America

Planktonic larvae of many benthic taxa settle and metamorphose in response to certain habitat cues. Although laboratory investigations of the importance of potential cues are numerous, field experiments are less common. We modified a field caging technique first developed for analysis of molting specificity of fiddler crab megalopae to test potential habitat cues affecting molting of megalopae of the non-native Asian shore crab Hemigrapsus sanguineus (de Haan). Potential cues consisted of waterborne substances from 2 potential habitats (cobble beach and salt marsh), and the material used to construct experimental cages. Experiments were conducted in 2002, 2003, and 2004 in Massachusetts and New York (USA). Megalopae (4 or 5 d post molt) were placed in either nylon mesh (500 μm) cages open to flooding seawater or transparent glass jars containing filtered seawater. Cages and jars were placed at identical intertidal heights at the field sites and retrieved 3 or 4 d later. The proportion of megalopae molting to the first crab stage was determined after the period of field exposure and for 2 d thereafter. More megalopae molted in cages than jars placed in the adult habitat (cobble beach) and in a marsh without adults. The cage mesh had little effect on molting response. We conclude that waterborne cues stimulate molting of H. sanguineus megalopae, and that cues are present in both the adult habitat and marsh. Molting of H. sanguineus megalopae is substantially less habitat-specific than molting of native fiddler crab megalopae.

Molecular characterization and effect of RNA interference of retinoid X receptor (RXR) on E75 and chitinase gene expression in Chinese shrimp Fenneropenaeus chinensis

Retinoid X receptor (RXR)/ultraspiracle (USP) is the heterodimeric partner of ecdysteroid receptor and is required for the molting process of arthropods. To better understand the molecular aspects governing the process of molting in shrimp, the full-length cDNA of two RXRs, named as FcRXR-1 and FcRXR-2 were obtained from Chinese shrimp Fenneropenaeus chinensis which were of 1715 and 1700 bp long, revealed a 1315 and 1300 bp open reading frame (ORF) respectively. Quantitative Real time PCR analysis showed a marked tissue-specific difference in the expression of FcRXR transcript, which revealed that the expression of FcRXR could be regulated in a tissue-specific manner. Moreover, high expression of FcRXR mRNAs was observed in late pre-molt period (D3) and post molt stages (A-B) of shrimp. Among the two isoforms, FcRXR-2 appeared in a considerably high level in all the stages compared to the FcRXR-1. In addition, we examined the temporal expression of two chitinase genes: FcChitinase (FcChi) and FcChitinase-1 (FcChi-1) during the molt cycle of F. chinensis. Both the FcChi and FcChi-1 transcripts were detected in all stages of molting, although considerable fluctuations observed through the molt cycle. Injection of double stranded RXR (dsRXR) into juvenile shrimp resulted in a maximum silencing effect at 48 h post injection. We analyzed the expression levels of FcChi, FcChi-1 and the ecdysone inducible gene E75 (FcE75) in samples of dsRXR injected shrimp. Significant reduction in levels of both FcE75, FcChi and FcChi-1 transcripts occurred in the silenced shrimp. This correlation suggested that RXR might involve in the downstream regulation of E75 and chitinase gene transcription in the ecdysone signaling pathway of decapod crustaceans.

Comparison of Four Induced Molting Methods Based on Subsequent Performance and Welfare of Single Comb White Leghorn Hens

A total of 400 Single Comb White Leghorn hens at 80 weeks of age were used in present study. Four treatment groups that were consisted of six replications with 10 hens per each replication were considered. In the first treatment, food and water were removed for the first 2, 4, 6 and 8 days. However, on days 3, 5, 7, 9 and on day 10 until day 28 hens were fed 45 g of food per hen (ON-OFF group). In the second and third groups, food was withdrawn for 10, 14 days, respectively and oyster shell and water were provided for ad libitum until day 28 (California and North Carolina treatments (CAL, NC groups)). The last group (full-food treatments (FF group)) was the hens that were non-food-deprived and were fed corn molt diet for 28 days ad libitum. In all treatment groups at day 29, hens were returned to a full food layer ration and received 16 h of light day(-1). Body weight, egg production, egg weight, relative eggshell weight, internal egg quality, egg specific gravity and mortality were determined. Differential leukocyte count and antibody response were also measured. The results demonstrated that induced molting increased egg production according to pre-molt egg production. There was not a significant difference in the rate of egg production during the peak period of post molt production for treatments. No significant differences were detected in differential leukocyte counts and antibody response against Sheep Red Blood Cell (SRBC) between treatments at pre molt and post molt of the experiment. This study indicated that diets with high corn level (FF groups) are effective and simplified nonfood removal procedure for welfare molting hens.

Combined effect of exposure to ammonia and hypoxia on the blue shrimp Litopenaeus stylirostris survival and physiological response in relation to molt stage

The effect of ambient ammonia, hypoxia and combination of both on survival and the physiological and immunological response of the blue shrimp Litopenaeus stylirostris in relation to molt stage was studied. Shrimp were submitted to 44.0-71.5 mg l­1 total ammonia-N corresponding to 2.0 mg l­1 unionized ammonia NH3-N and/or to 1.5 mg O2 l­1 (4.3 kPa) for 24 hours. Survival was recorded and the molt stages of both dead and surviving shrimp determined. Only shrimp in intermolt and premolt stages were sampled for analysis of haemolymph. Haemolymph was assayed for osmoregulatory capacity (OC), magnesium ion (Mg2+), calcium ion (Ca2+), total proteins, oxyhaemocyanin, lactate, glucose and total haemocyte count (THC).Low mortalities were recorded for shrimp submitted independently to ammonia or hypoxia. Seventy five percent of dead shrimp were in early post molt (stage A) in ammonia treatment, while hypoxia affected mainly late premolt animals (stage D2). A synergic effect of ammonia and hypoxia combination (A+O2 treatment) on mortality was observed, affecting nearly exclusively shrimp in late premolt stage D2.Analysis of molt stage repartition at the end of the experiment suggests that ammonia treatment may have accelerated molting.The common physiological response of shrimp to the different treatments was characterized by a reduced OC and an increase in Ca2+. Increase in Mg2+ could not be validated by the statistical analysis, as well as glycaemia variations. Plasmatic lactate level increased and THC decreased in shrimp submitted to hypoxia and the combination of hypoxia and ammonia. Total proteins concentration was reduced in ammonia and A+O2 treatments. The effect was more pronounced in late premolt shrimp than in intermolt shrimp. Combination of ammonia and hypoxia led to a physiological response stronger than this observed for ammonia-alone and/or hypoxia-alone treatments, except for oxyhaemocyanin.The effects of each external factor (ammonia, hypoxia) and the combination of both, and internal one (molt stage) are discussed.

The Potential Use of Dietary Salt Deficiency for the Force Resting of Laying Hens

Two experiments using a total of 240 laying hens housed in individual cages were conducted to evaluate dietary salt deficiency as a potential tool for the force resting of laying hens. The control group of hens received the corn-soy diet with 0.25% added salt. Another group of hens received a basal corn-soy diet with no added salt for six weeks then was returned to the control diet. The third group was subjected to the force molting technique recommended by Wilson et al. (1969). The drinking water, given ad libitum, and the basal diet contained 26 p.p.m. and 270 p.p.m. sodium, respectively. Hen weight, feed consumption, egg production, egg weight and egg specific gravity were recorded throughout each experiment.Feed consumption and body weight of hens receiving the low salt diet (Treatment 2) or forced molted (Treatment 3) decreased significantly and egg production ceased during the molt period. The reproductive organs of hens fed the low salt diet regressed to about 25% of the original size. When hens were returned to control feed, recovery was complete with significant increases in egg weight and egg specific gravity for hens on treatment two. Egg production was significantly higher for both the hens which received low salt and those force molted, compared to the control birds during the post molt period.The results of the experiments indicated that dietary salt deficiency is effective for the force resting of laying hens.

Changes in the daily rhythm of plasma corticosterone concentration related to seasonal conditions in the white-throated sparrow, Zonotrichia albicollis.

Circadian variations in concentrations of plasma corticosterone were investigated in the white-throated sparrow maintained on short (10-hr) or long (16-hr) daily photoperiods. In addition, the plasma concentrations of corticosterone were determined throughout a day in birds that were in the reproductively photosensitive spring migratory condition, the reproductively photorefractory post nuptial molt condition, and the fall migratory condition. Distinct unimodal rhythms were found in photosensitive birds. The daily rise occurred 12 hr after the offset of light in birds kept on both the short and the long photoperiodic regimens. There was no discernible daily variation in photorefractory birds kept on a 16 hr daily photoperiod and there was a bimodal rhythm in the birds that were in the fall migratory condition. The results are consistent with an hypothesis that assigns an important role to the circadian rhythm of corticosteroid concentration in the photoperiodic mechanism controlling seasonal reproductive and migratory conditions in the white-throated sparrow.