Physiology and behavior of the hen during induced molt

Design of a generic model based on physiology for persistent organic pollutants in laying hens: Applications on chlordecone and chlorinated paraffins

A Physiology Based Pharmacokinetic (PBPK) model has been developed to predict the kinetics of Persistent Organic Pollutants (POPs) in laying hens. Different datasets have enabled the calibration of the model for chlordecone (CLD), an organochlorine pesticide used in the French West Indies between 1972 and 1993, as well as for chlorinated paraffins (CPs), widely used for various industrial applications worldwide. For this purpose, the sensitivity analysis showed that intake parameters, laying rate, partition coefficients of yolk, hepatic clearance, percentage of metabolism and age were key parameters. Applied to CLD and CPs, this model shows a good capacity for prediction, with 88 % of the experimental values ranging within 1.5-fold of the predicted value at steady state for CPs and 100 % for CLD. The fine modelling of the physiology and the laying process contributes to precision of the model and gives genericity, enabling the switch from one bird species to another. The model can be implemented with other POPs if the clearance and partition coefficient are known.

Transcriptomic analysis of mechanism underlying the effect of induced molting on semen quality and reproductive performance in aged Houdan roosters

The reproductive performance of breeder roosters has significant economic importance in the poultry industry. Breeder roosters have severely reduced semen quality with age and will be at risk of culling in the following years. In order to extend the use of breeder roosters, we drew on the induced molting model of hens and selected 35 Houdan roosters aged 50 wk for induced molting. By comparing the body weight, testicular weight, semen quality, and reproductive performance before and after induced molting, we found that induced molting could restore the body weight and testicular weight to the levels before molting (P > 0.05). At the same time, it significantly improved sperm motility (P < 0.05) and also improved reproductive performance such as fertilization rate and hatching rate. To further reveal the mechanism underlying the effects of induced molting on semen quality and reproductive performance in aged Houdan roosters, we collected testes from 3 periods: 1 d before fasting (F0), 15 d after fasting (F15), and 32 d after recovery feeding (R32) for transcriptome sequencing analysis. A total of 5,671 genes were detected in F0, F15, and R32, and trend analysis of the 5,671 differential genes showed 2 significant trends (profile 5 and profile 2). KEGG enrichment analysis of the genes in the 2 profiles, revealed significantly enriched pathway regulation of actin cytoskeleton. In the regulation of actin cytoskeleton pathway, we found a protein kinase gene (SRC) and a senescence gene (ROCK2). SRC was highly expressed at F15, leading to the phosphorylation of key substrates, which in turn disrupted the Sertoli cell spermatid connection and the spermiogenesis process, resulting in no mature spermatozoa produced from F15, SRC expression was inhibited at R32, the expression level was reduced, and mature spermatozoa reappeared. The senescence gene ROCK2 was highly expressed at F15 compared to F0 and R32, which may have been responsible for inducing senescence atrophy in the testes.

Effect of induced molting on ovarian function remodeling in laying hens

Induced molting (IM) can restore the laying rate of aged laying hens to the peak level of laying and rejuvenate ovarian function for the second laying cycle. To explore the mechanism of ovarian function remodeling during IM in laying hens, in this study, ninety 71-wk-old laying lady hens with 60% laying rate and uniform weight were selected for molting induction by fasting. Samples (serum and fresh ovarian tissue) were collected on the day before fasting (F0), the 3rd and 16th days of fasting (F3, F16), and the 6th, 15th, 32nd days of refeeding (R6, R15, and R32), and the number of follicles in each period was counted. Then, the reproductive hormone levels in serum and antioxidant levels in ovarian tissues were detected at different stages, and the gene expression of the KIT-PI3K-PTEN-AKT pathway and GDF-9 in ovaries was measured by qRT-PCR. The results showed that the laying rate increased rapidly after refeeding and returned to the prefasting level by R32. At F16 and R6, the number of mature follicles significantly decreased; the number of primary and secondary follicles significantly increased; the contents of follicle stimulating hormone (FSH), luteinizing hormone (LH), estradiol (E2), and progesterone (P4) in serum decreased; the relative expression of KIT, PI3K, AKT, and GDF-9 significantly increased; and that of PTEN significantly decreased. At R15 and R32, except for GDF-9, which maintained a high expression state, other indicators showed opposing trends to those observed at F16 and R6. In conclusion, IM activated the KIT-PI3K-PTEN-AKT signaling pathway and promoted the activation of primordial follicles during the fasting period and early resumption of feeding; gonadotropin secretion increased gradually, which promoted the rapid development of primary and secondary follicles to mature follicles and ovulation. This study explained the mechanism of ovarian function remodeling in the process of IM and provided a theoretical basis for improving the ovarian function of laying hens and optimizing the IM program.

Effect of short-term fasting on the expression of ACTH (cMC2) receptor in the adrenal glands of chicken (Gallus domesticus)

<b>Domestic hen is a full model in terms of stress and adrenal function. The main hormone produced by the hens’ adrenals is corticosterone, synthesized and secreted by stimulating the HPA axis during stress. Direct activation of adrenal activity is conditioned by ACTH, which binds to the melanocortin receptor cMC2 in adrenals. It stimulates the synthesis and release of corticosterone. One of the factors that stimulate the HPA axis activity is the starvation, to which the hen is very sensitive. The purpose of this study was to determine the ACTH receptor cMC2 expression in the hens’ adrenals during the short-term fasting and after restoring the proper level of nutrition (refeeding). The results of the experiment show that 24-hour of food deprivation is stressful for the hen, as indicated by increased concentrations of corticosterone in the adrenals and in blood plasma. Changes in cMC2R expression and level of corticosterone in the adrenals during fasting and refeeding indicate a rapid increase of HPA axis activity in response to differentiated levels of nutrition. The results of this experiment confirm the direct effect of ACTH on the avian adrenals in corticosterone release.

Welfare issues associated with moulting of laying hens

A practice that is used to extend the period of lay of hens is induced moulting. It involves restriction of nutrients, and sometimes manipulation of lighting, with the consequent loss of bodyweight and feathers, regression of the reproductive tract and cessation of egg lay. When the period of moulting is completed, the reproductive tract will regenerate and egg production will resume, thereby extending the overall period of lay. Towards the end of the laying cycle of hens, the production and quality of eggs decline. At this point, some egg farmers will induce a moult in the flocks to reduce bird-replacement costs and improve profitability. In the Australian egg industry, less than 10% of layers are moulted. There are implications for the welfare of hens that are induced to moult, particularly due to loss of bodyweight and feathers. Histopathological studies have shown the extent to which loss of feathers may affect welfare from a physical perspective, and it terms of pain. It is apparent that induced moulting can lead to an increase in aggression and injurious pecking, and birds with poor feather cover are vulnerable to damage from this pecking. Induced moulting can increase stress, although the implications of this for the welfare of hens is not well understood. The endocrine events associated with induced moulting are reasonably well known and it is possible to manipulate the endocrine system to extend the lay of hens without the need to moult. Nevertheless, these approaches are unlikely to be adopted into practice. More importantly, hens should always have feed and water available and are in good condition before undergoing a moult. This is essential from the perspective of ensuring adequate standards of welfare of birds.

Effects of cage type on performance, welfare, and microbiological properties of laying hens during the molting period and the second production cycle

As most of the unenriched cages will soon switch to enriched cages, it is important to characterize all the effects in the laying hens for sustainable production. Laying hens can be used in several production periods by applying molting. The aim of this study was to determine the cage type (unenriched and enriched) on performance, welfare, and microbiological properties of laying hens during the molting period and the second production cycle. Overall, 840 brown laying hybrids were used in the experiment. Laying hens were reared on two different cage types (unenriched cage (UEC) and enriched cage (EC)) in the same poultry house. When the hybrids were 75 weeks old, they were subjected to force molting with whole grain barley. Performance, welfare, microbiological, and serological data of laying hens were obtained from 73 to 107 weeks of age. Egg production, egg weight, feed conversion ratio, breaking strength, albumen and yolk index, Haugh unit, feather condition, and breaking force of femur and metatarsus were better in the post-molting period. However, keel bone deformities and Newcastle disease virus antibody titers are the worst in the post-molting period. Stiffness of femur and metatarsus was increased with period. These results indicate that necessary precautions should be taken against the problems that may occur in the direction of bone and health. During the molting period, hens kept in EC had lower egg production but they returned to egg production at a high rate. EC type had a positive effect on egg production, feed conversion ratio, feather and foot condition, and breaking force of metatarsus.

Increased serum levels of advanced glycation end products due to induced molting in hen layers trigger a proinflammatory response by peripheral blood leukocytes

Induced molting (IM), a severe detriment to animal welfare, is still used in the poultry industry in some countries to increase or rejuvenate egg production and is responsible for several physiological perturbations, possibly including reactive oxidative stress, a form of metabolic stress. Because metabolic stress has been shown to induce a proinflammatory response involved in attempts to restore homeostasis, we hypothesized that similar responses followed IM. To confirm this hypothesis, we initially confirmed the establishment of oxidative stress during IM in 75-wk-old layers by demonstrating increased production of advanced glycation end products (AGE). Concomitant with increased oxidative metabolites, cellular stress was demonstrated in peripheral blood leukocytes (PBL) by increased levels of stress gene products (the glucocorticoid receptor, sirtuin-1, and heat shock protein 70 mRNA). Increased expression of stress proteins in PBL was followed by a proinflammatory response as demonstrated by increased levels of proinflammatory gene products (IL-6 and IL-1β mRNA); increased expression of these gene products was also demonstrated in direct response to AGE in vitro, thus establishing a direct link between oxidative and cellular stress. To establish a possible pathway for inducing a proinflammatory response by PBL, we showed that AGE increased a time dependent expression of galactin-3, Toll-like receptor-4, and nuclear factor - κB, all involved in the proinflammatory activation pathway. In vivo, AGE formed complexes with increased levels of circulating acute phase proteins (lysozyme and transferrin), products of a proinflammatory immune response, thereby demonstrating an effector response to cope with the consequences of oxidative stress. Thus, the harmful consequences of IM for animal welfare are extended here by demonstrating the activation of a resource-demanding proinflammatory response.

Salmonella Enteritidis infection, corticosterone levels, performance and egg quality in laying hens submitted to different methods of molting

In commercial layer poultry farming, molt induction is an important tool used by egg producers to prolong the production cycle of laying hens. Conventional molt induction programs involve total feed withdrawal, which raises questions about animal welfare and increased infection susceptibility. The high incidence of paratyphoid salmonellosis infections in commercial poultry farming is still an important health challenge because in addition to affecting the birds, such infections also cause public health problems. In this context, experiments were performed with laying hens at 79 wk of age to compare the conventional forced molting method (fasting) with an alternative method (free wheat bran supply) and determine their effect on the persistence of vaccine antibodies against Newcastle disease, the control and reduction of experimentally inoculated Salmonella Enteritidis, and the performance and egg quality of hens. A reduction (P < 0.05) of Salmonella Enteritidis in the crop and lower production of corticosterone were observed in the birds that received wheat bran compared with those subjected to total fasting. Moreover, a better performance (P < 0.05) with regard to egg production, egg mass, and feed conversion/kg and dozen eggs was observed in the hens that received the alternative treatment compared to the conventional forced molting method. Thus, the use of wheat bran for forced molting was found to be feasible and met the welfare needs of the hens.

Dietary Inositol Reduces Fearfulness and Avoidance in Laying Hens

Simple Summary

Brain inositol is known to affect memory, and the incidence of depression, anxiety, and obsessive-compulsive disorder in mammals. Phytate, a naturally occurring inositol ester in plants, binds other nutrients, making them unavailable for digestion. The addition of phytase, the enzyme capable of hydrolyzing phytate, to diets increases the release of both inositol and nutrients for absorption in the chicken digestive tract. In this study, we assessed how dietary phytase or pure inositol affected laying hen behaviour, fearfulness, aggression, and stress levels. To increase the probability of seeing effects, hens were not beak treated and were fed two balanced protein levels differing in digestible amino acid sufficiency. Inositol did not affect stress levels, as measured by heterophil-to-lymphocyte ratio, or the number of hen comb or skin lesions. However, regardless of the source, pure inositol or phytase derived inositol reduced the number of feathers in the vent area, suggesting an increase in feather pecking. Pure inositol reduced fearfulness in laying hens, but phytase-derived inositol did not.

Abstract

Myo-inositol (inositol) affects memory, and the incidence of depression and anxiety in mammals. An experiment was designed to determine if pure inositol (0.16%), or high levels of phytase (3000 FTU/kg) affect the behaviour of fully beaked Lohmann LSL lite hens fed amino acid sufficient (19% crude protein (CP)) and deficient diets (16% CP), from 19 to 59 weeks of age. The data collected included live-scan behaviour observations and novel object (NO) tests (both at 1, 10 and 40 weeks of the trial); heterophil-to-lymphocyte (H/L) ratios (week 1 and week 40 of the trial); end of trial feather cover, and comb and skin lesions; and daily mortality. Reducing CP increased sitting by 2.5%. Inositol, but not phytase, reduced the latency to peck at the NO by 300 sec. Inositol reduced vent feather cover by 12% and tended to increase mortality by 13%. No effects on H/L ratio, and comb or skin lesions were found. In conclusion, regardless of the source, inositol reduced vent feather cover, while it tended to increase mortality. Only pure inositol reduced fearfulness in laying hens.

Dietary zinc supplementation and the performance and behaviour of caged laying hens

There is considerable behavioural evidence demonstrating stress reactions in birds. Behaviour of birds can affect their performance parameters. Also, nutritional factors may affect the behaviour of laying hens. Dietary deficiencies, such as minerals can increase feather-pecking behaviour and cannibalism. In the present study, we evaluate the effect of dietary zinc (Zn) on performance and behaviour of laying hens with four treatments (40, 70, 100, 130 mg Zn/kg of diet) with 96 Hy-Line W-36 leghorn hens for 10 weeks. The results showed that egg production for hens receiving 130 mg Zn/kg of diet was significantly higher than for those receiving 40 and 70 mg Zn/kg of diet (P &lt; 0.05). Those hens receiving 130 mg Zn/kg of diet had lower feed consumption compared with those that had other treatments (P &lt; 0.05). Dietary inclusion of Zn caused an improvement to feed conversion ratio (P &lt; 0.05). There was a treatment × time interaction on feeding behaviour that hens received 130 mg Zn/kg of diet spent significantly less time at the feeder than the other treatments. Hens receiving 130 mg Zn/kg of diet spent significantly less time drinking than the hens that received 40 and 70 mg Zn/kg of diet. Also, those that received 130 mg Zn/kg of diet did more non-nutritive pecking and preening than the hens that received 40 and 70 mg Zn/kg of diet. High levels of Zn decreased the aggressive behaviour of hens compared with those that received 40 mg Zn/kg of diet (P &lt; 0.05). It can be concluded that Zn can improve laying performance, and can decrease aggressive behaviour.

Effects of different litter substrates and induced molt on production performance and welfare quality parameters of white Leghorn hens housed in multi-tiered aviary system

More than 90% of the commercial egg production in the United States is pledged to be in cage-free systems by 2025. Management practices like induced molting and litter area management have come under scrutiny because of the housing system change. The aim of this study was to determine the welfare and production implications of different litter substrates and also evaluate induced molting of hens in a cage-free system. Bovan White hens were housed in a multi-tier aviary system with daily access to open litter area of either Astroturf (AT), wood shavings (SH), or straw (ST) and bare concrete floor (CO) serving as control. At 68 wk of age, molt was induced in half of the hens whereas the other half continued without molting to 116 wk. Production and welfare parameters were measured periodically throughout first and second cycles. Litter substrate did not influence hen-day production and case-weight measurements. However, CO had the lowest total number of eggs produced during the first cycle (P < 0.05). Hen-day percentage was approximately 14% greater in molted hens during the second cycle with egg case weight being heavier in non-molt hens toward the end of second cycle (P < 0.05). The only welfare parameter influenced by litter substrate during the first cycle was a greater crop feather loss in AT than ST at mid-lay (P < 0.05). Keel deformations increased with age irrespective of the litter substrate with 91.5% of palpated hens having keel deformations at the end of first cycle (P < 0.05). Molting did not influence the keel palpation and footpad scores whereas frequency of moderate comb wound was greater in molt hens during molt (P < 0.05). Severe feather loss was seen in non-molt hens during the second cycle (P < 0.05). Litter substrate does not affect production and physical parameters of welfare of hens in a multi-tier aviary system. Additionally, induced molting can be successfully carried out in the multi-tier cage-free system.

Comparative histomorphological and ultrastructural study of the luminal epithelium of the isthmus in laying and moulting domestic fowls (Gallus domesticus)

This study describes ciliated, nonciliated and mitochondrial luminal epithelial cells of the isthmus in laying and moulting domestic fowls using histological and ultrastructural techniques. The ciliated cells were nonsecretory, while numerous electron-dense secretory granules were present in the nonciliated cells of laying birds. Mitochondrial cells, occurring in two morphologically distinct forms, constituted the third type of epithelial cell present in the isthmus. The SEM study showed that the luminal epithelium was dominated by ciliated cells, the cilia of which partially obscured adjacent nonciliated cells. The involution of the luminal epithelium in moulting birds occurred via autophagy, apoptosis and necrosis. Autophagic inclusions, which included autophagosomes and autolysosomes, were present in the early degenerative phases of ciliated, nonciliated and mitochondrial cells. Nonciliated cells underwent degeneration via apoptosis, which was characterized by nuclear and cytoplasmic condensation. Apoptotic and necrotic ciliated cells were evident during the intermediate and advanced stages of regression. The presence of apoptotic cell death was confirmed using the TUNEL assay. Loss of cilia via the formation of cilia packets was observed using TEM and SEM. Necrotic cell death occurred in mitochondrial cells during the intermediate and late stages of degeneration. In conclusion, the findings of the study on isthmus involution in moulting birds suggest that autophagy is a process confined to the early stages of degeneration, while apoptosis and/or necrosis occur in the terminal stages of regression.

Ultrastructure of the tubular glands in the isthmus region of the oviduct in laying and natural moulting commercial egg-type chickens

The study investigated the ultrastructural characteristics of tubular gland and duct cells, as well as luminal gland cells in the isthmus region of the oviduct of laying and natural moulting hens. Tubular glands in laying birds were composed of type 1 and 2 cells. Based on the preponderance of each cell type, in relation to the location of a developing egg in the oviduct of the domestic fowl, these gland cells may represent different functional states of the same cell. The findings of the study on natural moulting birds suggest that autophagy is a process confined to the early stages of degeneration, while necrosis occurs in the terminal stages.

Rapid Communication: MicroRNA co-expression network reveals apoptosis in the reproductive tract during molting in laying hens

The aim of this study was to determine the regulatory mechanisms of molting and recrudescence via studying the micro-RNA (miRNA) expression in the oviduct of laying hens. We performed a cDNA microarray analysis in the magnum tissue from the oviduct to identify the whole miRNA profiles through the molting and recrudescence periods. A total of 35 laying hens (47-wk-old) were divided into 7 groups (0 d: a control group; 6 and 12 d: 2 molting-period groups fed on a high-zinc diet; and 20, 25, 30, and 35 d: 4 recrudescence-period groups fed on a normal diet after a 12-d period on a high-zinc diet). An miRNA co-expression network (miRCN) was generated using the differentially expressed miRNA (DEM) according to the entire data integration. The significantly co-expressed miRNA ( = 111) were highly differentially expressed from 12 to 20 d, which was a transition period between molting and recrudescence, while their expression patterns were contrary to the estrogen changes. The targets of highly connected miRNA ( = 12) indicated the significant biological pathways and gene ontology (GO) terms, such as MAPK and Wnt signaling and magnesium-ion binding, which are associated with apoptotic activities. These results suggest that the miRNA of the miRCN might play a role in the apoptotic progression of the reproductive tract during molting.

Effect of calcium with and without probiotic, lactose, or both on organ and body weights, immune response and caecal microbiota in moulted laying hens

A total of 72 laying hens were used to investigate the effect of probiotic and lactose on body weight loss, tibia ash, antibody production against sheep red blood cell (SRBC), heterophile-to-lymphocyte (H/L) ratio and gut microbiota in a common moulting method for 14 d. Hens were randomly allocated to 6 experimental groups consisting of (i) full feed (FF), (ii) feed withdrawal (FW), (iii) FW with calcium (Ca), (iv) FW with Ca and offering 7 g/lit lactose in drinking water (CaL), (v) FW with Ca and offering 1 g/lit probiotic in drinking water (CaP), and (vi) FW with Ca and offering a mixture of lactose and probiotic in drinking water (CaLP). The results showed body weight loss in all FW groups were more than 25% that was significantly higher than FF group (p < 0.05). The relative organ weights of hens in FW groups were lower than FF group; especially, it was significant for liver and ovary (p < 0.05). No significant difference was observed between all groups for tibia ash. The highest H/L ratio was related to FW group and offering Ca and lactose numerically and probiotic alone significantly resulted in decrease of this ratio (p < 0.05). The results also showed no significant difference for antibody production against SRBC among experimental groups. The highest coliform bacteria numeration observed in FW group and lactose could significantly reduce this population (p < 0.05). Lactic acid bacteria (LAB) numeration demonstrated a significant difference among treatments, so that FF hens had higher LAB than others (p < 0.05). In addition, FW moulted hens had significantly lower LAB compared to other moulted hens (p < 0.05), except for Ca group. In conclusion, probiotic and lactose was effective in maintaining caecal microbiota balance and improving immunity in hens exposed to moulting.

Differential expression of vitelline membrane outer layer protein 1: hormonal regulation of expression in the oviduct and in ovarian carcinomas from laying hens

Vitelline membrane outer layer protein 1 (VMO1), a basic protein present in the outer layer of the vitelline membrane of eggs, plays essential roles in separating the yolk from the egg white and preventing infection from bacteria by forming a barrier of fibrous layers in avian eggs. Although VMO1 is expressed in the oviduct of hens, little is known about endocrine regulation of transcription of VMO1 in the oviduct and its expression in cancerous ovaries of laying hens. Results of present study indicated that expression of VMO1 mRNA increased in the chick oviduct in response to diethylstilbestrol (DES, a synthetic non-steroidal estrogen). VMO1 mRNA and protein were particularly abundant in the glandular epithelium (GE) and luminal epithelium (LE) of the magnum of the oviducts of chicks treated with DES. Also, during the regression and recrudescence phases of the oviduct during induced molting with zinc feeding, VMO1 expression decreased as the oviduct regressed and increased with remodeling and recrudescence of the oviduct in laying hens. In addition, changes in relative expression of specific microRNAs (miR-1623, miR-1552-3p, miR-1573, miR-22-3p, miR-124a and miR-1764) regulating VMO1 gene were detected in the oviducts during the molting period. Moreover, abundant expression of VMO1 was found in GE of cancerous, but not normal ovaries of laying hens. Results of the present study suggest that VMO1 is regulated by estrogen and target microRNAs in the chicken oviduct and that it is a potential diagnostic marker of ovarian cancer in laying hens.

Expression and regulation of avian cathepsin L in the oviduct during molting

Cathepsins (CTSs) are peptidases that have biological roles in degrading extracellular matrix, catabolism of intracellular proteins, and processing of pro-hormones. Of these, cathepsin L (CTSL) is closely associated with morphological changes in reproductive organs required for proper function in mammals, including humans and mice, but little is known about CTSL in avian species. In the present study, the expression of CTSL was investigated in the oviduct of hens during regression and recrudescence in response to molting. Our results revealed that expression of CTSL mRNA increased (P<0.001) when the oviduct underwent regression during the molting period in hens. In situ hybridization and immunohistochemial analyses detected CTSL mRNA and protein predominantly in the luminal (LE) and glandular epithelia (GE) during regression of the oviduct, but not during regeneration of the oviduct. Expression of CTSL decreased in the oviduct of chicks treated with diethylstilbestrol (DES, a synthetic estrogen agonist). Furthermore, we discovered four miRNAs including miR-23b, miR-551, miR-1464 and miR-1803 that regulate expression of the CTSL gene at the post-transcriptional level, which suggests that CTSL mRNA can be regulated by specific miRNAs via 3'-UTR in chickens. Results of the present research suggest that estrogen regulates expression of CTSL during regression of the oviduct during molting and that down-regulation of CTSL is likely a prerequisite for the normal regeneration of oviductal tissues following molting in laying hens.

Pivotal roles for hormonally regulated expression of the HEP21 gene in the reproductive tract of chickens for oviduct development and in ovarian carcinogenesis

Hen egg protein (HEP21) is a 21-kDa secreted protein and has a single copy of the Ly6/uPAR domain. Although HEP21 is expressed primarily in the chicken oviduct, its biological function(s) in the reproductive system of chickens is not known. Thus, in the present study, we investigated expression patterns of HEP21 with respect to hormonal regulation, oviduct development, changes in expression in laying hens undergoing induced molting, and in the development of ovarian carcinogenesis in laying hens. Results of present study indicated that HEP21 messenger RNA (mRNA) expression increased (P < 0.001) in the chicken oviduct in response to estrogen. In situ hybridization analyses revealed expression of HEP21 mRNA predominantly in glandular (GE) and luminal epithelia of the magnum of the chicken oviduct in response to estrogen. The expression of HEP21 mRNA decreased (P < 0.001) as the oviduct regressed during induced molting and increased (P < 0.001) with recrudescence of the oviduct following molting. HEP21 mRNA was most abundant in GE of the oviduct during recrudescence, but not during oviduct regression following induced molting. Moreover, we found abundant expression of HEP21 in GE of cancerous ovaries, but not in normal ovaries of hens. Collectively, results of present study suggest that HEP21 is an estrogen-responsive gene in the oviduct of hens that likely regulates development of the chicken oviduct, and egg production and formation. Furthermore, there is increased expression of HEP21 in epithelial-derived ovarian cancer suggesting that HEP21 could be used for diagnosis and monitoring carcinogenesis in laying hens and in women.

Evaluation of feeding various sources of distillers dried grains with solubles in non-feed-withdrawal molt programs for laying hens

An experiment was conducted using 588 Hy-Line W-36 hens (68 wk of age) to evaluate if laying hens can be successfully molted by ad libitum feeding various levels of 3 sources of distillers dried grains with solubles (DDGS). Treatment 1 consisted of a 47% corn (C):47% soy hulls (SH) molt diet (C:SH) fed for 28 d (positive control). Treatments 2, 3, and 4 were molt diets containing 94% DDGS from the 3 sources fed for 28 d. Treatments 5, 6, and 7 were 32% C: 42% SH: 20% DDGS, from each of the 3 DDGS sources, also fed for 28 d. At the end of the 28-d molt period, all hens were fed a 16% CP corn-soybean meal layer diet. Body weight loss during the molt period was significantly greater (P < 0.05) for hens fed the C:SH diet (26%) than hens fed the diets containing DDGS, and the reduction in BW loss varied among DDGS sources. Feed intake was lower (P < 0.05) for the C:SH control treatment compared with most DDGS treatments. Hens fed the C:SH diet had egg production near 0% during the last 3 wk of the molt period. Hens on the other treatments did not have mean egg production below 17% during the molt period (wk 1 to 4), and the reduction in egg production varied among DDGS sources. Postmolt hen-day egg production (5-41 wk) did not significantly differ among treatments; however, egg mass and egg specific gravity were generally reduced (P < 0.05) for hens fed the 94% DDGS molt diets compared with hens fed the C:SH diet. This study showed that molt and postmolt performance responses varied among DDGS sources; however, none of the molt diets containing 20 to 94% DDGS yielded molt period reductions in BW or egg production similar to a 47% C: 47% SH diet.

Obesity-induced dysfunctions in female reproduction: lessons from birds and mammals

Follicle wall rupture and ovum release, i.e., ovulation, has been described as a controlled inflammatory event. The process involves tissue remodeling achieved through leukocyte-mediated proteolysis. In birds, ovulation is the first step in the energy-intensive process of egg formation, yet hens that consume energy in excess of productive requirements experience impaired egg-laying ability. Broiler chickens, selected for rapid lean muscle gain, and coincidentally hyperphagia, develop adult obesity when given free access to feed. Obese broiler hens experience elevated circulating concentrations of insulin and leptin, changes in lipid and lipoprotein metabolism similar to those of human metabolic syndrome, as well as increased systemic inflammation. Overall, the manifestations in poultry are similar to those of women with polycystic ovary syndrome. It was shown recently that, in hens, as in mammals, changes in lipid synthesis and metabolism cause granulosa cell apoptosis and altered immune function and hormone production, further compromising ovarian function. To date, there is insufficient information on the means used by the ovary to direct leukocyte function toward successful ovulation. More information is needed regarding the control of proteolytic actions by leukocytes with regards to the roles of specific enzymes in both ovulation and atresia. The broiler hen has provided unique insight into the interrelations of energy intake, obesity, leukocyte function, and reproduction. Additional work with this model can serve the dual purposes of improving avian reproduction and providing novel insights into polycystic ovary syndrome in women.

Increased hepatic yolk precursor synthesis, secretion and facilitated uptake by follicles are involved in the rejuvenation of reproductive performance of molted hens (Gallus gallus domesticus)

Molt, a natural behavior that is initiated at the end of a lay cycle in birds, is implicated in the regression of the reproductive system in birds followed by a rejuvenation of egg-laying potential. The aim of the present study was to evaluate the physiological basis for the apparent rejuvenation of egg production that occurs following molting. Eighty-three-week-old Hy-line hens, were obtained and subjected to forced molting. Blood and tissue samples were obtained at the beginning of molt (at 83 weeks of age), during molt (at 85 weeks of age) and postmolt (at 89 weeks of age). The laying performance, egg quality, blood parameters and gene expression in the liver and the ovary were investigated before, during and after molt. There was an obvious increase in the postmolt laying rate from 70% premolt to 93% postmolt. Eggshell thickness, albumin height, Haugh unit and egg shape index were all significantly improved after molt. The circulating levels of estrogen and progesterone were lower in the postmolt hens, whereas the concentrations of luteinizing hormone and follicle stimulating hormone were not significantly affected by molt. These results indicate that enhanced hepatic yolk precursor synthesis and secretion contribute to increased postmolt laying performance. Molt enhanced the sensitivity of sex hormones in F1 follicles. Augmented gene expression in the ovary was involved in the rejuvenation of the reproductive performance of molted hens. These results suggest that facilitated yolk-precursor uptake by follicles is involved in the rejuvenation of the reproductive performance of molted hens.

Recrudescence mechanisms and gene expression profile of the reproductive tracts from chickens during the molting period

The reproductive system of chickens undergoes dynamic morphological and functional tissue remodeling during the molting period. The present study identified global gene expression profiles following oviductal tissue regression and regeneration in laying hens in which molting was induced by feeding high levels of zinc in the diet. During the molting and recrudescence processes, progressive morphological and physiological changes included regression and re-growth of reproductive organs and fluctuations in concentrations of testosterone, progesterone, estradiol and corticosterone in blood. The cDNA microarray analysis of oviductal tissues revealed the biological significance of gene expression-based modulation in oviductal tissue during its remodeling. Based on the gene expression profiles, expression patterns of selected genes such as, TF, ANGPTL3, p20K, PTN, AvBD11 and SERPINB3 exhibited similar patterns in expression with gradual decreases during regression of the oviduct and sequential increases during resurrection of the functional oviduct. Also, miR-1689* inhibited expression of Sp1, while miR-17-3p, miR-22* and miR-1764 inhibited expression of STAT1. Similarly, chicken miR-1562 and miR-138 reduced the expression of ANGPTL3 and p20K, respectively. These results suggest that these differentially regulated genes are closely correlated with the molecular mechanism(s) for development and tissue remodeling of the avian female reproductive tract, and that miRNA-mediated regulation of key genes likely contributes to remodeling of the avian reproductive tract by controlling expression of those genes post-transcriptionally. The discovered global gene profiles provide new molecular candidates responsible for regulating morphological and functional recrudescence of the avian reproductive tract, and provide novel insights into understanding the remodeling process at the genomic and epigenomic levels.

Effect of corticosterone on gene expression of feed intake regulatory peptides in laying hens

The present study was conducted to explore the effects of corticosterone (CORT) on the regulation of appetite-associated genes in laying hens. Forty eight laying hens were randomly divided into two groups: one received subcutaneous injection of CORT (2mg/kg body weight, CORT-exposed) and the other received sham-treatment (Control). Treatment of hens with CORT stimulated an increase (P<0.05) in plasma CORT, glucose, uric acid (UA), insulin, cholesterol (Chol) and triiodothyronine (T(3)), but the concentrations of plasma non-esterified fatty acids (NEFA) and triacylglycerol (TG) were decreased (P<0.05). CORT treatment had no significant effect (P>0.05) on the mRNA levels of neuropeptide Y (NPY), corticotropin-releasing hormone (CRH), melanocortin receptor 4 and 5 (MCR-4 and MCR-5) and cholecystokinin (CCK) in the hypothalamus when compared with control hens. However, the expression of pro-opiomelanocortin (POMC), agouti-related protein (AgRP) and melanocortin recepter 1 (MCR-1) were significantly (P<0.05) suppressed while the mRNA levels of ghrelin and cocaine-and amphetamine-regulated transcript (CART) were significantly upregulated (P<0.05) in CORT-treated hens. Treatment of laying hens with CORT had no significant (P>0.05) effect on the mRNA levels of CCK in the glandular stomach and the duodenum, and those of ghrelin in the glandular stomach, the duodenum and the jejunum. However, the mRNA levels of CCK in the jejunum and the ileum, and those of ghrelin in the ileum were significantly (P<0.05) suppressed by CORT treatment. In conclusion, these results suggest that CORT plays a unique role in some special neuropeptides (e.g., ghrelin, CART, POMC, CCK and MCRs) and a dynamic balance between these appetite-associated peptides in the hypothalamus and the gastrointestinal tract defines the feeding status of CORT-exposed laying hens.

Somatotrophs and lactotrophs: an immunohistochemical study of Gallus domesticus pituitary gland at different stages of induced moult

The objective of this study was to determine the distribution of somatotrophs and lactotrophs and conduct a morphometrical analysis of immunoreactive somatotrophs and lactotrophs in the pituitary glands of White Leghorn Hens (Gallus domesticus) during the period of induced moult. We divided the periods of induced moulting into three phases viz. 7, 14 and 21 days. The labeled alkalinephsphatase method with anti-GH (growth hormone) and anti-PRL (prolactin) as a primary antibody was used to detect somatotrophs and lactotrophs, in the midsagital sections of chicken adenohypophysis. Immunohistochemistry showed that somatotrophs are not only confined to the cephalo-caudal axis but can also be found in the caudal lobe; while lactotrophs were distributed in both lobes of the anterior pituitary gland at all stages of moulting (7, 14 and 21 days). Lactotrophs were of different shapes but somatotrophs were oval to round in morphology. At the given stages of induced moulting, some hypertrophied lactotrophs were also present after 7 days of induced moult in the anterior pituitary gland. However, there were moulting-related changes: from 7 to 21 days of induced moulting the immunoreactive-PRL cell population decreased, while the mean lactotroph size was more than that of somatotrophs. Basic quantitative and morphological information relating to somatotrophs and lactotrophs during the period of induced moult in laying hens is reported here and the changes brought about by induced moulting are restricted to PRL positive cells rather than GH positive cells.

Utilizing fungus myceliated grain for molt induction and performance in commercial laying hens

Molting in poultry is used to rejuvenate hens for a second or third laying cycle. Feed withdrawal was once the most effective method used for molt induction; however, it has being phased out due to food safety and animal welfare concerns. This study evaluated the utilization of fungus myceliated grain as a safe and effective alternative for inducing molt, enhancing immunity, reducing Salmonella growth, and returning to egg production. Laying hens were subjected to 1 of 5 treatments: 1) nonfed (NF), 2) full-fed (FF), 3) fungus myceliated meal (FM), 4) 90% fungus myceliated meal+10% standard layer ration (FM-90), and 5) 90% alfalfa meal+10% fungus myceliated meal (AF-90). Each treatment condition was replicated 9 times during a 9-d molt period. The results revealed that egg production for treatments 1 and 3 ceased completely by d 5, whereas hens in treatments 4 and 5 ceased egg production by d 6. The percentage of BW loss decreased significantly (P<0.05) in treatments 1 (57%), 2 (8%), 3 (35%), 4 (37%), and 5 (44%). Ovary weights of hens fed all molting diets decreased significantly from the full-fed control but did not differ significantly (P<0.05) from each other. Salmonella population in the crop, ovary, and ceca from hens differed significantly (P<0.05) among treatments. Return to egg production differed between treatments with higher production beginning in treatment 3 and ending in treatment 5. Antibody titers did differ (P<0.05) among treatments. From these results, fungus myceliated meal appears to be a viable alternative to conventional feed withdrawal and other methods for the successful induction of molt and retention of postmolt performance.