Nadia Everaert

Importance of albumen during embryonic development in avian species, with emphasis on domestic chicken

Depending on the bird species, about 33-86% of the egg content consists of albumen. In eggs from domestic fowl, albumen contains about 10.5% protein and 88.5% of water and may be regarded as the main water source for the developing embryo. Besides carbohydrates, lipids, and inorganic ions, over 90% of the solids in the albumen are proteins. Several factors are known to influence the amount and composition of the albumen: egg weight, age and genetics of the parent flock, amount and quality of the feed provided, environmental factors (e.g. temperature, light), position in laying sequence, and also storage conditions of eggs prior to incubation. The albumen content of an egg plays an important role during embryonic development. Not only for formation of sub-embryonic fluid, but albumen proteins are known to flow into the amniotic cavity, the yolk sac and finally the digestive tract of the embryo and are used as the main source of proteins for tissue synthesis. Partial removal of albumen had negative consequences on chick weight at hatch, reduced the amount of amniotic and allantoic fluid and may reduce the water content of the chick and the residual yolk. Replacing the removed albumen with saline, however, reduced the residual yolk weight without differences in water content, suggesting increased uptake and utilisation of yolk, possibly as a compensation for the removed albumen proteins. In addition to reduced chick weight at hatch, some authors report an asymmetric growth restriction where nutrients are diverted away from non-vital organs in favour of brain and heart, with a relative ‘sparing’ of these latter two organs. Partial albumen removal led to a reduced whole-body protein synthesis, similar to eggs containing naturally less albumen. Importantly, several studies reported some long-term effects of albumen removal on growth, indicating that prenatal environment will have life-long consequences.

Effects of maternal dietary EPA and DHA supplementation and breeder age on embryonic and post-hatch performance of broiler offspring

Breeder age and nutrition are amongst the most important factors affecting progeny growth and development. The present experiment was carried out to evaluate the effects of n-3 fatty acid (FA), with special emphasis on the ratio of eicosapentaenoic (EPA, 20:5 n-3) and docosahexaenoic (DHA, 22:6 n-3) acid, provided to the diet of ageing broiler breeder hens at different ratios, on the incubation parameters and the performance of the offspring. Four hundred and eighty Ross-308 broiler breeder hens were fed one of four different diets (120/treatment), with an equal fat content. The control diet was a basal diet, rich in n-6 FAs (CON). Blends of fish oil were used to enrich the three other diets in n-3 FA and to obtain different EPA/DHA ratios of 1/1 (EPA=DHA), 1/2 (DHA) or 2/1 (EPA). Every 5 weeks, incubation parameters were assessed. Every 15 weeks, offspring was reared until slaughter age on a standard diet. Breeder age affected almost all incubation and post-hatch parameters, whereas n-3 FA treatment only lowered egg weight (p < 0.0001) and consequently hatched chick weight (p < 0.0001). Supplementation of EPA resulted in a higher proportional liver weight (p = 0.0219) at hatch, a lower body weight up to 28 days post-hatch (p = 0.0418), a lower daily weight gain (p = 0.0498) and a higher feed conversion ratio (p = 0.0395) during the starter period (p = 0.0498), resulting in a higher overall offspring feed conversion ratio (p = 0.0317) compared to the control diet. DHA supplementation, on the other hand, resulted in a lower residual yolk weight (p = 0.0220) and a higher overall offspring mortality (p = 0.0125). In conclusion, supplementation of n-3 FA could not counter the adverse effect of breeder flock age, but did not harm incubation or improve post-hatch performance, either. EPA and DHA affected offspring development differently during early post-hatch life.

Adding mucins to an in vitro batch fermentation model of the large intestine induces changes in microbial population isolated from porcine feces depending on the substrate

Adding mucus to in vitro fermentation models of the large intestine shows that some genera, namely lactobacilli, are dependent on host-microbiota interactions and that they rely on mucosal layers to increase their activity. This study investigated whether this dependence on mucus is substrate dependent and to what extent other genera are impacted by the presence of mucus. Inulin and cellulose were fermented in vitro by a fecal inoculum from pig in the presence or not of mucin beads in order to compare fermentation patterns and bacterial communities. Mucins increased final gas production with inulin and shifted short-chain fatty acid molar ratios (Pxa0<xa00.001). Quantitative real-time PCR analyses revealed that Lactobacillus spp. and Bifidobacterium spp. decreased with mucins, but Bacteroides spp. increased when inulin was fermented. A more in-depth community analysis indicated that the mucins increased Proteobacteria (0.55 vs 0.25%, Pxa0=xa00.013), Verrucomicrobia (5.25 vs 0.03%, Pxa0=xa00.032), Ruminococcaceae, Bacteroidaceae and Akkermansia spp. Proteobacteria (5.67 vs 0.55%, Pxa0<xa00.001) and Lachnospiraceae (33 vs 10.4%) were promoted in the mucus compared with the broth, while Ruminococcaceae decreased. The introduction of mucins affected many microbial genera and fermentation patterns, but from PCA results, the impact of mucus was independent of the fermentation substrate.

Transition of maternal dietary n-3 fatty acids from the yolk to the liver of broiler breeder progeny via the residual yolk sac

The aim of the present study was to evaluate the transfer of maternal dietary fatty acids (FA) from the yolk to the developing offspring, with special emphasis on n-3 FA eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Six hundred forty Ross 308 breeders were housed from 6 to 58 wk of age in 16 pens resulting in 4 replicates per dietary treatment. They were fed 1 of 4 diets: a basal diet, rich in n-6 FA (CON), or an n-3 FA enriched diet formulated to obtain an EPA/DHA ratio of 1/1 (EPA=DHA), 1/2 (DHA), or 2/1 (EPA). At 28, 43, and 58 wk of age, 20 eggs per treatment were collected and analyzed for FA composition. At these same breeder ages, 600 fertilized eggs per treatment were incubated. At hatch the residual yolks of 25 chicks per treatment were collected and analyzed for FA composition. At every hatch, 180 chicks per treatment were raised under standard conditions and livers were sampled at d 1, 14, 28, and 38 d for FA analysis. Concentrations of EPA in the yolk and residual yolk of eggs laid by EPA-fed breeders were highest, next-to-highest for EPA=DHA-fed breeders, next-to-lowest for DHA-fed breeders, and lowest in those laid by control hens, reflecting the inclusion levels in the maternal diets. Yolk and residual yolk DHA concentrations, however, were not only elevated due to DHA supplementation, compared with the control diet, but also due to EPA supplementation. Offspring hepatic EPA concentrations were elevated until d 28 in all n-3 enriched groups, whereas hepatic DHA concentrations were only affected by EPA=DHA and DHA supplementation at d 1. No differences were found in hepatic DHA concentrations at later offspring ages. Considering the role of EPA and DHA in early development and growth, the maternal supply of these n-3 FA might improve offspring health and performance.

Differential Expression of Genes and DNA Methylation associated with Prenatal Protein Undernutrition by Albumen Removal in an avian model

Previously, long-term effects on body weight and reproductive performance have been demonstrated in the chicken model of prenatal protein undernutrition by albumen removal. Introduction of such persistent alterations in phenotype suggests stable changes in gene expression. Therefore, a genome-wide screening of the hepatic transcriptome by RNA-Seq was performed in adult hens. The albumen-deprived hens were created by partial removal of the albumen from eggs and replacement with saline early during embryonic development. Results were compared to sham-manipulated hens and non-manipulated hens. Grouping of the differentially expressed (DE) genes according to biological functions revealed the involvement of processes such as ‘embryonic and organismal development’ and ‘reproductive system development and function’. Molecular pathways that were altered were ‘amino acid metabolism’, ‘carbohydrate metabolism’ and ‘protein synthesis’. Three key central genes interacting with many DE genes were identified: UBC, NR3C1, and ELAVL1. The DNA methylation of 9 DE genes and 3 key central genes was examined by MeDIP-qPCR. The DNA methylation of a fragment (UBC_3) of the UBC gene was increased in the albumen-deprived hens compared to the non-manipulated hens. In conclusion, these results demonstrated that prenatal protein undernutrition by albumen removal leads to long-term alterations of the hepatic transcriptome in the chicken.

Limited evidence for trans-generational effects of maternal dietary supplementation with ¿-3 fatty acids on immunity in broiler chickens

The aim of the present study was to investigate whether the immune response of broiler chickens is modulated by including different omega-3 (ω-3) polyunsaturated fatty acids (PUFAs) in the maternal diet. Broiler breeder hens (nu2009=u2009120 birds per group) were fed one of four diets, differing in the ratios of n-6:n-3 PUFAs and eicosapentaenoic acid (EPA):docosahexaenoic acid (DHA). At 28 weeks of age, the eggs produced were incubated to obtain 720 chicks (nu2009=u2009180 per group). All broiler chicks were fed a control diet and were vaccinated against Newcastle disease virus (NDV). Blood samples were taken at different time points after immunisation with human serum albumin (HuSA) in Freunds adjuvant to determine the acute phase response, antibody response and cytokine production. Addition of EPA to the maternal diet was associated with greater ovotransferrin concentrations post-immunisation, compared to other groups. Altering the ratios of n-6:n-3 PUFA or EPA:DHA in the maternal diet did not affect the offspring in terms of production of caeruloplasmin, α1-acid glycoprotein, interleukin (IL)-1β, IL-6, IL-12 or tumour necrosis factor (TNF)-α. Dietary manipulation of the maternal diet did not influence the specific antibody response to HuSA or NDV, nor did it alter the levels of natural antibody binding to keyhole limpet haemocyanin in the offspring. Thus, maternal supplementation with n-3 PUFAs played a minor role in perinatal programming of the immune response of broiler chickens.

Effects of nutritional programing on growth and metabolism caused by albumen removal in an avian model

In mammalian models of prenatal undernutrition the maternal diet is manipulated, exerting both nutritional and hormonal effects on the offspring. In contrast, in the chicken, strictly nutritional effects can be applied. Prenatal protein undernutrition in chickens was induced by partial replacement of albumen with saline during early embryonic development (albumen-deprived group) and results were compared with a sham-manipulated and a non-manipulated group. Body weight of the albumen-deprived hens was reduced throughout the entire experimental period (0-55 weeks). The reproductive capacity was diminished in the albumen-deprived hens as reflected in the reduced number of eggs and lower egg weight. The plasma triiodothyronine levels were increased in the albumen-deprived group compared with the non-manipulated hens, but not the sham-manipulated hens. An oral glucose tolerance test (OGTT) at 10 weeks of age revealed a decreased glucose tolerance in the albumen-deprived hens. During adulthood, an age-related loss of glucose tolerance was observed in the hens, leading to disappearance of treatment differences in the OGTT. The offspring of the albumen-deprived hens (PA chicks) had reduced body weight until at least 3 weeks of age. In addition, the PA chicks had a decreased relative residual yolk weight at hatching. An insulin tolerance test revealed increased sensitivity to insulin for the PA chicks compared with the offspring of the non-manipulated (PN) and sham-manipulated hens (PS). In conclusion, prenatal protein undernutrition by albumen removal caused long-term effects on body weight, reproductive performance, and physiology.

Review on the effects of potential prebiotics on controlling intestinal enteropathogens Salmonella and Escherichia coli in pig production

Salmonella enterica serotypes (Salmonella sp.) are the second cause of bacterial foodborne zoonoses in humans after campylobacteriosis. Pork is the third most important cause for outbreak-associated salmonellosis, and colibacillosis is the most important disease in piglets and swine. Attachment to host cells, translocation of effector proteins into host cells, invasion and replication in tissues are the vital virulence steps of these pathogens that help them to thrive in the intestinal environment and invade tissues. Feed contamination is an important source for Salmonella infection in pig production. Many on-farm feeding strategies intervene to avoid the introduction of pathogens onto the farm by contaminated feeds or to reduce infection pressure when pathogens are present. Among the latter, prebiotics could be effective at protecting against these enteric bacterial pathogens. Nowadays, a wide range of molecules can potentially serve as prebiotics. Here, we summarize the prevalence of Salmonella sp. and Escherichiaxa0coli in pigs, understanding of the mechanisms by which pathogens can cause disease, the feed related to pathogen contamination in pigs and detail the mechanisms on which prebiotics are likely to act in order to fulfil their protective action against these pathogens in pig production. Many different mechanisms involve the inhibition of Salmonella and E.xa0coli by prebiotics such as coating the host surface, modulation of intestinal ecology, downregulating the expression of adhesin factors or virulence genes, reinforcing the host immune system.

Feeding broiler breeders a reduced balanced protein diet during the rearing and laying period impairs reproductive performance but enhances broiler offspring performance

ABSTRACT Mammalian studies have shown that nutritional constraints during the perinatal period are able to program the progeny (metabolism, performance). The presented research aimed to investigate if broiler breeders and their offspring performance could be influenced by reducing the dietary crude protein (CP) level with 25%. A total of 160 day‐old pure line A breeder females were randomly divided over 2 dietary treatments. The control group was fed commercial diets, whereas the reduced balanced protein (RP) breeders received an isoenergetic diet that was decreased with 25% in dietary CP and amino acid during their entire lifespan. The RP birds required an increased feed allowance, varying between 3 and 15%, to meet the same BW goals as their control fed counterparts. The difference in feed allocations and reduction of the dietary CP level resulted in a net protein reduction varying between 14 and 23%. At wk 27 and 40, the body composition of the breeders was changed as a result of the dietary treatment. At both ages, the proportional abdominal fat pad weight of the RP breeders was increased (P < 0.001), whereas the proportional breast muscle weight was only higher at wk 27 in the control group compared to the RP group (P < 0.001). Egg weight (P < 0.001) and egg production (P < 0.001) was decreased for the RP fed birds. The lower dietary CP level reduced the proportional albumen weight of the RP eggs (P = 0.006). Male offspring from RP breeders were characterized by an increase in BW from 28 d until 35 d of age (P = 0.015). Moreover, female progeny of RP breeders showed a reduced FCR (P = 0.025), whereas male progeny showed a tendency (P = 0.052) towards a lower FCR at 5 wk of age. In conclusion, lowering dietary CP levels in rearing and laying phase of breeders had a negative effect on breeder performance but enhanced live performance of the offspring.

Attenuating Effect of Zinc and Vitamin E on the Intestinal Oxidative Stress Induced by Silver Nanoparticles in Broiler Chickens

Silver nanoparticles (AgNPs) have been increasingly used as antimicrobial and disinfectant. However, intestinal model studies have shown that AgNPs induce oxidative stress. Hence, this study aims to investigate the effects of dietary supplemental zinc (Zn) and vitamin E (VE; α-tocopherol acetate) on attenuating AgNP-induced intestinal oxidative stress in broiler chickens. The chickens were divided into two groups as follows: (1) control group fed with a corn–soybean meal basal diet and (2) nano group, received drinking water containing 1000xa0mg/kg AgNPs. All the nano-exposed birds were divided into six dietary treatment groups, namely, the basal diets supplemented with (1) 60xa0mg/kg Zn as ZnSO4, (2) 120xa0mg/kg Zn, (3) 100xa0mg/kg VE, (4) 200xa0mg/kg VE, (5) 60xa0mg/kg Zn and 100xa0mg/kg VE, and (6) 120xa0mg/kg Zn and 200xa0mg/kg VE. Results showed that the AgNPs significantly reduced the body weights of the broilers after 42xa0days of oral administration of AgNPs (Pxa0<xa00.05), and this effect was not alleviated by any of the dietary treatments. The activity of superoxide dismutase (CuZn-SOD) increased in all the AgNP-treated birds (Pxa0<xa00.05); however, CuZn-SOD did not increase in birds fed with basal diet supplemented with 200xa0mg/kg VE. In this treatment, the VE exerted an antioxidant effect to prevent the activation of the CuZn-SOD enzyme. Furthermore, supplementing Zn increased the activities of catalase and glutathione peroxidase in the jejunal mucosa (Pxa0<xa00.05), which were accompanied with increased malondialdehyde levels (Pxa0<xa00.05) in the broilers. AgNP exposure resulted in a significant messenger RNA (mRNA) upregulation of toll-like receptor 4 (TLR4) and TLR2-1 in the jejunal mucosa (Pxa0<xa00.05). However, supplemental ZnVE did not reduce TLRs’ mRNA expression, except for the diminished TLR2-1 mRNA levels in birds fed with basal diet supplemented with 120xa0mg/kg Zn and 200xa0mg/kg VE. We concluded that although dietary Zn and VE supplementation did not attenuate growth depression effect of AgNP, it however attenuates intestinal oxidative stress in AgNP-treated broiler chickens.