Toll-like receptors (TLRs), type I transmembrane pattern recognition receptors (PRRs), are composed of the extracellular domain that is implicated in the recognition of microbial products and initiates the innate and adaptive immune response. Previous reports on TLRs in birds showed significant levels of inter- and intraspecific genetic variation. Little is known about the structure and function of the avian immune system, especially waterfowl species. This work aimed to identify and clone Anas platyrhynchos (mallard duck) TLR-3 (dTLR-3) and its expression level following challenge with velogenic Newcastle disease virus (NDV) as a model for waterfowl species. The mallard duck TLR-3 full-length cDNA sequence had been cloned, which consisted of 2457 nucleotides. The translated amino acid sequence showed identity degree as 97% with Muscovy duck, 95% with geese, 89% with helmeted guineafowls, 88% with the chickens TLR-3 gene, 82% with turkey TLR-3, and 79% with zebra finch, while it showed 54% with human one; the analysis data suggested that the new sequence is probably homologous to vertebrates’ TLR-3. The predicted protein encoded by the duck dTLR-3 mRNA sequence is composed of 819 amino acids. Analysis of the deduced amino acid sequence indicated that dTLR-3 has typical structural features and contains the main components of proteins in the TLR family. The dTLR-3 expressed in almost all examined tissues of mallard duck following quantitative real-time polymerase chain reaction (qPCR) analysis and using B-actin as a housekeeping gene. To check the functionality of the receptor and its role in viral infection, we evaluate the expression level in different tissues and its changes following NDV infection. The results showed significant (P < 0.05) upregulated in the brain at 24 h (1.84-fold), reached a peak at 48 h (4.82-fold), and recovered to normal levels at 72 h post-infection. These results indicate a complete and functional dTLR-3 that is orthologous to other vertebrate receptors with its potential role in early response against viral infection in mallard duck species.

The aim of the present study was to evaluate the effect rosemary (Rosmarinus officinalis L.) powder (RP) and vitamin E (VE) at different levels on humoral immunity of broilers during a 42-day production cycle. A total of 270 1-day-old male chicks were assigned to nine groups with three replicates of ten birds each, and diets were supplemented with 0, 0.5, or 1.0% RP and 0, 100, or 200 mg/kg VE, respectively. Commercial-inactivated vaccines against avian influenza (AI) and Newcastle disease (ND) viruses, and living infectious bronchitis virus (IBV) vaccine were administered by spray method. Sheep red blood cells (SRBC) were administered subcutaneously. Blood samples were collected from birds 1 week after each vaccination to determine antibody titers. At the 42nd day, blood samples were also assessed for globulin level, and lymphoid tissues (thymus, spleen, and bursa) were weighed. Neither antibody titers against viruses nor lymphoid tissues weight were affected by RP and/or VE (P > 0.05) treatments. However, broilers supplemented with 0 mg/kg of VE had lower antibody titers against SRBC than those fed 100 mg/kg of VE (P < 0.05) at the 24th day. A significant RP × VE interaction effect (P < 0.05) on plasma globulin level was observed. The findings of our study suggest that dietary RP and VE additives can interact and modulate the humoral immunity of broilers, but not sufficiently to improve antibody titers against specific virus during a 42-day production cycle.

The aim of this study was to find the effect of synthetic γ-aminobutyric acid (GABA) on the performance, antioxidant status, and immune response in broiler exposed to summer stress. A total of 400-day-old male broiler chickens (Ross 308) was randomly distributed into five treatments (5 replicates). One group served as a control (basal diet only) while the others were supplemented with GABA at the rate of 25 (GABA-25), 50 (GABA 50), 75 (GABA-75), and 100 (GABA-100) mg/kg feed. The experiment was continued for 35 days. Feed intake during the third week was significantly higher (P < 0.05) in GABA-75 and GABA-100, however, it increased significantly (P < 0.05) in GABA-100 during the fourth and fifth week. Overall mean feed intake was significantly (P < 0.05) high in GABA-75 and GABA-100. From the results, we found that body weight improved significantly (P < 0.05) in GABA-50 in week-3. During the fourth, fifth, and overall, body weight increased significantly (P < 0.05) in GABA-100. Significantly, high (P < 0.05) feed conversion ratio (FCR) was found in GABA-100 during the third, fourth, fifth, and on an overall basis. Mean Malondialdehyde (MDA) decreased significantly (P < 0.05) in GABA-100 while Paraoxonase (PON1) and Newcastle disease (ND) titer increased significantly (P < 0.05) in the same group. We concluded that performance traits, antioxidant status, and immune response improved in broiler supplemented 100 mg/kg GABA, exposed to cyclic heat stress.