Effect of Zinc Oxide Nanoparticles as Feed Additive on Blood Indices, Physiological, Immunological Responses, and Histological Changes in Broiler Chicks

Abstract

A feeding trial of 5-week duration was performed to assess the response of broiler chicks to dietary supplementation with different doses of myco-fabricated zinc oxide nanoparticles (ZONPs) on blood indices, physiological, immunological response, antioxidant status, intestinal microbial count, and histological changes in immune organs. A total of 162 3-day-old Ross 308 broiler chicks were weighed individually and distributed equally into 3 dietary treatments with 6 replicate of 9 chicks in each in a completely randomized design. Chicks were fed ad libitum a basal ration prepared as starter, grower, and finisher supplemented with 0 (T1, control), 40 (T2), and 60 (T3) mg zinc oxide nanoparticles (ZONPs)/kg feed. Results showed that supplementing with ZONPs at both studied levels increased the relative weights of the spleen, bursa, thymus, and liver and decreased the relative weight of the kidney, gizzard, and intestine. A significant increase in the concentrations of hemoglobin (Hb), hematocrit (PCV%), red and white blood cell counts, total protein (TP), globulin (GLOB), aspartate transferase (AST), alanine transferase (ALT), alkaline phosphatase (ALP), superoxide dismutase (SOD), glutathione peroxidase (GPx), and total antioxidant capacity (TAC) and a significant decrease in malonaldehyde (MDA), uric acid, and creatinine concentration were observed. Furthermore, all immunological organs showed histological alteration and increased both types of immunity in ZONPs groups with more pronounced effects in the T2 group.

Keywords: Antioxidants; Blood indices; Broilers; Immune response; Zinc oxide nanoparticles.

Fig. 1

Photomicrographs exhibiting the outcome of ZONPs supplement on the normal splenic architecture of the tested broilers. A In the control group, the spleen appeared with a normal structure of white pulp (cube) and red pulp areas (circle). In the 40-mg ZONPs group, B extensive mitotic cells (arrows) presented along splenic tissue. C Depletion of lymphocytic cells and increase blood cells inside lymph nodules (arrows). D Focal necrotic areas (arrows) with inflammatory cell infiltration in a disorganized red pulp structure. In the 60-mg ZONPs group, E obvious indistinct white pulp from red pulp area. F Red pulp marked a severe necrosis and apoptosis in splenic cords (arrow) with a dilated blood sinusoid (arrowhead) (hematoxylin and eosin stain, magnification power =  × 100, × 400, × 1000; scale bar = 200 µm, 50 µm, 20 µm)

Fig. 2

Photomicrographs displayed the histopathological alterations in the thymus of tested broilers as follows: A and D sections of the control group displayed the normal architecture of the thymus gland as a compact organ with incomplete lobules, each lobule has dark stained outer cortex (cube) and pale stained inner medulla (circle) homing immunocompetent cells mainly, T lymphocyte (arrow). Thymic lobules supported by fine connective tissue septa (arrowhead) and blood vessels (wave arrow). B and E Sections of the 40-mg ZONPs supplemented group highlighted the faint staining of the thymic cortex along with vacuolations (arrow) and reduction in lymphocyte number (cube). Thymic medulla revealed congestion in between aggregated lymphocytes (circle). Thymic capsule marked with fibrous tissue thickening, congested blood vessels, and infiltration of inflammatory cells (wave arrow). Seta between thymic lobules emphasized a thinning assembly (arrowhead). C and F Sections of the 60-mg ZONPs supplemented group revealed a very thin fibrous connective tissue septa rendering loss of demarcation between lobules (arrowhead), vacuolations (arrow) caused a light staining of both cortex and medulla (cube and circle, respectively). Notice congested blood vessel (wave arrow) (hematoxylin and eosin stain, photos of A, B, and C: magnification power =  × 100 and scale bar = 200 µm, photos of E, F, and G: magnification power =  × 400 and scale bar = 50 µm)

Fig. 3

Photomicrographs presented the histopathological modifications in the bursa of tested broilers as follows: A, B, and C Sections of the negative control group showed the normal construction of bursal follicles as an outer cortex (thick arrow), inner medulla (arrowhead), and interfollicular epithelium (circle). Bursal follicles are separated by fibrous connective tissue septa (wave arrow). Notice lymphocytes and plasma cells homing bursal follicle (thin arrow). D, E, and F Sections of the 40-mg ZONPs supplemented group highlighted obvious hyperplasia in the inter-follicular epithelium (arrow), vacuolations (circle), marked thickness in the underlying connective tissue (cube), appearance of multiple epithelial cyst (wave arrow), and decline in lymphocytes number (arrowhead). G, H, and I Sections of the 60-mg ZONPs supplemented group displayed a noticeable increase in the fibrous connective tissue thickness (cube) in between bursal follicles (arrow), high vacuolation within bursal follicle (circle), scattered small, and huge epithelial cyst (wave arrow), along with congested blood vessels (arrowhead) (hematoxylin and eosin stain, photos of A, D, and G: magnification power =  × 40 and scale bar = 500 µm, photos of B, E, and H: magnification power =  × 100 and scale bar = 200 µm, photos of C, F and I: magnification power =  × 400 and scale bar = 50 µm)

Fig. 4

Photomicrograph of left and right wattle as an indicator for cell-mediated immune response after injection with PHA-P. Photomicrograph (A) showed a left wattle (served as control) after being injected with 0.1 mL of sterile saline solution. Photomicrograph (B) showed a right wattle after being injected with 0.1 mL of PHA-P. Photomicrograph (C) showed right and left wattles in broilers after injection