Growth performance, feed utilization and non-specific immune response of gilthead sea bream (Sparus aurata L.) fed graded levels of a bioprocessed soybean meal

Insect meal derived from chironomid larvae and collected from aquatic environments was included in the feed of gilthead sea bream juveniles (75 ± 1.1 g) in a growth trial of 90 days. Three feeds, which were namely one control (L1) and two experimental diets (L2, L3), were analyzed and formulated as isonitrogenous (45%) and isolipidic (13%). In L1, the protein source was mainly soybean meal (32%), followed by fish meal (20%), wheat meal (20%), gluten corn (17%), and hemoglobin (11%). In L2, the proportion of soybean meal was increased (33.5%), followed by gluten corn (21%), wheat meal (14%), and hemoglobin (11%), whereas the fish meal source was reduced (15%) due to the inclusion of chironomids (5%). In L3, the proportion of fish meal was further reduced (8%) and that of chironomid meal was increased to 10% of the protein source. The L2 and L3 groups showed similar growth performances with respect to the L1 group. The feed conversion rate was favorable in all the groups, ranging from 1.18 (L1) to 1.22 (L3). Survival rates varied from 93.62% (L3) to 94.31% (L1). Feed palatability showed similar results for all diets. Although the inclusion of chironomid meal was used in small quantities, our results suggest a significant advantage in replacing 50% of the fish meal with the chironomid meal for growing gilthead sea bream fishes.

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Enterospora nucleophila (Microsporidia) in Gilthead Sea Bream (Sparus aurata): Pathological Effects and Cellular Immune Response in Natural Infections

Veterinary Pathology ◽

10.1177/0300985820927707 ◽

2020 ◽

Vol 57 (4) ◽

pp. 565-576

Author(s):

Amparo Picard-Sánchez ◽

M. Carla Piazzon ◽

Nahla Hossameldin Ahmed ◽

Raquel Del Pozo ◽

Ariadna Sitjà-Bobadilla ◽

...

Keyword(s):

Immune Response ◽

Cellular Immune Response ◽

Sparus Aurata ◽

Quantitative Polymerase Chain Reaction ◽

Gilthead Sea Bream ◽

Sea Bream ◽

Infection Prevalence ◽

In Vivo Models ◽

Cellular Immune ◽

Macrophage Aggregates

Enterospora nucleophila is a microsporidian responsible for an emaciative disease in gilthead sea bream ( Sparus aurata). Its intranuclear development and the lack of in vitro and in vivo models hinder its research. This study investigated the associated lesions, its detection by quantitative polymerase chain reaction, and the cellular immune response of naturally infected fish. The intensity of infection in the intestine was correlated with stunted growth and reduced body condition. At the beginning of the outbreaks, infection prevalence was highest in intestine and stomach, and in subsequent months, the prevalence decreased in the intestine and increased in hematopoietic organs and stomach. In heavy infections, the intestine had histologic lesions of enterocyte hypercellularity and proliferation of rodlet cells. Infected enterocytes had E. nucleophila spores in the cytoplasm, and a pyknotic nucleus, karyorhexis or karyolysis. Lymphocytes were present at the base of the mucosa, and eosinophilic granule cells were located between the enterocytes. In intestinal submucosa, macrophage aggregates containing spores were surrounded by lymphocytes and granulocytes, with submucosal infiltration of granulocytes. Macrophage aggregates appeared to develop into granulomata with necrotic areas containing parasite remnants. Immunohistochemistry revealed mast cells as the main type of granulocyte involved. Abundant IgM+ and IgT+ cells were identified by in situ hybridization in the submucosa when intracytoplasmic stages were present. This study describes the lesions of E. nucleophila in gilthead sea bream, an important aquaculture species.

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