Algae-based feed ingredient protects intestinal health during Eimeria challenge and alters systemic immune responses with differential outcomes observed during acute feed restriction

Abstract

Compounds in microalgae-derived feed ingredients in poultry diets may improve intestinal physiology and immunity to protect against damage induced by physiological and pathogen challenges, but mechanisms are examined sparingly. The study objective was to evaluate changes to intestinal morphology, permeability, and systemic immunity in broilers fed a proprietary microalgae ingredient during 2 separate challenge studies. In study 1, two replicate 28 d battery cage trials used 200 Ross 308 broilers each (n = 400) fed a control diet ± 0.175% algae ingredient. Half of the birds were subjected to a 12 h feed restriction challenge and fluorescein isothiocyanate dextran ( FITC-D ) intestinal permeability assay on d 28. Study 2 used 800 broilers randomly assigned to the same dietary treatments and housed in floor pens for 42 d. At d 14, intestine and spleen samples were collected from 10 birds/ diet. Half of the remainder was orally inoculated with 10X Coccivac-B52 vaccine in a 2 × 2 factorial treatment design (diet and Eimeria inoculation). The FITC-D assay was conducted at 1, 3, 7, and 14 d post-inoculation ( pi ) while intestinal and spleen samples were collected at 3, 7, 14, and 28 dpi for histomorphology and flow cytometric immune cell assessment. Study 1 validated intestinal leakage via FITC-D absorbance induced by feed restriction but showed no algae-associated protective effects. In study 2, algae preserved intestinal integrity during coccidiosis ( P = 0.04) and simultaneously protected jejunal villus height as early as 7dpi ( P < 0.0001), whereas intestinal damage resolution in control birds did not occur until 14 dpi. Algae inclusion increased splenic T cells in unchallenged broilers at d 14 by 29.6% vs. control ( P < 0.0001), specifically γδ T cell populations, without impacting performance ( P < 0.03). During Eimeria challenge, splenic T cells in algae-fed birds did not show evidence of recruitment to peripheral tissues, while control birds showed a 16.7% reduction compared to their uninoculated counterparts from 3 to 7 dpi ( P < 0.0001). This evidence suggests the algae ingredient altered the immune response in a manner that reduced recruitment from secondary lymphoid organs in addition to protecting intestinal physiology.

Potential of Spirulina platensis as a feed supplement for poultry to enhance growth performance and immune modulation

“…Furthermore, when broilers were given the 10X Coccivac-B52 vaccine orally while being fed microalgae-derived feed components, the intestinal integrity of the birds during coccidiosis was conserved, and the jejunal villus height was protected as early as 7 days after the challenge ( 57 ). However, the algal element changed the immune response (splenic T cells) in a way that decreased recruitment from secondary lymphoid organs ( 57 ).…”

Basal diet composition contributes to differential performance, intestinal health, and immunological responses to a microalgae-based feed ingredient in broiler chickens

“…Despite wheat-based diets reducing general populations of inflammatory cells, algae inclusion in both diets reduced γδ T cells, which are considered immunoregulatory ( Vantourout and Hayday, 2013 ). Broilers in this study were raised on 3X composted and reused bedding from a previous coccidiosis trial utilizing Eimeria vaccine strains ( Fries-Craft et al., 2021 ). Oocyst counts and lesion scores indicated no remaining oocysts or active cycling, suggesting that vaccine-strain Eimeria do not maintain viability in composted bedding (data not shown).…”

Intestinal Immune Cell Populations, Barrier Function, and Microbiomes in Broilers Fed a Diet Supplemented with Chlorella vulgaris

“…CD4 + (helper) T cells can differentiate into two types of effector T cells that activate the microbial properties of macrophages and initiate humoral immune responses by activating naïve antigen-specific B cells [44]. Fries-Craft et al showed that there were augmented CD3 + CD4 + T cell and CD3 + TCRγδ + T cell populations in the spleen of 14-day-old broilers fed a corn-soybean meal diet containing an algae-based feed ingredient [45]. It has been reported that the development of immune cells in broilers begins to increase on the 7th day of CD4 + T cells being present in the peripheral blood and reaches a peak around the 30th day [46].…”