Author ORCID Identifier

Date Available


Year of Publication


Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation


Agriculture, Food and Environment


Animal and Food Sciences

First Advisor

Dr. Sunday A. Adedokun


Three experiments were conducted to evaluate the interactive effects of dietary supplements in birds exposed to different stressors, on growth performance, nutrient, and energy digestibility, antioxidant status, intestinal permeability, and immune status. The first study was conducted to evaluate the effect of a commercially available algae-based antioxidant, containing Selenium yeast (EconomasE™, EcoE) and two inorganic sodium sources (NaCl and NaCl+NaHCO3) on growth performance, nutrient and energy digestibility and utilization, antioxidant, and immune status of broilers challenged with oral gavage of dexamethasone (DEX). The inclusion of either of the sodium sources did not affect plasma corticosterone and antioxidant status levels, growth performance, and the relative weights of the lymphoid organs. Homeostasis was altered with DEX, evident in the increased (P < 0.05) levels of corticosterone in the plasma, reduced (P < 0.05) growth performance, and nutrient digestibility. The EcoE supplementation did not mitigate the performance parameters however, its supplementation in the diet increased (P < 0.05) nutrient and energy utilization and decreased corticosterone serum levels.

The objective of the second study was to evaluate the effect of EconomasE™ (0 or 0.2 g/kg) and two inorganic sodium sources (NaCl or NaCl+NaHCO3) in layers exposed to different environmental temperatures. Dietary treatment did not improve performance, egg quality, intestinal morphology, keel bone, bone-breaking strength, and HSP 70 and 90 during ET1 and ET2. Exceptions to this were the increase (P < 0.05) in the albumen height and Haugh unit with EcoE and NaCl+NaHCO3 during TN2 and EcoE alone during the ET2 regimen, which suggests that the supplementation can improve the fresh appearance of the egg during ET conditions. Similarly, NaCl+NaHCO3 as the sodium source helped limit the effects of respiratory alkalosis by reducing Cl- levels and increasing HCO3- during the ET regimen. In normal temperature conditions, EcoE and NaCl+NaHCO3 diet were able to improve (P < 0.05) villus height and villus height: crypt depth ratio.

The third study evaluated the effect of DEX and coccidia vaccine challenge in broiler chickens fed diets supplemented with or without Natustat™ (a natural plant-derived proprietary product composed of at least one yeast-derived MOS plus organic mineral nutrients and plant extracts) on growth performance, nutrient and energy digestibilities and utilization, intestinal barrier integrity, and immune response. Throughout the experiment, birds were fed a standard corn-SBM diet supplemented with or without Natustat™ at 1 g/kg. Within each diet group, the birds were randomly assigned to four treatments: CON (no-challenge), dexamethasone (DEX), coccidia vaccine (Cocci), and a combination of Cocci and DEX (CocciDex) challenge. The DEX and CocciDex groups received dexamethasone in the feed at 1.5mg/kg of diet for 7 days, while the Cocci and CocciDex groups were orally gavaged with 20x coccidia vaccine. The DEX and CocciDex-challenge were able to induce stress and reduce performance, digestibility, intestinal permeability, and immune response. The coccidia vaccine challenge did not affect performance. However, total tract nutrient and energy utilization were impaired and the jejunal mRNA expression of (TLR4) and pro-inflammatory cytokines 7-days post-challenge was observed. Finally, Natustat™ supplementation did not mitigate the negative effect of the stressors on performance, nutrient and energy digestibility and utilization, and intestinal morphology and permeability. The supplementation had a tendency to increase the expression of anti-inflammatory cytokine (IL-10) 7-days post-challenge. It also increased IL-10 and decreased the mRNA expression of IL-6, 14-days post-challenge.

In conclusion, stress was induced in the birds especially with DEX and some with coccidia challenge and heat stress, and the supplements had a limited effect in mitigating the effect of the stressors.

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