Evaluation of potential alternatives to replace antibiotic growth promoters in broiler chicken diets
Creators: Goes, Emanuele C
Publisher: name: University of Alberta Library
Year: 2024

<p>The phasing out of antibiotic growth promoters (AGP) from livestock diets has increased the risk of enteric diseases in broilers; therefore, effective AGP replacements must be found. The objective of this Ph.D. thesis was to investigate three novel products as potential AGP replacements in broiler diets: chitosan oligosaccharides (COS), punicic acid (PA), and glucosamine-derived caramels. COS and PA were tested in broilers challenged with a natural, subclinical necrotic enteritis (NE) infection model. Birds were challenged with 15x the recommended dose of a commercial coccidiosis vaccine containing live Eimeria oocysts by gavage at 12 d, with a 24-hour feed withdrawal at 18 d. To investigate COS, a pilot study was conducted to evaluate the optimal molecular weight (14, 17, 25, 30, 95, 110, 180 or 220 kDa) and dietary inclusion level (0.2, 2 or 5 g/kg) compared with a Positive Control (PC; basal diet with antibiotic and coccidiostat) and Negative Control (NC; basal diet without medications). From this study, the most promising treatments to recover performance and mitigate NE were further investigated for their effects on gut health and immune response in broilers. Among the tested products, COS 95 kDa showed promise in enhancing broiler performance, increased the abundance of Lactobacillus species in the ceca compared to NC, enhanced the intestinal morphology integrity, and mitigated Eimeria infection at the same level as the PC. COS 95 kDa also contributed to a vigorous local immune response, increasing the serum levels of macrophage inflammatory protein-3α and interleukin-16 following the challenge. For the PA study, increasing levels of pomegranate seed oil (PSO), high in PA, were added to achieve a final PA concentration of 0.1, 0.25, 0.5, 1, 1.5, or 2% of the feed. Birds in these experimental treatments were compared to those fed PC and NC. Supplementation of PSO to achieve PA concentrations higher than 0.5% of the diet caused significant reductions in the feed intake, BW, and BW gain of broilers. In addition, PA at 2% predisposed the birds to more severe NE intestinal lesions than PC birds following the challenge. For the glucosamine-derived caramels study, treatments included a Control (basal diet), Control plus glucosamine at 0.24% of the diet, and diets supplemented with glucosamine caramels: either Light Caramel produced at 50°C (LC), Brown Caramel produced at 90°C (BC), LC plus caramelized fructose (LC+F), or BC plus caramelized fructose (BC+F); each product was added at 0.08, 0.16 and 0.24% of the diet. Broilers were raised in wire-floored cages as a model to induce lameness. LC at 0.24% enhanced the BW of broilers at 10 d, and LC at 0.16% tended to enhance BW and BWG at 25 and 38 d (P ≤ 0.09) compared to the Control. Regardless of dose, LC, BC, and BC+F reduced the lesions in the tibia of broilers at 40 d. None of the products tested were as effective as AGP for growth promotion and NE prevention. However, COS 95 kDa and LC should be further explored as a part of a strategy to replace in-feed AGP in broiler diets.</p>