Microbiota profile and antibiotic resistance genes in the caecal content of broiler chickens are influenced by dietary protein content and the plant protein source

Authors: OLUKOSI, OLUYINKA - University Of Georgia; SELVARAJ, RAMESH - University Of Georgia; Shanmugasundaram, Revathi; Oladeinde, Adelumola - Ade; ADELEYE, AJAO - University Of Georgia; LAWRENCE, JODIE - US Department Of Agriculture (USDA); Cudnik, Denice; Zock, Gregory

Submitted to: European Poultry Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 3/15/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: N/A

Technical Abstract: Soybean meal (SBM), canola meal (CM), and corn distillers dried grains with solubles (cDDGS) in reduced-protein diets affect chicken growth performance, immune response, and nutrient utilization. Hence, the objective of the current experiment was to study whether those effects are accompanied by changes in the microbiota profile. A total of 1,120 seven-day-old broiler chicks were distributed to a 4 × 2 (4 diets × with or without challenge) factorial arrangement until day 42 in 7 replications. The 4 diets were (i) a diet with a standard protein level of 20% crude protein (SP); (ii) a reduced-protein (16% crude protein) corn-SBM (RPSBM); (iii) an RP diet in which 8% CM replaced 6% SBM (RPCM); and (iv) an RP diet in which 10% cDDGS replaced 5% SBM (RPcDDGS). On day 14, birds were either orally gavaged with a mixed Eimeria (+E) solution or distilled water. Cecal samples were quantified for selected commensal bacteria, pathogens, and antimicrobial resistance genes on day 21. A high-throughput probe-based PCR was used to determine the abundance of 28 genes specific to commensal bacteria, bacterial pathogens, and antimicrobial resistance (AMR) determinants for tetracycline (tet), streptomycin (strB), sulphonamide (sul2), extended-spectrum ß-lactam (blaCTX) resistance, and mobile DNA elements (incI1 and incI2 plasmids) that transmit AMR. In addition, a SYBR-based qPCR targeting Lactobacillus spp. and Bifidobacterium spp. was performed on a subset of caecal samples. Irrespective of the Eimeria challenge, strB abundance was significantly lower in birds receiving RP than in birds fed SP diets (p < 0.01). The birds fed RPcDDGS had lower levels of strB than the birds fed SP (p < 0.01). There was a diet × Eimeria challenge interaction (P < 0.01) for the Lactobacillus population in the caecal content. There were no treatment differences in Lactobacillus content in unchallenged birds, but in the challenged group, Lactobacillus content was greater (P < 0.01) in RP-SBM compared to the other treatments. Bifidobacterium spp. was lower in the caecal content of Eimeria-challenged birds, but the diets had no effect. It is concluded that both the dietary protein level and the plant protein source influence the caecal microbial profile, including the population of bacteria that harbor AMR. Further studies will be needed to determine if these microbiome changes are advantageous or deleterious to the overall gut health of broiler chickens.