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Methionine supplementation and immune function in broilers experiencing an acute inflammatory challenge

Sommer, K., J. de Paula Dorigam, R. Whelan, B. Gorenz, M. Oelschlager, J. Jespersen and R. Dilger

Methionine is the first-limiting amino acid for broilers and plays a critical role in immune function. This study investigated the impact of graded supplemental levels of methionine in broilers undergoing a lipopolysaccharide (LPS) challenge. A total of 336 male broilers (Ross 308) were housed in batteries and allotted to 1 of 6 dietary treatments, with 7 replicates of 8 birds per replicate. Diets were provided in a 2-phase feeding program with a common starter diet and experimental grower diets provided d 0-10 and 10-28, respectively. Grower diets included a basal diet (0.136% digestible Met) supplemented with 0.360% L-Cys (0%DLM) and five other supplemented diets with graded levels of DL-Met (0.072%DLM- 0.360%DLM, with 0.072%DLM increments). To ensure the only limiting amino acid would be Met, other amino acids were included at approximately 15% over the AMINOChick 3.0 recommendations. All diets were provided ad libitum throughout the study. On study d 25 [0 hours post- stimulation (HPS)], all birds were challenged intraperitoneally with LPS derived from E. coli (O127:B8) at 2.0 mg/kg BW with 1 bird per pen was euthanized for sample collection at 5 HPS. Body weight gain during the grower phase was lowest (170 g, P < 0.01) in 0%DLM compared with 0.216%DLM or higher (1,067 g, 1,103 g and 1,112 g, respectively). Birds receiving 0%DLM had the least efficient feed conversion ratio (3.56 g/g, P < 0.01) compared with treatments ≥ 0.216%DLM (1.5). The treatments ≥ 0.216%DLM had, on average, 1.07 percentage points lower (P < 0.01) relative liver weights (%BW) at 5 HPS compared with 0%DLM (4.35%). Plasma concentrations of the acute phase protein, α-1-acid glycoprotein (AGP), were elevated (180. 3 μg/mL, P < 0.01) in 0%DLM compared with 0.144%DLM (88.3 μg/mL) and 0.288%DLM (76.5 μg/mL) treatments; however, there were no differences in interleukin-6 plasma concentrations.

In conclusion, broilers receiving diets deficient in Met exhibited a heightened response to LPS stimulation, as evident by the highest AGP production from hepatocytes, which may have contributed to increased relative liver weights. However, DL-Met supplementation ameliorated the effect of LPS as evidenced by benefits to growth performance, relative liver weights, and AGP concentrations.