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Title:Methionine and broiler health
Author(s):Oelschlager, Maci Lyn
Director of Research:Dilger, Ryan N
Doctoral Committee Chair(s):Dilger, Ryan N
Doctoral Committee Member(s):Parsons, Carl M; Emmert, Jason L; Jarosinski, Keith W
Department / Program:Animal Sciences
Discipline:Animal Sciences
Degree Granting Institution:University of Illinois at Urbana-Champaign
sulfur amino acids
Abstract:Innovations directed toward improving broiler health while maintaining efficiency are critical to meeting industry demands. Although substantial advancements in poultry rearing have been made in the past 50 years, unavoidable events which activate the immune system result in reductions in production efficiency and economic loss to the producer. Recently, novel diet formulations targeted at improving broiler efficiency and immune function have been investigated. Nutritional strategies are practical, easily understood by producers, relatively cheap to implement without major structural changes, and generate impactful results. Amino acids have known effects on the immune system. Most of the requirements for amino acids are estimated from models using data obtained from un-challenged broilers where pathogen exposure is minimized. Though adequate for growth, these estimates may not reflect the bird's needs for both optimal growth and immune function. Methionine, the first limiting amino acid for growth in a standard broiler diet, is used in many cellular activities, including methylation, sulfur donation, pyruvate production, polyamine generation, formylmethionine formation, and is a precursor to cysteine and the potent anti-oxidants, Tau and glutathione. To determine if these immune-related functions of Met affect its requirement levels in the diet during challenged conditions and impact broiler immune function, a total of 3 experiments were conducted to investigate the relationship between dietary Met and broiler health. First, it was necessary to establish a diet formulation that permits manipulation of dietary Met and cysteine levels capable of estimating the requirement of 2 Met sources, their relative bioefficacy, and their impact on organ growth and development. To accomplish this aim, 2 Met dose-titration experiments were conducted using DL-Met and DL-2-hydroxy-4-(methylthio) butanoic acid (DL-HMTBA) as Met sources. For Experiment 1, 7 low-CP dietary treatments were fed during the grower phase (d 10 – 24): low total sulfur amino acid (LTSAA), LTSAA supplemented with 0.36% L-cystine (Met0), and the Met0 supplemented with graded levels of DL-Met (0.072% increments; Met1 – Met5). For Experiment 2, 12 low-CP dietary treatments were fed to broilers during the grower phase (d 10 – 24): LTSAA, Met0, and Met0 supplemented with graded DL-Met (0.072% increments; Met1 – Met5) or DL-HMTBA (0.103% increments; HMTBA1 – HMTBA5). Growth performance was increased (P < 0.001) with Met supplementation. The LTSAA and Met0 differed for growth performance during d 10 – 24, but only during Experiment 2. From the fitted 1-slope broken-line regression analysis, the estimated requirement of supplemental DL-Met ranged from 0.18% – 0.19% (0.33% – 0.34% total Met) for BW gain and 0.12% – 0.15% (0.27% – 0.30% total Met) for gain:feed. From the same model, estimated requirements for supplemental DL-HMTBA were 0.22% (plus 0.15% Met) for BW gain and 0.17% (plus 0.15% Met) for gain:feed. The bioefficacy of DL-HMTBA relative to DL-Met was estimated using a nonlinear, exponential regression model and was 78% for BW gain and 82% for gain:feed. Absolute and relative gastrointestinal and immune organ weights and lengths were influenced by Met supplementation (P <0.048). Relative liver weight decreased (P < 0.001) in diets supplemented with at least Met2 or HMTBA3 and above compared with diets devoid of Met supplementation. A final experiment was conducted to examine the impact of dietary Met on the growth and immune performance of broilers and the requirement of supplemental DL-Met during an acute in vivo immune challenge. Broilers were fed 1 of 7 low-CP experimental grower (d 10 – 28) dietary treatments that included a low total sulfur amino acid (LTSAA), LTSAA supplemented with 0.36% L-cysteine (Met0), and the Met0 supplemented with graded levels of DL-Met (0.072% increments; Met1 – Met5) and challenged in vivo intraperitoneally (i.p.) with lipopolysaccharide (LPS) at 2.0 mg/kg of BW on d 25. Growth performance was improved (P < 0.001) with the addition of supplemental DL-Met before (d 10 – 24), during (d 24 – 26), and after (d 26 – 28) the in vivo LPS challenge. The estimated requirement of supplemental DL-Met from the 1-slope broken-line regression analysis numerically decreased for BW gain and gain:feed during the in vivo LPS challenge (d 24 – 26) by about 7% and 39%, respectively, compared with the requirement of supplemental DL-Met during the pre-challenge period (d 10 – 24). Dietary treatment had no impact (P > 0.05) on broiler body temperature. The ratio of heterophils to lymphocytes (H:L) decreased when at least Met3 or above was fed to broilers at all time-points following the in vivo LPS challenge. Additionally, dietary treatment had no impact (P > 0.05) on isolated splenic macrophage IL-6 production during an ex vivo stimulation by LPS assay. Absolute liver DM weights were impacted (P < 0.001) by dietary treatment at -24, 5, 24, and 72 hours post-stimulation (HPS), while relative liver DM weight was impacted (P < 0.010) only at -24, 5, and 72 HPS. Assorted main effects of dietary treatment, HPS, supplemental L-Cys, and supplemental DL-Met and their interaction effects on hepatic and splenic cytokine mRNA expression of IL-6, IL-1β, and IL-10 were observed, with pro-inflammatory cytokines appearing more influenced by dietary Met than anti-inflammatory cytokines. Overall, this research demonstrates the importance of Met in maintaining broiler health during an immune challenge. Specifically, impacts made by the amino acid Met may occur during the onset of the innate response and enhance liver efficacy.
Issue Date:2021-11-29
Rights Information:Copyright 2021 Maci Oelschlager
Date Available in IDEALS:2022-04-29
Date Deposited:2021-12

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