The current study investigated the effect of dietary l-histidine and beta-alanine supplementation on growth performance, meat quality, carnosine content, and gene expression of carnosine-related enzymes in broilers. A two-factor design was adopted in this study. A total of 640 1-day-old male broilers were assigned to eight treatments with factorial arrangement containing four levels of l-histidine (0, 650, 1300, or 1950 mg/kg) and two levels of beta-alanine (0 or 1200 mg/kg) supplementation; 0 mg/kg histidine and/or 0 mg/kg were treated as control groups. Each treatment including eight replicates with 10 birds each and the feeding trial lasted for 42 days. Dietary supplementation with l-histidine and beta-alanine did not affect average daily gain (ADG), average daily feed intake (ADFI), and feed conversion ratio (FCR) of broilers during the grower (22–42 days) and the entire phase (1–42 days), compared with the control group (p > 0.05). The only exception was a significantly reduced ADG in the 1950 mg/kg l-histidine group in the starter period (1–21 days, p < 0.05). l-Histidine at 1950 mg/kg significantly decreased redness (a*) and yellowness (b*) values of the meat at 45 min postmortem (p < 0.05), whereas it increased b* value and pH in breast muscle at 24 h postmortem. Moreover, dietary supplementation with beta-alanine alone or combination with l-histidine significantly increased ΔpH in breast muscle (p < 0.01). Dietary l-histidine markedly increased total superoxide dismutase activity and total antioxidant capacity (T-AOC) both in breast muscle (p < 0.01) and in plasma (p < 0.01), and it decreased malondialdehyde (MDA) concentration in breast muscle (p < 0.01). Dietary addition of beta-alanine, alone or combination, significantly increased T-AOC in breast muscle (p < 0.01) and markedly decreased MDA content both in breast muscle and in plasma (p < 0.01). Addition of l-histidine and beta-alanine significantly increased muscle peptide (carnosine and anserine) content (p < 0.05) and upregulated the expression of carnosine synthase, transporter of carnosine/ l-histidine, and l-histidine decarboxylase genes (p < 0.05), with greater change occurring in the combination group of 1300 mg/kg l-histidine and 1200 mg/kg beta-alanine. Overall, dietary l-histidine and beta-alanine could improve meat quality and antioxidant capacity, enhance the carnosine and anserine content, and upregulate the gene expression of carnosine synthesis-related enzymes in broilers.

中文翻译：

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补充β-丙氨酸和l-组氨酸对肉鸡生长性能、肉质、肌肽含量和肌肽相关酶mRNA表达的影响

目前的研究调查了日粮中添加l-组氨酸和 β-丙氨酸对肉鸡生长性能、肉质、肌肽含量和肌肽相关酶基因表达的影响。本研究采用双因素设计。总共 640 只 1 日龄雄性肉鸡被分配到 8 个处理组，其中包含四个水平的l-组氨酸（0、650、1300 或 1950 mg/kg）和两个水平的 β-丙氨酸（0 或 1200 mg/kg) 补充；0mg/kg组氨酸和/或0mg/kg作为对照组处理。每个处理包括 8 个重复，每组 10 只鸡，饲养试验持续 42 天。在饮食中补充升-组氨酸和β-丙氨酸不影响肉鸡在生长期间（22-42天）和整个阶段（1-42天）的平均日增重（ADG）、平均日采食量（ADFI）和饲料转化率（FCR）天），与对照组相比（p > 0.05）。唯一的例外是 1950 mg/kg l-组氨酸组在起始期（1-21 天，p < 0.05）的ADG 显着降低。1950 mg/kg 的l-组氨酸在死后 45 分钟显着降低肉的发红 (a*) 和发黄 (b*) 值 ( p < 0.05)，而在死后 24 小时增加 b* 值和胸肌的 pH 值. 此外，膳食补充剂单独或与l-组氨酸显着增加了乳房肌肉中的 ΔpH ( p < 0.01)。膳食l-组氨酸显着增加了胸肌 ( p < 0.01) 和血浆 ( p < 0.01) 中的总超氧化物歧化酶活性和总抗氧化能力 (T-AOC )，并降低了胸肌中的丙二醛 (MDA) 浓度 ( p < 0.01)。日粮中单独或联合添加 β-丙氨酸显着增加了胸肌中的 T-AOC ( p < 0.01)，并显着降低了胸肌和血浆中的 MDA 含量 ( p < 0.01)。添加l-组氨酸和 β-丙氨酸显着增加了肌肉肽（肌肽和鹅肌肽）的含量（p < 0.05) 并上调肌肽合酶、肌肽/ l-组氨酸转运蛋白和l-组氨酸脱羧酶基因的表达 ( p < 0.05)，1300 mg/kg l-组氨酸和 1200 mg/kg β-丙氨酸。总体而言，饮食升组氨酸和β-丙氨酸可以改善肉质和抗氧化能力，增强了肌肽和鹅的内容，并上调肉鸡肌肽合成相关酶的基因表达。