The effects of betaine supplementation on growth performance, blood components, nutrient digestibility, excreta noxious gas emission, and meat quality of broiler chickens were examined using different dietary crude protein (CP) and methionine (Met) levels. A total of 768 Ross 308 broiler chickens were allotted to four treatments, with 12 replications of each treatment conducted over 6 wk. Treatments were factorially designed, with 2 levels of CP [Starter: CP 21% (low Met) and 23% (high Met); Finisher: CP 18% (low Met) and 20% (high Met)] and 2 levels of betaine supplementation (0 and 0.12%). Body weight gain and feed conversion improved significantly as dietary levels of protein increased (P < 0.05), but the results for betaine supplementation differed. The concentrations of serum total protein, albumin, and glutathione peroxidase (GPx) were elevated by either the supplementary betaine or the CP (P < 0.05). In addition, serum albumin concentration significantly increased in groups fed low CP amounts and betaine 0.12% compared with groups fed low CP only (P < 0.05). Total tract digestibility of nitrogen in broilers fed high CP amounts or 0.12% betaine, was observed to be greater than that in groups fed low CP amounts or no betaine treatment (P < 0.05). Supplemental betaine affected excreta ammonia gas emission, and hydrogen sulfide concentrations decreased significantly in low CP-fed groups (P < 0.05). Breast meat quality and relative organ weights were not influenced by CP levels or dietary betaine supplementation. These results suggest that betaine does not increase productivity, but may affect serum total protein, albumin, GPx, excreta ammonia emission, and nitrogen digestibility in broiler chickens. In addition, betaine supplementation is more effective in increasing serum albumin concentration when it was added in low CP (low Met) diets.

中文翻译：

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不同水平粗蛋白和蛋氨酸日粮中添加甜菜碱对肉鸡生长性能、血液成分、全肠道养分消化率、排泄物有毒气体排放和肉质的影响。

使用不同的日粮粗蛋白 (CP) 和蛋氨酸 (Met) 水平检测了添加甜菜碱对肉鸡生长性能、血液成分、营养消化率、排泄物有毒气体排放和肉质的影响。总共 768 只 Ross 308 肉鸡被分配到四个处理中，每个处理重复 12 次，持续时间超过 6 周。处理是因子设计的，有 2 个 CP 水平 [起始：CP 21%（低 Met）和 23%（高 Met）；整理剂：CP 18%（低 Met）和 20%（高 Met）] 和 2 个水平的甜菜碱补充剂（0 和 0.12%）。随着日粮蛋白质水平的增加，体重增加和饲料转化率显着提高（P < 0.05），但甜菜碱补充剂的结果不同。血清总蛋白、白蛋白、补充甜菜碱或 CP 均升高谷胱甘肽过氧化物酶 (GPx) (P < 0.05)。此外，与仅喂食低CP的组相比，喂食低CP量和0.12％甜菜碱的组的血清白蛋白浓度显着增加（P <0.05）。观察到饲喂高 CP 量或 0.12% 甜菜碱的肉鸡的总肠道消化率高于饲喂低 CP 量或未处理甜菜碱的组（P < 0.05）。补充甜菜碱影响排泄物中氨气的排放，低 CP 喂养组的硫化氢浓度显着降低（P < 0.05）。胸肉质量和相对器官重量不受 CP 水平或膳食甜菜碱补充剂的影响。这些结果表明甜菜碱不会提高生产力，但可能会影响血清总蛋白、白蛋白、GPx、肉鸡排泄物中氨的排放和氮的消化率。此外，在低 CP（低 Met）日粮中添加甜菜碱补充剂可更有效地提高血清白蛋白浓度。