Betaine supplementation in dairy cattle has gained attention due to its potential benefits to production and health as a methyl donor, which can play a crucial role in the metabolism of dairy cows. The objective of the current meta-analysis was to quantify the effects of betaine supplementation on milk production, composition, beta-hydroxybutyric acid (BHBA), and non-esterified fatty acids (NEFA). A systematic literature search was carried out, all relevant studies were retrieved, and the meta-analysis was carried out. The mean difference (MD) for dry matter intake (DMI) using the random-effects model was 0.499 kg/day (P < 0.0001). The subgroup analysis indicated that supplementing betaine in heat-stressed cows increased DMI by 0.584 kg/day (P < 0.001), while in cows not exposed to heat stress, DMI was increased by 0.381 kg/day (P = 0.007). The energy-corrected milk (ECM) increased by 1.36 kg/day (P < 0.0001). The milk fat yield was significantly increased in betaine-supplemented cows (MD = 0.040 kg/day, 95% CI = 0.015 to 0.065). The milk protein yield (kg/day) (MD = 0.014, P = 0.138) was increased (MD = 0.035, P = 0.0005) by betaine supplementation. The lactose yield (kg/day) was also significantly higher (MD = 0.055, P = 0.020) in betaine-supplemented cows. The standardized mean difference (SMD) for NEFA (SMD = −0.447, 95% CI = −1.029 to 0.135, P = 0.114) and BHBA (SMD = −0.130, 95% CI = −0.491 to 0.234). In conclusion, the findings from this meta-analysis suggest that betaine supplementation positively influences DMI, ECM, milk fat yield, milk lactose yield, and milk protein yield. Subgroup analysis further indicated that the positive effects on DMI are greater in heat-stressed cows compared to those not exposed to heat stress. The analysis did not find significant effects on the levels of NEFA or BHBA, suggesting that betaine supplementation may not directly influence these metabolic parameters.

中文翻译：

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补充甜菜碱对奶牛干物质摄入量、牛奶特性、血浆非酯化脂肪酸和 β-羟基丁酸的影响：荟萃分析


奶牛补充甜菜碱因其作为甲基供体对生产和健康的潜在益处而受到关注，甲基供体在奶牛的新陈代谢中发挥着至关重要的作用。当前荟萃分析的目的是量化甜菜碱补充剂对产奶量、成分、β-羟基丁酸 (BHBA) 和非酯化脂肪酸 (NEFA) 的影响。进行了系统的文献检索，检索了所有相关研究，并进行了荟萃分析。使用随机效应模型的干物质摄入量 (DMI) 的平均差 (MD) 为 0.499 千克/天 (P < 0.0001)。亚组分析表明，在热应激奶牛中补充甜菜碱使 DMI 增加 0.584 kg/天 (P < 0.001)，而在未遭受热应激的奶牛中，DMI 增加 0.381 kg/天 (P = 0.007)。能量校正奶 (ECM) 增加了 1.36 千克/天 (P < 0.0001)。补充甜菜碱的奶牛的乳脂产量显着增加（MD = 0.040 kg/天，95% CI = 0.015 至 0.065）。补充甜菜碱可增加乳蛋白产量（公斤/天）（MD = 0.014，P = 0.138）（MD = 0.035，P = 0.0005）。补充甜菜碱的奶牛的乳糖产量（公斤/天）也显着更高（MD = 0.055，P = 0.020）。 NEFA（SMD = -0.447，95% CI = -1.029 至 0.135，P = 0.114）和 BHBA（SMD = -0.130，95% CI = -0.491 至 0.234）的标准化平均差 (SMD)。总之，这项荟萃分析的结果表明，补充甜菜碱对 DMI、ECM、乳脂产量、乳糖产量和乳蛋白产量产生积极影响。亚组分析进一步表明，与未遭受热应激的奶牛相比，热应激奶牛对 DMI 的积极影响更大。 分析没有发现对 NEFA 或 BHBA 水平有显着影响，这表明补充甜菜碱可能不会直接影响这些代谢参数。