This study evaluated the effects of rumen-protected folic acid (RPFA) and betaine (BT) on growth performance, nutrient digestion and blood metabolites in bulls. Forty-eight Angus bulls were blocked by body weight and randomly assigned to four treatments in a 2 × 2 factorial design. BT of 0 or 0·6 g/kg DM was supplemented to diet without or with the addition of 6 mg/kg DM of folic acid from RPFA, respectively. Average daily gain increased by 25·2 and 6·29 % for addition of BT without RPFA and with RPFA, respectively. Digestibility and ruminal total volatile fatty acids of neutral-detergent fibre and acid-detergent fibre increased, feed conversion ratio and blood folate decreased with the addition of BT without RPFA, but these parameters were unchanged with BT addition in diet with RPFA. Digestibility of DM, organic matter and crude protein as well as acetate:propionate ratio increased with RPFA or BT addition. Ruminal ammonia-N decreased with RPFA addition. Activity of carboxymethyl cellulase, cellobiase, xylanase, pectinase and protease as well as population of total bacteria, protozoa, Fibrobacter succinogenes and Ruminobacter amylophilus increased with RPFA or BT addition. Laccase activity and total fungi, Ruminococcus flavefaciens and Prevotella ruminicola population increased with RPFA addition, whereas Ruminococcus albus population increased with BT addition. Blood glucose, total protein, albumin, growth hormone and insulin-like growth factor-1 increased with RPFA addition. Addition of RPFA or BT decreased blood homocysteine. The results indicated that addition of BT stimulated growth and nutrient digestion in bulls only when RPFA was not supplemented.

中文翻译：

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瘤胃保护叶酸和甜菜碱补充剂对安格斯公牛生长性能、营养消化、瘤胃发酵和血液代谢物的影响

本研究评估了瘤胃保护叶酸 (RPFA) 和甜菜碱 (BT) 对公牛生长性能、营养消化和血液代谢物的影响。48 头安格斯公牛被体重阻止，并以 2 × 2 因子设计随机分配到四个处理组。0 或 0·6 g/kg DM 的 BT 分别在不添加或添加 6 mg/kg DM 来自 RPFA 的叶酸的情况下添加到日粮中。不加 RPFA 和加 RPFA 的 BT 分别增加了 25·2 和 6·29 % 的平均日增重。中性洗涤纤维和酸性洗涤纤维的消化率和瘤胃总挥发性脂肪酸随着不添加 RPFA 的 BT 的添加而增加，饲料转化率和血叶酸降低，但在 RPFA 的日粮中添加 BT，这些参数没有变化。DM的消化率，添加 RPFA 或 BT 会增加有机质和粗蛋白以及乙酸：丙酸的比例。瘤胃氨氮随 RPFA 添加而降低。羧甲基纤维素酶、纤维二糖酶、木聚糖酶、果胶酶和蛋白酶的活性以及总细菌、原生动物、琥珀酸纤维杆菌和嗜淀粉瘤胃杆菌随着 RPFA 或 BT 添加而增加。漆酶活性和总真菌，黄瘤瘤胃球菌和普氏菌人口随着 RPFA 添加而增加，而白色瘤胃球菌人口随着BT的增加而增加。随着 RPFA 的添加，血糖、总蛋白、白蛋白、生长激素和胰岛素样生长因子-1 增加。添加 RPFA 或 BT 可降低血液同型半胱氨酸。结果表明，仅当不补充 RPFA 时，添加 BT 才能刺激公牛的生长和养分消化。