铜和叶酸对奶公牛消化率和血液代谢的影响

Effects of copper and folic acid on nutrient digestibility and blood metabolites in dairy calves

为揭示铜和叶酸对奶公牛消化率和血液代谢的影响,试验将12月龄、体重(401±2.9)kg的8头荷斯坦奶公牛,随机分为4组,采用2(4 mg/kg日粮干物质的叶酸或过瘤胃叶酸)×2(10 mg/kg日粮干物质的硫酸铜或过瘤胃硫酸铜)因子的4×4拉丁方设计。结果显示,过瘤胃叶酸提高了干物质、有机物、粗蛋白质、中性洗涤纤维和酸性洗涤纤维的消化率(P<0.05),但过瘤胃硫酸铜相反(P<0.05)。过瘤胃叶酸较叶酸降低了粪氮、尿氮和总排泄氮以及血清中甘油三酯、乙酰乙酸和同型半胱氨酸浓度(P<0.05),增加了沉积氮和沉积氮/消化氮以及血清中葡萄糖、白蛋白、总蛋白质、游离脂肪酸和叶酸浓度(P<0.05)。过瘤胃硫酸铜较硫酸铜提高了粪氮和总排泄氮以及血清中游离脂肪酸和甘油三酯浓度(P<0.05),降低了尿氮/总排泄氮以及血清中白蛋白、总蛋白质和总胆固醇浓度(P<0.05)。两者对白蛋白、总胆固醇和乙酰乙酸存在交互作用(P<0.05)。结果表明,过瘤胃叶酸和过瘤胃硫酸铜在蛋白质和脂质代谢中存在交互作用。过瘤胃叶酸的添加效果优于叶酸,而过瘤胃硫酸铜在本试验条件下可能造成了铜的过量摄入。

The objective of this study was to determine the effects of copper and folic acid on nutrient digestibility and blood metabolites in dairy calves.Eight Holstein dairy calves(12 mouths-of-age and 401±2.9 kg of body weight) were used in a replicated 4×4 Latin square experiment with a 2(10 mg copper per kg diet DM as copper sulfate or rumen-protected copper sulfate [RPCu])×2(4 mg/kg folic acid per kg diet DM as folic acid or rumen-protected folic acid) factorial arrangement of treatments.The results showed that the digestibility of dry matter,organic matter,crude protein,neutral detergent fiber and acid detergent fiber increased significantly by RPFA supplementation, whereas decreased significantly by RPCu supplementation(P<0.05). Compared with folic acid,RPFA supplementation reduced fecal nitrogen(FN),urine nitrogen(UN),total nitrogen excretion(TN) and the serum concentrations of triglyceride,acetoacetate and homocysteine(P<0.05),and increased nitrogen retention(RN),the ratio of RN to digestible nitrogen(DN) and serum concentrations of glucose,albumin,total protein,free fatty acid and folic acid for dairy calves(P<0.05).Compared with Cu,RPCu supplementation increased fecal nitrogen,total nitrogen excretion and serum concentrations of free fatty acid and triglyceride(P<0.05),decreased FN/TN and serum concentrations of albumin,total protein and cholesterol(P<0.05).Furthermore,the interaction effect was observed on albumin,total cholesterol and acetoacetic acid.The results indicated that there is an interaction between RPFA and RPCu in protein and lipid metabolism.Compared with FA,RPFA promoted the growth and metabolism of dairy calves.RPCu may caused excessive copper intake in the study.