饲粮能量水平对草原红牛代谢及血清指标的影响

Effects of Dietary Energy Levels on Metabolism and Serum Parameters of Steppe Red Cattle

【目的】探讨饲粮不同能量水平对草原红牛气体代谢、养分消化代谢及血清指标的影响,以期为草原红牛饲养标准的制订和高效饲养提供参考依据。【方法】选用12头体重相近(365.08±2.76)kg、健康的草原红牛公牛,随机分为3组,分别饲喂增重净能为5.65(低能组)、6.05(中能组)和6.43 MJ·kg^-1(高能组)的饲粮。试验期20 d,其中,预试期18 d,正试期2 d。正试期利用“大型动物开放回流式呼吸测热装置”开展呼吸测热试验,采用全收粪尿法开展消化代谢试验,试验结束前颈静脉采集血液样本分离血清,测定血清生化指标。【结果】高能组甲烷产生量、甲烷产生量占干物质采食量比例、氧气消耗量及产热量显著高于其他组,二氧化碳产生量显著高于中能组(P<0.05),且各项指标均随饲粮能量水平升高而线性升高(P<0.05)。能量代谢参数分析表明,各组消化能采食量、代谢能采食量、总能消化率、总能代谢率、粪能排泄量和尿能排泄量等指标均无显著差异(P>0.05),但高能组甲烷能排放量、甲烷能占总能比值显著高于其他组(P<0.05),且随饲粮能量水平的升高而线性升高(P<0.05)。饲粮能量水平对草原红牛氮代谢的各项指标均无显著影响(P>0.05)。饲粮能量水平对干物质、有机物、粗脂肪、中性洗涤纤维和酸性洗涤纤维的表观消化率均无显著影响(P>0.05),但干物质和有机物的表观消化率有随饲粮能量水平升高而升高的趋势(P=0.059)。高能组血清总甘油三酯水平显著高于其他两组(P<0.05),血清尿素氮显著低于其他两组(P<0.05),且均随饲粮能量水平升高呈线性变化(P<0.05)。其他各组间血清指标无显著差异(P>0.05)。【结论】适宜提高饲粮能量水平可提高草原红牛的养分利用率,但能量供给过高时会以甲烷能形式损失。综合来看以中能组效果最佳,推荐350 kg草原红牛适宜消化能和消化蛋白日供给量分别为128.12 MJ·d^-1、749.50 g·d^-1,代谢能和沉积蛋白日供给量分别为121.78 MJ·d^-1、678.75 g·d^-1,净能日供给量为55.96 MJ·d^-1。

【Objective】This study was carried out to investigate the effects of dietary energy levels on gas metabolism,nutrient digestion and serum parameter of Steppe Red cattle.【Method】A total of twelve healthy Steppe Red cattle with body weight of 365.08±2.76 kg were randomly allocated into three groups.Each group was subject to one of the following 3 diets:5.65,6.05,and 6.43 MJ·kg^-1 of net energy for gain,defining as LE,ME and HE,respectively.Experimental period was 20 days with 18 days of adaptive phase and 2 days of testing phase,respectively.Equipment of macrofauna open-type with respiration and calorimetric function was used for respiratory calorimetry trial and digestive and metabolic trial during testing phase.Blood samples were collected from jugular vein of Steppe Red cattle to isolate serum,and serum biochemical parameters were detected.【Result】Data showed that methane output,methane output as a proportion of dry matter intake,oxygen consumption,and heat production in HE group were higher than those of other groups,while carbon dioxide output in HE group was higher than that of ME group(P<0.05),and all the indices above increased linearly with the increase of dietary energy(P<0.05).Analysis of energy metabolism parameters showed that digestible energy intake,metabolic energy intake,gross energy digestibility,gross energy metabolic rate,fecal energy output and urine energy output were not affected by dietary treatments(P>0.05).Methane energy output and methane energy output as a proportion of gross energy in HE group were higher than other groups(P<0.05),and the two indices increased linearly as dietary energy level increased(P<0.05).Nitrogen metabolism indices did not differ among groups(P>0.05).Apparent digestibility of dry matter,organic matter,ether extract,neutral detergent fiber and acid detergent fiber were not affected by dietary energy level(P>0.05),whereas dry matter and organic matter apparent digestibility increased linearly with the increase of dietary energy(P=0.059).HE group exhibited increased serum total triglyceride and decreased urea nitrogen(P<0.05),and both indices were linearly changed as dietary energy level increased(P<0.05).Other serum parameters were not affected(P>0.05).【Conclusion】Overall,increasing dietary energy level could enhance nutrient utilization,whereas energy would lose in the form of methane energy when dietary energy level was too high.In general,medium energy group achieved the best energy utilization,and the appropriate supply quantity of the digestible energy and protein for 350 kg Steppe Red cattle were 128.12 MJ·d^-1 and 749.50 g·d^-1,respectively;the metabolic energy and protein were 121.78 MJ·d^-1 were 678.75 g·d^-1,respectively;the net energy for gain was 55.96 MJ·d^-1.