The object of this experiment was to study the effect of adding different doses of exogenous com-pound enzyme preparation on in vitro rumen fermentation and milking performance of dairy cows. In the in vitro test, in vitro gas production method was applied, different doses of compound enzyme preparation with 0 ( control) , 0.5, 1.0 and 2.0 g/kg were added in substrate for 48 h simulate rumen fermentation in vitro, and the digestibility of nutrients in substrate, microbial protein ( MCP) production and in vitro fermentation param-eters were determined. In the animal test, eighty high-yielding Holstein multiparous dairy cows with similar milk production and days in lactation were selected and randomly assigned to each of the four groups according to randomized block design, and cows were fed compound enzyme preparation with 0 ( control) , 10, 20 and 40 g/(head·d) for 56 days, respectively. The In vitro test results showed that adding compound enzyme preparation in substrate had no significant effects on total gas production for 48 h, total volatile fatty acid ( VFA) concentration and the contents of individual VFA ( except isovalerate) ( P>0.05) , but significantly af-fected pH of fermentation fluid ( P=0.04) . With the increasing of adding dose of compound enzyme prepara-tion, acetate content tended to increase linearly (P=0.10), and butyrate content tended to decrease linearly ( P=0.07) . Adding compound enzyme preparation significantly increased degradation rate of neutral detergent fiber ( NDF) ( P<0.01) , and with the increasing of adding dose, the production of MCP tended to increase ( P=0.07) . The animal test results showed that adding compound enzyme preparation had no significant effect on milk production ( P>0. 05 ) , but milk production and 4% fat correction milk ( FCM ) production in 40 g/( head·d) group were the highest numerically, and were 1.4 and 2.6 kg/( head·d) higher than those in control group, respectively. Adding compound enzyme preparation had no significant effects on milk compo-sition rate and yield except solid no fat (SNF) rate (P>0.05), but the rates of milk fat and milk protein in 10 g/( head·d) group were the highest numerically, and were 0. 25 and 0. 01 percentage point higher than those in control group, and SNF rate in10 g/( head·d) group was significantly higher than that of the other groups ( P=0.04) . The above results indicate that adding exogenous compound enzyme preparation can affect in vitro rumen fermentation and nutrient digestion, and potentially affect milk production and milk composition rate in dairy cows, and the effects are dose dependent. Generally speaking, the recommended dose is 10 g/(head·d).%本试验旨在研究添加不同剂量的外源性复合酶制剂对体外瘤胃发酵以及奶牛产奶性能的影响. 体外试验采用体外产气法,在培养底物中添加0(对照)、0.5、1.0和2.0 g/kg的复合酶制剂,在体外模拟瘤胃发酵培养48 h,测定底物的营养物质降解率、微生物蛋白( MCP)产量及体外发酵参数. 动物试验利用高产荷斯坦奶牛开展,选择80头产奶量和泌乳天数接近的经产奶牛,分为4组,按照完全随机区组设计,将相同胎次的牛随机分配到各组中,分别饲喂0(对照)、10、20和40 g/(头·d)的复合酶制剂,试验期56 d. 体外试验结果表明:底物中添加复合酶制剂对体外48 h总产气量、总挥发性脂肪酸( TVFA)浓度和各挥发性脂肪酸( VFA)含量(除异戊酸含量外)没有显著影响( P>0.05) ,但显著影响发酵液pH( P=0.04). 随复合酶制剂添加量的增加,乙酸含量呈线性增加的趋势(P=0.10),丁酸含量呈线性下降的趋势(P=0.07). 复合酶制剂的添加显著提高中性洗涤纤维降解率( P<0.01) ,而且发酵液MCP产量随复合酶制剂添加量的增加呈上升趋势(P=0.07). 动物试验结果表明:饲粮中添加复合酶制剂对产奶量没有显著影响( P>0.05) ,但40 g/(头·d)组产奶量和4%校正乳产量在数值上最高,分别比对照组提高1.4和2.6 kg/(头·d). 除非脂固形物率外,饲粮中添加复合酶制剂对乳成分含量及产量没有显著影响( P>0.05) ,但10 g/(头·d)组乳脂率和乳蛋白率在数值上最高,分别比对照组高0.25和0.01个百分点,且该组奶牛的非脂固形物率显著高于其他组( P=0.04). 由以上2部分试验结果可见,添加外源性复合酶制剂会影响体外瘤胃发酵和营养物质的消化并潜在提高奶牛的产奶量和乳成分含量,且与复合酶制剂的添加量有关,综合考虑,推荐饲喂量为10 g/(头·d).
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