日粮中尿素氨化稻草水平对体外培养发酵总产气量、氨态氮和pH值的影响

本试验旨在研究日粮中添加不同比例的氨化稻草及精组比例对体外发酵产气规律的影响。以2头安装有永久性瘤胃瘘管的西门塔尔牛作为瘤胃液供体,以未氨化、4%尿素和6%尿素氨化的稻草为粗饲料,分别与精料混合料配制成6种比例日粮,其中精料与粗饲料的比例为0∶100、20∶80、40∶60、60∶40、80∶20、100∶0。采用体外产气法测定各种日粮体外发酵的产气规律。结果表明:同一尿素氨化水平下,随着精料比例增加,产气量显著增加(P<0.05),并且精料∶粗料为100∶0组极显著高于0∶100组(P<0.01);不同尿素氨化水平下,精料∶粗料为40∶60时,4%尿素氨化组48 h产气量显著高于未氨化组(P<0.05),并且高于6%氨化组,而精料∶粗料为0∶100、20∶80、60∶40、80∶20、100∶0时,3种尿素氨化水平产气量之间差异不显著(P>0.05)。表明使用4%尿素对稻草进行氨化处理、日粮精料∶粗料为40∶60时,日粮的可消化性最好。

Effect of Urea-Ammoniated Rice Straw on Total Gas Production,NH3-N and pH in vitro Incubation

The objective of the experiment was to study effects of urea-ammoniated straw rice and concentrate/roughage ratio on total gas production in vitro.Two Simmental cattle fitted with rumen cannulas were used as donors of rumen fluid.Rice straw ammoniated with three levels of urea,i.e.0%,4% and 6% urea was mixed with concentrates at six ratios,respectively.The concentrate/roughage ratios are 0∶100,20∶80,40∶60,60∶40,80∶20 and100∶0respectively.Total gas production was determined using in vitro incubation technique at 2,4,8,12,24,36 and 48 h,respectively.The results indicated that the to tal gas production increased with concentrate/roughage ratio in the same level of the urea-ammoniated rice straw,and concentrate/roughage ratio of 100∶0 group was significantly higher than 0∶100 group(P<0.01).The 48 h gas production of 4% urea-ammoniated rice straw was much higher than unammoniated rice straw(P<0.05),and higher than 6% urea-ammoniated rice straw when concentrate/roughage ratio was 40∶60.No differences were found in 48 h total gas production among three levels of urea-ammoniated rice straw in other groups(P>0.05).The results suggestedthat the digestibility of rations was the best when rice straw was ammoniated with 4% urea and mixed with concentrates at the ratio 40∶60.