肉牛玉米淀粉的消化率及其对氮沉积和能量转化效率的影响

The Digestibility of Corn Starch and Its Effect on Nitrogen Retention and Energy Conversion in Beef Cattle

研究了不同水平过瘤胃玉米淀粉量对能量代谢和氮沉积的影响。试验按４ ×４ 拉丁方设计，四头成年肉牛按１．２ 倍维持（１ ．２Ｍ） 饲养水平供给羊草，在此基础上过瘤胃生玉米淀粉量分别为０、３００ 、６００ 和９００ｇ／ｄ ，结果如下：过瘤胃玉米淀粉量为３００ 、６００ 和９００ｇ／ｄ 时玉米淀粉的瘤胃后消化率分别为６１ ．６３ 、７０ ．７８ 和５３．６４％ 。与对照组相比，过瘤胃玉米淀粉水平的增加可以提高可消化氮转化为沉积氮的效率（ＲＮ／ＤＮ） 和沉积氮（ＲＮ） ，ＲＮ（ｇ／ｄ）、ＲＮ／ＤＮ与过瘤胃玉米淀粉量（ｇ／ｄ） 之间有正相关，相关系数分别为０ ．９８８５ 和０ ．９６５７；过瘤胃玉米淀粉量３００、６００、９００ｇ／ｄ 与对照组相比，净能／ｋｇ 代谢体重（ＮＥｇ／Ｗ０ ．７５） 有极显著地提高（Ｐ＜ ０．０１），代谢能转化为体增重的效率（Ｋｆ） 分别为４８ ．２９ 、５５ ．９６ 、５５．２２ 和３６．１３％ ；Ｋｆ（ ％ ） 与过瘤胃玉米淀粉量（ｘ，ｇ／ｄ） 的回归方程为：Ｋｆ＝ ３４ ．０９３９ｘ０．０７０１７ ，ｎ ＝１６，ｒ＝ ０．９９０９。

The experiment estimated the effects of various levels of rumen by-pass corn starch on energy metabolism and nitrogen retention in beef cattle.Four mature steers with permanent rumen and abomasum cannulas were fed at 1.2 maintenance diet of Chinese wild rye as the basic diet according to a 4×4 Latin square design.The levels of rumen by-pass corn starch were 0,300g/d,600g/d and 900g/d,respectively.The results were as follows:The post-ruminal digestion of corn starch of 300g/d,600g/d and 900g/d groups were 61.63%,70.78%and 53.64%,respectively.Compared with the control group,the nitrogen retention/digestible nitrogen(RN/DN)and nitrogen retention(RN)(g/d) of 300g/d,600g/d and 900g/d groups increased significantly(P<0.05).RN/DN and RN showed positive linear correlation with rumen by-pass corn starch(r=0.9885 and r=0.9657 respectively).Compared with control group,net energy gain per kg metabolic weight(NEg/W 0.75 )of 300g/d,600g/d and 900g/d groups raised significantly(P<0.01),with the ratio of metabolizable energy converted into body weight(Kf(%)) as 48.29%,55.96%,55.22% and 36.13% respectively.Kf(%) has the following positive curve relation to the levels of rumen by-pass corn starch(x,g/d),Kf(%)=34.0939x 0.07017 ,r=0.9909,n=16.