Effects of Diet Categories on Feces/Urine Features of Dairy Cows and Nitrogen Emission

摘要

[Objective]Through study of different diet categories' effects on lactating cows' feces/urine features and nitrogen emission, and in order to reduce and control the nitrogen emission.[Method]12 China Holsteins each with the weight of 514 kg and at the age of 3 to 5 years old are selected for this experiment to carry out test and research on their feces/urine features and nitrogen emission. The cows are divided into 3 groups which are fed with Diet A which takes dry corn straw as forage with forage to concentrate ratio of 40∶ 60, Diet B and Diet C (both take corn silage as forage) with forage to concentrate ratio of 40∶ 60 and 60∶ 40 respectively. [Result]The results show that diet categories have certain effects on dairy cows' output of feces and urine. Feces output of Diet A (straw type) is more than that of Diet B (silage type with low forage to concentrate ratio) which is more than that of Diet C (silage type with high forage to concentrate ratio). Feces output of Diet A group exceeds that of Diet B and Diet C groups by 6.10% and 10.08% respectively. Feces output of Diet B exceeds that of Diet C by 3.75%. The difference is insignificant(P﹥0.05). In terms of urine output of these three diet groups, Diet C is more than that of Diet B which is more than that of Diet A. Urine output of Diet C exceeds that of Diet B and Diet A by 22.75% and 56.30% respectively. Urine output of Diet B exceeds that of Diet A by 27.33%. The difference is significant(P﹤0.05). At the same time, diet categories have significant effects on dairy cow's nitrogen balance. Straw-typed diet's milk nitrogen and urinary nitrogen contents as well as nitrogen digestibility are far lower than those of silage-typed diet (P﹤0.01). Under conditions of taking corn silage as forage, as diet's concentrate refines, nitrogen digestibility and urinary nitrogen both increase remarkably (P﹤0.01) while fecal nitrogen and milk nitrogen's increase is not obvious (P﹥0.05). [Conclusion]Moreover, it shows that Straw-typed diet's absorbed nitrogen is mainly discharged through feces. When corn silage is taken as forage, as diet's concentrate refines, proportion of fecal nitrogen reduces while that of urinary nitrogen increases, and fecal nitrogen and urinary nitrogen's proportions in total feces/urine nitrogen are basically the same.