In dairy production systems, the use of strategies to increase production can be used, however some care must be taken to avoid the loss of nitrogen in the system, which is directly related to the environmental impacts. The aim with this study was to evaluate and the effect of the use of CP levels in concentrate in intensive systems on the productive performance and nitrogen metabolism of dairy cows in a tropical forage-based system. Sixteen multiparous Holstein-Zebu crossbreed cows in the middle and final third of lactation were used in a replicated 4 × 4 Latin square design with a 2 × 2 factorial arrangement of treatments design with 2 grazing systems (traditional and intensive) and 2 CP levels (18 and 22% CP) in concentrate. In intensive system, fertilization and irrigation were performed, while in traditional system, there was no fertilization and irrigation. Grazing systems affected all milk yield and composition variables, except for milk protein and solids. Greater milk yield was observed for cows in intensive system. Milk solids content was greater for cows supplemented with 18% CP level. Milk fat, protein, lactose, and solids yield was greater for cows in intensive system. Nitrogen use efficiency was greater for cows in traditional system. Milk N excreted was similar between supplemented cows, however, it was greater for cows in intensive system compared to cows in traditional system as well as 22% CP level. There was a grazing systems effect for ruminal ammonia nitrogen concentration with lesser values for cows in traditional system. The 22% CP level increased ruminal ammonia nitrogen. The results obtained in this study showed that cows in pastures under intensive system showed protein and energy imbalance in the rumen. The increase in CP levels does not affect the productive characteristics of these animals, only resulting in higher costs and higher N excretion to the environment.

在乳制品生产系统中，可以使用增加产量的策略，但是必须小心避免系统中氮的损失，这与环境影响直接相关。这项研究的目的是评估在集约化系统中使用CP浓度对热带饲草系统中奶牛的生产性能和氮代谢的影响。泌乳中期和哺乳期最后三分之一的16头荷斯坦-泽布杂种奶牛用于复制的4×4拉丁方设计，采用2×2因子排列的处理设计，带有2个放牧系统（传统和集约化）和2 CP水平（浓度为18％和22％CP）。在集约化系统中，进行施肥和灌溉，而在传统系统中，没有施肥和灌溉。除牛奶蛋白和固体外，放牧系统影响所有牛奶产量和成分变量。在集约化系统中，奶牛的产奶量更高。补充了18％CP水平的奶牛的乳固体含量更高。在集约化系统中，牛奶的脂肪，蛋白质，乳糖和固体产量更高。在传统系统中，母牛的氮利用效率更高。补充奶牛之间排出的牛奶N相似，但集约化系统中的牛奶N高于传统系统中的牛奶，CP水平为22％。放牧系统对瘤胃中氨氮浓度的影响较小，而传统系统中对奶牛的影响较小。22％的CP水平增加了瘤胃氨氮。这项研究获得的结果表明，在集约化系统下的牧场中，牛的瘤胃中蛋白质和能量不平衡。CP水平的增加不会影响这些动物的生产特性，只会导致更高的成本和对环境的N排泄。