The objective of this study was to determine the nitrogen balance of Holstein cows grazing on an intensive silvopastoral system (ISS) with wild sunflower (Tithonia diversifolia (Hemsl.) A. Gray) and kikuyu grass (Cenchrus clandestinus (Hochst. Ex Chiov) Morrone) or on a monoculture (MONO) of kikuyu grass, and supplemented with polyunsaturated fatty acids (PUFAs), in order to compare the efficiency of animal nitrogen use in both systems, which is important for sustainable animal production. A concentrate with three different lipid combinations was used: control concentrate (D1)—3% commercial saturated fat; concentrate 2 (D2)—1% soybean oil, 0.5% fish oil, and 1.5% of bypass fat rich in n-3 fatty acids; and concentrate 3 (D3)—2.5% soybean oil and 0.5% fish oil. The variables under study were analyzed during two rotations in a randomized complete block (RCB) design. The dry matter intake was evaluated by the marker’s method, using chromium oxide as an external marker and indigestible dry matter as an internal marker. The production of milk, urine, and feces was measured for 5 days to quantify nitrogen (N). The urine volume was estimated using creatinine. Nitrogen consumption (grams/day) was similar for cows in both systems (p > 0.05). A significantly higher excretion of N in the urine (p < 0.05) was found in the cows of the MONO group. The percent apparent nitrogen digestibility was higher (p < 0.05) in cows of the ISS group (75.68%) than in cows of the MONO group (73.95%). The N utilization efficiency was significantly higher (p < 0.05) in cows of the ISS group (23.24%) than in cows of the MONO group (19.39%). Therefore, the ISS with wild sunflower and unsaturated fat supplementation could be a positive strategy to improve the nitrogen balance and the productive efficiency of dairy cows in highland tropical regions, reducing the losses of nitrogen to the environment and contributing to the sustainability of the dairy production systems.

本研究的目的是确定荷斯坦奶牛在集约化林牧系统 (ISS) 上放牧野生向日葵 ( Tithonia diversifolia (Hemsl.) A. Gray )和基库尤草 ( Cenchrus clandestinus ) 的氮平衡。(Hochst. Ex Chiov) Morrone) 或基库尤草的单一栽培 (MONO)，并补充多不饱和脂肪酸 (PUFA)，以比较两种系统中动物氮利用的效率，这对于可持续动物生产很重要. 使用具有三种不同脂质组合的浓缩物：对照浓缩物 (D1)—3% 商业饱和脂肪；浓缩物 2 (D2)——1% 大豆油、0.5% 鱼油和 1.5% 富含 n-3 脂肪酸的旁路脂肪；和浓缩物 3 (D3)——2.5% 的豆油和 0.5% 的鱼油。在随机完整区组 (RCB) 设计中，在两次轮换期间分析了研究中的变量。干物质摄入量采用标记法评估，以氧化铬为外部标记，难消化干物质为内部标记。牛奶、尿液的产生，并测量粪便 5 天以量化氮 (N)。使用肌酐估计尿量。两种系统中奶牛的氮消耗量（克/天）相似（p  > 0.05)。 在 MONO 组的奶牛中发现尿液中 N 的排泄量显着更高（p < 0.05）。ISS 组奶牛的表观氮消化率百分比（75.68%）高于 MONO 组奶牛（ 73.95  %）。ISS组奶牛的氮利用效率（23.24%）显着高于MONO组奶牛（19.39%）（p  < 0.05）。因此，添加野生向日葵和不饱和脂肪的 ISS 可能是改善高原热带地区奶牛氮平衡和生产效率的积极策略，减少氮对环境的损失，有助于奶制品生产的可持续性系统。