Department of Wildland Resources, Quinney College of Natural Resources, Utah State University, Logan, UT 84322, USA; Estación Experimental Agropecuaria Bordenave, Instituto Nacional de Tecnología Agropecuaria. Bordenave, Buenos Aires 8187, Argentina.
Agriculture and Agri-Food Canada, Lethbridge Research and Development Centre, Lethbridge, AB T1K 4H3, Canada.
Sci Total Environ. 2020 Dec 1;746:140788. doi: 10.1016/j.scitotenv.2020.140788. Epub 2020 Jul 12.
We tested the effect of increasingly diverse combinations of tanniferous legumes (birdsfoot trefoil-BFT, sainfoin-SF) and alfalfa (ALF) on cattle performance, methane (CH) emissions and nitrogen (N) balance. Pairs of heifers (401 ± 49.6 kg) grazed three spatial replications of 7 treatments (n = 3/treatment): monocultures (BFT, SF, ALF) and all possible 2- and 3-way choices among strips of these legumes in a completely randomized block design of two 15-d periods during 2 consecutive years. Average daily gains (ADG) of heifers grazing the tanniferous legumes (1.05 kg/d) were 40% greater (p < 0.10) than of heifers grazing ALF (0.74 kg/d) during the first year. Heifers grazing the 3-way choice had greater intakes (10.4 vs 7.8 kg/d; p = 0.064) and ADG (1.21 vs. 0.95 kg/d, p = 0.054) than those grazing monocultures, suggesting a nutritional synergism among legumes. The average CH emissions for legume monocultures vs. 2- and 3- way choices was 222 vs. 202 and 162 g/kg BW gain (p > 0.10), respectively. For heifers grazing SF and BFT compared with ALF, blood urea N was less (14.3 and 16.8 vs 20.8 mg/dL; p < 0.05) as were urinary N concentrations (3.7 and 3.5 vs 6.0 g/L; p < 0.05), but fecal N concentrations were greater (34.5 and 35.5 vs 30.5 g/kg, respectively; p < 0.05). Combining both tanniferous legumes (SF-BFT) led to the greatest declines in urinary N (2.24 g/L) and urea-N (1.71 g/L) concentration, suggesting that different types of tannins in different legumes result in associative effects that enhance N economy. In addition, heifers grazing 3-way choices partitioned less N into urine (40.7 vs 50.6%; p = 0.037) and retained more N (36.1 vs 25.2%, p = 0.046) than heifers grazing monocultures. In summary, combinations of tanniferous legumes with alfalfa improved animal performance and reduced environmental impacts relative to monocultures, resulting in a more sustainable approach to beef production in pasture-based finishing systems.
我们测试了富含单宁的豆科植物（红三叶草-BFT、苦马豆素-SF）和紫花苜蓿（ALF）的不同组合对牛生产性能、甲烷（CH）排放和氮（N）平衡的影响。每对小母牛（401±49.6kg）在 7 种处理的 3 个空间重复（n=3/处理）中放牧：小母牛在两年的连续两个 15 天期间，在完全随机的块设计中，以条状形式放牧单一种植（BFT、SF、ALF）和这些豆科植物之间的所有可能的 2 种和 3 种选择。第一年，放牧富含单宁的豆科植物（1.05kg/d）的小母牛的平均日增重（ADG）比放牧 ALF（0.74kg/d）的小母牛高 40%（p<0.10）。放牧 3 种选择的小母牛的摄入量（10.4 比 7.8kg/d；p=0.064）和 ADG（1.21 比 0.95kg/d，p=0.054）高于放牧单种植的小母牛，表明豆科植物之间存在营养协同作用。富含单宁的豆科植物单种植与 2 种和 3 种选择的平均 CH 排放量分别为 222 和 202 和 162g/kg BW 增重（p>0.10）。与 ALF 相比，放牧 SF 和 BFT 的小母牛的血液尿素氮较低（14.3 和 16.8 比 20.8mg/dL；p<0.05），尿液氮浓度较低（3.7 和 3.5 比 6.0g/L；p<0.05），但粪便氮浓度较高（34.5 和 35.5 比 30.5g/kg，分别；p<0.05）。结合两种富含单宁的豆科植物（SF-BFT）导致尿液氮（2.24g/L）和尿素氮（1.71g/L）浓度的最大下降，表明不同豆科植物中的不同类型的单宁会产生增强氮素利用的协同作用。此外，放牧 3 种选择的小母牛将较少的氮排入尿液（40.7 比 50.6%；p=0.037）并保留更多的氮（36.1 比 25.2%，p=0.046），而不是放牧单种植的小母牛。总之，与单种植相比，富含单宁的豆科植物与紫花苜蓿的组合提高了动物生产性能并减少了环境影响，从而为牧场育肥系统中的牛肉生产提供了更可持续的方法。
