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.
J Anim Sci. 2021 Nov 1;99(11). doi: 10.1093/jas/skab291.
A diversity of forages with different types and concentrations of nutrients and plant secondary compounds may lead to complementary relationships that enhance cattle performance and welfare. We determined whether grazing combinations of tanniferous legumes (Lotus corniculatus, birdsfoot trefoil [BFT], Onobrychis viciifolia, sainfoin [SF]), and alfalfa [ALF] (Medicago sativa) influence foraging behavior, performance, and hair cortisol concentration in beef cattle compared with grazing the same legumes as monocultures. Twenty-one pairs of heifers grazed three spatial replications of seven treatments: monocultures of BFT, SF, or ALF, and all possible two- and three-way choices among strips of these legumes: SF-BFT, ALF-BFT, ALF-SF, and ALF-SF-BFT in two periods of 25 d each (adaptation phase + experimental period) during two consecutive years. The lowest incidence of grazing events occurred in the BFT treatment (42.0% of the total scans recorded; P < 0.10), with the rest of the treatments ranging between 47.8% (SF-BFT) and 52.6% (ALF-SF) of the total scans recorded. Heifers selected a varied diet, preferring SF over BFT or ALF in a 46:27:27 ratio for the three-way choice, and in a 70:30 ratio for both two-way choices. Heifers preferred BFT over ALF (62:38 ratio) in a two-way choice. All treatments followed similar daily grazing patterns (P > 0.10), with two major grazing events (1 h after sunrise and 3 h before dark). No differences among treatments were observed for the number of steps taken by heifers on a daily basis, motion index, or the percentage of time heifers spent standing (1,599, 5,356, and 45.3%, respectively; P > 0.10), suggesting that heifers on choice treatments did not invest extra time in walking, searching, or patch switching activities relative to heifers grazing monocultures. Heifers grazing the three-way choice gained more body weight (1.27 kg/d) than the average gains observed for animals grazing in all legume monocultures (1.00 kg/d; P = 0.014) or two-way choices (0.97 kg/d; P = 0.007), suggesting a synergism among pasture species for the treatment with the highest diversity. No differences in hair cortisol concentration were observed among treatments, with values ranging between 1.4 (BFT) and 2.12 ng/g (three-way choice; P > 0.10). Thus, forage diversity has the potential to enhance animal performance without affecting grazing efficiency, likely explained by the spatial arrangement of the forage species presented in the study.
多种具有不同类型和浓度的营养物质和植物次生化合物的饲料可能会产生互补关系，从而提高牛的性能和福利。我们确定了与单独放牧相比，放牧富含单宁的豆科植物（百脉根、三叶草、苦马豆、红豆草）和紫花苜蓿（Medicago sativa）的组合是否会影响肉牛的采食行为、性能和皮质醇浓度。21 对小母牛在 7 种处理的 3 个空间重复中放牧：三叶草、红豆草或紫花苜蓿的单播，以及这些豆科植物条带之间所有可能的两两和三三选择：SF-BFT、ALF-BFT、ALF-SF 和 ALF-SF-BFT，每个处理期为 25 天，共两个连续年份进行两个时期（适应期+实验期）。在记录的总扫描中，BFT 处理的采食事件发生率最低（42.0%；P < 0.10），其余处理的采食事件发生率在 47.8%（SF-BFT）到 52.6%（ALF-SF）之间。小母牛选择了多样化的饮食，在三选的情况下，小母牛更喜欢 SF 而不是 BFT 或 ALF，比例为 46:27:27，在两个二选的情况下，小母牛更喜欢 SF 而不是 ALF，比例为 70:30。小母牛在二选时更喜欢 BFT 而不是 ALF（62:38 比例）。所有处理的每日放牧模式相似（P > 0.10），有两个主要的放牧事件（日出后 1 小时和天黑前 3 小时）。小母牛每天行走的步数、运动指数或站立时间百分比在处理之间没有差异（分别为 1,599、5,356 和 45.3%；P > 0.10），这表明与单播相比，选择处理的小母牛在行走、寻找或斑块转换活动中没有投入额外的时间。放牧三选的小母牛比所有豆科单播（1.00 kg/d；P = 0.014）或两选（0.97 kg/d；P = 0.007）的平均增重（1.27 kg/d）更多，这表明在高多样性的处理中，牧草物种之间存在协同作用。处理之间的皮质醇浓度没有差异，范围在 1.4（BFT）和 2.12ng/g（三选；P > 0.10）之间。因此，饲料多样性有可能提高动物的性能，而不会影响放牧效率，这可能是由于研究中呈现的饲料物种的空间排列。
