Data from: Modelling the effect of grazing management of tannin-containing legumes feeding sites on environmental impact by cows grazing grass-dominated rangelands swards

A model of a ruminant, MINDY, was used to explore the impact of grazing patches of tannin-containing legumes on environmental impact by cows grazing on grass-dominated rangelands swards. MINDY was initialized as a pregnant beef cow grazing on a grass (<i>Bromus biebersteinii</i>; meadow brome-Control), with the addition of a patch with tannin-containing legumes (<i>Lotus corniculatus</i>-birdsfoot trefoil-Tre, or <i>Onobrychis viciifolia</i>-sainfoin-Sain). Twenty-five scenarios (treatments) were established as a product of frequency (weekly, fortnightly, and monthly) and dietary proportions (0.05, 0.10, 0.15, and 0.20 of total forage allocation) of either Sain or Tre. Methane production and N excretion increased with legume availability. As legumes proportion increased, dry matter intake (DMI), animal performance, methane (CH4) production and urinary nitrogen (UN) excretion increased with a greater magnitude for Sain. Methane yield was lower than the Control at weekly allocation of legumes. Environmental costs in terms of CH4 emission increments per unit of production relative to Control were greater at monthly allocations when the levels of legume in the diet were low (0.5 to 0.10). Legumes in the diet at 0.15 to 0.20 yielded the lowest costs regardless of the frequency of allocation. Environmental costs in terms of UN increments per unit of production relative to Control were the lowest at 0.15-0.20 of legumes in the diet regardless of the frequency of allocation. This study suggests that strategic allocation of either sainfoin or birdsfoot trefoil when beef cattle graze grass-dominated rangelands swards can reduce environmental impact, while increasing secondary production of the system at the same levels of resource allocation.

本研究采用反刍动物模型MINDY，探究在以禾本科为主的草原牧场草地中放牧的肉牛，其采食含单宁类豆科植物斑块对环境影响的效应。模型初始设置为一头妊娠肉牛，采食草地雀麦（*Bromus biebersteinii*，Meadow Brome，对照组），并额外添加含单宁的豆科植物斑块，分别为百脉根（*Lotus corniculatus*，Birdsfoot Trefoil，简称Tre）与红豆草（*Onobrychis viciifolia*，Sainfoin，简称Sain）。本研究共设置25个处理场景，由两种豆科植物的施用频率（每周、每两周、每月）与日粮占比（总饲草分配的0.05、0.10、0.15、0.20）组合而成。甲烷产量与氮排泄量随豆科植物可获得性提升而升高。随着日粮中豆科植物占比增加，干物质采食量（Dry Matter Intake, DMI）、动物生产性能、甲烷（CH₄）产量与尿氮（Urinary Nitrogen, UN）排泄量均显著提升，且红豆草组的提升幅度更为显著。当每周施用豆科植物时，甲烷产率低于对照组。相较于对照组，以单位产量对应的甲烷排放增量计算的环境成本，在日粮豆科水平较低（0.05~0.10）且采用每月施用方式时更高。当日粮豆科占比为0.15~0.20时，无论施用频率如何，环境成本均最低。相较于对照组，以单位产量对应的尿氮排泄增量计算的环境成本，在日粮豆科占比为0.15~0.20时最低，且不受施用频率影响。本研究表明，在肉牛放牧于以禾本科为主的草原牧场草地时，战略性施用红豆草或百脉根，可在维持同等资源投入水平的前提下降低环境影响，同时提升系统的次级生产性能。