Animal and Grassland Research and Innovation Centre, Teagasc Moorepark, Fermoy, Co. Cork, P61 C996, Ireland; School of Agriculture and Food Science, University College Dublin, Belfield, Dublin 4, Ireland.
INRAE, L'institut Agro, Physiologie, Environnement et Génétique pour l'Animal et les Systèmes d'Elevage, F-35590 Saint-Gilles, France.
J Dairy Sci. 2021 Jun;104(6):6803-6819. doi: 10.3168/jds.2020-19246. Epub 2021 Mar 23.
The objective of this study was to investigate the effect of altering autumn pasture availability and farm system intensity on the productivity of spring-calving dairy cows during autumn. A total of 144 Holstein-Friesian and Holstein-Friesian × Jersey crossbred dairy cows were randomly assigned to 2 whole farm system (FS) intensities and 3 autumn pasture availability (PA; measured above 3.5 cm) treatments in a 2 × 3 factorial arrangement. The 2 farm systems consisted of a medium intensity (MI: 2.75 cows/ha, target postgrazing sward height of 4.0-4.5 cm) and high intensity system (HI: 3.25 cows/ha, target postgrazing sward height of 3.5-4.0 cm, + 1.8 kg of concentrate dry matter [(DM)/cow per day]. Within each farm system treatment, cows were further subdivided into 3 different PA management strategies: high PA (HPA), medium PA (MPA), and low PA (LPA). The experimental period lasted for 11 wk from September 1 to housing of all animals on November 20 (±2 d) over 3 yr (2017-2019, inclusive). To establish the different average pasture covers for each PA treatment during autumn and in particular at the end of the grazing season, grazing rotation length was extended by +13 and +7 d for HPA and MPA, respectively, beyond that required by LPA (37 d). There were no significant FS × PA interactions for any of the pasture, dry matter intake, or milk production and composition variables analyzed. There were also no differences in pregrazing sward characteristics or sward nutritive value between FS with the exception of daily herbage allowance, which was reduced for HI system (12.2 vs. 14.2 kg of DM/cow). Milk and milk solid yield were greater for HI groups (15.9 and 1.55 kg/cow per day, respectively) compared with MI (15.4 and 1.50 kg/cow per day, respectively). Mean paddock pregrazing herbage mass was significantly higher with increased PA ranging from a mean of 1,297 kg of DM/ha for LPA to 1,718 and 2,111 kg of DM/ha of available pasture for MPA and HPA, respectively. Despite large differences in pregrazing herbage mass, there was no difference in cumulative pasture production and only modest differences in grazing efficiency and sward nutritive value between PA treatments. On average, closing pasture covers were 420, 650, and 870 kg of DM/ha for LPA, MPA, and HPA, respectively, on December 1. In addition to maintaining similar grazing season lengths and achieving big differences in availability of pasture on farm into late autumn, PA treatment had no significant effect on dry matter intake, milk production, and body condition score during the study period. The results of this study indicate that greater cow performance and pasture utilization can be achieved through a greater daily concentrate allocation along with an increased stocking rate. Moreover, the potential to adapt grazing management practices to increase the average autumn pasture cover in intensive grazing systems is highlighted. In addition, a high dependence on high-quality grazed pasture during late autumn can be ensured without compromising grazing season length while also allowing additional pasture to be available for the subsequent spring.
本研究旨在探讨改变秋季牧场的可利用性和农场系统强度对秋季产犊奶牛春季生产性能的影响。共有 144 头荷斯坦奶牛和荷斯坦奶牛 × 泽西牛杂交奶牛被随机分配到 2 个全农场系统(FS)强度和 3 个秋季牧场可利用性(PA;测量值高于 3.5cm)处理中,采用 2×3 析因设计。2 个农场系统包括中等强度(MI:2.75 头/公顷,目标放牧后草地高度为 4.0-4.5cm)和高强度系统(HI:3.25 头/公顷,目标放牧后草地高度为 3.5-4.0cm,+1.8kg 浓缩物干物质[DM]/奶牛/天)。在每个农场系统处理中,奶牛进一步分为 3 种不同的 PA 管理策略:高 PA(HPA)、中 PA(MPA)和低 PA(LPA)。实验期为 3 年(2017-2019 年)的 9 月 1 日至 11 月 20 日(±2d)的 11 周,在此期间,所有动物都被关在圈里。为了在秋季,特别是在放牧季节结束时,为每个 PA 处理建立不同的平均牧场覆盖,HPA 和 MPA 的放牧轮牧长度分别延长了+13 和+7d,而 LPA(37d)则需要更长的时间。在分析的任何牧场、干物质摄入量或牛奶生产和组成变量方面,FS 与 PA 之间没有显著的相互作用。除了每日草料供应量外,FS 之间也没有在放牧前的草地特征或草地营养价值方面存在差异,HI 系统的每日草料供应量减少(12.2 与 14.2kg DM/奶牛)。HI 组的牛奶和牛奶固体产量更高(分别为 15.9 和 1.55kg/奶牛/天),而 MI 组(分别为 15.4 和 1.50kg/奶牛/天)。随着 PA 的增加,平均放牧前草地质量显著增加,从 LPA 的平均 1297kg DM/公顷到 MPA 和 HPA 的可用牧场分别为 1718 和 2111kg DM/公顷。尽管放牧前的草地质量存在很大差异,但 PA 处理之间在累积牧场产量和放牧效率以及草地营养价值方面没有差异。平均而言,12 月 1 日 LPA、MPA 和 HPA 的关闭牧场覆盖分别为 420、650 和 870kg DM/公顷。除了保持相似的放牧季节长度并在秋季后期实现农场牧场供应的巨大差异外,PA 处理对研究期间的干物质摄入量、牛奶产量和身体状况评分没有显著影响。本研究结果表明,通过增加每日浓缩物分配和增加饲养密度,可以实现更高的奶牛生产性能和牧场利用率。此外,强调了通过适应放牧管理实践来增加集约放牧系统中秋季平均牧场覆盖率的潜力。此外,在不影响放牧季节长度的情况下,可以确保在秋季后期对高质量放牧草地的高度依赖,同时还可以为随后的春季提供更多的牧场。