McCarthy B, Delaby L, Pierce K M, McCarthy J, Fleming C, Brennan A, Horan B
Animal and Grassland Research and Innovation Centre, Teagasc Moorepark, Fermoy, Co. Cork, Ireland.
INRA, AgroCampus Ouest, UMR 1348, Physiologie, Environnement et Génétique pour l'Animal et les Systèmes d'Elevage, F-35590 Saint-Gilles, France.
J Dairy Sci. 2016 May;99(5):3784-3797. doi: 10.3168/jds.2015-9763. Epub 2016 Feb 18.
The production and utilization of increased quantities of high quality pasture is of paramount importance in pasture-based milk production systems. The objective of this study was to evaluate the cumulative effects of alternative integrated grazing strategies, incorporating alternative stocking rate (SR) and grazing severities, on pasture productivity and grazing efficiency over multiple years within farm systems using perennial ryegrass dominant pastures. Three whole-farm SR treatments were compared over 4 complete grazing seasons (2009 to 2012 inclusive): low (2.51 cows/ha; LSR), medium (2.92 cows/ha; MSR), and high (3.28 cows/ha; HSR). Each system had its own farmlet containing 18 paddocks and remained on the same treatment for the duration of the study. Stocking rate had a significant effect on all grazing variables with the exception of soil fertility status and sward density. Increased SR resulted in increased total annual net pasture accumulation, improved sward nutritive value, and increased grazed pasture utilization. Total annual net pasture accumulation was greatest in HSR [15,410kg of dry matter (DM)/ha], intermediate for MSR (14,992kg of DM/ha), and least for LSR (14,479kg of DM/ha) during the 4-yr study period. A linear effect of SR on net pasture accumulation was detected with an increase in net pasture accumulation of 1,164.4 (SE=432.7) kg of DM/ha for each 1 cow/ha increase in SR. Pregrazing pasture mass and height and postgrazing residual pasture mass and height were greatest for LSR, intermediate for the MSR, and lowest for the HSR. In comparison with the LSR, the imposition of a consistently increased grazing severity coupled with increased whole farm SR in MSR and HSR treatments arrested the decline in sward nutritive value, typically observed during mid-season. Incorporating the individual beneficial effects of SR on pasture accumulation, nutritive value, and utilization efficiency, total proportional energy (unité fourragère lait) utilization per hectare increased significantly with increasing SR (+0.026 and +0.081 for MSR and HSR, respectively). These results quantify the significant effect of grazing management practices on the feed production capability of modern perennial ryegrass pastures for intensive grazing dairy production systems. Furthermore, these results highlight the importance of consistently imposing grazing treatments over multiple years, and within integrated whole farm systems, to accurately assess the longer term effects of alternate grazing management practices on pasture productivity.
在以牧草为基础的牛奶生产系统中，增加优质牧草的产量和利用率至关重要。本研究的目的是评估替代综合放牧策略（包括替代载畜率和放牧强度）对以多年生黑麦草为主的农场系统中多年牧草生产力和放牧效率的累积影响。在4个完整的放牧季节（2009年至2012年）比较了三种全农场载畜率处理：低（2.51头奶牛/公顷；低载畜率）、中（2.92头奶牛/公顷；中载畜率）和高（3.28头奶牛/公顷；高载畜率）。每个系统都有自己的包含18个围场的小农场，并在研究期间保持相同的处理。载畜率对所有放牧变量都有显著影响，但土壤肥力状况和草层密度除外。载畜率增加导致年总净牧草积累增加、草层营养价值提高和放牧牧草利用率提高。在4年研究期内，高载畜率下年总净牧草积累最大（15410千克干物质/公顷），中载畜率居中（14992千克干物质/公顷），低载畜率最小（14479千克干物质/公顷）。检测到载畜率对净牧草积累有线性影响，载畜率每增加1头奶牛/公顷，净牧草积累增加1164.4（标准误=432.7）千克干物质/公顷。放牧前牧草质量和高度以及放牧后残留牧草质量和高度在低载畜率下最大，中载畜率居中，高载畜率下最低。与低载畜率相比，中载畜率和高载畜率处理中持续增加的放牧强度与全农场载畜率增加相结合，阻止了草层营养价值在季节中期通常出现的下降。综合载畜率对牧草积累、营养价值和利用效率的个体有益影响，每公顷总比例能量（单位饲料牛奶）利用率随着载畜率增加而显著提高（中载畜率和高载畜率分别提高+0.026和+0.081）。这些结果量化了放牧管理措施对现代多年生黑麦草牧场集约化放牧奶牛生产系统饲料生产能力的显著影响。此外，这些结果突出了在多年内以及在综合全农场系统中持续实施放牧处理以准确评估替代放牧管理措施对牧草生产力长期影响的重要性。
