Herb species inclusion in grazing swards for dairy cows—A systematic review and meta-analysis

Abstract

A systematic review and meta-analysis were conducted to estimate the effect of herb species on milk production and urinary nitrogen (UN) excretion from grazing dairy cows. Grazing swards consisting of herb species grown with either a grass species or a grass and legume (multispecies swards) were compared with non-herbcontaining swards consisting of a grass species grown as a monoculture or grass-legume swards (simple swards). A literature search was completed using the online databases CAB Direct, Web of Science, and Google Scholar, using the search strategy "dairy cow", "herb OR forb OR phorb", and "grazing". Milk production data, variance, and sample size were required for eligibility. In all, 116 studies were identified. Following eligibility screening, 11 papers from 6 journals, published between 2006 and 2018, were available for analysis. Studies were from New Zealand (N = 7), Australia (N = 3), and the United States (N = 1). The population was either Holstein Friesian or Holstein Friesian × Jersey dairy cows, with a range in mean daily milk yield (MY) from 12.1 kg to 34.7 kg (mean = 18.6 kg). A total of 25 comparisons were used for milk production analysis, with 324 and 284 cows included in multispecies and simple sward groups respectively. Data analysis was conducted in R using a random effects, robust variance estimation model (R Foundation for Statistical Computing, Vienna, Austria). Heterogeneity was reported using the I 2 statistic. Milk production was significantly increased. Analysis of MY resulted in a weighted mean difference (WMD) of +1.20 kg/d (95% CI = 0.90, 1.49; I 2 = 4%). Fat and protein kg were also significantly increased (WMD +0.06 kg/d; CI = 0.01, 0.11). Urinary nitrogen excretion was estimated from milk urea nitrogen when reported (n = 6). A WMD of −28.1 g of N/d (95% CI = −81.1, 24.9) was generated, with heterogeneity high among studies (I 2 = 75%). This meta-analysis shows the potential benefits of multispecies swards. Although we saw no significant difference in UN excretion, an increase in milk production was found.

Animal board invited review: Grassland-based livestock farming and biodiversity

“…More recently, there has been growing research and agricultural industry interest in multispecies swards, and the potential that these offer for simultaneous delivery of environmental gains along with improved livestock performance ( Huyghe et al, 2012 , Grace et al, 2019 , McCarthy et al, 2020 , Cummins et al, 2021 ). More complex grasslands, such as these and semi-natural grasslands, allow greater opportunities for selective feeding, and the choices made by grazing animals can have a marked effect on floristic diversity.…”

Developments in nutrition for pasture-based cattle and sheep systems in Ireland

“…This increased understanding of pasture nutritive value, in regard to rumen turnover, metabolisable energy (ME) supply and post-ruminal AA flows, can aid in the development of future nutritional strategies to increase the efficiency and productivity of pasture-based systems. Such nutritional strategies could include development of improved pasture management practices (O'Donovan et al, 2002), optimisation of concentrate supplementation (Baudracco et al, 2010), selection of superior plant genetics (Lee et al, 2012) and the development of binary or multi-species pastures (McCarthy et al, 2020).…”

Clover in agriculture: combined benefits for bees, environment, and farmer

“…Diverse swards which incorporate a variety of legume and forb species may, therefore, increase herbage production, benefitting livestock performance, and may also improve soil nutrient retention and reducing leaching. Multispecies swards have been demonstrated to have dry matter yields comparable to grass-only or grass plus clover swards (Vibart et al 2016;McCarthy et al 2020). For instance, Vibart et al (2016) reported mean annual dry matter yields of 11,101 kg ha −1 and 12,021 kg ha −1 for simple and diverse pastures respectively.…”