Field indicators of leaf nutritive value for perennial ryegrass and tall fescue pastures under different growing and management conditions

Abstract

In livestock grazing-based systems, the timely knowledge of forage quantity and its nutritive value are essential for matching the herd demands. Usually, farmers use chemical in vitro analysis to determine nutritive value of pastures. However, these destructive methods are time-consuming, making it impractical to rapidly inform grazing management decisions. Alternatively, field indicators of nutritive AbstractField indicators of forage nutritive value could help farmers with rapid management decisions to optimize timing and intensity of grazing and meet objectives regarding animal nutrition. The objective of this research was to evaluate the likely relationships among leaf blade nutritive value, herbage mass and leaf stage of pasture regrowth under different growing seasons and residual sward heights. Experiments were performed on perennial ryegrass (Lolium perenne L.) and tall fescue (Festuca arundinacea Schreb.) pastures during spring and summer of 2016. In both pastures, three residual sward height treatments (3, 6 and 12 cm) were imposed on plots arranged in a split plot design, replicated in three blocks. Sward plots were harvested 5-6 times at intervals spaced 7-10 days apart to measure herbage mass, plant morphology, neutral detergent fibre (NDF), and the 24-hr in vitro digestibility of NDF (NDFD) and dry matter (DMD) of leaf blades. Pastures showed strong (R 2 : .62 to .70), but variable, negative relationships between NDFD and herbage mass that varied with the rate at which pasture grew in each season of experimentation. Although there was a consistent NDFD decline as leaf stage of regrowth progressed (R 2 : .75 to .97), the NDFD also decreased as residual sward height increased, most notably in tall fescue. Additionally, findings indicate that the greater leaf length plasticity of tall fescue compared to residual sward heights may offer opportunities to manage both post-and pre-grazing targets to achieve tall fescue forages with a similar high nutritive value as perennial ryegrass. However, the evaluation of this hypothesis at the farm level and its impacts on animal intake and performance warrants further careful investigations. K E Y W O R D Sforage nutritive value, herbage mass, leaf stage, leaf tissue digestibility, pasture management, plant morphogenesis

Forage yield gap analysis for tall fescue pastures in Argentina: A modelling approach

“…Darbysh.] is widely spread (Scheneiter et al, 2016) as a prime temperate, perennial grass species (Milne, 2009) that is better adapted to relatively less fertile soils and has similar nutritive value than perennial ryegrass (Lolium perenne L) (Insua et al, 2020).…”

“…Darbysh.] is widely spread (Scheneiter et al., 2016) as a prime temperate, perennial grass species (Milne, 2009) that is better adapted to relatively less fertile soils and has similar nutritive value than perennial ryegrass ( Lolium perenne L ) (Insua et al., 2020). Tall fescue has a relatively deep rooting system and tolerates dryer conditions and hotter weather than perennial ryegrass (Hannaway et al., 2009), which makes it more resilient under predicted increase in droughts due to climate change phenomena in vast grassland areas of the world (Norton et al., 2016).…”