The effects of growth temperature on digestibility and fibre concentration of seven temperate grass species

Abstract

The effects of growth temperature on digestibility and fibre concentration of seven grass species: Kentucky bluegrass (Poa pratensis L), timothy (Phleum pratense L), meadow foxtail (Alopecurus pratensis L), perennial ryegrass (Lolium perenne L), red fescue (Festuca rubra L), tufted hair-grass (Deschampsia caespitosa L (PB)) and meadow fescue (Festuca pratensis Huds) were investigated in growth chamber and greenhouse experiments. Seedlings from each grass species were established in a greenhouse and then transferred at five weeks of age to three growth chambers with day/night temperatures of 9/5, 13/9 and 17/13°C, respectively. Three pots of each species from each temperature treatment, and from the greenhouse control, were harvested weekly for three weeks. The rate of decline of in vitro true digestibility (IVTD) and in vitro cell wall digestibility (IVCWD) increased with increasing temperature for all species. Each degree of increase in temperature decreased the IVTD by an average of 0.22 g kg−1 dry matter (DM) day−1 between 9 and 13°C, and by 0.35 g kg−1 DM day−1 between 13 and 17°C. On average, the neutral detergent fibre (NDF) increased at a rate of 0.78 g kg−1 DM day−1 for each degree increase in temperature between 9 and 17°C. The effects of temperature were less for perennial ryegrass and meadow fescue than for the other species. Perennial ryegrass was consistently ranked as highest in digestibility, followed by meadow fescue; tufted hair-grass had the lowest digestibility. The rate of decline in digestibility was slower for perennial ryegrass and meadow fescue than for the other species.