Thein vitrodigested cell wall and fermentation characteristics of grasses as affected by temperature and humidity during their growth

Abstract

Total cell wall, in vitro digested cell wall and fermentation-gas production were determined in the separated tops and stubble of five tropical and two temperate grass species grown under controlled temperatures and humidities. As the day/night temperatures increased from 18/10 to 25/17 C C the total cell wall and in vitro digested cell wall increased. With a further increase to 32/24 °C the total cell wall increased, but not the in vitro digested cell wall. In vitro digested cell-wall values were also calculated from a previously derived relationship between in vitro digested cell wall and total cell wall. The differences between observed and calculated values increased (negatively) with increasing growth temperature suggesting that the in vitro digested cell wall was depressed with increasing growth temperatures, but the extent of this depression was small.In vitro gas production from the fermentation of plant tops or stubble in buffered rumen fluid for 24 h was significantly affected by growth temperature and humidity, apparently because of changes in chemical composition induced by the treatments. The volume of gas produced between 24 and 48 h fermentation times was appreciably lower from stubble than from plant tops and this was thought to be due to a higher resistance of part of the cell wall of stubble to digestion by rumen bacteria. Gas production in this period was slightly lower in the tops of grasses grown at the lower temperatures, but this could have been an indirect effect from an associated decrease in the total cell wall.TMTROTyTTPTTOTtf digestible dry matter, and they were led to conclude that the digestibility of cell-wall material was The digested cell wall of both tropical and tern-reduced at the higher temperatures. As the in vitro perate grass species when expressed as an amount digestible cell wall was not directly determined in digested per 100 g forage organic matter tends to this experiment, the conclusion is not unequivocal, be constant (Moir, 1972a(Moir, , 1974. Variation about For the direct determination of in vitro digestible the 'constant' digested cell wall could be due to cell wall, protein and ash corrections are required genetic variation within grass species, or to envir-on the cell-wall residue from extraction of the on mental effects on the cell wall during growth of plant, and on the similarly extracted residue from the plant. A knowledge of factors influencing the in vitro digestion (Moir, 19726). This is a formidable digested cell wall could help plant breeders in the task when there are a large number of plant samples selection of grasses with a high content of digestible for analysis and may be impracticable in pot cell wall.experiments that yield only small amounts of plant In a factorial experiment in which grasses were tissues. Moir (1976) has described a simple method grown at different controlled temperatures and for demonstrating differences between plants in the humidities, Wilson, Taylor & Dolby (1976) found properties of their cell walls by measuring the that t...

Temperature effects on lignin, hemicellulose and cellulose in tropical and temperate grasses

“…This helps to explain the minimal change in DMD of the tropical species with temperature in the current experimental material (Wilson and Ford 1973) even though the cell wall content decreased, and the steeper fall in DMD at high temperatures compared with cell wall levels , associated with a decreased digestibility of the cell wall (Moir et al 1977).…”

Environmental Influences on Fiber Component Concentrations of Warm‐season Perennial Grasses1

“…Previous controlled-environment studies have investigated the effects of separate environmental influences on various quality indices of tropical and temperate grasses (2,4,5,6,7,8,10,13,16,17,18,20,21). Wilson and Minson (19) recently reviewed many of these relationships as they apply to tropical grasses.…”

Tiller Development Influences Seasonal Change in Cell Wall Digestibility of Big Bluestem(Andropogon gerardii)

“…Fales et a6 (1981) demonstrated that the xylose content of tall fescue increased in late spring and decreased in late summer, and attributed the variation in hemicellulose content to photoperiod length. The cell wall digestibility of both cool-and warm-season grasses decreases as temperature increases Dirven 1971, 1976;Moir et al 1977), and digestibility is further reduced by ageing (Deinum and Dirven 1975;Wilson 1976). Levels of p-coumaric ($A) and ferulic (FA) acids (Akin et al 1987), and of indigestible neutral detergent fibre (NDF) (Fales 1986) increase with temperature in tall fescue, suggesting that, at least in cool-season grasses, an increase in lignification contributes to the decrease in cell wall digestibility.…”