The effect of interval between harvests and nitrogen application on the proportion and digestibility of cell wall, cellulose, hemicellulose and lignin and on the proportion of lignified tissue in leaf cross-section in two perennial ryegrass varieties

Abstract

The effect of six intervals between harvests and two levels of N application on the proportion and digestibility of cell wall was studied in two perennial ryegrass (Lolium perenne) varieties in the first and second harvest years in a field experiment. In the oase of four of the six intervals between harvests the proportion and digestibility of cellulose, hemicellulose and lignin and the N content of cell wall were determined. Diets derived from three of the harvesting treatments were fed, at maintenance level, to sheep as a partial in vivo check on the in vitro procedures. The effect of six intervals between harvests and two levels of N application on the proportion of lignified tissue in leaf cross-section was determined in two varieties in the first harvest year.Effects of interval between harvests and time of year on herbage digestibility were due to effects on both proportion and digestibility of cell wall, particularly the latter. Hemicellulose digestibility appeared to be rather more affected by interval between harvests and rather more closely associated with the proportion of lignin than was cellulose digestibihty. The proportion of cell wall was particularly low and its digestibility particularly high in April and early May.The N in cell wall accounted for about 10% of total N in harvested herbage on all treatments. The ratio of cellulose to hemicellulose averaged 1:0-88 and hemicellulose was rather more digestible than cellulose. Cellulose and cell wall were less digestible in vitro than in vivo.The application of N tended to reduce the proportion of cell wall and to increase its digestibility in leafy but not in stemmy crops.Interval between harvests and N application had no effect on the proportion of lignified tissue in leaf cross-section.

In saccodegradation of organic matter and crude protein of fresh grass (Lolium perenne) in the rumen of grazing dairy cows

“…The decrease in FOM with increasing plant development may be due to increased lignification of NDF. An increase of indigestible NDF with maturation was observed by Wilman et al (1977). The decrease in rates of OM and CP degradation with maturation is believed to result not only from the increase in resistance of cell walls to microbial breakdown, which additionally will lead to a slower release of cell contents, but, in the case of CP, also from the increase in proportion of N associated with cell walls (Sanderson &Wedin 19896).…”

Effect of nitrogen fertiliser supply and winter cutting on morphological composition and herbage digestibility of aDactylis glomerata L sward in spring

“…On the other hand, other studies show that the nitrogen effect is small 8±10 and that it depends on the duration of the growth period. 11 Spring grazing usually tends to increase herbage digestibility, because stems are shorter. 12 Winter grazing has a similar effect.…”

Nitrogen concentrations in the cell wall and lignocellulose of smooth homegrass herbage*

“…Existing data are inconsistent on N fertilizer effects on NDFN (cell wall N) concentration. Wilman et al (1977) applied 525 kg of N ha"' to perennial ryegrass and observed no response in NDFN concentration. Wilman and Wright (1978) reported that N Tmble 3.…”

“…Few studies have examined N fertilizer effects on N concentrations in the cell wall (NDF) and lignocellulose (ADF) of grass. Whitehead et al (1986) reported that increasing amounts of N fertilizer on perennial ryegrass (Lolium perenne L.) increased total N, nitrate and water-soluble N concentrations, but did not affect concentrations of cell-wall N. Wilman et al (1977) showed no effect of N fertilizer on cell wall N as a percentage of total N. Wilman and Wright (1978), however, reported that applying N fertilizer increased slightly the concentration of cell wall N of perennial ryegrass. Field studies of herbage grasses have not examined nitrification inhibitor and ammonium-N fertilizer effects on cell wall N. There are no data on the effect of a legume-grass association on grass celi-wall N.…”