Cell‐Wall Concentration and Components in Stratified Canopies of Alfalfa, Birdsfoot Trefoil, and Red Clover¹

Abstract

Much of the Variability in digestibility and voluntary intake of herbage is closely associated with variation in cell‐wall (CW) concentration and components. This study was conducted to compare CW characteristics of total herbage and plant parts of alfalfa (Medicago sativa L.) birdsfoot trefoil (Lotus corniculatus L.), red clover (Trifolium pratense L.), and white clover (Trifolium repens L.), and to evaluate relationships between CW characteristics and in vitro digestible dry‐matter (IVDMD) concentration. Plants were sampled four times during spring growth and three times during summer regrowth. With the exception of white clover, subsamples were divided into leaves (leaf blades) and stems (remaining plant) and grouped by stem‐node segment. The CW concentration in total herbage generally was least in white clover and greatest in alfalfa. Within species, CW concentration was least for leaves and greatest for stem segments from plant bases. Stems of red clover had a lower CW concentration than stems of alfalfa or birdsfoot trefoil. Cell‐wall lignin concentration was greatest in birdsfoot trefoil and least in the two clover species. Within species, CW‐lignin concentrations of leaves and stems were similar. Both CW and CW‐lignin concentrations were inversely related to IVDMD concentration in stem segments and total herbage with correlation coefficients ranging from –0.40 to –0.98. The relationships was inconsistent in leaves. Inclusion both CW and CW‐lignin concentrations in linear multiple‐regression equations acounted for 95 and 84% of the observed variation in IVDMD concentration in stems and total herbage, respectively.

The effect of development stage on chemical composition of alfalfa leaf and stem

“…The data collected are consistent with a report by Ignjatović et al(1998), who found a higher content of NDF and ADF in the stem. Analysing NDF content in different stem segments and leaves of several leguminous plants, Buxton and Hornstein, 1986, found the highest amount of NDF in the stem base of alfalfa and lowest in its top leaves. Based on various studies, Minson (1990) concluded that the content of cell walls in leaves increased with plant age only up to 10%, so that declining quality of fibre feeds is closely related with a decreasing proportion of leaves in total plant biomass and reduced quality of stems.…”

“…This is consistent with the findings reported by Aman (1984), who found 20-60gkg -1 lignin in leaves and 50-120 gkg -1 DM in stalk. Buxton and Hornstein (1986) specified that lignin content was highest in the stalk base and lowest at the top.…”

Genetic Variation for Forage Quality of Alfalfa Stems

“…Kephart et al (1986) Growth habit was evaluated before the first harvest by using the five-point scale described by Small and Brookes (1984). From the harvested herbage, ten stems from each plot were evaluated for maturity via the mean-stage-by-count system described by Kalu and Fick (1981) Buxton and Hornstein 1986) (Table l). Likewise, Halim (1986) found that CW lignin concentration of alfalfa stems was not affected by severe, continuous water stress' Possibly CW lignin concentration could be used to screen for genotypes with potentially high stem digestibility.…”

Water-stress effects on forage quality of alfalfa

“…There was also a significant treatment x year interaction arising from the difference in stress levels within (Buxton et al, 1985;Buxton and Hornstein, 1986). …”

“…Table A5) lends support to this contention. Buxton et al (1986) reported CW concentration in stem bases of alfalfa ranging from 500 g kg~^ dry matter at the prebud stage up to 740 g kg"^ dry matter at the early-pod stage. They also found that the rate of increase in CW concentration of stem bases slowed at later harvests.…”