An assessment of the quality of forage from its cell-wall content and amount of cell wall digested

Abstract

Grasses and legumes comprising poor to good quality temperate and tropical species were fed to either cattle or sheep in 36 digestibility experiments. Cell wall in these forages was the ash-free and protein-free residue after sequential extraction with acidpepsin, organic solvents and either water for grasses or ammonium oxalate for legumes. The average amount of cell wall digested per 100 g forage OM was 40-0 + 0-59 g in grasses and 19-8 ± 1-85 g in legumes. It was considered that within grasses and within legumes the physiology of ruminant digestion, rather than forage quality, was the main determinant of the average amount of cell wall digested and the difference between grasses and legumes was due to interaction of the ruminant digestion process with the physical structure of the cell wall. Of forage factors governing variation about the physiological average, the total cell wall had some effect on the amount of cell wall digested, but the lignin concentration in the cell wall had no effect.Among grasses and legumes the average, apparently undigested, protein-free non-cell-wall component was 6-2 ±0-13 g per 100 g forage OM. This component and digestible protein relative to total protein varied among different sets of data. It was concluded that only the component of digestible organic matter which was governed by the relative proportions of cell walls and cellular contents was predictable from chemical composition. It was considered that selection in plant breeding should be based on both digestible cell wall and cell-wall content instead of digestible organic matter.

Digestible cell wall and undigested cellular contents of two grasses of low net energy value for growing cattle

“…Digestible cell-wall values of 41 and 37 % for the two grasses were close to 40 % of forage OM, as has been found in other grasses (Moir, 19726). At 14% of forage OM, apparently undigested total cellular contents were only a little higher than values found by Moir, Laws & Blight (1975).…”

“…With suitable equipment the sequential procedure is adaptable to large-scale work and it has been used in a number of studies of forage digestibility. Moir (19726) found by this procedure that digestible cell wall (% cell wallx% digestibility/100) was relatively constant at about 40% of forage organic matter (OM) over a wide range of both temperate and tropical grass species. The apparently undigested cellular contents varied only between 9 and 13% of forage OM (Moir, 1974;Moir, Laws & Blight, 1975).…”

“…The apparently undigested cellular contents varied only between 9 and 13% of forage OM (Moir, 1974;Moir, Laws & Blight, 1975). Protein-free apparently undigested cellular contents ranged between 4-8 and 7-2% of forage OM, with lowest values in forage of low cell-wall content (Moir, 1974), and highest values in forage of high cell-wall content (Moir, 19726).…”

Differences between related grasses, times of year and plant parts in digestibility and chemical composition

“…There is some evidence that the proportion of should be made up as far as feasible with cell content cell content is lower and the digestibility of cell wall (which is quickly available and has a positive effect on higher in perennial than in Italian ryegrass (Wilman intake) rather than with cell wall (which is digested & Wright 1978 a, b). more slowly and can restrict intake) (Moir 1972; Italian ryegrass may be higher than perennial Osbourn et al 1974) and there should be an ryegrass in water-soluble carbohydrate (WSC) appropriate balance of soluble carbohydrate and (Spedding & Diekmahns 1972) and perennial ryegrass protein, probably with a higher proportion of soluble may be higher than meadow fescue (Dent & Aldrich carbohydrate than is commonly found (Beever 1993(Beever ). 1963Moller et al 1973).…”

Roles of structural phenylpropanoids in forage cell wall digestion

“…Animal physiology also plays an important role (Moir 1972). It has been shown that Camelidae use fibre more efficiently than sheep (Kayouli et a1 1991).…”