RUMINANT NUTRITION SYMPOSIUM: Improving cell wall digestion and animal performance with fibrolytic enzymes1

Using phase microscopy, the authors made studies of the formation and properties of spherical protoplasts of the organisms Candida utilis, Oospora suaveolens, and Geotrichum lactis, produced by digestion of the cell walls in isotonic medium with a lytic preparation obtained from the filtrates of the growth medium of Micromonospora AS. The susceptibility of various species of yeast and molds to cell wall digestion and further liberation of protoplasts was variable. MgSO4 (0.8 to 1.0 M final concentration) was a satisfactory stabilizer for producing osmotically sensitive spherical bodies. On dilution, these fragile structures lysed immediately. The naked protoplasts were able to grow, as indicated by changes in morphology. On prolonged incubation abnormal cells were formed. Reversion to normal cells was observed but was very rare. Details of the emergence of the Oospora suaveolens protoplasts were described. Protoplasts were also prepared from a variety of bacteria.

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Ruminal and total plant cell-wall digestibility estimated by a combinedin situmethod utilizing mathematical models

British Journal Of Nutrition ◽

10.1079/bjn19970176 ◽

1997 ◽

Vol 78 (4) ◽

pp. 583-598 ◽

Cited By ~ 14

Author(s):

Pekka Huhtanen ◽

Aila Vanhatalo

Keyword(s):

Cell Wall ◽

Incubation Period ◽

Plant Cell Wall ◽

Intestinal Cell ◽

Cell Wall Digestibility ◽

Stages Of Growth ◽

Cell Wall Digestion ◽

Intestinal Digestion ◽

Ruminal Digestion

Three ruminally and duodenally cannulated non-lactating Finnish Ayrshire cows were used to investigate ruminal and intestinal digestion of cell-wall carbohydrates by a combinedin situmethod. Five grasses cut at 10 d intervals were incubated in the rumen for 0, 6, 12, 24, 48, 72 and 96 h, and the undegraded residues were exposed to intestinal digestion. With advancing maturity of grass both the rate and extent of cell-wall digestion decreased. At early stages of growth the decreases were faster for the rate of digestion and at late stages of growth for the extent of digestion. Applying a passage rate of 0.02/h in one compartmental rumen model resulted in digestibility values markedly lower than typically observedin vivo.However, applying a rumen model incorporating a selective retention of particles and time-dependent release of particles from the non-escapable pool resulted in much higher digestibility values. Recovery of lignin after 96 h ruminal incubation with a subsequent mobile-bag incubation was very low (from 244 to 460 mg/g). Intestinal disappearance of neutral-detergent fibre (NDF) and hemicellulose decreased with advancing maturity of grass and with increasing length of preceding ruminal incubation period, i.e. with decreasing potential digestibility of the material. Disappearance of hemicellulose was much greater than that of cellulose for intact grasses but the difference diminished with increasing length of preceding rumen incubation period. On average, 195 mg/g of potentially digestible NDF disappeared from the mobile bags in the intestines. The post-ruminal digestion as a proportion of the total NDF digestibility varied between 0.034 and 0.058. Despite methodological problems both in ruminalin situand intestinal mobile bag techniques, these methods can be used to investigate ruminal and intestinal cell-wall digestion and to partition cell-wall digestibility between ruminal and post-ruminal digestion providing that appropriate rumen models are used.

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