Offered Papers Theme A: Efficient Production from Grassland

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It is necessary first to understand some of the basic concepts associated with the digestion of the plant biomass within the rumen when considering mechanisms for altering/enhancing N-conversion efficiency in the forage-fed ruminant. Although it is generally assumed that breakdown of plant proteins in the rumen is mediated by microbial enzymes, there is increasing evidence to suggest that both plant and microbial proteases are active during degradation of ingested fresh forage (Beha et al., 2002; Kingston-Smith & Theodorou, 2000; Kingston-Smith et al., 2003, 2004). After fresh plant biomass enters the rumen and prior to extensive plant cell wall degradation, there is often a phase of rapid proteolysis in excess of that needed to maintain the rumen microbial population and we now believe that plant enzymes largely mediate this initial proteolysis. Recent evidence also suggests a role for plant lipases in the rumen (Lee et al., 2003). An understanding of the mechanisms that underlie these processes is essential if we are to devise plant-based strategies to manipulate them. This paper presents a new rumen model which, by taking account of the plants biological attributes, provides us with a novel framework for describing the plant contribution to rumen function in grazing livestock.

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The Death of Plants in Animals

It is necessary first to understand some of the basic concepts associated with the digestion of the plant biomass within the rumen when considering mechanisms for altering/enhancing N-conversion efficiency in the forage-fed ruminant. Although it is generally assumed that breakdown of plant proteins in the rumen is mediated by microbial enzymes, there is increasing evidence to suggest that both plant and microbial proteases are active during degradation of ingested fresh forage (Beha et al., 2002; Kingston-Smith & Theodorou, 2000; Kingston-Smith et al., 2003, 2004). After fresh plant biomass enters the rumen and prior to extensive plant cell wall degradation, there is often a phase of rapid proteolysis in excess of that needed to maintain the rumen microbial population and we now believe that plant enzymes largely mediate this initial proteolysis. Recent evidence also suggests a role for plant lipases in the rumen (Lee et al., 2003). An understanding of the mechanisms that underlie these processes is essential if we are to devise plant-based strategies to manipulate them. This paper presents a new rumen model which, by taking account of the plants biological attributes, provides us with a novel framework for describing the plant contribution to rumen function in grazing livestock.