Evidence in support of a role for plant-mediated proteolysis in the rumens of grazing animals

Abstract

The present work aimed to differentiate between proteolytic activities of plants and micro-organisms during the incubation of grass in cattle rumens. Freshly cut ryegrass was placed in bags of varying permeability and incubated for 16 h in the rumens of dairy cows that had previously grazed a ryegrass sward, supplemented with 4 kg dairy concentrate daily. Woven polyester bags (50 mm pore size) permitted direct access of the micro-organisms and rumen fluid enzymes to the plant material. The polythene was impermeable even to small molecules such as NH 3 . Dialysis tubing excluded micro-organisms and rumen enzymes/metabolites larger than 10 kDa. DM loss was 46·3 % in polyester, 36·2 % in polythene and 38·1 % in dialysis treatments. It is possible that the DM loss within polythene bags occurred due to a solubilisation of plant constituents (e.g. water-soluble carbohydrates) rather than microbial attachment/degradation processes. The final protein content of the herbage residues was not significantly different between treatments. Regardless of bag permeability, over 97 % of the initial protein content was lost during incubations in situ. Electrophoretic separation showed that Rubisco was extensively degraded in herbage residues whereas the membrane-associated, light-harvesting protein remained relatively undegraded. Protease activity was detected in herbage residues and bathing liquids after all incubation in situ treatments. Although rumen fluid contains proteases (possibly of plant and microbial origin), our results suggest that, owing to cell compartmentation, their activity against the proteins of intact plant cells is limited, supporting the view that plant proteases are involved in the degradation of proteins in freshly ingested herbage.

The potential of novel Festulolium (2n = 4x = 28) hybrids as productive, nutrient‐use‐efficient fodder for ruminants

“…; Kingston‐Smith et al. ) and hence current efforts to mitigate impact of ruminant farming through selection of improved forage genotypes. Shaw () demonstrated that Fg was significantly more stable under rumen‐like conditions than Lolium species.…”

“…Extensive nitrogen loss to the environment due to poor incorporation of dietary N by ruminants causes both pollution of ground water and contributes to nitrous oxide production. This is due to excessive proteolysis in the rumen, for which plant-mediated proteolysis is a contributory factor (Zhu et al 1999 ;Wallace et al 2001 ;Kingston-Smith et al 2005 ) and hence current efforts to mitigate impact of ruminant farming through selection of improved forage genotypes. Shaw ( 2006 ) demonstrated that Fg was signifi cantly more stable under rumen-like conditions than Lolium species.…”

Plant-based strategies towards minimising ‘livestock's long shadow’

“…However, how the plant cells die and how they use their endogenous constituents to prevent death has an impact on nutrient availability for the ruminal microorganisms. For instance, it has been demonstrated that exposing forage species to the ruminal conditions of heat and anoxia in the absence of a microbial inoculum is sufficient to promote rapid degradation of plant protein by the plant's own proteases (61)(62)(63) . Stress-induced proteolysis in plants is a phenomenon that has been widely reported for biotic and abiotic stresses (64)(65)(66)(67) .…”

A randomised, double-blind, placebo controlled cross-over study to determine the gastrointestinal effects of consumption of arabinoxylan-oligosaccharides enriched bread in healthy volunteers

“…The aim of probiotic and prebiotic inclusions into the diet are to increase beneficial gut bacteria and their activities, thus generating benefits to human health. These benefits include protection from gastroenteritis by pathogen inhibition [1], an improved tolerance to lactose [2], toxins [3] and cholesterol reduction [4], vitamin synthesis [3], improved mineral bioavailability [5], potential protection from bowel cancer [6-8], reduced symptoms of irritable bowel syndrome [9], improved digestion, gut function [10] and immune regulation [11]. …”