Publications by authors named "Nicola D Walker"

There is an urgent requirement internationally to reduce enteric methane (CH4) emissions from ruminants to meet greenhouse gas emissions reduction targets. Dietary supplementation with feed additives is one possible strategy under investigation as an effective solution. The effects of the CH4 inhibitor 3-nitrooxypropanol (3-NOP) at reducing CH4 emissions in beef have been shown mainly in adult cattle consuming backgrounding and high-energy finishing diets.

View Article and Find Full Text PDF

While the physical dimensions of climate change are now routinely assessed through multimodel intercomparisons, projected impacts on the global ocean ecosystem generally rely on individual models with a specific set of assumptions. To address these single-model limitations, we present standardized ensemble projections from six global marine ecosystem models forced with two Earth system models and four emission scenarios with and without fishing. We derive average biomass trends and associated uncertainties across the marine food web.

View Article and Find Full Text PDF

Pelagic and benthic systems usually interact, but their dynamics and production rates differ. Such differences influence the distribution, reproductive cycles, growth rates, stability and productivity of the consumers they support. Consumer preferences for, and dependence on, pelagic or benthic production are governed by the availability of these sources of production and consumer life history, distribution, habitat, behavioural ecology, ontogenetic stage and morphology.

View Article and Find Full Text PDF

The objective of the current study was to employ a DNA-based sequencing technology to study the effect of active dry yeast (ADY) supplementation, diet type, and sample location within the rumen on rumen bacterial community diversity and composition, and to use an RNA-based method to study the effect of ADY supplementation on rumen microbial metabolism during high-grain feeding (HG). Our previous report demonstrated that the supplementation of lactating dairy cows with ADY attenuated the effect of subacute ruminal acidosis. Therefore, we used samples from that study, where 16 multiparous, rumen-cannulated lactating Holstein cows were randomly assigned to 1 of 2 dietary treatments: ADY (Saccharomyces cerevisiae strain Y1242, 80 billion cfu/animal per day) or control (carrier only).

View Article and Find Full Text PDF

The aim of this study was to identify ruminal bacteria that form stearic acid (18 : 0) from linoleic acid (cis-9,cis-12-18 : 2). One 18 : 0-producing isolate, P-18, isolated from the sheep rumen was similar in morphology and metabolic properties to 'Fusocillus' spp. isolated many years ago.

View Article and Find Full Text PDF

The Butyrivibrio group comprises Butyrivibrio fibrisolvens and related Gram-positive bacteria isolated mainly from the rumen of cattle and sheep. The aim of this study was to investigate phenotypic characteristics that discriminate between different phylotypes. The phylogenetic position, derived from 16S rDNA sequence data, of 45 isolates from different species and different countries was compared with their fermentation products, mechanism of butyrate formation, lipid metabolism and sensitivity to growth inhibition by linoleic acid (LA).

View Article and Find Full Text PDF

Peptidases of Prevotella spp. play an important role in the breakdown of protein to ammonia in the rumen. This study describes a peptidase cloned from Prevotella albensis M384.

View Article and Find Full Text PDF

Eubacterium pyruvativorans I-6(T) is a non-saccharolytic, amino-acid-fermenting anaerobe from the rumen, isolated by its ability to grow on pancreatic casein hydrolysate (PCH) as sole C source. This study investigated its metabolic properties and its likely ecological niche. Additional growth was supported by pyruvate, vinyl acetate, and, to a lesser extent, lactate and crotonate, and also by a mixture of amino acids (alanine, glycine, serine and threonine) predicted to be catabolized to pyruvate.

View Article and Find Full Text PDF

The aim was to investigate known and potential new inhibitiors of dipeptidyl peptidases (DPP) for their effects on ruminal microorganisms. Gly-Phe diazomethylketone (GPD), Ala-Ala chloromethylketone (AAC), benserazide (DL-serine 2-(2,3,4- trihydroxybenzyl) hydrazide), and diprotin A (Ile-Pro-Ile) inhibited DPP activities of Prevotella albensis, P. ruminicola, P.

View Article and Find Full Text PDF

Ruminal bacteria of the genus Prevotella play a crucial role in peptide breakdown in the rumen, a component of protein catabolism that leads to the inefficient use of dietary protein by ruminant animals. This is the first report of the cloning of a peptidase gene from a ruminal bacterium. Part of the dipeptidyl peptidase type IV (DPP-IV) gene from Prevotella albensis M384(T) was cloned using degenerate primers designed from conserved regions found within other known DPP-IV sequences.

View Article and Find Full Text PDF

A PHP Error was encountered

Severity: Warning

Message: fopen(/var/lib/php/sessions/ci_sessionjtb2mkvon4036e9t0nppdi195ofa8j6f): Failed to open stream: No space left on device

Filename: drivers/Session_files_driver.php

Line Number: 177

Backtrace:

File: /var/www/html/index.php
Line: 316
Function: require_once

A PHP Error was encountered

Severity: Warning

Message: session_start(): Failed to read session data: user (path: /var/lib/php/sessions)

Filename: Session/Session.php

Line Number: 137

Backtrace:

File: /var/www/html/index.php
Line: 316
Function: require_once