Quantification of cytosol and membrane proteins in rumen epithelium of sheep with low or high CH4 emission phenotype.

BACKGROUND: Ruminant livestock are a major contributor to Australian agricultural sector carbon emissions. Variation in methane (CH4) produced from enteric microbial fermentation of feed in the reticulo-rumen of sheep differs with different digestive functions. METHOD: We isolated rumen epithelium enzymatically to extract membrane and cytosol proteins from sheep with high (H) and low (L) CH4 emission. Protein abundance was quantified using SWATH-mass spectrometry. RESULTS: The research found differences related to the metabolism of glucose, lactate and processes of cell defence against microbes in sheep from each phenotype. Enzymes in the methylglyoxal pathway, a side path of glycolysis, resulting in D-lactate production, differed in abundance. In the H CH4 rumen epithelium the enzyme hydroxyacylglutathione hydrolase (HAGH) was 2.56 fold higher in abundance, whereas in the L CH4 epithelium lactate dehydrogenase D (LDHD) was 1.93 fold higher. Malic enzyme 1 which converts D-lactate to pyruvate via the tricarboxylic cycle was 1.57 fold higher in the L CH4 phenotype. Other proteins that are known to regulate cell defence against microbes had differential abundance in the epithelium of each phenotype. CONCLUSION: Differences in the abundance of enzymes involved in the metabolism of glucose were associated with H and L CH4 phenotype sheep. Potentially this represents an opportunity to use protein markers in the rumen epithelium to select low CH4 emitting sheep.

The structure-toxicity relationship challenge at hazardous waste sites.

It is shown that the use of a combination of two programs, MULTICASE and META can help assess the carcinogenic risk factor posed by the disposal of industrial organic materials in the ecosystem. MULTICASE is a knowledge-based computer system that had been trained to identify molecular substructures believed to be conducive to carcinogenic potential and META is an expert system trained to predict the aerobic biodegradation products of organic molecules. The programs can be used to assess the health hazard of the discarded chemicals by evaluating their chemical structure, their biodegradability and the structures of the predicted biodegradation products. Several examples of the application of the methodology are described in this paper.

Rendering practices and inactivation of transmissible spongiform encephalopathy agents.

The authors describe the historic form of rendering and provide details on present-day practice. Possible future directions for the rendering industry are considered. The role of rendered meat-and-bone meal (MBM) as a dietary supplement in propagating the United Kingdom (UK) epidemic of bovine spongiform encephalopathy (BSE) is discussed, together with the role of MBM in spreading BSE outside the UK. Evidence that customarily used rendering processes did not substantially inactivate the agents of BSE or scrapie is presented. In addition, the influence that the abandonment of solvent extraction (as an adjunct to rendering) in the UK might have had on BSE infectivity levels in MBM is discussed. The BSE-related safety of tallow and by-products of tallow are considered. Data that associate the BSE agent with a new variant form of Creutzfeldt-Jakob disease in humans, predominantly but not exclusively, in the UK, are also discussed.

Bovine spongiform encephalopathy: the causal role of ruminant-derived protein in cattle diets.

Although bovine spongiform encephalopathy (BSE) has occurred in other European countries, the major epidemic has been in the United Kingdom (UK), where there have been more than 163,000 cases so far. BSE has been linked to the practice of feeding meat-and-bone meal (MBM), putatively contaminated with scrapie agent, to cattle. A ban on the feeding of MBM to ruminants in the UK has resulted in a significant decline in the number of reported cases. It is considered that BSE in other European countries probably originated through the use of British MBM in the diets of cattle in these affected countries. Recently, in the UK, a new variant form of Creutzfeldt-Jakob disease in humans has been discovered, which does not appear to have occurred before the advent of BSE. It may have been caused by BSE agent, possibly as a consequence of dietary exposure. The use of MBM in the diets of any livestock species has now been prohibited in the UK.

Inactivation of the bovine spongiform encephalopathy agent by rendering procedures.

Bovine brain infected with the bovine spongiform encephalopathy (BSE) agent was used to spike material processed in pilot scale facsimiles of 12 rendering processes which are used within the European Union, and three which are not. The raw materials for experimental rendering represented those used in practice, and consisted of appropriate proportions of BSE-infected brain tissue, bovine or porcine intestine, and bovine bone. Meat and bone meal, and tallow were produced from the rendered tissues. Suspensions of all the meat and bone meal samples were assayed in inbred mice for BSE infectivity, and two of the tallow fractions were tested similarly. Four of the 15 processes produced meat and bone meal with detectable BSE infectivity. Neither of the tallow samples had detectable infectivity.

Effect of rendering procedures on the scrapie agent.

A pool of scrapie-infected sheep brains was used to spike mixtures of porcine bone and intestine. These were processed in pilot-scale facsimiles of 12 rendering procedures that were in use within the European Union in 1991, and three that were not. Meat and bone meal, and tallow, were produced from the rendered tissues. Suspensions of all the meat and bone meal samples, and two of the tallow samples were assayed in mice for scrapie infectivity. Neither of the tallow samples had any detectable infectivity but the meat and bone meal samples were positive, except for those produced by processes involving exposure to hyperbaric steam. In addition, greaves were produced from the scrapie-spiked raw materials by an atypical low-temperature process and subjected to solvent extraction with hot heptane. The treated greaves were then exposed to steam to drive off residual solvent. Although the starting titre of infectivity in these greaves was low, there appeared to be no reduction in infectivity as a result of the treatments with hot heptane and steam. However, there was no detectable infectivity in the meat and bone meal prepared from the greaves produced by the atypical low-temperature process after it had been exposed to hyperbaric steam.