Beef production from feedstuffs conserved using new technologies to reduce negative environmental impacts

End of project reportMost (ca. 86%) Irish farms make some silage. Besides directly providing feed for livestock, the provision of grass silage within integrated grassland systems makes an important positive contribution to effective grazing management and improved forage utilisation by grazing animals, and to effective feed budgeting by farmers. It can also contribute to maintaining the content of desirable species in pastures, and to livestock not succumbing to parasites at sensitive times of the year. Furthermore, the optimal recycling of nutrients collected from housed livestock can often be best achieved by spreading the manures on the land used for producing the conserved feed. On most Irish farms, grass silage will remain the main conserved forage for feeding to livestock during winter for the foreseeable future. However, on some farms high yields of whole-crop (i.e. grain + straw) cereals such as wheat, barley and triticale, and of forage maize, will be an alternative option provided that losses during harvesting, storage and feedout are minimised and that input costs are restrained. These alternative forages have the potential to reliably support high levels of animal performance while avoiding the production of effluent. Their production and use however will need to advantageously integrate into ruminant production systems. A range of technologies can be employed for crop production and conservation, and for beef production, and the optimal options need to be identified. Beef cattle being finished indoors are offered concentrate feedstuffs at rates that range from modest inputs through to ad libitum access. Such concentrates frequently contain high levels of cereals such as barley or wheat. These cereals are generally between 14% to 18% moisture content and tend to be rolled shortly before being included in coarse rations or are more finely processed prior to pelleting. Farmers thinking of using ‘high-moisture grain’ techniques for preserving and processing cereal grains destined for feeding to beef cattle need to know how the yield, conservation efficiency and feeding value of such grains compares with grains conserved using more conventional techniques. European Union policy strongly encourages a sustainable and multifunctional agriculture. Therefore, in addition to providing European consumers with quality food produced within approved systems, agriculture must also contribute positively to the conservation of natural resources and the upkeep of the rural landscape. Plastics are widely used in agriculture and their post-use fate on farms must not harm the environment - they must be managed to support the enduring sustainability of farming systems. There is an absence of information on the efficacy of some new options for covering and sealing silage with plastic sheeting and tyres, and an absence of an inventory of the use, re-use and post-use fate of plastic film on farms. Irish cattle farmers operate a large number of beef production systems, half of which use dairy bred calves. In the current, continuously changing production and market conditions, new beef systems must be considered. A computer package is required that will allow the rapid, repeatable simulation and assessment of alternate beef production systems using appropriate, standardised procedures. There is thus a need to construct, evaluate and utilise computer models of components of beef production systems and to develop mathematical relationships to link system components into a network that would support their integration into an optimal system model. This will provide a framework to integrate physical and financial on-farm conditions with models for estimating feed supply and animal growth patterns. Cash flow and profit/loss results will be developed. This will help identify optimal systems, indicate the cause of failure of imperfect systems and identify areas where applied research data are currently lacking, or more basic research is required

Analysis of the mechanical performance of a biodegradable magnesium stent in a remodelling artery

Coronary stents made from degradable biomaterials such as magnesium alloy are an emerging technology in the treatment of coronary artery disease. Biodegradable stents provide mechanical support to the artery during the initial scaffolding period after which the artery will have remodelled. The subsequent resorption of the stent biomaterial by the body has potential to reduce the risk associated with long-term placement of these devices, such as in-stent restenosis, late stent thrombosis, and fatigue fracture. Computational modelling such as finite-element analysis has proven to be an extremely useful tool in the continued design and development of these medical devices. What is lacking in computational modelling literature is the representation of the active response of the arterial tissue in the weeks and months following stent implantation, i.e., neointimal remodelling. The phenomenon of neointimal remodelling is particularly interesting and significant in the case of biodegradable stents, when both stent degradation and neointimal remodelling can occur simultaneously, presenting the possibility of a mechanical interaction and transfer of load between the degrading stent and the remodelling artery. A computational modelling framework is developed that combines magnesium alloy degradation and neointimal remodelling, which is capable of simulating both uniform (best case) and localised pitting (realistic) stent corrosion in a remodelling artery. The framework is used to evaluate the effects of the neointima on the mechanics of the stent, when the stent is undergoing uniform or pitting corrosion, and to assess the effects of the neointimal formation rate relative to the overall stent degradation rate (for both uniform and pitting conditions). Experimental mechanical and corrosion testing is conducted to characterise the mechanical and corrosion behaviour of magnesium WE43 alloy, a candidate base material for biodegradable magnesium stents. Previously developed uniform and pitting corrosion models are calibrated based on in vitro mechanical and corrosion testing of magnesium WE43 alloy specimens. The calibrated pitting corrosion model can capture the mechanical and corrosion behaviour of magnesium WE43, including the vii experimentally observed non-linear reduction in failure strength with mass loss, whereas the uniform corrosion model is incapable of capturing this trend. An enhanced computational modelling framework is developed, building on the previous investigations, that combines magnesium alloy degradation and neointimal remodelling in order to simulate corrosion of a magnesium stent in a remodelling artery. The enhanced computational modelling framework, accounts for two major physiological stimuli responsible for neointimal remodelling and is combined with the magnesium stent pitting corrosion model, which has been calibrated for Mg WE43 alloy. The enhanced modelling framework is used to simulate different neointimal growth patterns and to explore the effects the neointimal remodelling has on the mechanical performance (scaffolding support) of a bioabsorbable magnesium stent. In conclusion, the work performed in this thesis utilising computational modelling and experimental corrosion testing has led to an enhanced understanding of the mechanical performance of biodegradable magnesium stents in a remodelling artery.2020-02-1

Analysis of the mechanical performance of a biodegradable magnesium stent in a remodelling artery

Coronary stents made from degradable biomaterials such as magnesium alloy are an emerging technology in the treatment of coronary artery disease. Biodegradable stents provide mechanical support to the artery during the initial scaffolding period after which the artery will have remodelled. The subsequent resorption of the stent biomaterial by the body has potential to reduce the risk associated with long-term placement of these devices, such as in-stent restenosis, late stent thrombosis, and fatigue fracture. Computational modelling such as finite-element analysis has proven to be an extremely useful tool in the continued design and development of these medical devices. What is lacking in computational modelling literature is the representation of the active response of the arterial tissue in the weeks and months following stent implantation, i.e., neointimal remodelling. The phenomenon of neointimal remodelling is particularly interesting and significant in the case of biodegradable stents, when both stent degradation and neointimal remodelling can occur simultaneously, presenting the possibility of a mechanical interaction and transfer of load between the degrading stent and the remodelling artery. A computational modelling framework is developed that combines magnesium alloy degradation and neointimal remodelling, which is capable of simulating both uniform (best case) and localised pitting (realistic) stent corrosion in a remodelling artery. The framework is used to evaluate the effects of the neointima on the mechanics of the stent, when the stent is undergoing uniform or pitting corrosion, and to assess the effects of the neointimal formation rate relative to the overall stent degradation rate (for both uniform and pitting conditions). Experimental mechanical and corrosion testing is conducted to characterise the mechanical and corrosion behaviour of magnesium WE43 alloy, a candidate base material for biodegradable magnesium stents. Previously developed uniform and pitting corrosion models are calibrated based on in vitro mechanical and corrosion testing of magnesium WE43 alloy specimens. The calibrated pitting corrosion model can capture the mechanical and corrosion behaviour of magnesium WE43, including the vii experimentally observed non-linear reduction in failure strength with mass loss, whereas the uniform corrosion model is incapable of capturing this trend. An enhanced computational modelling framework is developed, building on the previous investigations, that combines magnesium alloy degradation and neointimal remodelling in order to simulate corrosion of a magnesium stent in a remodelling artery. The enhanced computational modelling framework, accounts for two major physiological stimuli responsible for neointimal remodelling and is combined with the magnesium stent pitting corrosion model, which has been calibrated for Mg WE43 alloy. The enhanced modelling framework is used to simulate different neointimal growth patterns and to explore the effects the neointimal remodelling has on the mechanical performance (scaffolding support) of a bioabsorbable magnesium stent. In conclusion, the work performed in this thesis utilising computational modelling and experimental corrosion testing has led to an enhanced understanding of the mechanical performance of biodegradable magnesium stents in a remodelling artery.2020-02-1

The LysR-Type Transcriptional Regulator VirR Is Required for Expression of the Virulence Gene vapA of Rhodococcus equi ATCC 33701

The virulence of the intracellular pathogen Rhodococcus equi in foals is dependent on the presence of an 81-kb virulence plasmid encoding the virulence protein VapA. Expression of this protein is induced by exposure to oxidative stress, high temperatures, and low pHs, which reflect the conditions encountered by R. equi when it enters the host environment. The aim of this study was to determine whether the LysR-type transcriptional regulator VirR, which is encoded by the virulence plasmid, is required for the expression of vapA. It was shown that the virR gene is cotranscribed with four downstream genes, one of which encodes a two-component response regulator. The expression of VapA, as monitored by Western blotting, was completely dependent on the presence of virR. Maximal expression was observed when vapA was present together with the complete virR operon, suggesting that at least one of the virR operon genes, in addition to virR, is required for the expression of vapA to wild-type levels. The transcriptional start site of vapA was determined to be a cytidine located 226 bp upstream from the vapA initiation codon. His-tagged VirR protein was expressed in Escherichia coli and purified by nickel affinity chromatography. DNA binding studies showed that purified VirR binds to a DNA fragment containing the vapA promoter. We therefore conclude that VirR is required for the activation of vapA transcription