Procaine penicillin [penicillin (procaine salt)] added to a good practical ration improved the growth of chicks in a laboratory used for poultry for ten years. Chicks from the same batch in two other laboratories, where birds had not been kept before, grew equally well on the ration with and without penicillin, and growth was the same as that on the penicillinsupplemented diet in the usual chick laboratory. The growth depression in the absence of dietary penicillin was not due to differences in management or to recognizable disease. It is suggested that it is due to an ‘infection’ hitherto undescribed and shown to be transmissible and counteracted by penicillin.

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The efficiency of Ireland’s grass-based livestock systems can be attributed to high outputs, low production costs and a low carbon footprint relative to housed systems. Methane (CH4) is a potent greenhouse gas (GHG) of which enteric fermentation from livestock production is a key source, being directly responsible for 57% of Irish agricultural GHG emissions. There are a number of strategies including dietary manipulation and breeding initiatives that have shown promising results as potential mitigation solutions for ruminant livestock production. However, the majority of international research has predominantly been conducted on confined systems. Given the economic viability of Irish livestock systems, it is vital that any mitigation methods are assessed at pasture. Such research cannot be completed without access to suitable equipment for measuring CH4 emissions at grazing. This review documents the current knowledge capacity in Ireland (publications and projects) and includes an inventory of equipment currently available to conduct research. A number of strategic research avenues are identified herein that warrant further investigation including breeding initiatives and dietary manipulation. It was notable that enteric CH4 research seems to be lacking in Ireland as it constituted 14% of Irish agricultural GHG research publications from 2016 to 2021. A number of key infrastructural deficits were identified including respiration chambers (there are none currently operational in the Republic of Ireland) and an urgent need for more pasture-based GreenFeed™ systems. These deficits will need to be addressed to enable inventory refinement, research progression and the development of effective solutions to enteric CH4 abatement in Ireland.

<p>It is predicted that climate change will result in more extreme and frequent weather events including flooding and drought. Nitrous oxide (N<sub>2</sub>O) is a potent greenhouse gas having 298 times the global warming potential of CO<sub>2</sub>. The ‘Birch effect’, the term given to high  N<sub>2</sub>O fluxes following the drying and re-wetting of soils, is an accelerator of this process. Multi species grasslands have been shown have higher nitrogen use efficiency and potential for drought resilience and recovery. This experiment analysed the nitrogen dynamics of multi-species grasslands by means of quantifying the responses of soil mineral nitrogen (NH<sub>4</sub><sup>+</sup> and NO<sub>3</sub><sup>-) </sup>and N<sub>2</sub>O fluxes during an eight week simulated drought, re-wetting and fertiliser application two weeks after the re-wetting event. A simplex experimental design was used to determine species and functional group effects which could potentially influence responses. The hypothesis of this study was therefore that multi species grasslands would mitigate the ‘Birch effect’ resulting in less erratic transformations of soil mineral nitrogen and lower N<sub>2</sub>O fluxes compared to monocultures. This study also predicted a lasting legacy effect of drought on soil systems resulting in prolonged heightened N<sub>2</sub>O fluxes. Drought resulted in a depletion of soil NO<sub>3-</sub>, increased  levels of NH<sub>4</sub><sup>+ </sup>and background level N<sub>2</sub>O emissions. Following re-wetting soil mineral N underwent transformations from NH<sub>4</sub><sup>+</sup> to NO3- indicating nitrification. Four times more N<sub>2</sub>O emissions were recorded during re-wetting period compared to fertilizer application. There was no lasting legacy effect of drought and re-wetting on N<sub>2</sub>O fluxes observed during fertilizer application two weeks after re-wetting bar T. repens which has implications for grassland management strategies.</p>