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Perennial ryegrass (Lolium perenne L.) is a commonly grown pasture species in temperate agriculture, mainly serving as a primary energy source for dairy cows. However, its limited persistence often leads to missed production potential and early resowing, especially in countries that experience summer drought, e.g., Australia and New Zealand. Therefore, understanding the factors influencing perennial ryegrass pasture persistence is crucial for sustainable land management and climate resilience in pasture-based animal production systems. Significant gaps in knowledge exist regarding the factors influencing pasture persistence, as the number of conducted studies in this area remains limited. This study aimed to investigate the factors influencing the expression of persistence in perennial ryegrass populations using airborne and ground-based sensors. A field experiment was conducted in the southwest region of Victoria, Australia, involving ten commercial perennial ryegrass cultivar–endophyte combinations in two different populations. Persistence was evaluated using sensor-based and conventional pasture measurements over two consecutive autumns. The results revealed significant fixed effects of cultivar, endophyte, and environment and their interactions on persistence traits of perennial ryegrass. Cultivars Alto, Samson, and One50 exhibited high levels of persistence when infected with novel endophyte strains. Furthermore, prolonged environmental stresses were found to drive directional selection within pasture populations. The findings emphasise the importance of selecting appropriate cultivar–endophyte combinations and early detection of signs of poor persistence to optimise sward longevity and financial returns from pasture-based animal production systems. This study fills a knowledge gap regarding the factors influencing pasture persistence and provides valuable insights for sustainable pasture management strategies. [ABSTRACT FROM AUTHOR]

Context: The incidence of extreme heat events (prolonged temperatures above 35°C) is increasing in the northern Victorian dairying region in Australia. This increase is having a significant effect on the performance of perennial ryegrass, which has traditionally been the major perennial species in these pastures. Aim: During seven extreme heat events, forage sampling was conducted on commercial farms to evaluate the effects of high temperatures on the nutritive characteristics of perennial ryegrass, tall fescue and lucerne. Our hypothesis was that reductions in nutritive characteristics with an increasing external temperature would vary among species. Methods: Before, during and after heat events, replicated samples of the three forage species were collected and analysed for in vitro dry matter digestibility (IVDMD), neutral detergent fibre (NDF), acid detergent fibre (ADF), water soluble carbohydrates (WSC) and crude protein (CP). Several anti-nutritive compounds (alkaloids in perennial ryegrass, and saponins and coumestrols in lucerne) were also measured. Key results: None of the temperate forage species evaluated maintained nutritive quality under high temperatures. Linear mixed model (LMM) analyses showed that for each degree rise between 23°C and 40°C, IVDMD and WSC concentrations decreased by 0.2% while NDF and ADF concentrations increased by 0.2% and 0.15% respectively. Concentrations of the alkaloid, ergovaline, in the base of the perennial ryegrass tiller were close to, or above, the recommended threshold level for animal health and welfare in three of the six samples taken during heat events. Conclusions: These results suggest that extreme heat events have a detrimental effect on the nutritive characteristics of the evaluated forage species. Implications: Heat-induced decreases in nutritive characteristics will potentially have serious implications for milk production and farm productivity. Further research, undertaken under controlled conditions of temperature, humidity and plant growth stage, is recommended to determine the full effect of these extreme summer conditions on forage nutritive characteristics. The effects of extreme heat events on the nutritive characteristics of pastures were studied in three farms in northern Victoria, Australia. Nutritive quality decreased at high temperatures in all species, with implications for milk production. Further research is recommended. [ABSTRACT FROM AUTHOR]

Case Report: Perennial ryegrass toxicosis (PRGT) is a common disease entity in Australia, presenting as an association of clinical signs including alterations in normal behavioural, ataxia ('staggers'), ill thrift and gastrointestinal dysfunction ('scours'). Clinical signs can range in severity from mild (gait abnormalities and failure to thrive) to severe (seizures, lateral recumbency and death). Presentation across the flock is usually highly variable. PRGT is caused by toxins produced by the endophytic fungus Neotyphodium lolii, a symbiont of perennial ryegrass that is present in pastures across the temperate regions of Australia and Tasmania. A particular feature of PRGT in Australia is the occasional occurrence of large-scale sheep losses, suggesting other factors are influencing mortality rates compared with other PRGT risk zones such as North America and New Zealand. During 2011, producers in the state of Victoria experienced a mild outbreak of PRGT that affected large numbers of animals but with limited mortalities. Clinical samples taken from affected sheep showed a high incidence of dehydration and electrolyte abnormalities., Conclusion: We speculate that changes in hydration status may be a contributory aetiological factor in those years in which high numbers of deaths are associated with PRGT outbreaks in Australia., (© 2014 Australian Veterinary Association.)