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Ruminant livestock are raised under diverse cultural and environmental production systems around the globe. Ruminant livestock can play a critical role in food security by supplying high-quality, nutrient-dense food with little or no competition for arable land while simultaneously improving soil health through vital returns of organic matter. However, in the context of climate change and limited land resources, the role of ruminant-based systems is uncertain because of their reputed low efficiency of feed conversion (kilogram of feed required per kilogram of product) and the production of methane as a by-product of enteric fermentation. A growing human population will demand more animal protein, which will put greater pressure on the Earth’s planetary boundaries and contribute further to climate change. Therefore, livestock production globally faces the dual challenges of mitigating emissions and adapting to a changing climate. This requires research-led animal and plant breeding and feeding strategies to optimise ruminant systems. This study collated information from a global network of research farms reflecting a variety of ruminant production systems in diverse regions of the globe. Using this information, key changes in the genetic and nutritional approaches relevant to each system were drawn that, if implemented, would help shape more sustainable future ruminant livestock systems.

Mixed crop–livestock long-term experiments (LTE) are critical to increase the understanding of sustainability in complex agroecosystems. One example is the ‘Palo a Pique’ LTE which has been running for 25 years in Uruguay (from 1995 to present), evaluating four pasture–crop rotations under livestock grazing with no-till technology in soils with severe limitations. The results demonstrate that cropping systems reduced soil organic carbon (SOC) compared with permanent pastures, and that perennial pastures rotating with crops were critical to mitigate SOC losses. Data from the ‘Palo a Pique’ LTE has contributed to the establishment of new national policies to secure the sustainability of agricultural-based systems. Although the original purpose of the LTE was oriented to crops and soils, a demand for sustainable livestock intensification has gathered momentum over recent years. As a result, the current approach of the ‘Palo a Pique’ LTE matches each pasture–crop rotation with the most suitable livestock strategy with the common goal of producing 400 kg liveweight/ha per year. General approaches to the pursuit of sustainable livestock intensification include shortening the cycle of production, diversifying animal categories, increasing liveweight gain and final animal liveweight, and strategic livestock supplementation. Prediction of trade-offs between environmental, economic, and production indicators can be addressed through monitoring and modeling, enabling the timely anticipation of adverse sustainability issues on commercial farms. The ‘Palo a Pique’ LTE serves as a framework to address contemporary and future questions dealing with the role of ruminants on climate change, competition for land, nutrient dynamics, and food security.

This trial provided information about effects of defoliation frequency, defoliation intensity and winter management (grazing or rest) on the productivity, morphology and plant population of a 3-year-old plantain (Plantago lanceolata) stand. Plant population density declined drastically over time independently of grazing management, with the greatest decrease in summer. Winter grazing had a critical effect on the productivity and population remaining 6 months later. Frequent grazing during summer increased plantain contribution. Grazing intensity reduced crown weight and diameter of individual plants. Further studies are required to determine the interactions of defoliation management with pastures of different age including the natural reseeding as a mechanism to maintain plant recruitment. Keywords: defoliation, grazing, morphology, population

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Se evaluaron siete asociaciones, dos gramíneas y una leguminosa, sembradas en diferentes proporciones y un monocultivo (pasto ovillo). La investigación se realizó de septiembre de 2012 a septiembre de 2014 en el Colegio de Postgraduados, Campus Montecillo, México. La restricción a la leguminosa fue en un 10 y 50% como mínimo y máximo, respectivamente. Los tratamientos consistieron de las siguientes asociaciones: 20-40-40, 00-50-50, 4020-40, 50-00-50, 20-70-10, 70-20-10,100-00-00, 40-4020% de ovillo (Ov), ballico perenne (Ba) y trébol blanco (Tr), respectivamente. Los tratamientos se distribuyeron aleatoriamente en 24 parcelas experimentales de 9 por 8 m, de acuerdo a un diseño de bloques completamente al azar con tres repeticiones. Las asociaciones que presentaron mayor tasa de crecimiento en los dos años fueron; 20-70-10, 20-40-40 y 40-20-40 con un promedio de 57 kg MS ha-1 d-1, y la menor tasa de crecimiento el monocultivo ovillo (10000-00) con 32 kg MS ha-1 d-1 (p< 0.05). La asociación que obtuvo la mayor población de plantas (m-2) durante los dos años en ovillo fue el monocultivo ovillo con 32 plantas m-2 y las menores: 21 y 15 plantas m-2 con las asociaciones 4040-20 y 20-40-40, respectivamente (p< 0.05). En promedio del primer año de radiación interceptada encontramos 87% disminuyendo al segundo año en 84%. Todas las asociaciones aportaron mayor tasa de crecimiento en comparación con el monocultivo ovillo; además, existe una estrecha relación con la tasa de crecimiento y radiación interceptada.

La productividad primaria neta aérea (PPNA) es uno de los atributos ecosistémicos más importantes, siendo el principal control de la carga ganadera en pastizales. Tradicionalmente se ha estimado a partir de cortes periódicos de biomasa. La información espectral permite estimar la PPNA a bajo costo y en tiempo real sobre áreas extensas. Para ello se requiere la calibración de modelos que relacionen información espectral con la PPNA estimada mediante cortes de biomasa a campo, cuantificando un factor clave en esta relación: la eficiencia de conversión de la radiación en biomasa (Eficiencia en el Uso de la Radiación: EUR). En este trabajo combinamos datos de PPNA estimada a campo, con datos obtenidos de imágenes de satélite y estaciones meteorológicas, para estimar EUR y generar modelos de estimación de la PPNA en tiempo real en pastizales naturales con y sin siembras en cobertura de leguminosas, en la región de Sierras y Lomadas del Este. La EUR para pastizales naturales fue de 0,24 g MS/MJ (Materia Seca/Mega Joules), mientras que en los sitios intersembrados la EUR fue aproximadamente el doble, dependiendo del sistema analizado. Los modelos para estimar PPNA explicaron el 70 y 58% de la varianza de los datos (p<0,001), con r2 de predicción de 0,67 y 0,55 (p><0,001), para pastizales naturales e intersiembras respectivamente.><0,001), con r2 de predicción de 0,67 y 0,55 (p<0,001), para pastizales naturales e intersiembras respectivamente.

Beef cattle production in Uruguay is limited by heifer mating age when grazing natural pastures. Lotus pedunculatus cv. Grasslands Maku is a forage species that was recently introduced to Uruguayan farming systems, with high potential to improve herbage production in acid and low fertility soils. This paper provides information about winter and spring performance of Hereford x Angus heifers grazing an improved Lotus pedunculatus cv. Grasslands Maku pasture when fed at different pasture allowances. Four pasture allowances (3, 5, 10 and 16 kg DM/100 kg animal liveweight/day) from June 30 to October 9 (P1) followed by one pasture allowance of 9 kg DM/100 kg animal liveweight/day from October 9 to November 28 (P2), were assigned to 9 months old Hereford x Angus heifers weighing 129 kg. Measurements included herbage mass, botanical composition, pasture growth rate, sward height and animal liveweight. Liveweight gains were evaluated using a repeated measurement model in time. Pasture mass decreased from 4000 kg DM/ha to 1100, 1050, 1350 and 2000 kg DM/ha for the herbage allowances of 3, 5, 10 and 16% respectively during P1. Legume content at the end of P1 was 550, 400, 700 and 700 kg DM/ha for 3, 5, 10 and 16% of total pasture mass respectively. Herbage mass increased by 328 kg DM/ha per cm sward height (P