Unpalatable Perennial Grass Invasion in Central-East Argentina Native Grasslands: Processes, Implications and Recovery

In temperate semiarid central-east Argentina, unpalatable perennial grasses (UPG) have been steadily invading native grasslands formerly dominated by palatable perennial grasses (PPG). The objective of this contribution is to provide a synthesis of underlying processes and implications of UPG invasion, as well as recovery strategies. Results have shown that heavy selective grazing on PPG reduces their superior competitive ability. Gaps formed due to reduced competition by PPG provide safe sites for UPG establishment. The development of large, long-lived tussock of UPG, in combination with high standing crop accumulation, impairs PPG establishment even in absence of grazing. UPG produce sclerophyllous tissues, high in fibre and lignin and low in protein and mineral content. Senesced tissues of UPG decompose and mineralize nutrients slower than that of PPG, although they show a relatively low potential to cause nutrient immobilization in soil bacteria. UPG are less productive than PPG, which in combination to their low nutritive value commonly reduce carrying capacity and secondary productivity to half or less of potential values. The analysis and interpretation of current available knowledge point out that conservative and flexible stocking, in combination with controlled grazing and fire, should be implemented to recover and maintain a sustainable use of native grasslands in central-east Argentina

Use of Unpalatable Forages by Ruminants: The Influence of Experience with the Biophysical and Social Environment

Unpalatable forage resources (low nutrient density, potentially toxic metabolites) are widespread and represent a challenge for ruminant nutrition, health, and welfare. Our objective was to synthesize the role of biophysical and social experience on the use of unpalatable forages by ruminants, and highlight derived behavioural solutions for the well-being of soils, plants, and animals. Environmental experiences early in life modulate gene expression and promote learning, which alters morpho-physiological and psychological mechanisms that modify behavioural responses and change food and habitat selection. In this process, ruminants can become better adapted to the habitat where they are reared. Moreover, experiential learning provides flexibility in diet selection, which is critical for changing foraging environments. Learned associations between unpalatable and palatable foods, if ingested in appropriate amounts, sequence, and close temporal association, induce the development of preference for the former type of food. In this way, a more uniform use of resources can be achieved from the landscape level down to the individual plant, with the associated benefits to ecosystem integrity and stability. Ruminants can also learn the medicinal benefits of ingesting foods with toxins (e.g., condensed tannins and saponins with antiparasitic properties). This knowledge on behavioural processes can be translated into behavioural applications that provide low-cost solutions to many challenges that producers face in managing sustainable livestock production systems

Floristic diversity under different intensities of large herbivore grazing in mountain grasslands of the Ventania System, Buenos Aires

En pastizales de regiones subhúmedas, el pastoreo moderado de grandes herbívoros promovería la diversidad florística. Nuestro objetivo fue evaluar la diversidad florística y la composición botánica en diferentes intensidades de pastoreo por grandes herbívoros en pastizales serranos del Sistema de Ventania, Buenos Aires, Argentina. El muestreo abarcó un área de 200 ha, y comprendió comunidades de flechillas (“flechillales”) sometidas al pastoreo de caballos cimarrones y ganado vacuno. Se seleccionaron nueve parcelas de 1 ha sometidas a diferentes intensidades de pastoreo. Sobre la base de la estimación de la cobertura de cada una de las especies presentes se describió el patrón de diversidad florística, se comparó la cobertura y riqueza de especies, y se evaluaron los cambios en la composición florística, en relación al gradiente de intensidad de pastoreo. El disturbio por pastoreo afectó la riqueza específica de los flechillales y la máxima riqueza se registró en intensidades de pastoreo intermedias. Dicha respuesta se debió principalmente a un mayor número de especies latifoliadas y de gramíneas invernales. En términos de cobertura aérea, el pastoreo favoreció a las latifoliadas únicamente. El pastoreo modificó la composición botánica de los flechillales, apareciendo como más notable el reemplazo de gramíneas invernales (Piptochaetium hackelii, Briza subaristata, Nassella filiculmis) por una gramínea estival de palatabilidad baja (Aristida spegazzinii) a intensidades elevadas de pastoreo. En los pastizales serranos del Sistema de Ventania, el pastoreo moderado favorecería la diversidad florística, aumentando la riqueza de especies de latifoliadas y gramíneas invernales mientras que las altas intensidades favorecerían el reemplazo de las gramíneas invernales palatables por gramíneas de palatabilidad menor.In sub-humid grasslands moderate grazing by large herbivores may promote increases in plant diversity. Our objective was to evaluate changes in floristic diversity and floristic composition at different grazing intensities by large herbivores in mountain grasslands of the Ventania System, Buenos Aires, Argentina. Sampling comprised an area of 200 ha, on needlegrass grasslands grazed by feral horses and cattle. Nine 1 ha plots were selected to represent a grazing intensity gradient, and we evaluated plant species cover in order to describe the plant diversity pattern, species richness and cover, and floristic composition in relation to the grazing intensity gradient. Plant diversity was greater at moderate grazing intensity mainly due to the increment of dicots and cool-season grasses richness. In terms of cover, grazing only increased dicots’ aerial cover. Grazing was associated with changes in the floristic composition of needlegrass grasslands, through inducing the replacement of cool-season grasses (e.g. Piptochaetium hackelii, Briza subaristata, Nassella filiculmis) by an unpalatable warm-season grass (Aristida spegazzinii). In mountain grasslands of the Ventania System, moderate grazing intensity appears to favor plant diversity by increasing dicots and cool-season grasses richness, whereas high grazing intensity may promote the replacement of palatable cool-season grasses by unpalatable warm season grasses

Nitrogen resorption in perennial grasses with different palatability, native to the Caldenal

La reabsorción de nutrientes en las plantas permite su conservación y uso en la construcción de nuevos tejidos, por lo cual podría esperarse que fuera más acentuada en especies adaptadas a crecer con baja disponibilidad de nutrientes. En el Distrito del Caldén, las gramíneas de palatabilidad baja reúnen características distintivas de especies adaptadas a condiciones de poca fertilidad (e.g., tejido esclerenquimatoso abundante, baja concentración de nutrientes), características que en las gramíneas palatables son menos manifiestas. Por lo tanto, cabría esperar una mayor eficiencia y/o proficiencia de reabsorción y de utilización de nitrógeno (N) en Nassella tenuissima Trin. (palatabilidad baja) que en Poa ligularis Nees ex. Steud. (palatabilidad alta). El objetivo de este trabajo fue comparar la dinámica del N en hojas y raíces, vivas y muertas, de ambas especies en distintos momentos del ciclo anual de crecimiento. La concentración de N en los compartimientos analizados fue similar entre especies, o mayor en P. ligularis. Esto determinó una eficiencia y/o proficiencia de reabsorción y de utilización de N similar entre especies, o mayor en N. tenuissima que en P. ligularis. En ambas especies, la eficiencia de reabsorción de N promedio fue mayor a nivel foliar que a nivel radical. Los resultados obtenidos no permiten inferir un comportamiento claramente diferencial en la economía del uso de N entre las gramíneas de baja y de alta palatabilidad del Caldenal.Nutrient resorption in plants represents a conservation mechanism which could be expected to be more significant in those species adapted to nutrient limitations. In the Caldenal District, unpalatable grasses meet characteristics commonly present in species adapted to unfertile conditions (abundance of structural tissue, low nutrient concentration), whereas in palatable grasses those traits are less manifest. So, it could be expected a higher nitrogen (N) resorption efficiency and/or proficiency and N use efficiency in Nassella tenuissima Trin. (unpalatable grass) than in Poa ligularis Nees ex. Steud. (palatable grass). Our objective was to compare the N concentration in leaves and roots, live and death, of both species at different times along an annual growth cycle. Nitrogen concentration in all plant compartments was similar between both species or higher in P. ligularis, determining similar or higher N resorption efficiency and proficiency and N use efficiency in N. tenuissima than in P. ligularis. Average N resorption efficiency was higher in leaves that in roots for both species. Our results did not allow inferring a clear differential behavior in N use economy between these unpalatable and palatable grasses of the Caldena

Conditioned Flavor Aversion: A Mechanism for Goats to Avoid Condensed Tannins in Blackbrush

It has been hypothesized that herbivores instinctively avoid tannin-containing plant parts in response to the adverse effects of tannins on forage digestion. However, we found that goats learned to avoid condensed tannins (CTs) from blackbrush current season\u27s growth by associating the flavor of foods containing CTs with aversive postingestive consequences. The aversive consequences experienced by goats apparently are not related to digestion inhibition and may depend on the structure of CTs and on how CTs are bound with other cell constituents. These observations suggest several areas of inquiry related to the interaction between CTs and herbivores. A better understanding of the physiological effects of CTs and how herbivores perceive these effects is essential to our knowledge of chemically mediated interactions between plants and mammalian herbivores. With few exceptions, the effects of food flavor have not been separated from those associated with postingestive consequences, even though our data show that postingestive consequences strongly influence palatability. We also need to know how herbivores learn which plant species to eat and which to avoid while foraging in areas that contain a variety of plant species and parts with different kinds and concentrations of CTs. Condensed tannins are pervasive in nature and can defend plants from herbivory, but since many important forages contain high levels of tannins, the presence or absence of tannins per se does not reliably indicate food quality. To predict the ability of a tannin-producing plant to deter herbivores requires a full understanding of how changes in CT structure and binding affect herbivores

The grazing paddock in the extensive systems of South Patagonia. Perception and management of heterogeneous grazing

La producción ganadera extensiva en la Patagonia Sur se realiza sobre cuadros de pastoreo de gran superficie, escasa receptividad animal y fragilidad ambiental elevada. El manejo histórico del pastoreo, desde fines del siglo XIX, causó la desertificación del paisaje en gran parte del territorio. Diferentes esfuerzos institucionales buscaron mejorar el manejo de los pastizales a través de adecuar la carga animal en los cuadros. No obstante, la heterogeneidad del paisaje dentro de éstos permite que los animales se concentren en los lugares que más prefieren. En este contexto, el desarrollo de recomendaciones técnicas para controlar el pastoreo heterogéneo requiere un conocimiento actualizado de la percepción de los productores frente a esta problemática. Por ello, se llevó adelante una encuesta a 82 productores ganaderos extensivos de Santa Cruz con el objetivo de caracterizar el manejo que realizan en los cuadros de pastoreo, los criterios para su diseño y su visión sobre el problema del pastoreo heterogéneo. Un porcentaje alto de productores (~75%) detecta la problemática, pero sólo 8.3% de ellos aplica más de 2 tecnologías para enfrentarla. En su conjunto, los productores muestran conocer una gran variedad de tecnologías. Sin embargo, los entrevistados señalaron diversas limitantes que determinan que las tecnologías no se consoliden como prácticas de uso común. El sistema extensivo de producción en la Patagonia Sur se sigue llevando adelante mayormente bajo un esquema de mínima intervención del paisaje, tal como en sus inicios. Es posible que sea necesario revisar el sistema de transferencia tecnológica desde las instituciones de investigación y extensión, pero también es imprescindible que el Estado participe diseñando e implementando políticas orientadas a proveer instrumentos idóneos para incentivar, promover, apoyar y monitorear la adopción de tecnología.The extensive livestock system of South Patagonia is carried out on large-scale paddocks, with low animal carrying capacity and high environmental fragility. The historical grazing management, since the end of the 19th century, has caused the desertification of the landscape in a large part of the territory. Different institutional efforts have sought to promote be�er management of rangelands based on adapting the stocking rate of the paddocks. However, the heterogeneity of the landscape within the paddocks still allows the concentration of animals in the most preferred places. In this context, the development of technical recommendations that allow the control of the heterogeneous grazing, requires an updated knowledge about the perception of the producers facing this problem. For this reason, a survey was carried out to 82 extensive livestock producers in Santa Cruz, seeking to characterize the management they perform in the paddocks, the criteria for their design and how they visualize the problem of heterogeneous grazing. A high percentage of producers (~ 75%) detects the problem, but only 8.3% applies more than 2 technologies to address it. The producers, as a whole, show knowledge of an important variety of technologies. However, different limitations indicated by the interviewees, determine that the technologies are not consolidated as common use practices. The extensive system in South Patagonia continues to be carried out mainly under a scheme of minimal intervention of the landscape, just as in its beginnings. It may be necessary to review the technology transfer system from research and extension institutions. However, the participation of the State is also essential, through the design and implementation of policies that provide suitable instruments to encourage, promote, support and monitor the adoption of technology

Structural and functional recovery of intershrub spaces after 10-years of grazing exclusion in a semiarid steppe of northeastern Patagonia

En las estepas arbustivas del noreste de la Región Patagónica, el sobrepastoreo del ganado doméstico genera la formación de islas arbustivas distribuidas en una matriz degradada de suelo desnudo o con escasa cobertura vegetal. La recuperación estructural y funcional de los espacios entre arbustos mediante la remoción del ganado dependería de la magnitud de la degradación. Si el sistema ha atravesado un umbral crítico de degradación, la sola remoción del disturbio no sería suficiente para revertir las alteraciones provocadas por el pastoreo. El objetivo del trabajo fue evaluar la recuperación de espacios entre arbustos en un sitio representativo del sistema en estudio luego de 10 años de exclusión del pastoreo, mediante la comparación de la cobertura y propiedades físicoquímicas del suelo entre áreas clausuradas y pastoreadas. Se realizaron mediciones en cuatro áreas clausuradas y en áreas aledañas sometidas a pastoreo continuo. Se comparó la cobertura (vegetación, pavimento de erosión, costra biológica, suelo desnudo y broza), el tamaño de los espacios entre arbustos, la tasa de infiltración, la textura y el contenido de nutrientes del suelo. La cobertura aérea de gramíneas perennes y de costras biológicas fue mayor en las áreas clausuradas (27% y 45%, respectivamente) que en las pastoreadas (<1% y 3%). El tamaño de los espacios entre arbustos fue mayor en las áreas pastoreadas que en las clausuradas. La tasa de infiltración y las propiedades físicoquímicas del suelo no difirieron entre las condiciones de clausura y pastoreo, aunque la densidad aparente y el contenido de arena en la capa superficial del suelo fueron ligeramente mayores (7% y 3%, respectivamente) en las áreas pastoreadas. La exclusión del pastoreo por un período de 10 años resultó en el restablecimiento de gramíneas perennes y costras biológicas, sugiriendo que la alteración estructural y funcional de los espacios entre arbustos aún no ha superado un umbral crítico de degradación.In shrubby steppes of northeastern Patagonia, overgrazing of domestic livestock produces the formation of shrub islands distributed in a degraded matrix of bare soil or sparce vegetation cover. The structural and functional recovery of intershrub spaces through livestock removal would depend on the magnitude of degradation. If the system has crossed a critical threshold of degradation, the sole removal of the disturbance would be not sufficient to reverse the changes caused by grazing. The objective of this study was to assess the recovery of intershrub spaces in a site representative of the study system after 10 years of livestock grazing exclusion, by comparing soil coverage and soil physicochemical properties between ungrazed and grazed areas. Data sets were collected in four plots excluded from grazing and in areas adjacent to each plot that remained under continuous grazing. We measured the size of the intershrub spaces, and soil coverage (vegetation, erosion pavement, biological soil crusts, litter and bare soil), texture, nutrient content and infiltration rate. We found that the aerial coverage of perennial grasses and biological soil crusts was higher in ungrazed areas (27% and 45%, respectively) than in grazed areas (<1% and 3%, respectively). The size of the intershrub spaces was higher in grazed areas than in ungrazed areas. The physicochemical properties of soil and infiltration rate did not differ between ungrazed and grazed areas, except that bulk density and sand content in the soil-surface layers were slightly higher (7% and 3%, respectively) in grazed areas. The sole exclusion of grazing for a period of 10 years allowed the recovery of perennial grasses and biological crusts, suggesting that the structural and functional alterations of the intershrub spaces has not yet exceeded a critical threshold of degradation

Desaparición ruminal de FDN y FDA de distintas fuentes de fibra con grano de maíz y bicarbonato de sodio en la dieta

La inclusión de granos es una estrategia común para acelerar los engordes, que conlleva una eventual disminución del pH ruminal afectando la degradación de la fibra. La adición de bicarbonato de sodio como buffer dietario para contrarrestar dichos efectos es controversial. Si bien se presume que el agregado de grano influye en la degradación ruminal de la fracción fibrosa del recurso de base, se tiene escaso conocimiento acerca de la dimensión de tal efecto y si habría alguna interacción con el agregado de bicarbonato. Es por ello que el objetivo de este trabajo fue evaluar las curvas de desaparición de la FDN y FDA de distintos recursos fibrosos en ambientes ruminales con agregados contrastantes de grano y bicarbonato de sodio.Fil: Ortiz, Daniela Alejandra. Universidad Nacional de La Pampa; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional La Pampa-San Luis. Estación Experimental Agropecuaria Anguil; ArgentinaFil: Camiletti, Fátima Karina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional La Pampa-San Luis. Estación Experimental Agropecuaria Anguil; ArgentinaFil: Volpi Lagreca, G.. Universidad Nacional de La Pampa; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional La Pampa-San Luis. Estación Experimental Agropecuaria Anguil; ArgentinaFil: Alende, Mariano. Instituto Nacional de Tecnología Agropecuaria. Centro Regional La Pampa-San Luis. Estación Experimental Agropecuaria Anguil; ArgentinaFil: Murcia, Vanina Nerea. Instituto Nacional de Tecnología Agropecuaria. Centro Regional La Pampa-San Luis. Estación Experimental Agropecuaria Anguil; ArgentinaFil: Porta Siota, F.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional La Pampa-San Luis. Estación Experimental Agropecuaria Anguil; ArgentinaFil: Hurtado, A.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional La Pampa-San Luis. Estación Experimental Agropecuaria Anguil; ArgentinaFil: Gelid, L.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional La Pampa-San Luis. Estación Experimental Agropecuaria Anguil; ArgentinaFil: Pordomingo, Adriana Beatriz. Universidad Nacional de La Pampa; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional La Pampa-San Luis. Estación Experimental Agropecuaria Anguil; ArgentinaFil: Pordomingo, Anibal Javier. Universidad Nacional de La Pampa; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional La Pampa-San Luis. Estación Experimental Agropecuaria Anguil; ArgentinaFil: Distel, Roberto Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; Argentina. Universidad Nacional del Sur. Departamento de Agronomía; Argentina42° Congreso Argentino de Producción AnimalBahía BlancaArgentinaAsociación Argentina de Producción Anima

Candidate CSPG4 mutations and induced pluripotent stem cell modeling implicate oligodendrocyte progenitor cell dysfunction in familial schizophrenia

Schizophrenia is highly heritable, yet its underlying pathophysiology remains largely unknown. Among the most well-replicated findings in neurobiological studies of schizophrenia are deficits in myelination and white matter integrity; however, direct etiological genetic and cellular evidence has thus far been lacking. Here, we implement a family-based approach for genetic discovery in schizophrenia combined with functional analysis using induced pluripotent stem cells (iPSCs). We observed familial segregation of two rare missense mutations in Chondroitin Sulfate Proteoglycan 4 (CSPG4) (c.391G > A [p.A131T], MAF 7.79 × 10−5 and c.2702T > G [p.V901G], MAF 2.51 × 10−3). The CSPG4A131T mutation was absent from the Swedish Schizophrenia Exome Sequencing Study (2536 cases, 2543 controls), while the CSPG4V901G mutation was nominally enriched in cases (11 cases vs. 3 controls, P = 0.026, OR 3.77, 95% CI 1.05–13.52). CSPG4/NG2 is a hallmark protein of oligodendrocyte progenitor cells (OPCs). iPSC-derived OPCs from CSPG4A131T mutation carriers exhibited abnormal post-translational processing (P = 0.029), subcellular localization of mutant NG2 (P = 0.007), as well as aberrant cellular morphology (P = 3.0 × 10−8), viability (P = 8.9 × 10−7), and myelination potential (P = 0.038). Moreover, transfection of healthy non-carrier sibling OPCs confirmed a pathogenic effect on cell survival of both the CSPG4A131T (P = 0.006) and CSPG4V901G (P = 3.4 × 10−4) mutations. Finally, in vivo diffusion tensor imaging of CSPG4A131T mutation carriers demonstrated a reduction of brain white matter integrity compared to unaffected sibling and matched general population controls (P = 2.2 × 10−5). Together, our findings provide a convergence of genetic and functional evidence to implicate OPC dysfunction as a candidate pathophysiological mechanism of familial schizophrenia