Keynote paper presented at the International Leucaena Conference, 1‒3 November 2018, Brisbane, Queensland, Australia.This paper presents the current status of Leucaena leucocephala (leucaena) feeding systems and proposes research priorities for leucaena development in Argentina. Although research on leucaena as forage for cattle production began in the late 1960s, it was not widely adopted until 2010 (5 decades later). The recent adoption is related to the incorporation of the ‘Australian technology package’, previously adapted for use by farmers in the neighboring region of the Paraguayan Chaco. In June 2018, we surveyed 8 properties with about 2,400 ha of leucaena in silvopastoral systems for beef cattle production in the Argentinean Chaco region, as well as 10 smallholder farms with about 10 ha of leucaena protein banks for dairy cattle in the northeast of Argentina. In the silvopastoral systems, leucaena condition was excellent on most properties in the 750‒1,350 mm/year rainfall zone and low/poor on only 1 farm due to low rainfall (600 mm/year). In protein banks, leucaena condition was excellent or good on 6 of the properties and low/poor on the remaining 4, attributed to ingress of weeds and/or overgrazing. Grass condition was good in most of the systems but was low/poor in 2 silvopastoral systems due to very high stocking rates imposed to restrict leucaena height. Although there is high potential for leucaena development in Argentina, expansion should take place carefully with leucaena planted only on areas suitable for successful establishment, and using appropriate management practices to reduce establishment failures and costs, restrict leucaena height, enhance grass persistence, improve grazing strategies and manage mimosine toxicity problems.
Keynote paper presented at the International Leucaena Conference, 1‒3 November 2018, Brisbane, Queensland, Australia.This review describes the history of research in Leucaena leucocephala (leucaena) feeding systems carried out by the National Institute of Agricultural Technology (INTA) over the last 5 decades and discusses the main limitations resulting in poor adoption in Argentina. Leucaena was introduced in the subtropical region of the north of the country in the late 1960s and early 1970s. Since then, INTA has conducted research to evaluate forage and animal productivity, leucaena accessions, rhizobial strains, contribution to soil carbon and total nitrogen and density effects on competition and other ecosystem interactions in silvopastoral systems. In spite of the convincing research results showing the excellent potential of leucaena to increase forage quality and animal production in suitable areas, there has been poor adoption of this forage tree legume on a broad scale.
RESUMENEl objetivo del estudio fue evaluar el efecto del clima y un protocolo de sincronización de celo sobre el inicio de la pubertad, gestación y parición de borregas Texel x Romney fuera de la estación reproductiva. El experimento se llevó a cabo en la Estación Experimental Agropecuaria (EEA) del INTA (Corrientes, Argentina) con 26 borregas Texel x Romney de 11 meses de edad y 47.0 ± 2.2 kg de peso. Se utilizó un protocolo de sincronización de celo por medio de esponjas intravaginales con acetato de medroxiprogesterona -MAP (60 mg) por siete días y 400 UI de eCG al retiro de las esponjas. Dos machos Dorper fértiles fueron introducidos el día del retiro de las esponjas. El diagnóstico de gestación por ultrasonografía rectal se realizó a los 50 días de la monta. Se obtuvieron datos meteorológicos para calcular el índice de temperatura-humedad (ITH) y determinar el grado de estrés calórico. El 69.2% de las ovejas fueron montadas a las 48 h, 15 borregas fueron consideradas como gestantes y nueve parieron. Durante la gestación, las ovejas estuvieron expuestas a estrés severo y extremo el 23 y 50% de estos días. El promedio de peso al nacer fue 1.5 ± 0.5 kg.Palabras clave: ovejas de lana; pubertad; sincronización; estrés calórico; peso al nacimiento
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