ABSTRACT.- CONTEXT:The Latin America-Caribbean (LAC) region has the potential to pursue a sustainable expansion of livestock production and capitalise on the growing global demand for dairy and beef products. However, it is necessary to understand the predominant production systems and their biophysical, economic, social, and environmental performances. OBJECTIVE:This study aimed to compare the milk production systems of nine countries of the region according to their major biophysical, socio-economic, and environmental performance indicators.

ABSTRACT.- Ramularia collo-cygni (Rcc) is the causal agent of Ramularia leaf spot (RLS). The main management tool is the use of foliar fungicides, the impact of which on cereal safety is unknown. Therefore, the aim of this thesis was to optimise the management of ramulariosis in barley and to minimise fungicide residues in grain. -- RESUMEN.- Ramularia collo-cygni (Rcc) es el agente causal de ramulariosis. La principal medida para su manejo es la utilización de fungicidas foliares cuyo impacto en la inocuidad del grano es desconocido.

ABSTRACT.- Management practices during the rearing of dairy heifers should allow an adequate body growth and reproductive development to attain puberty several months before the first conception. Proposed target age and body weight (BW) at first calving for Holstein heifers are between 22-24 months and 82% of mature BW, respectively, for which heifers must conceive at around 15 months of age with 60% of their mature BW.

ABSTRACT.- The process of intensification of the dairy sector has been characterized in recent decades by the increase in milk production per hectare, the increase in livestock density, the inclusion of more concentrates in the diet, and the improvement of the genetic merit of dairy cows. The use of models has productive, environmental, and economic advantages. The objectives of the study were to describe a new model, "OLE!

ABSTRACT.- Uruguay's dairy can potentially enhance milk productivity competitively, but intensification risks elevating nitrogen (N) surplus, heightening environmental concerns. This study quantified farm-gate N inputs and outputs, calculating N surplus (input-output) and N use efficiency (NUE=output/input) for 17 commercial modal dairy systems identified in the 2014 and 2019 national surveys and six prospective intensified systems based on experimental pastoral farmlets achieving near-maximal rainfed productivity. .-.-.-.-.-.-.-.-.-.