Abstract
Livestock production is one of the most important economic activities of the Mercosur countries (Argentina, Brazil, Paraguay and Uruguay). In Uruguay it represents one of the main sources of incomes from exports which are destined to multiple markets worldwide. In recent years, the international demand on the conditions of production of livestock products, with special emphasis on environmental issues and animal welfare has increased. In this way, the aim of this PhD thesis is to characterize different production systems from a productive, behavioral, welfare, and environmental point of view. This work was carried out in two different species, cattle and pigs, and in different production systems. The first two chapters deal with three steers production systems with different degrees of intensification: confined system, pastoral conditions and an intermediate option that combines confinement and grazing for six hours. They are characterized in productive aspects, as well as the general use of time and daily trends in each behavior and its association to the environmental conditions. At the same time, social interactions were registered in the three production systems and several physiological indicators determined, in order to analyze their influence on animal welfare. In the remaining two chapters two contrasting systems of pig production are assessed: a traditional indoor fattening system and an alternative outdoor system with access to pastures. Both systems are characterized in productive and environmental aspects and meat quality characteristics. General behavior and agonistic social behavior are also characterized, as well as other physiological parameters.
This thesis has characterized the proposed systems and it has been found that any of them seriously compromise the welfare of the animals. Nevertheless, we found that the different production systems affected the behavior of the animals and could cause different levels of stress. On the other hand, systems including grazing may have a reduced biological efficiency of nutrient utilization, both in cattle and pigs. From an environmental point of view, an approximation to the distribution patterns of nutrients in the soil has been found.