## 4 Grazing
### Grazing Systems  
The choice of grazing system is the key to the success or failure of an agricultural operation, both economically [25] and environmentally. Continuous grazing entails grazing the same plot, during the grazing season, year after year [140], generally with a relatively low stocking rate. According to [PERSON] et al. [72] long grazing periods negatively affect methane uptake in the soil and, consequently, decrease carbon sequestration in pastures and soil. In addition, continuous grazing is one of the factors responsible for the degradation of ecosystems where overgrazing occurs [64]. In continuous grazing systems, excessive trampling harms the pasture and the soil [58]. On the other hand, according to [PERSON] [62], in continuous grazing systems, nutrients are returned to the soil through feces and urine. In the Patagonian steppe, in South America, grazing with domestic herbivores is still recent. However, it has caused severe degradation, mainly due to continuous intensive grazing, albeit in very large and very heterogeneous enclosures [140]. The diversity of plant species leads to selective grazing and excess dry residues on the soil surface, which translates into the replacement of preferred species by non-preferred species [25; 140], not necessarily being those intended in the pasture, in terms of nutritional value. However, we must remember that there are no good or lousy grazing systems. Some grazing systems are designed to achieve particular objectives according to the soil and climate conditions, the relief, the soil, the animal genotypes, and the production system. In this context, [PERSON] et al. [141] state that, considering the diversity of plant species, soil types, and climatic conditions of rangeland ecosystems around the world, agronomic practices and pasture improvements for achieving \"intensification\" targets differ widely across countries and regions. This statement is corroborated by [PERSON] [140] when he states that, for a grazing system to be beneficial and function properly, the needs of vegetation, soil, and animals, which are part of these production systems, must be taken into account. Continuous grazing has some limitations, as it allows for selectivity and causes heterogeneity in the pasture. In this way, overgrazed and undergrazed areas occur simultaneously [140; 142], reducing the possibility of the recovery of the more grazed areas [143]. However, in a study carried out in plots dominated by weedy shrubs (_Cistus Ladanifer_ L.), the authors concluded that continuous grazing with 2 to 3 AU/ha led to a decrease in the number of shrubs and an increase in desirable herbaceous plants with good nutritional value, especially from the _Poaceae_ and _Fabaceae_ botanical families [143]. On the other hand, using pasture intermittently, through deferred grazing in several plots (multi-paddock), leads to satisfactory productive, ecological, and economic results [144]. Deferred grazing involves grazing the plot in longer or shorter grazing periods depending on the amount of pasture, generally with a high stocking rate [1]. Thus, it is crucial to define the number of plots to reduce the occupation time of each one; not all need to have the same area, but they do need to have the same production capacity [58]. In this sense, [PERSON] [140] infers that deferred grazing makes it possible that areas preferred by animals are not as harmed as in continuous grazing, regarding the vigor and production of plants in these areas. [PERSON] et al. [64] carried out a study of Yak grazing in China in which they compared three levels of deferred grazing--low stocking rate--0.75 yak/ha; average stocking rate--1 yak/ha; and high stocking rate--1.25 yak/ha--with a plot where there was no grazing. The authors state that, in the plot without grazing, there was a more outstanding production of pasture biomass (1272 kg/ha), followed by the plot with a low stocking rate (1250 kg/ha), the plot with a medium stocking rate (1076 kg/ha), and, finally, the plot with a high stocking rate (925 kg/ha).