Publication Date

1989

Description

The savannah of the Colombian and Venezuelan plains have been relatively well studied from a floristic point of view and several major plant communities are recognized (Blydenstein, 1967). Nevertheless, the potential contribution of these plant communities to ruminant production have not been studied, except for the largest of these associations, that of the well­drained high savannah. Paladines and Leal (1979) have shown that it has low carrying capacity and sustains low levels of ani­mal production both per head and per animal, despite moder­ate levels of primary productivity. In effect, animal weight gains range from 70-90 kg head-1 and 18-40 kg ha-1, with stocking rates of 0.2-0.5 AU ha-1 (1 AU = 350 kg). The low animal gains are due to the low nutritive value of the savannah veg­etation even when immature (Hoyos, 1987; Vera et al., this congress), while the low performance per unit area is further affected by the need to burn mature herbage every 12-18 months, which results in a reduced carrying capacity. Under these conditions it has been clearly demonstrated that few man­agement practices, other than judicious use of fire, can increase ammal performance (Paladines and Leal, 1979). The potential role of the other plant communities has not been documented. Nevertheless, it is a popular belief among local graziers that the value of the savannah in general, and therefore its potential animal productivity, increases as the percentage of poorly­drained and seasonally-flooded savannahs increase in the land­scape. The purpose of the research reported here was to make a pre­liminary assessment of the different plant communities, both in terms of primary productivity and animal weight gains, based on data collected during the course of a large replicated grazing systems experiment which covered over 2000 has of savannah. Indications of potential differences among plant communities would help in deciding whether further specific research would be required.

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Variability of a Tropical Savannah and its Influence on Management Practices and Animal Weight Gains

The savannah of the Colombian and Venezuelan plains have been relatively well studied from a floristic point of view and several major plant communities are recognized (Blydenstein, 1967). Nevertheless, the potential contribution of these plant communities to ruminant production have not been studied, except for the largest of these associations, that of the well­drained high savannah. Paladines and Leal (1979) have shown that it has low carrying capacity and sustains low levels of ani­mal production both per head and per animal, despite moder­ate levels of primary productivity. In effect, animal weight gains range from 70-90 kg head-1 and 18-40 kg ha-1, with stocking rates of 0.2-0.5 AU ha-1 (1 AU = 350 kg). The low animal gains are due to the low nutritive value of the savannah veg­etation even when immature (Hoyos, 1987; Vera et al., this congress), while the low performance per unit area is further affected by the need to burn mature herbage every 12-18 months, which results in a reduced carrying capacity. Under these conditions it has been clearly demonstrated that few man­agement practices, other than judicious use of fire, can increase ammal performance (Paladines and Leal, 1979). The potential role of the other plant communities has not been documented. Nevertheless, it is a popular belief among local graziers that the value of the savannah in general, and therefore its potential animal productivity, increases as the percentage of poorly­drained and seasonally-flooded savannahs increase in the land­scape. The purpose of the research reported here was to make a pre­liminary assessment of the different plant communities, both in terms of primary productivity and animal weight gains, based on data collected during the course of a large replicated grazing systems experiment which covered over 2000 has of savannah. Indications of potential differences among plant communities would help in deciding whether further specific research would be required.