Abstract
The objective of this study was to evaluate the chemical composition of the forage apparently consumed by steers in a natural grassland on region of Campanha, in Rio Grande do Sul, Brazil, subjected or not to different inputs: NP - natural pasture without inputs; FNP - fertilized natural pasture and INP - improved natural grassland with fertilization and over-seeded with cultivated winter species. Three Angus steers testers and a variable number of regulator animals per experimental unit were utilized in order to maintain 13 kg of DM/100 kg of live weight (LW) as forage allowance. One time at each season, hand plucking samples were performed along the daily grazing time simulating forage harvested by the animals. The collected samples after drying and grind were submitted to chemical analysis to determine the forage quality. Except in winter and spring, the values of neutral detergent fiber were higher than the critical value of 550 g/kg of DM, which could limit forage intake, demonstrating that the values of forage on offer provided (15.6; 13.7; 13.5; 15.8 kg of DM/100 kg of LW/day in summer, autumn, winter and spring, respectively) were not restrictive to intake. The oversowing of winter cultivated species or fertilization positively alter the degradable fiber content. The seasons had marked influence on the chemical composition of forage apparently consumed; positively increasing some fractions of forage chemical composition in the seasons in which native or cultivated winter species increased their participation. The forage chemical composition is the determining factor in animal performance in natural pasture.
Highlights
Pastures and especially natural grasslands are the most economic source of nutrients to feed ruminants because of their ability to digest fibrous feeds
The objective of this study was to evaluate the chemical composition of the forage apparently consumed by steers in a natural grassland on region of Campanha, in Rio Grande do Sul, Brazil, subjected or not to different inputs: NP natural pasture without inputs; FNP - fertilized natural pasture and INP - improved natural grassland with fertilization and over-seeded with cultivated winter species
The botanical diversity of the natural pastures on vertisoils in the Campanha region of south Brazil, when managed with adequate forage allowance, has enough quality to meet their nutritional requirements for steers in the finishing phase
Summary
Pastures and especially natural grasslands are the most economic source of nutrients to feed ruminants because of their ability to digest fibrous feeds. On the natural grasslands from Pampa Biome, forage quality can be limited by their botanical composition but specially by the interaction between species composition and season of the year (Silveira et al, 2005). Seasonal fluctuation in forage quality from pastures results both from morphological alterations of plants as function of its phenological evolution and from seasonal replacement of flora species, as occurs in some natural grasslands. This flora can be substantially altered by grazing pressure, soil fertility or introduction (by direct drilling) of exotic species (Nabinger et al, 2009). Composition and quality of forage available and the forage selected by the animals is the starting point for the structuring of sustainable production systems
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