Abstract
The aim of this study was to evaluate the effects of different grazing intensities on forage production and animal performance of yearling steers kept under permanent grazing in an integrated crop-livestock system. The treatments consisted of areas with sward heights of 10; 20; 30 and 40 cm, and one treatment with no grazing. The pastures were of bristle oat (Avena strigosa Schreb.) and annual ryegrass (Lolium multiflorum Lam.) following soybean (Glycine max (L.) Merr.). The variables forage mass, forage allowance and residual straw showed a positive and linear fit to the increasing sward height (P≤0.0001). Average daily gain of steers displayed a quadratic response (P = 0.0017), being optimal with increases in grazing height up to values of near 30 cm, showing a weight gain per animal of approximately 1.0 kg day-1. A similar response was seen for live weight at slaughter and carcass characteristics (P≤0.0305). The results suggest that sward heights close to 30 cm provide greater individual gains, due to the increase in forage available to each animal and the better quality of the consumed forage without compromising the residual straw destined for the following crop.
Highlights
The use of cover crops to feed livestock makes the economic stability and sustainability of no-tillage integrated crop-livestock systems (ICL-NT) possible
Forage mass (FM) and blade mass (BLM) were linearly related to sward height (P < 0.0001)
Yearling steers individual performance in black oat and annual ryegrass pasture is optimized by managing sward height close to 30 cm, which corresponds to a herbage mass around 3.800 kg DM ha-1
Summary
The use of cover crops to feed livestock makes the economic stability and sustainability of no-tillage integrated crop-livestock systems (ICL-NT) possible. Grazing intensity (GI) is a fundamental variable for grassland management. It is under human control and defined by the rate of animal stock and its distribution over space and time (e.g. resting periods defined for rotational stocking). The grazing animal increases the number of feeding stations visited in response to the restricted forage allowance (BAGGIO et al, 2008). In such a situation, grazing animals have higher energy costs, which result in limited performance and affects carcass characteristics when destined for finishing and slaughter (LOPES et al, 2008)
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