Sward Structural Characteristics and Performance of Beef Heifers Reared under Rotational Grazing Management on Campos Grassland

Cezar Wancura Barbieri,Franciele Gusatto,Émerson Mendes Soares,Gabriela Machado Dutra,Régis Maximiliano R Carvalho,Felipe Xavier De Lima,Fernando Luiz F De Quadros,Leandro Bittencourt De Oliveira,Felipe Jochims

doi:10.4236/ajps.2014.57114

Abstract

This study aimed to evaluate the effect of two rest intervals on structural sward characteristics and productive performance of beef heifers reared on Campos grassland managed on rotational grazing. The treatments were two intervals between grazing of 375 and 750 DD (degree days), based on thermal cumulative sum for leaf expansion of native grasses belonging to two functional groups. The experimental design was a randomized complete block design with two treatments and three replications. The tested animals were beef heifers with initial age of 12 months and average weight of 185.2 ± 17.4 kg. Measures in the pasture were: herbage mass, mass of green leaf blades, stem mass, dead material mass and green leaf allowance. The 750 DD rest interval presented higher herbage mass (24%), higher green herbage mass and 19% more leaves in the canopy. This rest interval also presents a high proportion of dead material and stems in the sward structure. In the other way, the 375 DD rest interval presents better chemical characteristics, with 20% more crude protein in the hand plucking samples. Heifers’ dry matter intake was similar between the rest intervals (2.04% of live weight) and the bite mass was also similar (0.22 g DM per bite) but the animal performance was higher in the 375 DD rest interval. The stocking density showed similarity between treatments with an average of 875 kg/LW/ha. The live weight gain per area was higher in 40 kg/LW/ha (P = 0.117) for 375 DD rest interval, reaching 251 kg/LW/ha produced over the 149 experimental days. Based on these results, we can conclude that the treatment of shortest interval between defoliation gave the highest gain individual animals in warm seasons.

Highlights

The combination of high stocking rates and inappropriate management applied to the natural grasslands of the Pampa Biome, known as Campos Grasslands [1], usually results in low animal performance rates
Herbage mass (HM) differed among the rest periods tested (P = 0.01) being 24% higher in the paddocks managed with 750 degree day (DD) interval
Grasses contribution for A and B groups were similar for both treatments, being 52% and 51% of herbage mass (HM), respectively for 375 and 750 DD

Summary

Introduction

The combination of high stocking rates and inappropriate management applied to the natural grasslands of the Pampa Biome, known as Campos Grasslands [1], usually results in low animal performance rates. Those lower rates make beef cattle production activity less profitable than other production options beyond animal production, conservation of this biome is important due to its plant diversity and ecossistemic services provided. According to the same authors, heifers are the main livestock category reared in this forage resource This category doesn’t provide short term economic return, when compared to fattening steers or breeding cows, heifers need to receive appropriate attention to obtain suitable conditions to be mated. Reduction of age at first mating has positive impacts in the whole local production system [4]

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