Diego Bendersky, Sebastian Lopez Valiente, Carlos Robson, Angela Jorgelina Flores, Celina Borrajo:
Management for Optimal Grazing Distribution of an Andropogon lateralis Community in Corrientes, Argentina

DIEGO BENDERSKY¹, SEBASTIAN LOPEZ VALIENTE², CARLOS ROBSON², ANGELA JORGELINA FLORES², CELINA BORRAJO^1
1National Institut of Agricultural Technology, Plant Production, Argentina
²National Institut of Agricultural Technology, Animal Production, Argentina

Heterogeneous subtropical grassland in central Corrientes (Argentina) comprises a great number of communities. The ``pajonal'', dominated by Andropogon lateralis, accumulates a high density of inflorescences during the fall which difficult the grazing by herbivores. Undesirable grazing distribution results in inefficient forage utilisation. Managers can increase uniformity of grazing and increase the utilisation. The aim of this study was to determine the pattern of cattle distribution on pajonal in winter after cutting it to facilitate grazing. The study was carried out in a paddock (90ha) at INTA's Mercedes Experimental Station with 5ha of pajonal. Seven Braford heifers fitted with GPS collars were used to determine spatial distribution of grazing during 6 consecutive days pre-cut and 6 consecutive days post"=cut the pajonal, in August 2009. The GPS collars were provided by the Project PICT 06 N1488, ANPCyT/UNMDP, Argentina. Stocking rate was 1 heifer ha^-1 (average 210kg heifer^-1), they were supplemented with 1.3kg heifer^-1 día^-1 of sunflower pellets on a deferred grassland. GPS collars recorded animal locations at one minute intervals. Only grazing locations were considered. Locations recorded 20m around water points, mineral supplement, and data points with animal velocities < 0.5 and > 10m min^-1 were discarded. An index was calculated to determine the site selection: ISci= Tri x Sri^-1; where Tri = (grazing time in community) x (total time of grazing)^-1 and Sri = (face of community) x (face of the paddock)^-1. Similar indices between communities indicate similar preference in the selection. The ISci was analysed by ANOVA ($\alpha$ = 0,05). Post-cut forage availability of pajonal was 32% lower than pre"=cut and cut forage was conserved as hay. During pre"=cut the ISci was smaller in pajonal than in the rest of the paddock (0,13 vs. 1,10 respectively). When the pajonal was cut, the heifers grazed it and there were no differences between ISci for the pajonal and the non"=pajonal areas of the paddock (0,84 vs. 0,90 respectively). Cutting pajonal improves its utilisation efficiency.

Keywords: Argentina, Corrientes, GPS-collars, grazing behaviour

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Contact Address: Diego Bendersky, National Institut of Agricultural Technology, Plant Production3470 Mercedes, Argentina, e-mail: diegobcorreo.inta.gov.ar