FR 26. Feed suplementation with diets based on local resources in postcalving dual purpose cows Guárico state highlands, Venezuela. II. Effect on the reproduction performance

The biological impact of two grazing systems was evaluated in Panicum maximum pastures: 1. Intensive grazing (IG), characterized by high total (± 2 AU/ha) and instantaneous (±100 AU/ha) stocking rates, short grazing periods (1 - 3 days) and pasture resting time (32-92 days) according to forage availability. 2. Traditional grazing (TG), characterized by low stocking rate (± 1 AU/ha), long grazing periods (10 - 15 days) and least paddock rotation. A complete randomized design, with two replicates of 4 has each was used. A total of 64 heifers, with a range live weight from 120 to 260 kg was used. IG resulted in higher live weight gain (P < .0001), leaf yield (P < .0001), rate of tillering, leaf and stem ratio and plant density than TG. Nevertheless, IG had lower total biomass and plant diameter than TG. Also, IG resulted in a higher plant trampling and soil compaction than TG. There was not significant difference on CP, NDF and ADF concentrations between the two grazing systems. It was concluded that, the highest live weight gain obtained with IG was closely associated to the high availability of good quality forage. Further evaluation is required to quantify the long term effects on plant, soil and animal behaviour.