Protein-energy supplementation for different categories of animals in beef cattle on natural and cultivated pastures of the Brazilian Pantanal.

The goal of this study was to evaluate the effect of protein-energy supplementation during the dry period on the performance of different categories of beef cattle in different management systems of natural and cultivated pastures in the Brazilian Pantanal. Different categories of animals (weaned calves, heifers, primiparous and multiparous cows) were stratified by weight and distributed in one of the following feeding treatments: T1 - natural pasture (grazed), with liquid supplementation (control); T2 - natural pasture (deferred grazing), with liquid supplementation; T3 - cultivated pasture (deferred grazing),with liquid supplementation, from June to September 2006. A continuous stocking method was adopted (0.3, 0.6 and 0.6 of Animal Unit per hectare (AU/ha) for T1, T2 and T3, respectively). Forage availability and quality, supplement intake by livestock, animal performance and ingestive behavior were evaluated over two periods, totaling 90 days of evaluation. Analysis of variance showed differences between initial weight and finished weight in each period between different feeding treatments and animal categories. Animal weight gains were observed during the initial period (mid-season drought), when 440 to 2.800 kg DM forage/ha was available, while weight losses were observed in the final period (late-season drought) when 580 to 800 kg DM forage/ha was available. In the late-season drought, T3 allowed less weight loss among the categories. Primiparous and multiparous cows lost more weight and these higher losses may be related to the higher demand for dry matter intake these categories require. Considering forage offer as the limiting factor during the second period, we concluded that protein-energy supplementation is viable only when the stocking rate is adjusted according to availability of forage.