Respuesta al método de pastoreo y la oferta de forraje en campo natural en el período otoño-invernal

This study seeks to determine how grazing methods and forage supply, as the main modifiable variables, in addition to soil conditions, affect primary and secondary productivity and the plant composition of the vegetation cover. A 2x2 factorial design experiment was conducted on pasture 13 of the Mario A. Cassinoni Experimental Station (La - 32.387511°S and Lo -58.033235°W), evaluating two levels of supply (high and low, with combinations of 12% in autumn and 8% in winter, and 8% in autumn and 6% in winter, respectively) and two grazing methods (rotational and continuous) are being evaluated. The animals used were Holstein steers. The OF levels are adjusted monthly according to forage availability (kg DM/ha) and expected growth rate, regulating stocking rates based on monthly weighing data. The evaluation period ran from 24 April 2024 to 26 August 2024, covering the autumn and winter seasons. The aim of the study was to determine the botanical composition and primary and secondary production for the different treatments. The area was classified into three zones—Low, Medium, and Litosols—corresponding to contrasting soil types, according to cartography and visual field estimates. The variables determined were forage height (cm), forage mass present (kg DM/ha), botanical composition, and average daily gains of the animals (kg BW/a/day). For the analysis of the results, the statistical software InfoStat was used, applying multivariate descriptive techniques and analysis of variance (ANOVA), followed by Tukey's mean comparison tests with a significance level of 10%. Height was influenced by both forage supply and grazing method, with the rotational method with high supply standing out as the one that allowed for greater heights to be achieved. Likewise, a strong influence of soil conditions was observed: the highest heights were recorded in low-lying areas, while the lowest were found in lithosols. The botanical composition was mainly determined by soil conditions. An effect associated with both supply and grazing method was also observed, resulting in contrasting sets in terms of vegetation type and productivity. With regard to growth rate, effects attributable to both the area and the grazing method were evident. Low-lying areas showed a higher growth rate compared to lithosol areas, as did the rotational method compared to the continuous method. In the case of forage mass, a marked influence of the three variables (supply, method and area) was observed. Forage utilisation was determined by the method, supply and contrasting soil conditions. Animal productivity was mainly affected by forage supply. Lower losses in average daily gain were recorded under conditions of high supply, especially within the rotational system, while in the continuous method no significant differences were observed between supply levels.