Sward height determines pasture production and animal performance in a long-term soybean-beef cattle integrated system

To improve our knowledge on the effects of different grazing intensities on integrated crop-livestock systems (ICLS) and thus define solid management goals to maximize plant and animal responses in these systems, we analyzed 16 years of data regarding to herbage mass, daily herbage accumulation, total herbage production, stocking rate, individual average daily gain and live weight gain per hectare from a long-term ICLS in southern Brazil. Treatments consisted of different grazing intensities (defined by the sward heights of 10, 20, 30 and 40 cm) by steers on mixed black oat (Avena strigosa Schreb.) and Italian ryegrass (Lolium multiflorum Lam.) pastures under continuous stocking. Herbage mass was consistently correlated to sward height, increasing by 88.7 kg DM ha(-1) for each centimeter of sward height. The sward management heights of 20, 30 and 40 cm were similar with an average of 1.08 kg LW-1 animal(-1) day(-1), decreasing at a rate of 0.03 kg LW animal(-1) day(-1) for each cm decrease under 19 cm following a segmented equation. Stocking rate and live weight gain per area responded linearly decreasing by 35.8 kg LW ha(-1) and 12.1 kg LW ha(-1) for each cm increase in sward height, respectively. The long-term pasture and animal production presented a consistent pattern over the 16 experimental years, showing that swards managed under 19 cm are detrimental to animal individual performance despite of increases in the live weight gain per area. We conclude that managing the sward heights between 20 and 30 cm (moderate grazing intensities) maximize both plant and animal production and should be adopted as the management goal for mixed black oat and Italian ryegrass pastures within an ICLS meeting the global demand for increased food production and sustainability of the agroecosystems.