Sheep performance and forage quality in grass-legume pastures with different canopy heights

Abstract

Context Canopy height is an important grazing management tool in grass and multispecies pastures. Aim To evaluate the effect of different canopy heights on the nutritional value of forage and animal productivity in pastures formed by Aruana guineagrass (Megathyrsus maximus cv. Aruana) combined legumes [Macrotyloma (Macrotyloma axillare), Calopo (Calopogonium mucunoides) and Stylo (Stylosanthes macrocephala + Stylosanthes caweedstata)] managed under continuous stocking with sheep. Methods The treatments consisted of four forage canopy heights (15, 30, 45 and 60 cm) in a randomised block design with four replicates, totalling 16 experimental units (paddocks). The following parameters were assessed: total herbage mass, proportion of botanical and morphological components in samples obtained by grazing simulation, nutritional value and digestibility of forage, animal performance, stocking rate, and animal productivity. Key results Herbage mass was higher in taller pastures (45–60 cm; P < 0.0001). The proportion of legumes in herbage mass increased throughout the experimental period (P < 0.0001), and the highest proportion of legumes in the grazing simulation was observed in autumn (P < 0.0001). Pastures measuring 15 cm had a higher crude protein content (P < 0.0001), but the average daily weight gain was higher (P = 0.0404) in pastures maintained at 30 and 45 cm (100.3 and 87.4 ± 11.44 g/animal day−1, respectively). Stocking rate (P < 0.0001) and animal productivity (P = 0.0267) were lower in 60-cm pastures. Conclusion Multispecies pastures of Aruana guineagrass combined with Macrotyloma, Calopo and Stylo forage legumes should be managed at 15–45 cm under continuous stocking. Implications This study provides an option for combining forage species in intercropped tropical pastures, and indicates a range of pasture heights that will ensure animal productivity and pasture sustainability.