Herbage responses of Tamani and Quênia guineagrasses to grazing intensity

Abstract

AbstractNew forage cultivars require defoliation studies for recommending proper grazing management. Our objective was to characterize herbage accumulation (HA), plant‐part composition and nutritive value of guineagrass [Megathyrsus maximus (Jacq.) B. K. Simon & S. W. L. Jacobs] rotationally stocked under two grazing intensities. The experimental design was a randomized complete block with three replicates of a 2 × 2 factorial arrangement of two guineagrass cultivars (‘BRS Quênia’ and ‘BRS Tamani’) and two grazing intensities. Heavy (HGI) and lax (LGI) grazing intensities were imposed as post‐grazing stubble heights: 15 and 25 cm for Tamani, and 20 and 35 cm for Quênia, respectively. The experimental period was from March 2015 to March 2017, comprising eight seasons (autumn 2015, winter 2015, spring 2015, summer 2016, autumn 2016, winter 2015, spring 2016, and summer 2017). In the spring 2016 and summer 2017, pre‐grazing HM was sampled as two strata above the stubble height, each comprising 50% of the sampled height (upper and lower stratum). Total herbage accumulation was similar across years, cultivars, and intensities (16,810 kg DM ha−1). Quênia and Tamani had the greatest HA during summer. The leaf proportion was least in the HGI pastures. Under HGI, the lower stratum of both cultivars had the greatest stem proportion and the least nutritive value. The greatest herbage CP concentration and the least NDF, ADF, iNDF and LIG concentrations occurred in the upper stratum. Based on these results, 35 and 55 cm are recommended as target heights for initiation of grazing, and 25 and 35 cm as post‐grazing stubble heights for Tamani and Quênia, respectively.