Manejo do milheto em pastoreio rotativo para maximizar a taxa de ingestão por vacas leiteiras

Avaliaram-se os efeitos da estratégia de pastoreio rotacionado sobre a dinâmica do rebaixamento do milheto (Pennisetum glaucum (L.) R. Br.) pastejado por vacas leiteiras. Os tratamentos consistiram de um fatorial entre duas alturas pré-pastejo, 60 e 40cm, e duas pós-pastejo, 20 e 10cm, alocados em um delineamento em blocos ao acaso com quatro repetições. A estrutura do pasto foi avaliada durante o processo de pastejo a cada 10 minutos, por meio de medições de altura. A taxa de rebaixamento da altura do pasto no tratamento 40-20 apresentou-se relativamente constante ao longo de todo o rebaixamento. O tratamento 60-10 apresentou o maior declínio na taxa de rebaixamento. A taxa de rebaixamento no tratamento 40-10 diminuiu em ritmo mais lento em relação à dos tratamentos com 60cm de altura pré-pastejo. As maiores taxas de ingestão foram observadas nos tratamentos de altura pré-pastejo de 60cm, e considerou-se como a melhor estratégia de manejo a combinação 60-20cm de altura do pasto

Daily Forage Intake by Cattle on Natural Grassland: Response to Forage Allowance and Sward Structure

We investigated the hypothesis that not only forage allowance but also sward structure affects daily forage intake by beef heifers on natural grasslands of the Pampa Biome (southern Brazil). We used data from a long-term experiment, which has been managed by forage allowance levels since 1986. The objective was to investigate sward management targets that maximize daily forage intake. During January and December 2009, we evaluated the effect of forage allowance on forage mass, sward height and tussock frequency, and its consequences on dry matter intake (DMI). The experiment was arranged in a randomized complete block design with two replicates. Treatment was level of daily forage allowance (4, 8, 12, and 16 kg dry matter [DM] per 100 kg of animal body weight [BW]). Data were analyzed using regression, principal component analysis, and descriptive analyses from three-dimensional contour graphs with the data of sward structure, DMI, and DMI rate. Results demonstrated that DMI was positively correlated to forage allowance. However, higher levels of forage allowance can cause lower intake rates of forage and nutrients. We concluded that sward targets which promoted higher DMI and DMI rate were: daily forage allowance of ∼ 12 kg of dry matter per 100 kg of the animal's body weight, forage mass between 1 800 and 2 300 kg DM·ha-1, sward height between 11.5 and 13.4 cm, and tussock frequency lower than 30% of occurrence in the pastures. Within these targets, a high intake of nutrients was obtained, indicating the potential use of sward structure as a tool for managing natural grasslands in order to promote high intake of forage and nutrients by cattle. © 2016 Society for Range Management. Published by Elsevier Inc. All rights reserved.The Rangeland Ecology & Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information