Produção e comportamento animal em pastagem natural manejada sob pastoreio rotativo – análise conjunta de experimentos

Abstract

The aim of this work was to study, through a joint analysis of experiments, the effects of rotational grazing, using rest intervals based on duration of leaf expansion of native grasses, on the primary and secondary production as well as grazing behaviour of beef heifers. Then, it was elaborated a database from experiments conducted using beef heifers managed in a natural grassland under rotational grazing, using two rest intervals between grazing: 375 and 750 degree-day (DD). The experimental design of the area was randomized blocks where the two rest intervals were the treatments with three area replicates for each treatment. The database was composed by eight experiments performed between 2010 and 2014, it was considered as fixed effects the treatments and climatic seasons; studies and experimental error as random effects. The mean area production was 411 kg body weight/hectare/year, considering a mean stocking rate of 915 kg body weight per hectare and an average daily gain of 0,276 kg body weight per day. The use of rotational grazing, using grazing rest intervals based on duration of leaf expansion of native grasses, was able to increase the utilization efficiency of natural grasslands areas, making possible adequate individual gain for rearing beef heifers between weaning and breeding at 24 months old. Beef heifers have a diurnal grazing pattern when managed in natural grassland under rotational grazing. However, there are significant grazing activities during dark periods as well as climatic season differences in the moment when animals perform those activities. Grazing behaviour assessments in beef heifers managed in natural grasslands, performed only on diurnal period, do not contemplate the required period to represent all grazing activities. To contemplate all grazing activities, it is necessary to perform the grazing behaviour assessments between dawn and midnight.