Patterns of Defoliation in Kikuyu Grass Swards Under Intermittent Stocking.

Recent studies have shown that in intermittent stocking method the short-term herbage intake rate is maximized when the level of defoliation do not exceed 40% of pre-grazing height. Although there is some indication that from that level of defoliation animals start to graze undesirable horizons, there is still a lack of information on how is the pattern of defoliation of individual tillers during the grazing down process. Thus, the aim of this study was to evaluate the dynamics of defoliation in kikuyu grass pastures (Pennisetum clandestinum Hochst. Ex. Chiov.) testing the hypothesis that the transition between grazing horizons occurs when animals defoliate around 40% of initial height. The experiment was conducted using a pre-grazing height of 25 cm that was submitted to levels of defoliation of 40, 50, 60 and 70% of the initial height. The experiment was assigned according a randomized complete block design with four treatments and three replications. Pastures were grazed down in 24 hours by dried cows and assessments related to the dynamics of defoliation were conducted by using marked tillers technique. Results showed that the frequency of defoliation of individual tiller increased linearly with the stocking density and the technique of extended tiller underestimated the magnitude of frequency of defoliation regardless of severity of defoliation. From 40% of severity of defoliation, the probability of defoliation of senescent leaves and stems+pseudostems increased from two to three times, respectively. Moreover, with a level of defoliation of 40% approximately 25% of the grazed area was grazed twice or three times and there was a linear increase in exploitation of undesirable horizon as the levels of defoliation increased. It was concluded that the transition between grazing horizons start before 40% of defoliation of pre-grazing height.