Management practices for tropical grasses and their effects on pasture and milk production

Abstract

Two experiments examined the effect different pasture management strategies had on individual cow milk yield during the summer wet season. In control treatments pasture was continuously grazed. In managed pastures the aim was to produce swards with a high leaf and low stem content. The grasses Panicum maximum cv. Gatton and Brachiaria decumbens were used in both experiments. Experiment one consisted of three pasture treatments; the stock were 1 8 Friesian cows. The control treatment was grazed continuously with no pasture management and was compared with two subjectively applied management treatments in which pasture was either slashed or stocked at variable rates in an attempt to increase pasture quality. The experiment lasted 17 weeks. Each time pastures were slashed or extra cows were added milk yield per cow fell. The lower each grass was slashed or the greater the number of cows added to a paddock the greater the fall in milk yield. Measurements of pasture yield, height and structural composition showed that slashing and variable stocking could increase the leaf percentage in the pasture, but not without seriously decreasing total leaf yield. In experiment two, 24 Friesian cows were used to compare the following treatments over a 10-week period (a) control-continuous grazing, (b) rotational grazing using a 2-week grazing, 2-week spelling regime and (c) rotational grazing with slashing after each grazing period. Milk yields averaged 10.6, 9.8 and 9.6 kg/cow day1, respectively (P> 0.05), and 10.1 and 9.9 kg/cow day-1 for B. decumbens and P. maximum pastures (P> 0.05). As in the first experiment, leaf percentage was increased by management treatments, but not without decreasing total pasture yield to the level where it limited milk production. Leaf yields could only be increased with an associated increase in total pasture yield. It was concluded that grazing management decisions should be based on total pasture on offer rather than any percentage component of total yield.