The Use of Liveweight‐gain Trials for Pasture Evaluation in the Tropics

Abstract

Two methods of measuring the liveweight gain of cattle on sown pastures are described in a 15 ac grazing trial. During the first 12 months of grazing, stocking rate was varied within and between pasture species. In the remaining 21 months, stocking rate was maintained at the same level between all pastures, but varied with the overall seasonal changes in grass availability. The relative merits of the two methods are discussed, and it is concluded that the trial using the same stocking rate on all species offered the more effective and practicable method of comparing pasture production differences of the order 30-50%.The results showed significant improvements in liveweight gain in the latter 21 months of the experiment, resulting from the inclusion of a legume, Centrosema pubescens in a Hyparrhenia rufa sward, and from the use of Hyparrhenia rufa rather than Panicum maximum in association with Centrosema pubescens. The ability of unfertilized ley pastures to produce over 300 lb/ac of liveweight gain in favourable years was clearly demonstrated.

The Use of Liveweight‐gain Trials for Pasture Evaluation in the Tropics

“…The trial was easier to conduct than the variable-stocking-rate designs which have been described by Stobbs (9) and Stobbs and Joblin (12); sound practical management of livestock Field experiments in the tropics are frequently hampered by inherent variation in the experimental material greater than that met with in more temperate latitudes (8). The results of index cropping with sorghiun demonstrated this point.…”

“…The design used in this experiment provided a useful means of comparing pasture mixtures using only limited amounts of land and livestock. The trial was easier to conduct than the variable-stocking-rate designs which have been described by Stobbs (9) and Stobbs and Joblin (12); sound practical management of livestock was possible and the results are applicable to farming practice in Uganda. Field experiments in the tropics are frequently hampered by inherent variation in the experimental material greater than that met with in more temperate latitudes (8).…”

The Choice of Fixed or Variable Stocking Rates in Grazing Experiments

“…Marten and Donker, 1968). Stobbs and Joblin (1966) describe a modified P & T method, suitable for use where differences in pasture production are of the order of 30-50 per cent, in which a common stocking rate, near the capacity of the best treatments, was used over all treatments. The overall stocking rate was varied seasonally according to the growth rate of the stock and a subjective assessment of the pastures; as all treatments were managed alike, differences were expressed as variations in liveweight gain.…”

“…Stobbs and Joblin, 1966). It is difficult to obtain reliable measurements of liveweight change over short periods, and considerable experience in the adjustment of stocking rate may be required, but this approach merits further examination.…”

The Use of Liveweight–gain Trials for Pasture Evaluation in the Tropics

“…Stobbs and Joblin (12) suggested a more objective approach for the evaluation of pastures which showed differences of the order of 30-50%. They suggested that a common stocking rate, similar to the capacity ofthe best treatment, should be used on all treatments, but that the overall stocking rate should be varied seasonally according to the growth of the stock and a subjective assessment of the condition of the pasture.…”