An assessment of Coastcross II Bermudagrass and kikuyu for growing out young beef animals.

Abstract

The immediate aim of this study was to relate herbage availability, liveweight gain and stocking rate to one another under continuous and rotational grazing so that management recommendations could be formulated for Coastcross II Bermudagrass and kikuyu. In addition, these data would be used for an economic evaluation of growing out young beef animals on these two pasture species. The broad long term goal was to use this information to persuade farmers to make more use of planted pastures and thereby reduce the stocking pressure on the veld. Besides pursuing the primary objectives, the study offered an opportunity to make an observational assessment of the put-and-take technique for use in grazing trials. In relation to fixed stocking, variable stocking appeared to have no distinct advantage in this study. This conclusion is drawn from the fact that little success was achieved in applying put-and-take at a high level of precision. It was therefore recommended that future trials should make use of fixed stocking, except when variation in herbage availability is very large and predictable. In such cases the use of put-and-take would be warranted. Liveweight gain of animals was linearly related to herbage availability. In two seasons liveweight gain of animals on Coastcross was higher for continuous grazing than for rotational grazing at equivalent herbage availability, but in other seasons there was no difference between the two methods of grazing. At equivalent levels of herbage availability liveweight gain was higher in early summer than in late summer. Herbage availability decreased linearly witilin each season and on average, rotational grazing resulted in increasingly greater herbage availability than continuous grazing, as stocking rate was increased on Coastcross. However, no difference between the two grazing methods was evident on kikuyu. Finally, the relationship between liveweight gain and stocking rate was also described by a linear function. On average, the stocking rate at which maximum liveweight gain per ha occurred (SRmax) was higher for rotational grazing than continuous grazing on Coastcross, but not on kikuyu. However, no difference was evident between the two grazing methods in each season. During the study period annual rainfall varied from 506 mm to 990 mm. This offered a unique opportunity to examine the relation between some of the pasture production parameters measured and annual rainfall. The length of the grazing season and SRmax increased, but liveweight gain of animals at SRmax declined as annual rainfall increased. This caused seasonal liveweight gain at SRmax to increase initially, but then to reach a maximum and decrease as annual rainfall increased from 500 to 1000 mm. From this information it was possible to build two models which can be used to predict liveweight gain per ha and profit per ha from stocking rate and annual rainfall. These models can either be built into farm planning programmes or used directly by agricultural advisors. In tl1is thesis they have been used to show that there is a wide range in stocking rates and levels of annual rainfall within which it is possible to make substantial profits by grazing young beef animals on dryland pastures. This study has therefore provided forceful information which can be used to persuade farmers to make more use of planted pastures, and in so doing, conserve the veld.