Voluntary feed intake by sheep and digestibility of shadedStenotaphrum secundatumandPennisetum clandestinumherbage

Abstract

SUMMARY: The effects of shade (50% of ambient light transmission) on the quality of established swards of buffalo grass (Stenotaphrum secundatum) and kikuyu grass (Pennisetum clandestinum) were examined at Wollongbar Research Station, northern New South Wales. Sarlon cloth was used to shade plots of the two species, after cutting to 8 cm, from November 1985 to March 1986. Herbage was harvested from shaded and adjacent unshaded plots for chemical analyses and for feeding as dry chaff to penned sheep at the University of Queensland research farm at Mt Cotton.Shade markedly decreased the voluntary feed intake (VI) ofP. dandestinumby 30·7% over the two harvests while VI ofS. secundatumwas not significantly affected. Shade had no effect on thein vitroandin vivodigestibility ofP. clandestinumherbage but marginally increased that ofS. secundatum. These shade effects resulted in a 14·2% increase forS. secundatumand a 34% decrease forP. clandestinumin the intake of digestible dry matter of shaded compared with unshaded herbage.The reduced VI of the shade-grown herbage ofP. clandestinumwas associated with a higher proportion of stem (21v. 8% for unshaded herbage), a lower proportion of leaf (48v. 54%), and a lower concentration of total nonstructural carbohydrates (TNC) (0.9v. 2.1%). InS. secundatum, there were similar, but smaller, changes in proportion of stem and TNC percentage in shade-grown herbage but, in contrast toP. clandestinum, these potential detriments to VI were offset by an increase in proportion of leaf and a decrease in the proportion of dead material. Average moisture content of shaded herbage (76%) was higher than that of unshaded herbage (70%). Nitrogen and potassium concentrations in plant tissue were higher in the shaded herbage.The higher yielding capacity and maintenance of nutritive quality of shadedS. secundatumcompared with shadedP. clandestinumindicates the potential usefulness ofS. secundatumfor plantation agriculture.