
TY  - JOUR
A1  - Stobbs, TH 
T1  - The effect of plant structure on the intake of tropical pastures. II.* Differences in sward structure, nutritive value, and bite size of animals grazing <I>Setaria anceps</I> and <I>Chloris gayana</I> at various stages of growth
JF  - Australian Journal of Agricultural Research
JO  - Aust. J.  Agric. Res.
Y1  - 1973
VL  - 24
IS  - 6
SP  - 821
EP  - 829
KW  - 
UR  - https://doi.org/10.1071/AR9730821 
N2  - Bite size (organic matter content per bite) of cows grazing swards of Chloris gayana (rhodes) and Setaria anceps (setaria) regrown for 2, 4, 6, and 8 weeks was measured using oesophageal fistulated animals. Sward canopy structure was measured by stratification into five vertical layers, each 15 cm high; for each layer weights of leaf and stem components were estimated. Chemical composition and in vitro digestibility of plant fractions and oesophageal fistulae samples were determined. Cows grazing the 4 week regrowths of rhodes grass had a larger bite size (0.32 g OM/bite) than when grazing 2 week regrowths (0.27 g OM/bite) when the availability of herbage and leaf material was lowest. Despite a marked increase in herbage yield as the pastures matured (up to 8427 kg/ha) the mean bite size decreased to a mean of 0.15 g OM/bite at 6 and 8 weeks. The bite size of cows grazing setaria pastures was lower than on the rhodes grass pastures but followed a similar pattern. A high density of leaf within the sward (sward leaf density) as well as a low stem content were considered to be the main factors affecting bite size. Setaria and rhodes grass pastures had both low sward bulk densities (a range of 14&ndash;96 kg/ha cm) and low sward leaf bulk densities (a range of 12&ndash;43 kg/ha cm) compared with temperate pastures. Basal layers of the sward contained more dense herbage (up to 148 kg/ha cm), but sward leaf density was usually less than 80 kg/ha cm and apparently inaccessible. ___________________ *Part I, Aust. J. Agric. Res., 24: 809 (1973). 
ER  -

