New Zealand Journal of Agricultural Research abstracts
Effects of contrasting sward heights within forage species on short-term
ingestive behaviour of sheep and goats grazing grasses and legumes
Y. GONG
M. G. LAMBERT
AgResearch Grasslands
Private Bag 11008
Palmerston North, New Zealand
J. HODGSON
Plant Science Department
Massey University
Private Bag 11222
Palmerston North, New Zealand
Abstract An experiment was designed to separate the effects
of sward height on ingestive behaviour, from the confounding effects of forage
species and maturity stages which occurred in a previous experiment. Two grass
species (perennial ryegrass (Lolium perenne) and cocksfoot (Dactylis
glomerata)) and two white clover (Trifolium repens) cultivars
(`Grasslands Tahora' and `Grasslands Kopu') with height contrasts within each
forage, were grazed at a vegetative stage of growth by four sheep and four
goats. Turves (41 x 27 cm) were extracted from the established plots where
monoculture swards were growing, and presented after canopy structure was
characterised, to animals individually confined in metabolism crates. Animal
responses in bite weight, bite rate, and bite dimensions (depth, area, and
volume) to variation in sward structure brought about by increases of height
within forage species were evaluated. Independent variation of surface height
from bulk density was achieved in cocksfoot (r = -0.22;
P < 0.1), but height was confounded with bulk density in
ryegrass (r = 0.50; P < 0.001) and clover (r
= -0.49; P < 0.01). Bite weight, rate, depth, and volume
were more sensitive to variation in sward surface height than in bulk density.
Animals usually increased bite depth, hence bite volume and bite weight, and
reduced bite rate significantly, in response to increasing height of swards
irrespective of forage species. Bite area generally responded little to
variations in either height or bulk density. Sheep usually had greater absolute
mean values for most bite variables than goats, and there were few significant
interactions of animal species x sward height effects on bite variables within
each forage species. Sward height had a dominant effect, and bulk density had
no significant effect on ingestive behaviour in cocksfoot where independent
variation in height and bulk density was achieved. In ryegrass, where the
variation in sward height was correlated with bulk density, sward height still
had a dominant effect, but the interactive effect between sward height and bulk
density was significant for goat grazing. In white clover, where there was a
negative association between sward height and bulk density, the effect of bulk
density was only significant for sheep.
Keywords grasses; clover; height; bulk density; sheep; goats;
ingestive behaviour; bite weight; bite rate; bite depth; bite area; bite
volume
New Zealand Journal of Agricultural Research, 1996, Vol. 39: 83-93
0028-8233/96/3901-0001 $2.50/0 (c) The Royal Society of New Zealand
1996
PDF file of entire paper: medium quality (772K); (scanned from paper original: notes about this process)
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