The effects of shard structure and bite weight (W) on bite rate in cat
tle (Bos taurus) were examined to explain the behavioural components o
f handling time. Three oesophageally fistulated steers grazed homogene
ous, hand-constructed swards of Paspalum dilatatum Poir. or Medicago s
ativa L., in a sward area of approximately 0.36 m2, for 60-212 s- Thre
e types of jaw movements (JM) were distinguished: manipulative JM that
gather herbage into the mouth, chewing JM, and compound JM that manip
ulate fresh herbage and chew herbage already in the mouth within one c
ycle of opening and closing of the jaws. Intake rate (I, g min-1) was
a discontinuous asymptotic function of W: I = W/max (0.0337,0.0201 + 0
.0095W). Sward height and bulk density did not significantly affect I
beyond the effects of W. Time per bite was 2.0 s when W almost-equal-t
o 1.29 g, and increased linearly with when W > 1.29 g. Linear regressi
on of time perbite on total number of JM explained 96% of the variance
. A non-linear relation between total JM per bite and W comprised a li
near relation between total chews per bite and W, and a constant numbe
r of total manipulative JM per bite. When W increased up to c. 1.5 g,
chewing requirements were met by compound JM, Above W of 1.5 g, the ov
erlap of chewing and manipulation reached a maximum, so total JM incre
ased with W. The importance of compound JM and the potential for overl
ap between chewing and searching are discussed in the context of forag
ing models.