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Abstract
The objective of this study was to investigate the effect of age of calf on the behaviour
of Zebu and crossbred calves during restricted suckling (RS) periods. The behaviours
of 20 Zebu and 16 crossbred calves were recorded during two 30-min sessions each day
after milking when the calves and their dams were brought together in a group for
suckling. This was made for a time period of 2 weeks/month for 6 months postpartum.The
total suckling duration was significantly longer in Zebu calves (11.8+/-0.19 min)
compared to the crossbred calves (9.4+/-0.19 min), but decreased significantly in
both breeds with increasing age from 1 to 6 months. The number of suckling bouts decreased
from a mean of 3.8 at 1 month of age to 1.1 at 6 month (P<0.05). The duration of each
suckling bout decreased significantly from a mean of 3.5+/-0.15 min at 1 month of
age to 1.6+/-0.01 min at 6 months (<0.05). The frequency of crossbred calves cross-suckling
(3.7%) was significantly higher than that of the Zebu calves (1.9%; P<0.05). The frequency
of calves cross-suckling decreased significantly from 4.2% at 1 month of age to 2.3%
at 6 months. The duration and number of bouts of cross-suckling was significantly
higher in the crossbred calves (duration 0.9+/-0.06 min; bouts 3, 7) than in the Zebu
calves (duration 0.5+/-0.06 min; bouts 2, 7) and decreased with increasing age of
calf. The duration and number of bouts of inter-sucking was significantly higher in
the crossbred calves (duration 0.6+/-0.07 min; bouts 1, 6) than in the Zebu calves
(duration 0.1+/-0.04 min; bouts 0, 5) and decreased with increasing age of calf. Exploration
increased in duration as the calves increased in age from 1 to 6 months (P<0.05).
The duration of play increased significantly with the increase in age of calf from
1 to 6 months, and occurred mainly after nursing.