|dc.description.abstract||A mixed model study was carried out on the field data records of
9798 Simmmental and 1725 Hereford calves born during the period
1992 to 1994, and obtained from the Animal Improvement Institute,
Irene. The records were used to evaluate the influence of type
of management systems used by breeders, type of vegetation, sex
of calf, age of dam, year of birth and season of birth on 205 day
weight of calves and some two way interactions between these
effects. The analysis were carried separately for each breed.
Type of management did not significantly affect the 205 day
weight of Hereford calves, the least-squares means of calves from
extensive, semi-extensive and intensive systems were 195.8, 196.9
and 197 kg, respectively. However, the effect was highly
significant (P<.01) for Simmmental calves with weaning weights
of 217.4, 238.3 and 261.2 kg for extensive, semi-extensive and
intensive production systems, respectively. The Simmmental data
were divided for further analysis according to the three
All the main effects on the 205 day weight of Simmmental calves
were highly significant for all the management systems.
Simmmental calves raised in the combination of fynbos and
pastures under the semi-extensive management system weaned the
heaviest calves (295.8 kg) and those raised in the mixed
grassveld under the extensive system weaned the least (202.4 kg) .
The Simmmental male calves were 10, 9.8 and 17.9 kg heavier than
female calves in the extensive, semi-extensive and intensive
systems respectively. The mature age of the dam was between the
52 to 57, 58 to 117 and 52 to 57 month age groups with weaning
weights of 230.7, 257.7 and 266.4 kg in the extensive, semi-extensive
and intensive systems respectively. The deviations of
weight of calves of the mature dams from those of young dams (16
to 27 months) were
26.9, 30 and 20 kg under the extensive, semi-extensive and
intensive systems, respectively.
The main effects on the 205 day weight of Hereford calves, except
the type of management, were highly significant (P<.01). The
Hereford calves raised in the sweetveld areas produced the
highest weights (218.6 kg) but those raised on the karroo were
the lightest (188.1 kg). The best calving seasons were autumn
and winter, with the mean weight of 215.1 kg and 202.9 kg,
respectively. Summer and spring born calves weighed 180.2 and
188.2 kg, respectively. The Hereford male calves were 13.2 kg
heavier than the heifers. The maturity age of the dams was
between the 72 to 95 month age group with the deviation of 20 kg
in weaning weight of their calves from those of the young dams
(22 to 27 months old).
The sex and age-of-dam interaction for both breeds indicated an
overall correction factor for sex of calf and of age of dam.
Multiple adjustment factors were used to remove sex of calf
differences, whereas additive adjustment factors were used to
remove age-of-dam differences.||en