Performance of exotic dairy cattle in the southern highlands of Tanzania and prospects for genetic improvement
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Date
1995
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Sokoine University of Agriculture
Abstract
Th i s
study
aimed
was
at
evaluating
the
performance
of
exotic dairy cattle in five large farms in Iringa and Mbeya
reg i ons.
Mai n
aspects
stud i ed
i ncluded
calf
mortality
rates, reproductive traits, milk yield, milk composition,
and lifetime performance traits.
Rates of abortion ranged from 1.8 to 9.5% while rates of
stillbirths varied between 3.4 and 9.8%. Death rates ranged
from 9.3 to 25.5% for unweaned calves and from 13.2 to
29.6% for weaned calves. Diarrhoea/ scours, pneumonia and
nutritional problems were the main causes of calf deaths.
Mean ages at first calving and calving intervals for the
five farms ranged from 33 to 39 months and 375 to 489 days,
respectively. Overall mean lactation milk yield, lactation
1 engt-h,
dry period for individual farms ranged from 2197
kg, 270 to
respective!y. The most
to
2642
affecting
calvi ng,
1actati on
and
pari ty
days
321
and
i mportant
performance
current
86
to
165
non-geneti c
traits
calving
were
days,
factors
year
i nterval .
of
Milk
production in most farms was declining, a trend attributed
to
deterioration
estimates
calving
were
i n
management.
0.14±0.01,
i nterval,
Weighted
0.21±0.02
1actati on
length
and
and
repeatabi1ity
0.37±0.01
lactation
for
milk yield, respectively.
Mean percentages of milk components on test-days did not
differ much from those recorded for Friesians elsewhere in
the tropics. Stage of lactation, calendar month, parity and
year of recording highly influenced their variations. Milk
yield on test-days had strong negative correlations with
BF%
(-0.47) and protein percent (-0.53).
BF and protein
percentages were positively correlated (0.59).
Day-to-day variation of milk yield was higher at Uyole than
at Thimbu and was associated with level of milk production
and inaccurate recording. The most variable milk component
was protein whose variation was ascribed mainly to errors
of determination.
Part and cumulative milk records were highly influenced by
parity,
year
and
season
of
calving.
Effect
of
calving
interval was noticeable from the sixth month of lactation.
Records in mid-1actation had the highest correlation with
305-day yield. Ratio and regression extension factors were
derived based on findings from this study.
Performance
in
1i feti me
traits
were
similar
to
those
reported elsewhere in the tropics. Age at first calving and
first lactation yield had high association with lifetime traits used in this study and were important estimators of
lifetime milk production.
Several
options of culling procedures were proposed and
discussed. It was concluded that there is great opportunity
for genetic improvement of dairy cattle
in the southern
calves
i s
highlands of
i mproved, the downward trend in performance is reversed,
Tanzania
provided
viability
of
recordi ng is improved and a culling procedure is adopted.
Description
Keywords
Performance of exotic, Dairy cattle, Southern highlands, Tanzania, Genetic improvement