Abstract:
A study was conducted to assess the productive and reproductive
performance and related to the effects of environmental factors and
animal factors of Sahiwal cattle in the dry zone of Sri Lanka. Data was
collected on calving, lactation, age at first calving and birth weight of
calves were tabulated and analyzed in relation to ambient temperature
(AT), relative humidity (RH) and rainfall (RF) during the period of
2000-2006. The mean AT fluctuated between 26.6°C and 34.9°C while
RH varied between 64.7% and 87.6%. The annual RF (817.2±157.1
mm) was follow-up bimodal, reaching the highest level from October
to December and a very small elevation from March to May. The
majority of the calves (47%) were born from February to May. Birth
weight of male (19.39± 3.18 kg) and female calves (18.84±3.20kg)
were not significantly different. Gestation length (285.73±56.24 days)
was not different between the sexes. Lactation length (279.5±52.18
days) and lactation yield (1401.92±540.5 liters) decline with the parity,
Total milk yield increases till third lactation and reach a peak yield of
1497.6±521 lit in 281.5±51 days and decline there after. Mean ambient temperature of the month (r=-0.342) is significantly (p<0.05) correlated
to birth weight. The results suggest that the prepartum period as the
most vulnerable stage to environmental stress. Mean temperature and
relative humidity, as the most important environmental factors affecting
the performance. Alleviating heat stress during prepartum is suggested
as a means for improving reproduction performance of cows and birth
weight of calves.
