June, 1958] V. N. AMBLE, K. S. KRISHNAN AND J. S. SRIVASTAVA 81
SUMMARY
The paper deals with the statistical study of the breeding data pertaining to the
Red Sindhi herds maintained at Hosur in Madras State and at Bangalore in the
Southern Regional Station of the National Dairy Research Institute. The records
studied pertained to a period of about 30 years and consisted of about 1200
lactation records from 343 cows in the case of the Hosur herd and about 1450 lactation
records from 404 cows in the case of the Bangalore herd. The number of bulls used
on these herds were 52 and 36 respectively.
After a brief review of the practices followed in respect of feeding, management
and breeding of these herds breeding regularity was examined by studying the age
at first calving and the inter-calving period. The average age at first calving for
both the herds was 41.7 ± 4 months while the interval between first two calvings
was 546 ± 10 days for the Hosur herd and 447±8 days for the Bangalore herd.
Progressive changes in the levels of production of important milk characteristics
were examined, both by making overall comparisons of the cows belonging to different
generations and through daughter-dam comparisons. In order to obtain a better
comparison of the genetic makeup of the cows in the different generations, genera-
tionwise comparisons adjusting for the variation from period to period due to changes
in feeding, management and other environmental factors were carried out. The
results indicated that while there was little overall improvement through breeding
in the Hosur herd, a progressive improvement in lactation yield of about 170 lb. per
generation was secured in the Bangalore herd.
Sixteen bulls used on the Hosur herd and twelve used on the Bangalore herd,
accounting for about 80 and 63 per cent of the cows with records, could be
progeny tested for important milk characteristics. The index based on the
daughters' first lactation average, corrected for the variation in the dams' level of
production by regression, was worked out for evaluating the sires. These indices
for the bulls at the Hosur Farm corresponded to herd averages of 3700 lb. for lactation
yield, 11½ lb. for yield per day of lactation, 7 lb. for yield per day of calving interval
300 days for lactation period. The corresponding averages for the Bangalore herd
were 2700 lb. for lactation yield, 10 lb. for yield per day of lactation, 7 lb. for yield
per day of calving interval and 210 days for lactation period. Two bulls, viz. No. 56
and 129(0) in the Hosur herd, and two bulls, Victory and Unique, in the Bangalore
herd had sire indices for lactation yield exceeding the respective herd averages by
20 per cent.
The value of early records as selection criteria for improved performance in later
lactations was examined by working out repeatability coefficients. The estimates
of repeatability for lactation yield was 0.61 and 0.54 respectively for the Hosur and
the Bangalore herds.
The heritable components of the variations observed in respect of the different
characters were estimated by working out heritability coefficients by the intrasire
regression method. The heritability coefficients for lactation yield was high being
0.34 and 0.37 for the two herds. On the other hand calving interval and age at first
calving had very low, non-significant values of heritability.
1 AR/58
7