Thesis

ABSTRACT : Data on various grades of Holstein Friesian × Sahiwal cattle maintained at Military Dairy Farm, Bowenpally, Secunderabad, over a period of 19 years (1988 – 2006) were analyzed for studying their mean performance and for the estimation of genetic parameters of various production and reproduction traits of the FS genetic grade cows. The genetic grades studied, included Sahiwal cows with Holstein Friesian inheritance of 3/8 (35.9375% to 39.0625%), 7/16 (40.625% to 46.875%), 5/8 (53.125% to 68.75%), 3/4 (71.875% to 78.125%), 7/8 (81.25% to 87.50%), 15/16 (90.625% to 93.75%) and FS (about 55% to 75%). The overall least-squares means of body weights at birth, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 15, 18, 21, 24 and 27 months of age were 26.08, 36.74, 51.04, 67.06, 83.02, 98.73, 113.35, 130.10, 141.21, 153.23, 164.25, 175.87, 188.21, 221.82, 253.85, 292.09, 316.06 and 336.28 kg, respectively. Genetic grades significantly affected the body weights at birth, 1, 2, 3, 21, 24 and 27 months of age, whereas period of birth significantly affected (P<0.01) the body weights at all the ages studied. Season of birth significantly affected the body weights at 3, 4, 5, 6, 10, 11, 12 and 21 months of age only. The overall least-squares means for total lactation milk yield, 300-day lactation milk yield, lactation length, peak yield, milk yield per day of lactation and milk yield per day of calving interval were 2864.32 kg, 2593.84 kg, 329.03 days, 13.30 kg, 8.69 kg and 6.40 kg, respectively. Genetic grades, period of calving and parity significantly affected all the production traits studied. Season of calving significantly affected (P<0.01) all the production traits studied except for the lactation length. The overall least-squares means of age at first service, age at first calving, service period, number of inseminations per conception, gestation period, dry period, calving interval and breeding efficiency were 640.24 days, 983.14 days, 183.28 days, 2.34, 275.93 days, 127.85 days, 450.42 days and 73.45%, respectively. Genetic grades significantly affected (P<0.01) age at first service, service period, number of inseminations per conception and calving interval, while period of calving significantly affected (P<0.01) age at first service, age at first calving, service period, dry period, calving interval and breeding efficiency. Season of calving had significant influence on service period, gestation period, dry period and calving interval. Significant effect (P<0.01) of parity was observed on service period, number of inseminations per conception, dry period and calving interval while sex of calf significantly affected number of inseminations per conception and gestation period only. The genetic analysis of adjusted data of FS grade cows revealed that the heritabilities of body weights ranged from 0.08 + 0.08 at birth to 0.99 + 0.32 at 18 months of age. Genetic correlations among the body weights at various ages ranged from -0.14 ± 0.12 (between birth weight and 6 months weight) to 0.97 ± 0.01 (between body weights at 12 months and 15 months of age). The phenotypic correlations ranged from 0.09 (between birth weight and 12 months weight) to 0.88 (between body weights at 12 and 15 months of age). The estimates of heritability for total lactation milk yield, 300-day lactation milk yield, lactation length, peak yield, milk yield per day of lactation, milk yield per day of calving interval, age at first calving, service period, gestation period, dry period, calving interval and breeding efficiency were 0.20, 0.18, 0.06, 0.16, 0.27, 0.17, 0.60, 0.03, 0.05, 0.02, 0.07 and 0.06, respectively. Total lactation milk yield was found to be genetically positively correlated with all the other traits studied except with gestation period, while 300-day lactation milk yield and lactation length were positively correlated with all the other traits studied. Peak yield and age at first calving were positively correlated with all the other traits except with gestation period and dry period. Service period was also positively correlated with all the other traits except with gestation period while gestation period was negatively correlated with all the traits except with lactation length and calving interval. The phenotypic correlations were positive among majority of the traits studied. The estimates of repeatability for total lactation milk yield, 300-day lactation milk yield, lactation length, peak yield, service period, gestation period, dry period and calving interval were 0.13, 0.56, 0.50, 0.12, 0.04, 0.07, 0.03 and 0.07, respectively. The Most Probable Producing Ability (MPPA) of the cows was computed based on total lactation milk yield and 300-day lactation milk yield. The results of the present study revealed that Frieswal cows of G3 genetic grade (5/8) outperformed the other grades in their overall performance. The genetic variation existing in the body weights, production and reproduction traits offered good scope for further genetic improvement through selection of the sires.

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