Urmila PannuDIPTI SOHAL2016-12-262016-12-262015http://krishikosh.egranth.ac.in/handle/1/930271324 records of 283 Rathi cows maintained at Livestock Research Station, Nohar were used over a period of 42 years (from 1974 to 2015) in the present investigation. The performance of Rathi cows were evaluated in terms of reproduction and production parameters in the study. Attempts were made to estimate the precise genetic parameters by considering different environmental effects simultaneously. The reproduction parameters obtained from over all lactation records were average age of heifers at first calving were observed to be 1629.93±41.989 days, calving interval of 428.65±15.073 days with service period of 152.05±14.882 days. The production traits were estimated as lactation length of 267.28±8.38 days, dry period of 163.88±7.915 days, 1663.72±65.586 kg milk yield with 6.25±0.131 kg milk yield per day of lactation length and 1621.37±57.825 kg three hundred days milk yield. A mixed model least-squares analysis showed highly significant effect of sire on all the traits. Effect of period and season of birth was nonsignificant for age at first calving. Effect of period of calving and parity was significant for all the traits except dry period and milk yield whereas effect of season was highly significant for all reproduction and production traits. The reproduction performance was better during fifth period and during winter season, whereas, production performance was better during sixth period and winter season. The regression of reproduction and production traits on age at first calving was non-significant for all traits except calving interval, service period and milk yield per day of lactation length. Heritability estimates were low to moderate for most of reproduction and production traits while age at first calving has higher heritability estimate. The genetic and phenotypic correlations among different traits were positive and high while correlation of age at first calving and dry period with milk yield, three hundred days milk yield and milk yield per day of lactation length was found negative and low. The relative efficiency of four lactation curve models viz. Exponential function, Parabolic function, Inverse Polynomial function and Gamma function were compared. Inverse Polynomial Function described the highest coefficient of determination (R2 = 99.92%) and with least value (0.0604 kg) of root mean squares error (RMSE), suggesting Inverse Polynomial function being best mathematical model for prediction of fortnightly test day milk yields in Rathi Cattle.enThesis