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The present investigation was undertaken to study the effect of non-genetic factors, viz., service period (SP), dry period (DP) and gestation period (GP) on various milk production traits in Kankrej cattle. 1235 lactation records (2nd-7th) of 475 Kankrej cows, progeny of 75 bulls that were maintained at University Livestock Research Station, Sardarkrushinagar (Gujarat), calved during 1980-2014, were studied. The effects of service period (111.64 ± 52.55 days) and dry period (143.17±28.78 days) on total lactation milk yield (2089.45±582.38 kg),305 days milk yield (2045.66±531.92 kg) and lactation length (282.90±49.46 days) were highly significant (pis less than 0.01), while the effect of gestation period (288.86±7.14 days) was non-significant on all these production traits. Cows which took more time to conceive after parturition produced more milk with longer lactation length

Aim:The aim was to estimate genetic factors affecting the first lactation milk production traits in Kankrej cattle of North Gujarat.Materials and Methods:The 475 first lactation records of Kankrej cows that were maintained at the Livestock Research Station, Sardarkrushinagar Dantiwada Agricultural University, Sardarkrushinagar, Gujarat, over a period of 35 years from 1980 to 2014 were studied. The least squares maximum likelihood program was used to estimate genetic parameters of first lactation traits. Heritability was estimated through paternal half-sib analysis in adjusted data.Results:The heritability estimate for production traits was 0.40±0.17, 0.45±0.17, 0.35±0.18, and 0.20±0.14 for standard 300 days milk yield (F300Y), total lactation milk yield (FLY), wet average (FWA), and lactation length (FLL), respectively, in the first parity. All the genetic and phenotypic correlations among different production efficiency traits were high and positive. Genetic correlations between F300Y and FLY, FLL, and FWA were 0.80±0.20, 0.59±0.16, and 0.81±0.32, where as the phenotypic correlations were 0.969, 0.688, and 0.868, respectively. Genetic correlations of FLY with FLL and FWA were 0.60±0.13 and 0.79±0.20, whereas the phenotypic correlations were 0.777 and 0.817, respectively. Genetic and phenotypic correlation between FLL and FWA was 0.63±0.28 and 0.31, respectively.Conclusion:The heritability estimate of all first parity lactation traits waslow to medium (0.20-0.45) indicated the scope for further improvement in this trait through selection as well as managemental practice. Higher genetic and phenotypic correlation between thefirst lactation milk production traits gives theidea that genetic gain due to selection for one trait also givesmorecorrelated response of selection for other traits which is economically advantageous.