Essay On Lactation

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MATERIALS AND METHODS Source of the data Data in the lactation records of Friesian cows intrinsic in Sakha and El-Karada Experimental Farms, Animal Production Research Institute (APRI), Ministry of Agriculture, Kafr-Elsheikh Governorate, Egypt were used in the analysis. Because of excluding some incomplete records and traits limitations (i.e., cows were removed with (1) no measurements on milk traits or with records from 500, d length of lactation; (2) duplicate termination codes and (3) duplicate records, thus; the final total number of records used in the statistical record analyses was 5728 from 2040 Friesian cows sired by 139 bulls over the years from 1979 to 2016. The sires having less than 5 daughters were excluded from the study. …show more content…

Data analysis Data were analyzed using Harvey program statistic (Harvey, 1990) to determine the fixed effects to be contained in the analytical model. The statistical model included season (1 to 4) and year (1979 to 2015) of birth, parity of cow (1 to 5) and farm (1 =Sakha and 2 =El-Karda). All effects are significant for all traits was contained in the analytical model. Covariance components were estimated for univariate and bivariate analysis for all traits with derivative-free restricted maximum likelihood (REML) procedures using the MTDFREML program of Boldman et al, (1995). The basic multiple model was: Y = Xß + Zd + Wpe + e Where: Y is a vector of observations, ß = is a vector of fixed effects with incidence matrix X. d ~ NID (0, Ic σ2pe) is a vector of direct additive genetic effect with incidence matrix Z, Pe ~ NID (0, A σ2d) is a vector of random maternal permanent environmental effects with incidence matrix W, and e ~ NID (0, In σ2e) is a vector of random residual effects. Also, σ2d is the direct additive genetic variance; σ2pe is the maternal permanent environmental variance, σ2e. is the residual variance (temporary environment), A is the additive relationship matrix, Ic and In are identity matrices of order equal to the number of maternal permanent environmental effects and the number of records, respectively. Convergence reached when the simplex variance was less than 10-8 and then several extra rounds of iterations were

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