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Information Journal Paper

Title

ESTIMATION OF GENETIC AND ENVIRONMENTAL TRENDS FOR SOME OF GROWTH TRAITS IN KORDI

Pages

  29-36

Abstract

 Data on 3337 Kordi lambs that were collected over a period of 1993 to 2003 in Shirvan station of KORDI SHEEP, used to estimation of GENETIC AND ENVIRONMENTAL TRENDs. Considered traits were included birth weight (BW), weaning weight (WW), six month weight (6MW) and nine month weight (9MW). Genetic parameters and thus breeding values, required for estimation of genetic trend, were determined for each trait applying Derivative Free Restricted Maximum Likelihood procedures under uni-variate ANIMAL MODELs. Six statistical models including different combinations of direct genetic, maternal genetic and maternal permanent environmental effects were fitted into each trait, using DFREML software. Likelihood ratio test was used to determine the most suitable model for each trait. The test indicates that the model including direct and maternal genetic effects, with covariance between them, was the most suitable model for BW. The model including direct genetic effects as well as, maternal permanent environmental effects was the most suitable one for WW and 6MW, The model including direct genetic effects as only random effect was the most suitable one for 9MW. Genetic trends were estimated by regressing the mean of breeding values on year. The additive genetic trends for BW, WW, 6MW and 9MW using univariate analysis were estimated 0.80±1.87, 72.90±16.97, 59.63±21.20 and 136.52±28.21 gr per year, respectively. The phenotypic trends for BW, WW, 6MW and 9MW were estimated 14.13±1.25, 69.50±35.1, 59. -90.53±68.12 and 133.32±65.24 gr per year, respectively the maternal genetic trend for BW was 4.90±2.22 gr per year. The environmental trends of traits, the differences between phenotypic and genetic trends, for BW, WW, 6MW and 9MW were -2.97±2.84, - 3.40±0.87, -150.15±89.10 and -3.20±11.30 gr per year, respectively.

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