Effect of additive and maternal genetic effects on the genetic parameters estimates of bark1 sheep in Egypt [electronic resource]

Includes reference.

Genetic parameters and (Co)variance component were estimated for birth weight (BW), weight at 120 day (W120d) weight at 180 day (W180d) and yearling weight (YW) for a flock of 2248 Barki sheep (1303 males and 945 females) progeny of 74 unrelated rams over a period of 23 years from 1979 to 2001. Analyses were carried out by REML, fitting an animal model and ignoring or including maternal genetic or permanent environmental effects. Four animal models were fitted for all traits studied, and the best model was chosen after testing improvement in log-likelihood values. The fixed effects in the model were year of birth, sex, type of birth and age of dam. Number of days between birth date and the date of obtaining measurement of each record was used as a covariate .Direct heritabilities estimates were inflated substantially for BW and W120d traits when maternal effects were ignored and vice versa for W180d and YW. Based on the most appropriate fitted model, direct heritability of BW, W120d, W180d and M were 0.24±0.05, 0.20±0.03, 0.19±O.03, and 0.18±.02, respectively. Corresponding maternal heritabilities were 0.10±0.02, 0.07±0.02, 0.07±0.02 and 0.07±0.03 for above traits, respectively. Maternal genetic effects contributed 10 to 14% of the total phenotypic variance for BW, and their effect diminished further with other traits.

Summary in Arabic.

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