Study of the genetic and phenotypic trend of body weight traits and determined of environmental effects for Arabi sheep

In this study environmental effects, genetic and phenotypic trends for body weight traits in different age in Arabi Sheep estimated. In this study used a total of 11365 records on birth weight, 6930 records of weaning weight, 3275 records of 6 month weight, 2043 records of 9 month weight and 1750 records of 12 month weight. The data used in this study, collected during 1994-2015 in Khuzestan province. The breeding value of the animal were estimated by restricted maximum likelihood method. The SAS statistical software was used to evaluate the effect of environmental factors and Wombat software was employed to estimate animals breeding value. The SPSS software was used for estimation of the trends. Environmental factors such as birth year, Sex, birth type and age of Mather were significant on all traits and were fixed effects in model. Animal’s age was introduced to the model as covariate. Estimation of direct genetic trend for birth weight, weaning weight, 6 month weight, 9 month weight and 12 month weight were as -0.07, -17, 2, 1 and 1 gr per year respectively. The phenotypic trend for considered traits was respectively 5, 256, 76, 83 and 194 gr per year. It can be concluded that reduction of the average breeding value in the genetic trends and the oscillation in the phenotypic trend are due to reduction of recording accuracy and entering livestock with low breeding value to the herd or negative impact of environmental factors on the production potential of livestock.