The effect of some non-genetic factors on growth traits in Lori-Bakhtiari sheep

In order to investigate of environmental factors that affect some growth traits in Lori-Bakhtiari sheep, 7721 records of birth weight, 6462 records of one month weight, 7275 records of weaning weigh, 5745 records of 6 month weight, 3326 records of 9 month weight and 3088 records of yearling weight collected in Shahrekord sheep breeding station during 1989-2012 for Lori-Bakhtiari sheep were used. The SAS statistical software was used to determine the effect of environmental factors. The results of this study showed that environmental factors like birth year, sex, type of birth, and the age of mother have significant effect on all traits. Also the interaction between the sex of lamb-type of birth was significant for traits birth weight, weaning weigh, 6 month weight and 9 month weight (p<0.01). The interaction between the age of mother and type of birth was significant for birth weight (p<0.01) and the interaction between the age of mother and sex of lamb was significant for 6 month weight (p<0.01) and weaning weight (p<0.05). The significant effects of deliberated environmental factors could be altering the incidence of phenotypic growth traits. So if these factors have been not considered in estimating of breeding value of animals, could be biased the estimation significantly. Consequently the calculated values of genetic trend would be very far from reality.