Serum protein profile could be considered as a useful indicator of physiological and pathological condi-tions, but several factors may interfere with the interpretation. This study was conducted to evaluate serum protein fractions in association with age, body weight, birth type and birth season in a meat-type sheep. Blood samples were randomly taken from 96 healthy Lori-Bakhtiari ewes in the Shooli breeding station in Iran. The sampled animals randomly belonged to different age, birth type, birth season and body weight groups. Total protein and other fractions were determined by Biuret and electrophoresis methods, respec-tively. IgG levels were measured by ELISA method. Total protein, albumin, total globulins, albu-min/globulins ratio, α1, α2, β and γ globulins and IgG levels averages were 5.82, 2.35, 3.47, 0.69, 0.06, 0.42, 0.15, 2.82 and 1.56 g/dL, respectively. Total protein had high correlations with total and γ globulins, while albumin and IgG were almost independent from other fractions. Levels of serum protein fractions in adults were also independent from body weights at different ages. Serum protein profile was significantly affected by age and birth season (P<0.05), where by older ewes had lower levels of α2, γ and total globulins and higher albumin/globulin ratios. The winter-born ewes significantly had higher γ globulins levels and probably more immune system activities, compared to the spring-born ewes. Body weight and birth type did not have any significant effect on the studied serum protein fractions. This study suggested that the age and birth season should be considered for interpretation of the serum protein profiles.
