Twelve lactating Holstein-Friesian and twenty five lactating Egyptian buffaloes belonged to the experimental Station of Assiut University, were used throughout this study. Representative monthly samples from four successive milkings were collected from each animal. Sampleswere immediately used for the determination of total milk proteins and its electrophoretic fractions.
Resuls obtained can be summarized as follows: Calving season had a significant (P/ 0.05) effect only on total milk yield, total milk protein % and immuno-globulin fraction of milk whey protein. Thus, winter calvers of both genus yield more milk and protein and immunoglobulin than summer calvers.
Other milk chemical compounds were not significantly affected by animal's calving season. Also, milk yield and composition were unaffec ted by genus x calving season interaction or calving season x lactation period interaction.