I bought 25 RIR chicks which two were lost during shipping. I have decided that I wanted more chicks and ordered 30 more chicks, there will be about 4 weeks apart in age, will I have any problems putting them together right off the bat.
I would raise them separatly until they are about the same size. When or if you do combine them there will be pecking as they establish their pecking order and some may be more aggressive than others. Every integration is different. The birds are all different.