I've just started watching the series and noticed that on numerous occasions SG1 kill Jaffa just outside the Stargate, but their bodies are never brought back for study. They obviously have never done this because Teal'c often tells his team to bring back his body so the scientists can learn something about the Goa'uld.
For example, in episode 16 of season 1, Teal'c says this to Daniel, and by the end of the episode at least 6 Jaffas are killed right outside of the Stargate.
So, although there is this desperate need to study the Jaffa and the Goa'uld, why is this never done?