Posted 22 April 2012 - 06:19 am
I am not a particular student of the Somme, or casualty figures, but I believe that the raw materials for the compilation of German losses exist, if they have not been satisfactorily pulled together already. In particular, a soldier by soldier resource called Verlusten is now being put on-line, although its use is quite labor-intensive. Also, many medical records were not destroyed in the fire-bombing of the Prussian Archives in 1945, as they were stored elsewhere. (I think that they presently are not accessable.) Just as a general comment, while the German official histories are extensive (I have about 110 volumes from the three main series, a mostly but not entirely complete set, counting a few duplicates), but I think that generally they do not comprehensively give day by day losses.
I generally do not use or even read secondary sources, but our Jack Sheldon is an entirely reliable student of the war, and from memory I believe he has written a volume on the Somme (I am too lazy to walk 15 feet to my shelves and check, it is 2:10 AM.). He works so extensively from original German sources that I myself hesitate to characterize his books as "secondary sources".
I have used the French official histories, but a lot less than the German, and I am tempted to comment that they often seem to steer away from unpleasant losses and reverses. However, they probably, on the whole, did "better" than the UK forces when the battle commenced, so that may not apply. Again, I do not remember noticing them compiling extensive casualty figures in my infrequent use of them. Also, the French medical services were, IMHO, significantly poorer than those of other major combatents, and perhaps that lack bled over (pardon the pun) to the casualty figure question; to my mind they are linked.
Your question is interesting, so I have commented, and appoligize if I have not actually answered your core question, only offering comments.