if semen doses were stored properly, as much as possible use them if they are 4 days old  or less.  and use them only on females that are on standing heat. In our practice here were we only buy semen doses from stud farms we can achieve as much as 90% concepcion rate and 13.5 total born but of course the genetics of your breeding animals play a very important role on this. proper feeding pre and post breeding is also important