Proportion of EST sequences assigned to contigs in each library. The proportion of ESTs assigned to contigs in each library is shown when ignoring (blue) or including (red) an additional 360 singletons with high similarity to contig sequences (BLAST score > 170). Inclusion of such singletons does not have a significant effect because they mainly represent chimeras associated with highly expressed milk transcripts. Interestingly, in all libraries from a milk-producing gland, more than 80% of ESTs are asssigned to contigs irrespective of lactation phase (day 130 or day 260) or sampling depth (76–1,887 ESTs). Thus a large proportion of transcripts from lactating tissue are covered by multiple EST counts in the data.