Exploration of Proteomics Analysis of Crop Milk in Pigeons (Columba livia) during the Lactation Period

Pigeon milk is a curdlike substance separated from the mature crop epithelium of breeders, associated with the rapid growth and development of squabs. The aim of this study was to investigate in detail the variations in the content of several important ingredients in crop milk. In this study, we utilized proteomic techniques to Crop milk investigate the composition and changing pattern of crop milk protein of squabs on days 1 (D1), 3 (D3), and 7 (D7). Our results indicated that the crude protein contents in crop milk decreased with age, and they were up to 50% during the first 3 days. The proteomic data showed that a total of 2558 proteins were identified in all samples from three stages, and the top 15% crop milk proteins were ribosomal protein, keratin, peroxiredoxin, annexin, heat shock protein, and eukaryotic translation protein based on liquid chromatographytandem mass spectrometry (LC-MS/MS) analysis and normalized spectral abundance factors (NSAFs) calculation. Furthermore, the compositions of crop milk protein between DI and D3 were quite similar [51 differentially expressed proteins (DEPs)], while great proteomic differences were observed between D 1 /D3 and D7 (more than 240 DEPs). Additionally, gene ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that up-regulated DEPs mainly participate in immune response, while down-regulated DEPs were involved in cell differentiation and development as well as tRNA aminoacylation biosynthesis. In conclusion, DEPs were mainly related to protein synthesis, immunity, and antioxidation, which provided effective information for the development of artificial squab milk products in the future.

Automated summary

This study investigated the composition and changes in crop milk protein of squabs using proteomic techniques. The results showed that crude protein contents in crop milk decreased with age, and a total of 2558 proteins were identified with significant differences between different stages. The differential expressed proteins were mainly related to protein synthesis, immunity, and antioxidation, providing valuable information for future development of artificial squab milk products.