Pigeon and chick. (Credit: Dr. Tamsyn Crow
ScienceDaily (Sep. 28, 2011) — Production of crop milk, a secretion from the crops of parent birds, is rare among birds and, apart from pigeons, is only found in flamingos and male emperor penguins. Essential for the growth and development of the young pigeon squab, pigeon 'milk' is produced by both parents from fluid-filled cells lining the crop that are rich in fat and protein.
Researchers from CSIRO Livestock Industries and Deakin University, Australia, compared the global gene expression profiles of the crops of four 'lactating' and four 'non-lactating' female pigeons. As the pigeon genome has not yet been sequenced, they used a chicken microarray to find the genes involved. Genes predominantly over-expressed in 'lactating' birds were those involved in stimulating cell growth, producing antioxidants and in immune response. They also found genes associated with triglyceride fat production, suggesting the fat in the 'milk' is derived from the pigeon's liver.
Lead author, Meagan Gillespie, says, "It is possible that if antioxidant and immune proteins are present in pigeon 'milk', they are directly enhancing the immune system of the developing squab as well as protecting the parental crop tissue." She continues, "This study has provided a snap-shot view of some of the processes occurring when 'lactation' in the pigeon crop is well established. Due to the unusual nature of 'lactation' in the pigeon it would be interesting to investigate the early stages of the differentiation and development of the crop in preparation for 'milk' production to further ascertain gene expression patterns that characterize crop development and 'lactation' in the pigeon."
She concludes, "This mechanism is an interesting example of the evolution of a system with analogies to mammalian lactation, as pigeon 'milk' fulfills a similar function to mammalian milk."
The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by BioMed Central, via EurekAlert!, a service of AAAS.
- Meagan J. Gillespie, Volker R. Haring, Kenneth A. McColl, Paul Monaghan, John A. Donald, Kevin R. Nicholas, Robert J. Moore, Tamsyn M. Crowley. Histological and global gene expression analysis of the 'lactating' pigeon crop. BMC Genomics, 2011; 12: 452 DOI: 10.1186/1471-2164-12-452
BioMed Central (2011, September 28). Pigeon 'milk' contains antioxidants and immune-enhancing proteins. ScienceDaily. Retrieved September 28, 2011, from http://www.sciencedaily.com /releases/2011/09/110919074253.htm