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Crop milk

February 15, 2024

Not to be confused with the confectionary Ptasie mleczko, or "Bird's milk".

Crop milk is a secretion from the lining of the crop of parent birds in some species that is regurgitated to young birds. It is found among all pigeons and doves where it is also referred to as pigeon milk. Crop milk is also secreted from the crop of flamingos and the male emperor penguin,[1][2][3] suggesting independent evolution of this trait.[4] Unlike in mammals where only females produce milk, crop milk is produced by both males and females in pigeons and flamingos; and in penguins, only by the male.[5] Lactation in birds is controlled by prolactin, which is the same hormone that causes lactation in mammals.[6][5] Crop milk is a holocrine secretion, unlike in mammals where milk is an apocrine secretion.[5] Crop milk contains both fat and protein, as with mammalian milk, but unlike mammalian milk, it contains no carbohydrates.[5]

A rock pigeon feeding squabs.

Pigeon milk edit

Crop milk bears little physical resemblance to mammalian milk, though in pigeons it's compositionally similar.[4] Pigeon milk is a semi-solid substance somewhat like pale yellow cottage cheese. It is extremely high in protein and fat, containing higher levels than cow or human milk.[7] A 1939 study of pigeon crop milk showed, however, that the substance did not contain carbohydrates (sugars), unlike mammalian milk.[8] It has also been shown to contain anti-oxidants and immune-enhancing factors which contribute to milk immunity.[9] Like mammalian milk, crop milk contains IgA antibodies. It also contains some bacteria.[6] Unlike mammalian milk, which is an emulsion, pigeon crop milk consists of a suspension of protein-rich and fat-rich cells that proliferate and detach from the lining of the crop.[10]

Pigeon's milk begins to be produced a couple of days before the eggs are due to hatch. The parents may cease to eat at this point in order to be able to provide the squabs (baby pigeons and doves) with milk uncontaminated by seeds, which the very young squabs would be unable to digest. The baby squabs are fed on pure crop milk for the first week or so of life, or about 10-14 days. After this the parents begin to introduce a proportion of adult food, softened by spending time in the moist conditions of the adult crop, into the mix fed to the squabs, until by the end of the second week they are being fed entirely on softened adult food.

Pigeons normally lay two eggs. If one egg fails to hatch, the surviving squab gets the advantage of a supply of crop milk sufficient for two squabs and grows at a significantly faster rate.[11] Research suggests that a pair of breeding pigeons cannot produce enough crop milk to feed three squabs adequately, which explains why clutches are limited to two.[12]

Other birds edit

 
A greater flamingo chick in Zoo Basel is fed crop milk

Crop milk evolved independently in flamingos and the male emperor penguin.[1][2][3][4] In flamingos, crop milk produced in the first weeks is a bright red, relatively thin liquid.[5] Though it resembles blood in color, it contains no red blood cells; the red color is from the presence of canthaxanthin.[5] After the first few weeks, the color fades gradually; flamingos can produce crop milk for up to the first 6 months of their young's life.[5]

References edit

  1. ^ a b Levi, Wendell (1977). The Pigeon. Sumter, S.C.: Levi Publishing Co, Inc. ISBN 0-85390-013-2.
  2. ^ a b Silver, Rae (1984). (PDF). The Journal of Experimental Zoology. 232 (3): 617–625. doi:10.1002/jez.1402320330. PMID 6394702. Archived from the original (PDF) on 13 September 2016.
  3. ^ a b Eraud, C.; Dorie, A.; Jacquet, A.; Faivre, B. (2008). "The crop milk: a potential new route for carotenoid-mediated parental effects" (PDF). Journal of Avian Biology. 39 (2): 247–251. doi:10.1111/j.0908-8857.2008.04053.x.
  4. ^ a b c Ornithology, British Trust for (2012-08-22). "Crop milk". BTO - British Trust for Ornithology. Retrieved 2023-04-30.
  5. ^ a b c d e f g Ann M. Ward, Amy Hunt, Mike Maslanka, and Chris Brown, Nutrient Composition Of American Flamingo Crop Milk (PDF){{citation}}: CS1 maint: multiple names: authors list (link)
  6. ^ a b Gillespie, M. J.; Stanley, D.; Chen, H.; Donald, J. A.; Nicholas, K. R.; Moore, R. J.; Crowley, T. M. (2012). Salmon, Henri (ed.). "Functional Similarities between Pigeon 'Milk' and Mammalian Milk: Induction of Immune Gene Expression and Modification of the Microbiota". PLOS ONE. 7 (10): e48363. Bibcode:2012PLoSO...748363G. doi:10.1371/journal.pone.0048363. PMC 3482181. PMID 23110233.
  7. ^ Ehrlich, Paul R.; Dobkin, David S.; Wheye, Darryl (1988), "Bird Milk", stanford.edu
  8. ^ Davis, W.L. (1939). "The Composition of the Crop Milk of Pigeons". Biochem. J. 33 (6): 898–901. doi:10.1042/bj0330898. PMC 1264463. PMID 16746989.
  9. ^ , archived from the original on 2011-09-24
  10. ^ Gillespie, M. J.; Haring, V. R.; McColl, K. A.; Monaghan, P.; Donald, J. A.; Nicholas, K. R.; Moore, R. J.; Crowley, T. M. (2011). "Histological and global gene expression analysis of the 'lactating' pigeon crop". BMC Genomics. 12: 452. doi:10.1186/1471-2164-12-452. PMC 3191541. PMID 21929790.
  11. ^ Vandeputte-Poma, J.; van Grembergen, G. (1967). "L'evolution postembryonnaire du poids du pigeon domestique". Zeitschrift für vergleichende Physiologie (in French). 54 (3): 423–425. doi:10.1007/BF00298228. S2CID 32408737.
  12. ^ Blockstein, David E. (1989). "Crop milk and clutch size in mourning doves". The Wilson Bulletin. 101 (1): 11–25. JSTOR 4162684. The fact that none of the nearly 300 species of Columbiformes has a clutch size larger than two eggs suggests that there is limited plasticity in crop-milk production.

External links edit

  • Article on Bird Milk from stanford.edu
  • Article on the relationship between crop milk and clutch size in Mourning Doves (.pdf)

February 15, 2024
crop, milk, confused, with, confectionary, ptasie, mleczko, bird, milk, secretion, from, lining, crop, parent, birds, some, species, that, regurgitated, young, birds, found, among, pigeons, doves, where, also, referred, pigeon, milk, also, secreted, from, crop. Not to be confused with the confectionary Ptasie mleczko or Bird s milk Crop milk is a secretion from the lining of the crop of parent birds in some species that is regurgitated to young birds It is found among all pigeons and doves where it is also referred to as pigeon milk Crop milk is also secreted from the crop of flamingos and the male emperor penguin 1 2 3 suggesting independent evolution of this trait 4 Unlike in mammals where only females produce milk crop milk is produced by both males and females in pigeons and flamingos and in penguins only by the male 5 Lactation in birds is controlled by prolactin which is the same hormone that causes lactation in mammals 6 5 Crop milk is a holocrine secretion unlike in mammals where milk is an apocrine secretion 5 Crop milk contains both fat and protein as with mammalian milk but unlike mammalian milk it contains no carbohydrates 5 A rock pigeon feeding squabs Contents 1 Pigeon milk 2 Other birds 3 References 4 External linksPigeon milk editCrop milk bears little physical resemblance to mammalian milk though in pigeons it s compositionally similar 4 Pigeon milk is a semi solid substance somewhat like pale yellow cottage cheese It is extremely high in protein and fat containing higher levels than cow or human milk 7 A 1939 study of pigeon crop milk showed however that the substance did not contain carbohydrates sugars unlike mammalian milk 8 It has also been shown to contain anti oxidants and immune enhancing factors which contribute to milk immunity 9 Like mammalian milk crop milk contains IgA antibodies It also contains some bacteria 6 Unlike mammalian milk which is an emulsion pigeon crop milk consists of a suspension of protein rich and fat rich cells that proliferate and detach from the lining of the crop 10 Pigeon s milk begins to be produced a couple of days before the eggs are due to hatch The parents may cease to eat at this point in order to be able to provide the squabs baby pigeons and doves with milk uncontaminated by seeds which the very young squabs would be unable to digest The baby squabs are fed on pure crop milk for the first week or so of life or about 10 14 days After this the parents begin to introduce a proportion of adult food softened by spending time in the moist conditions of the adult crop into the mix fed to the squabs until by the end of the second week they are being fed entirely on softened adult food Pigeons normally lay two eggs If one egg fails to hatch the surviving squab gets the advantage of a supply of crop milk sufficient for two squabs and grows at a significantly faster rate 11 Research suggests that a pair of breeding pigeons cannot produce enough crop milk to feed three squabs adequately which explains why clutches are limited to two 12 Other birds edit nbsp A greater flamingo chick in Zoo Basel is fed crop milkCrop milk evolved independently in flamingos and the male emperor penguin 1 2 3 4 In flamingos crop milk produced in the first weeks is a bright red relatively thin liquid 5 Though it resembles blood in color it contains no red blood cells the red color is from the presence of canthaxanthin 5 After the first few weeks the color fades gradually flamingos can produce crop milk for up to the first 6 months of their young s life 5 References edit a b Levi Wendell 1977 The Pigeon Sumter S C Levi Publishing Co Inc ISBN 0 85390 013 2 a b Silver Rae 1984 Prolactin and Parenting in the Pigeon Family PDF The Journal of Experimental Zoology 232 3 617 625 doi 10 1002 jez 1402320330 PMID 6394702 Archived from the original PDF on 13 September 2016 a b Eraud C Dorie A Jacquet A Faivre B 2008 The crop milk a potential new route for carotenoid mediated parental effects PDF Journal of Avian Biology 39 2 247 251 doi 10 1111 j 0908 8857 2008 04053 x a b c Ornithology British Trust for 2012 08 22 Crop milk BTO British Trust for Ornithology Retrieved 2023 04 30 a b c d e f g Ann M Ward Amy Hunt Mike Maslanka and Chris Brown Nutrient Composition Of American Flamingo Crop Milk PDF a href Template Citation html title Template Citation citation a CS1 maint multiple names authors list link a b Gillespie M J Stanley D Chen H Donald J A Nicholas K R Moore R J Crowley T M 2012 Salmon Henri ed Functional Similarities between Pigeon Milk and Mammalian Milk Induction of Immune Gene Expression and Modification of the Microbiota PLOS ONE 7 10 e48363 Bibcode 2012PLoSO 748363G doi 10 1371 journal pone 0048363 PMC 3482181 PMID 23110233 Ehrlich Paul R Dobkin David S Wheye Darryl 1988 Bird Milk stanford edu Davis W L 1939 The Composition of the Crop Milk of Pigeons Biochem J 33 6 898 901 doi 10 1042 bj0330898 PMC 1264463 PMID 16746989 Mysteries of pigeon milk explained archived from the original on 2011 09 24 Gillespie M J Haring V R McColl K A Monaghan P Donald J A Nicholas K R Moore R J Crowley T M 2011 Histological and global gene expression analysis of the lactating pigeon crop BMC Genomics 12 452 doi 10 1186 1471 2164 12 452 PMC 3191541 PMID 21929790 Vandeputte Poma J van Grembergen G 1967 L evolution postembryonnaire du poids du pigeon domestique Zeitschrift fur vergleichende Physiologie in French 54 3 423 425 doi 10 1007 BF00298228 S2CID 32408737 Blockstein David E 1989 Crop milk and clutch size in mourning doves The Wilson Bulletin 101 1 11 25 JSTOR 4162684 The fact that none of the nearly 300 species of Columbiformes has a clutch size larger than two eggs suggests that there is limited plasticity in crop milk production External links editArticle on Bird Milk from stanford edu Article on the relationship between crop milk and clutch size in Mourning Doves pdf Smithsonian National Zoo article on Common Crowned Pigeon includes paragraph on crop milk Retrieved from https en wikipedia org w index php title Crop milk amp oldid 1204455465, wikipedia, wiki, book, books, library,

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