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 exocrine secretion. [5] Crop milk contains both fat and protein, as with mammalian milk, but unlike mammalian milk, it contains no carbohydrates. [5]
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]
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]
Poultry are domesticated birds kept by humans for the purpose of harvesting useful animal products such as meat, eggs or feathers. The practice of raising poultry is known as poultry farming. These birds are most typically members of the superorder Galloanserae (fowl), especially the order Galliformes. The term also includes waterfowls of the family Anatidae and other flying birds that are kept and killed for their meat such as the young pigeons, but does not include wild birds hunted for food known as game or quarry.
Digestion is the breakdown of large insoluble food compounds into small water-soluble components so that they can be absorbed into the blood plasma. In certain organisms, these smaller substances are absorbed through the small intestine into the blood stream. Digestion is a form of catabolism that is often divided into two processes based on how food is broken down: mechanical and chemical digestion. The term mechanical digestion refers to the physical breakdown of large pieces of food into smaller pieces which can subsequently be accessed by digestive enzymes. Mechanical digestion takes place in the mouth through mastication and in the small intestine through segmentation contractions. In chemical digestion, enzymes break down food into the small compounds that the body can use.
Flamingos or flamingoes are a type of wading bird in the family Phoenicopteridae, which is the only extant family in the order Phoenicopteriformes. There are four flamingo species distributed throughout the Americas, and two species native to Afro-Eurasia.
The rock dove, rock pigeon, or common pigeon is a member of the bird family Columbidae. In common usage, it is often simply referred to as the "pigeon", although this is the wild form of the bird; the pigeons most familiar to people are the domesticated form of the wild rock dove.
Prolactin (PRL), also known as lactotropin and mammotropin, is a protein best known for its role in enabling mammals to produce milk. It is influential in over 300 separate processes in various vertebrates, including humans. Prolactin is secreted from the pituitary gland in response to eating, mating, estrogen treatment, ovulation and nursing. It is secreted heavily in pulses in between these events. Prolactin plays an essential role in metabolism, regulation of the immune system and pancreatic development.
A mammary gland is an exocrine gland in humans and other mammals that produces milk to feed young offspring. Mammals get their name from the Latin word mamma, "breast". The mammary glands are arranged in organs such as the breasts in primates, the udder in ruminants, and the dugs of other animals. Lactorrhea, the occasional production of milk by the glands, can occur in any mammal, but in most mammals, lactation, the production of enough milk for nursing, occurs only in phenotypic females who have gestated in recent months or years. It is directed by hormonal guidance from sex steroids. In a few mammalian species, male lactation can occur. With humans, male lactation can occur only under specific circumstances.
The mourning dove is a member of the dove family, Columbidae. The bird is also known as the American mourning dove, the rain dove, colloquially as the turtle dove, and it was once known as the Carolina pigeon and Carolina turtledove. It is one of the most abundant and widespread of all North American birds and a popular gamebird, with more than 20 million birds shot annually in the U.S., both for sport and meat. Its ability to sustain its population under such pressure is due to its prolific breeding; in warm areas, one pair may raise up to six broods of two young each in a single year. The wings make an unusual whistling sound upon take-off and landing, a form of sonation. The bird is a strong flier, capable of speeds up to 88 km/h (55 mph).
Breast milk or mother's milk is milk produced by mammary glands located in the breast of a human female. Breast milk is the primary source of nutrition for newborns, containing fat, protein, carbohydrates and variable minerals and vitamins. Breast milk also contains substances that help protect an infant against infection and inflammation, whilst also contributing to healthy development of the immune system and gut microbiome.
Reproductive success is an individual's production of offspring per breeding event or lifetime. This is not limited by the number of offspring produced by one individual, but also the reproductive success of these offspring themselves.
Adenotrophic viviparity means "gland fed, live birth". This is the reproductive mode of insects such as tsetse flies (Glossinidae), keds (Hippoboscidae) and bat flies, as adenotrophic viviparity is a characteristic feature of the superfamily Hippoboscoidea. It has also been observed in members of the subfamily Mesembrinellinae.
The domestic pigeon is a pigeon subspecies that was derived from the rock dove or rock pigeon. The rock pigeon is the world's oldest domesticated bird. Mesopotamian cuneiform tablets mention the domestication of pigeons more than 5,000 years ago, as do Egyptian hieroglyphics. Research suggests that domestication of pigeons occurred as early as 10,000 years ago.
Vitellogenin is a precursor of egg yolk that transports protein and some lipid from the liver through the blood to the growing oocytes where it becomes part of the yolk. Normally, it is only found in the blood or hemolymph of females, and can therefore be used as a biomarker in vertebrates of exposure to environmental estrogens which stimulate elevated levels in males as well as females. "Vitellogenin" is a synonymous term for the gene and the expressed protein. The protein product is classified as a glycolipoprotein, having properties of a sugar, fat and protein. It belongs to a family of several lipid transport proteins.
Ducula is a genus of the pigeon family Columbidae, collectively known as imperial pigeons. They are large to very large pigeons with a heavy build and medium to long tails. They are arboreal, feed mainly on fruit and are closely related to the other genus of fruit-eating doves, Ptilinopus. Both genera display brightly coloured plumage, predominantly green, often with contrasting under-parts of purple, orange or red. Some Ducula have prominently swollen ceres. They have large gapes and swallow seeds whole, playing an important role in seed dispersal.
In culinary terminology, squab is an immature domestic pigeon, typically under four weeks old, or its meat. Some authors describe it as tasting like dark chicken.
Lactation describes the secretion of milk from the mammary glands and the period of time that a mother lactates to feed her young. The process naturally occurs with all sexually mature female mammals, although it may predate mammals. The process of feeding milk in all female creatures is called nursing, and in humans it is also called breastfeeding. Newborn infants often produce some milk from their own breast tissue, known colloquially as witch's milk.
Oscar Riddle was an American biologist. He is known for his research into the pituitary gland and for isolating the hormone prolactin.
Milk fat globule membrane (MFGM) is a complex and unique structure composed primarily of lipids and proteins that surrounds milk fat globule secreted from the milk producing cells of humans and other mammals. It is a source of multiple bioactive compounds, including phospholipids, glycolipids, glycoproteins, and carbohydrates that have important functional roles within the brain and gut.
A Folliculostellate (FS) cell is a type of non-endocrine cell found in the anterior lobe of the pituitary gland.
Toxeus magnus is a species of jumping spider of the genus Toxeus. It is endemic to Taiwan and Southeast Asia. The species was originally classified as a part of the genus Myrmarachne in 1933 by Saitō in his work Notes on the spiders from Formosa, but it was later reclassified as Toxeus by the Polish arachnologist Jerzy Prószyński in November 2016. The species is notable for being a non-mammalian animal that nurses its offspring through a form of lactation.
Milk immunity is the protection provided to immune system of an infant via the biologically active components in milk, typically provided by the infant's mother.
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: CS1 maint: multiple names: authors list (link)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.