07 May 2020
The Young of Iceland’s Domestic Animals (Series IV) — Chick and Piglet
Issued on: 2020-05-07
Size: 30 x 30 mm
Perforation: Die Cut14
Printing: Offset lithography CMYK
Denominations: 50g til Evropu (face value ISKr 250 on day of issue); 50g utan Evropu (face value ISKr 315 on day of issue)
Designer Hlynur Ólafsson / Bára Kristinsdóttir
Number per sheet 10
696A-B The young of Iceland’s domestic animals IV – Chick and piglet. 50g to Europe (250 ISK), 50g outside Europe (315 ISK)
The chicken (Gallus gallus domesticus) is a type of domesticated fowl, a subspecies of the red junglefowl (Gallus gallus). Chickens are one of the most common and widespread domestic animals, with a total population of 23.7 billion as of 2018. up from more than 19 billion in 2011. There are more chickens in the world than any other bird or domesticated fowl. Humans keep chickens primarily as a source of food (consuming both their meat and eggs) and, less commonly, as pets. Originally raised for cockfighting or for special ceremonies, chickens were not kept for food until the Hellenistic period (4th–2nd centuries BC).
Genetic studies have pointed to multiple maternal origins in South Asia, Southeast Asia, and East Asia, but with the clade found in the Americas, Europe, the Middle East and Africa originating in the Indian subcontinent. From ancient India, the domesticated chicken spread to Lydia in western Asia Minor, and to Greece by the 5th century BC. Fowl had been known in Egypt since the mid-15th century BC, with the “bird that gives birth every day” having come to Egypt from the land between Syria and Shinar, Babylonia, according to the annals of Thutmose III.
Fertile chicken eggs hatch at the end of the incubation period, about 21 days. Development of the chick starts only when incubation begins, so all chicks hatch within a day or two of each other, despite perhaps being laid over a period of two weeks or so. Before hatching, the hen can hear the chicks peeping inside the eggs, and will gently cluck to stimulate them to break out of their shells. The chick begins by “pipping”; pecking a breathing hole with its egg tooth towards the blunt end of the egg, usually on the upper side. The chick then rests for some hours, absorbing the remaining egg yolk and withdrawing the blood supply from the membrane beneath the shell (used earlier for breathing through the shell). The chick then enlarges the hole, gradually turning round as it goes, and eventually severing the blunt end of the shell completely to make a lid. The chick crawls out of the remaining shell, and the wet down dries out in the warmth of the nest.
Hens usually remain on the nest for about two days after the first chick hatches, and during this time the newly hatched chicks feed by absorbing the internal yolk sac. Some breeds sometimes start eating cracked eggs, which can become habitual. Hens fiercely guard their chicks, and brood them when necessary to keep them warm, at first often returning to the nest at night. She leads them to food and water and will call them toward edible items, but seldom feeds them directly. She continues to care for them until they are several weeks old.
The domestic pig (Sus scrofa domesticus or only Sus domesticus), often called swine, hog, or simply pig when there is no need to distinguish it from other pigs, is a large, domesticated, even-toed ungulate. It is variously considered a subspecies of the Eurasian boar or a distinct species. The domestic pig’s head-plus-body length ranges from 0.9 to 1.8 m (35 to 71 in), and adult pigs typically weigh between 50 and 350 kg (110 and 770 lb), with well-fed individuals often exceeding this weight range. The size and weight of hogs largely depends on their breed. Compared to other artiodactyls, a pig’s head is relatively long, pointed, and free of warts. Most even-toed ungulates are herbivorous, but domestic pigs are omnivores, like their wild relative.
When used as livestock, domestic pigs are farmed primarily for the consumption of their flesh, called pork. A group of pigs is called a passel, a team, or a sounder. The animal’s bones, hide, and bristles are also used in products. Domestic pigs, especially miniature breeds, are kept as pets.
Female pigs reach sexual maturity at 3–12 months of age, and come into estrus every 18–24 days if they are not successfully bred. The variation in ovulation rate can be attributed to intrinsic factors such as age and genotype, as well as extrinsic factors like nutrition, environment and the supplementation of exogenous hormones. The gestation period averages 112–120 days.
Estrus lasts two to three days, and the female’s displayed receptiveness to mate is known as standing heat. Standing heat is a reflexive response that is stimulated when the female is in contact with the saliva of a sexually mature boar. Androstenol is one of the pheromones produced in the submaxillary salivary glands of boars that will trigger the female’s response. The female cervix contains a series of five interdigitating pads, or folds, that will hold the boar’s corkscrew-shaped penis during copulation. Females have bicornuate uteruses and two conceptuses must be present in both uterine horns for pregnancy to be established. Maternal recognition of pregnancy in pigs occurs on days 11 to 12 of pregnancy and is marked by progesterone production from a functioning corpus luteum (CL). To avoid luteolysis by PGF2α, rescuing of the CL must occur via embryonic signaling of estradiol 17β and PGE2. This signaling acts on both the endometrium and luteal tissue to prevent the regression of the CL by activation of genes that are responsible for CL maintenance. During mid to late pregnancy, the CL relies primarily on luteinizing hormone (LH) for maintenance until parturition. Animal nutrition is important prior to reproduction and during gestation to ensure optimum reproductive performance is achieved.