Colostrum - Shonyu

Japanese: 初乳 - しょにゅう

This refers to the milk that accumulates in the breasts at the time of birth, and the thick, yellowish milk that comes out 3 to 5 days after birth. With each postpartum feeding or milking, its composition and appearance become closer to that of normal milk. Colostrum contains little lactose but is rich in other components, and is particularly rich in immunoglobulins as a protein and vitamin A as a vitamin. In order to give newborn calves immunity and prevent infection, dairy cows usually feed their newborn calves with colostrum for three days. However, colostrum is easily coagulated when heated, and cannot be used as market milk or as raw milk for processing.

[Nishida Tomoko]

Human colostrum

When the breast is compressed during the second half of pregnancy, a thick, translucent, yellowish liquid comes out in droplets from the nipple; this continues for 3-5 days after birth, but for the next 6-10 days it becomes transitional milk with a whitish tinge and less viscosity, after which it becomes opaque, white mature milk. Colostrum contains many fat globules of various sizes, and large colostrum globules made of large mononuclear and polymorphonuclear leukocytes can be seen, but these disappear when milk secretion becomes active. It is richer in protein and more nutritious than mature milk, and its high salt and lipid content improves laxation. The difference in composition between colostrum and mature milk is thought to be to maintain the nutrition of newborns, who do not drink much milk.

[Masao Arai]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

Japanese:

分娩(ぶんべん)時に乳房にたまっている乳、および分娩後3～5日間に出る黄色を帯びた濃厚な乳をいう。分娩後の哺乳(ほにゅう)あるいは搾乳ごとにその成分や外観は常乳に近づく。初乳には乳糖は少ないが他の成分は多く、タンパク質では免疫グロブリンが、ビタミン類ではビタミンAがとくに多い。新生子に免疫性を与えて感染を防ぐため、乳牛では普通新生子にかならず3日間は初乳を与える。しかし初乳は加熱によって凝固しやすく、市乳、加工用原料乳に用いることはできない。

［西田恂子］

ヒトの初乳

妊娠後半期に乳房を圧迫すると乳頭から滴状になって出てくる半透明で黄色を帯びた濃厚な液で、出産後も3～5日間みられるが、以後6～10日間は白色を帯びた粘り気の少ない移行乳になり、その後は不透明な白色の成乳となる。初乳には多数の大小不同な脂肪球が含まれ、大単核白血球や多核白血球からなる大きな初乳球がみられるが、乳汁分泌が盛んになると消失する。成乳に比べてタンパク質に富み栄養価が高いほか、塩類や脂質を多く含むので通じをよくする。初乳と成乳における成分の違いは、哺乳量の少ない新生児の栄養を維持するためと考えられている。

［新井正夫］

出典　小学館　日本大百科全書(ニッポニカ)日本大百科全書(ニッポニカ)について　情報 | 凡例

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