seven or eight months but are not usually bred until they are 15 – 18 months old.
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小母牛一般在2岁前进行自然或人工配种
The heifer is bred (naturally or by insemination) before the age of 2 years.
每个乳区都有独立的分泌系统，互不相 通，每个乳区有一个乳头。
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乳房由含有能够产生乳的腺体
The udder is composed of glandular （ 腺 体 ） tissue which contains milk-producing cells.
It is encased in muscular tissue, which gives cohesion to the body of the udder and protects it against injury from knocks and blows.
大约需要800 – 900 L血液方能产生1L乳
Approx. 800 – 900 l of blood needed for formation of one litre of milk.
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The lactation cycle（哺乳期）
Secretion of milk in the cow’s udder begins shortly before calving
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Colostrum（初乳）
牛初乳是指乳牛产犊后3～4d内所分泌的 乳汁，乳汁色泽黄而浓稠，具有特殊的乳 腥味和苦味。这些乳汁是母牛为了供给牛 犊在新生环境下，低抗外来病毒及细菌而 天然合成的。
