牛奶的基本知识.ppt

第三篇乳品工艺学
第一章乳的基础知识
第一节奶牛的基础知识
Milk production began 6 000 years ago or even earlier.
The dairy animals of today have been developed from untamed animals which, through thousands of years, lived at different altitudes and latitudes exposed to natural and, many times, severe and extreme conditions.
Table
表1中是不同种类动物乳汁的营养组成是平均数,影响因素还很多,包括:breed, feeding, climate, etc.
牛乳(Cow milk)
乳是哺乳动物生命之初唯一食物
Milk is the only food of the young mammal during the first period of its life.
乳可以提供能量,并含有动物生长所需的物质
The substances in milk provide both energy and the building materials necessary for growth.
乳也含有抗体
Milk also contains antibodies which protect the young mammal against infection.
1头犊牛大约需要1000L牛乳
A calf needs about 1 000 litres of milk for growth, and that is the quantity which the primitive cow produces for each calf.
1头奶牛1个泌乳周期大约分泌6000L牛乳,
现在有些奶牛产奶量超过14000L。
Selective breeding has resulted in dairy cows which yield an average of more than 6 000 litres of milk per calf, . six times as much as the primitive cow.
Some cows can yield 14 000 litres or more.
黄牛产乳量也可达600 kg左右
乳用水牛则可达1000 kg~2000 kg。
小母牛7-8个月就可以达到性成熟,通常15-18个月才进行配种。
Before a cow can start to produce milk she must have calved first. Heifers(小母牛) reach sexual maturity (性成熟)at the age of seven or eight months but are not usually bred until they are 15 – 18 months old.
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.
奶牛的孕期为265-300天
The period of gestation is 265 – 300 days
小母牛在2-
A heifer produces her first calf at the age of about 2 – years.
奶牛的怀孕时间9个月
 The gestation period is 9 months.
奶牛产犊后泌乳期为10个月(通常按305天计算)
 After calving the cow gives milk for 10 months.
奶牛产犊后1-2个月再进行配种
 1 – 2 months after calving the cow will again be bred.
奶牛一生大约产5胎后就宰杀。我国8-10胎
After having given birth to some 5 calves, the cow is generally slaughtered.