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近40—50年来,美国的畜牧业与饲料生产发生了极为重大的变化。在畜牧业方面,他们始终把希望寄托于高产家畜品种,向资金高度积累的专门化方向发展,使集约化部门肉蛋奶的产量大大增加。美国的奶牛业在国民经济中已成为独立部门,采取了逐渐减少奶牛头数,增加个体产奶量的措施,保证了牛奶产量的日益增加。据粮农组织的统计,美国在1945—1985年的40年间,奶牛的年均头数由2500万头减少到1120万头,头均产奶量由2100千克提高到5485千克,年总产奶量由5650万吨提高到6140万吨。
In the last 40-50 years, there has been a very significant change in the livestock production and feed production in the United States. In the area of livestock husbandry, they have always pin their hopes on high-yielding domestic animal species and have been moving towards a highly-funded and highly specialized specialization that has greatly increased the output of meat and dairy products in intensive sectors. The dairy industry in the United States has become an independent department in the national economy and has taken measures to gradually reduce the number of cows and increase individual milk production, thus ensuring an ever-increasing milk production. According to FAO statistics, the annual average number of cows in the United States decreased from 25 million heads to 11.2 million heads in the 40 years between 1945 and 1985, while the average annual milk production increased from 2100 to 5,485 kg. The total annual milk production From 56.5 million tons to 61.4 million tons.