CARD Livestock Model Documentation: Beef
记录了美国牛肉产业的结构变化，包括生产规模扩大、生产者数量减少、大型育肥场占比上升，以及技术进步带来的生产效率提升，适合了解美国牛肉产业演变的读者。
The U.S. beef industry has experienced continuing structural change. The size of production enterprises within the industry has expanded while the total number of producers has decreased. The percentage of fed cattle from large commercial feedlots (capacity greater than 1, 000 head) has increased from less than 39 percent in 1964 to over 73 percent in 1981 (Van Arsdall and Nelson 1983). Large commercial producers have lower costs per head than smaller operations and are able to produce beef on a year-round basis, reducing seasonality within the industry. Also, through improved production practices and technological innovation, beef cow-calf producers have increased calving rates, reduced death loss, increased the rate of gain, and increased feed efficiency. These improvements are attributed to improved breeding techniques and disease control as well as to the increased use of growth-stimulating implants and feed additives (Gilliam 1985).