Sasaki Osamu, Takeda Hisato, Nishiura Akiko
Institute of Livestock and Grassland Science, NARO, Tsukuba, Japan.
Anim Sci J. 2020 Jan-Dec;91(1):e13342. doi: 10.1111/asj.13342.
Increasing herd-life length and culling parity with increasing conception rate (CR) is necessary to increase lifetime profit from dairy cow production. Economic values of days open (DO) were determined by calculating changes in fertility traits, herd-life length, and milk yield when the simulated CR were changed in increments of 1% from -5% to 5% from the basal levels, which were obtained for Hokkaido and regions other than Hokkaido separately. When CR increased, number of artificial inseminations, DO, and milking length decreased. Furthermore, culling parity, and annual milk yield increased. Herd-life length increased in Hokkaido and decreased in the other regions. The economic values of CR were 1,623.8 to 946.8 yen and of DO were 857.4 to 399.0 yen. Relative economic values of milk yield to days open per genetic standard deviation were higher in the other regions than in Hokkaido where the economic effect of selection for DO was expected to be equal to selection for 305-day milk yield and herd life. If the survival rate of multipara cows in the other regions increases, then the economic value of DO would similarly increase in Hokkaido.
提高牛群寿命并随着受孕率（CR）的提高而提高淘汰胎次，对于增加奶牛生产的终身利润是必要的。通过计算当模拟受孕率从基础水平以1%的增量从-5%变化到5%时（北海道和北海道以外地区分别获得基础水平），繁殖性状、牛群寿命和产奶量的变化，来确定空怀天数（DO）的经济价值。当受孕率提高时，人工授精次数、空怀天数和挤奶时长减少。此外，淘汰胎次和年奶产量增加。北海道的牛群寿命增加，其他地区则减少。受孕率的经济价值为1623.8至946.8日元，空怀天数的经济价值为857.4至399.0日元。每遗传标准差的产奶量相对于空怀天数的相对经济价值在其他地区高于北海道，在北海道，选择空怀天数的经济效果预计与选择305天产奶量和牛群寿命的效果相当。如果其他地区经产母牛的存活率提高，那么北海道空怀天数的经济价值也会同样增加。
