Department of Dairy Science, University of Wisconsin-Madison 53706.
Department of Dairy Science, University of Wisconsin-Madison 53706.
J Dairy Sci. 2012 Sep;95(9):5442-5460. doi: 10.3168/jds.2011-4972.
Our objective was to compare the economic and reproductive performance of programs combining timed artificial insemination (TAI) and different levels of AI after estrus detection (ED) using a daily Markov-chain model. A dairy herd was modeled with every cow following daily probabilistic events of aging, replacement, mortality, pregnancy, pregnancy loss, and calving. The probability of pregnancy depended on the combination of probability of insemination and conception rate (CR). All nonpregnant cows had a probability of pregnancy between the end of the voluntary waiting period and days in milk cutoff for AI. After the cutoff, cows were labeled as do not breed and replaced when milk production was below a minimum milk threshold. A similar model was created to represent a replacement heifer herd to simulate and adjust the supply and demand of replacements. The net value (NV) of a program was the sum of milk income over feed cost, replacement and mortality cost, income from newborns, and reproductive costs. The model was used to compare the NV of 19 programs. One program used 100% TAI (42% CR for first TAI and 30% for second-and-later services), whereas the other programs combined TAI with ED. The proportion of cows receiving AI after ED for the combined programs ranged from 30 to 80%, with levels of CR of 25, 30, and 35%. As the proportion of cows receiving AI after ED increased, the CR of cows receiving TAI decreased. The combined programs with CR of 35% for cows receiving AI after ED had the greatest NV and reproductive performance at all levels of ED. The program using 100% TAI had greater NV and better reproductive performance than all programs with 25% CR after ED inseminations, whereas it had very similar performance to combined programs with up to 60% of cows receiving AI after ED and 30% CR. The factor with the greatest relative contribution to the differences among programs was income over feed cost, followed by replacement and reproductive costs. Adjusting the days in milk cutoff for AI to match the supply and demand of heifer replacements improved the NV of all programs except for those with 25% CR after ED, which had either no change or a decrease in NV. In summary, the economic value of reproductive management programs combining TAI and ED depended on the proportion of cows receiving AI after ED and the resulting CR. Adjusting the heifer supply and demand increased the NV of programs with heifer surplus and decreased the NV of programs with heifer deficit.
我们的目标是使用每日马尔可夫链模型比较结合定时人工授精（TAI）和发情后不同水平人工授精（ED）的方案的经济和繁殖性能。使用每日概率事件对奶牛群进行建模，这些事件包括老化、替换、死亡、妊娠、妊娠损失和产犊。妊娠概率取决于授精概率和受孕率（CR）的组合。所有未怀孕的奶牛在自愿等待期结束后和牛奶截止日用于人工授精之间都有怀孕的可能性。截止日后，当产奶量低于最低产奶量阈值时，奶牛被标记为不繁殖并被替换。创建了一个类似的模型来代表后备牛群，以模拟和调整后备牛的供需。一个方案的净价值（NV）是牛奶收入减去饲料成本、替换和死亡成本、新生牛的收入和繁殖成本的总和。该模型用于比较 19 个方案的 NV。一个方案使用 100%的 TAI（第一次 TAI 为 42%，第二次及以后服务为 30%），而其他方案则将 TAI 与 ED 结合使用。联合方案中发情后接受 AI 的奶牛比例从 30%到 80%不等，CR 水平为 25%、30%和 35%。随着发情后接受 AI 的奶牛比例增加，接受 TAI 的奶牛的 CR 降低。发情后接受 AI 的奶牛的 CR 为 35%的联合方案在所有 ED 水平下均具有最大的 NV 和繁殖性能。使用 100%TAI 的方案比发情后接受 AI 的所有方案（25%CR）的 NV 和繁殖性能都要好，而与发情后接受 AI 的奶牛比例高达 60%、CR 为 30%的联合方案的性能非常相似。对方案之间差异贡献最大的因素是饲料成本以上的收入，其次是替换和繁殖成本。调整 AI 的牛奶截止日以匹配后备牛的供需，可以提高所有方案的 NV，除了发情后接受 AI 的方案（25%CR），这些方案的 NV 要么没有变化，要么下降。总之，结合 TAI 和 ED 的繁殖管理方案的经济价值取决于发情后接受 AI 的奶牛比例和由此产生的 CR。调整后备牛的供需可以增加后备牛过剩的方案的 NV，减少后备牛短缺的方案的 NV。
