Integrative understanding and evaluation residual feed intake in dairy cattle

剩余采食量（RFI）是衡量饲料利用率的活重和生产校正指标。它已被认为是衡量牲畜饲料效率的可靠方法。RFI定义为实际采食量与根据维持体重的平均需要量和生产水平预测的采食量之差。肉用动物生长期间RFI的评价方法已经在牛肉、猪和家禽中得到了很好的研究，但目前还没有评价雌性种畜RFI的方法。这是因为育龄女性（如奶牛）的多功能能量需求使测量变得复杂，但肯定不会减少有用性。由于饲料反映了与产奶和仔猪生长相关的大量可变成本（40-50%），因此RFI的遗传改良可能具有重大的经济意义。因此，对繁殖雌性的RFI研究应给予高度重视。拟议的研究将开发基于科学的方法，以奶牛为模型准确评估育种雌性的RFI。认为奶牛RFI存在遗传差异，可用于饲料利用率的遗传改良。此外，从首次泌乳母牛（HRFI）获得的RFI与她的一生RFI （CRFI）可能存在高度的遗传相关性，如果是这样，HRFI可以用来预测她的CRFI。本研究旨在1)开发一种基于科学的创新方法来评估奶牛的RFI；2)鉴定奶牛个体间RFI的遗传差异，进行遗传改良；3)研究利用动物的HRFI来预测其CRFI的可能性。虽然该研究项目将以奶牛为模型，但其理论和方法将广泛应用于其他行业的雌性种畜。这项研究计划将通过更好地了解饲料利用，在农业科学领域取得重大的知识进步。它将通过提高牛奶和肉类生产的饲料利用率，大大有利于加拿大和全球的乳制品和其他国内畜牧业。

Residual feed intake (RFI) is a liveweight and production corrected measurement of feed utilization. It has been recognized as a robust measurement of feed efficency in livestock. RFI is defined as the difference between the actual feed intake and that predicted on the basis of mean requirements for body weight maintenance and levels of production. Methods for evaluating RFI for meat producing animals during growth have been well studied in beef, swine and poultry, but there is no method available for evaluating RFI for female breeding stock. This is because the multifunctional energy requirements of breeding females, such as dairy cows, complicates the measure, but certainly does not diminish usefulness. Since feed reflects a large amount (40-50%) of the variable costs associated with milk production and conceptus' growth, genetic improvement of RFI can potentially be of great economic importance. Therefore, RFI research in the breeding female should be given a high priority. The proposed research will develop science based methods to evaluate RFI of breeding females accurately using the dairy cow as a model. I believe that genetic diferences of RFI exist in dairy cows and this can be used in the genetic improvement of feed utilization. Also high genetic correlation between RFIs obtained from a first lactation heifer (HRFI) and her life time RFI (CRFI) may exist and if so HRFI can be use to predict her CRFI. This proposed research is aimed to 1) develop an innovative science based methodology to evaluate RFI for dairy cow; 2) identify the genetic differences in RFI among individual cows for genetic improvement; and 3) investigate the possibility of using an animal's HRFI to predict her CRFI. Although the research project will use the dairy cow as a model, the theory and methodology will have broad applications across female breeding stock for other industries. This research program will present a major knowledge advancement in the field of agriculture sciences through better understanding feed utilizations. It will significantly benefit the dairy and other domestic animal industries of Canada and globally by improving feed utilization for milk and meat production.