Integrative understanding and evaluation residual feed intake in dairy cattle

剩余采食量（RFI）是对饲料利用率的一种经体重和生产校正的测量。它已被公认为牲畜饲料效率的可靠测量方法。RFI定义为实际采食量与根据体重维持和生产水平的平均需求预测的采食量之间的差异。已经在牛肉、猪和家禽中充分研究了评价生长期间产肉动物RFI的方法，但没有评价雌性种猪RFI的方法。这是因为繁殖雌性动物（如奶牛）的多功能能量需求使测量复杂化，但肯定不会减少有用性。由于饲料反映了大量（40-50%）的可变成本与牛奶生产和孕体的增长，遗传改良的RFI可能是非常重要的经济意义。因此，繁殖雌性的RFI研究应给予高度优先考虑。该研究将以奶牛为模型，开发基于科学的方法来准确评估繁殖雌性的RFI。本研究认为，奶牛RFI存在遗传差异，这可用于饲料利用的遗传改良。从第一次泌乳的小母牛（HRFI）获得的RFI和她的一生RFI（CRFI）之间也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。这项拟议的研究旨在：1）开发一种创新的基于科学的方法来评估奶牛的RFI; 2）确定个体奶牛之间RFI的遗传差异，以进行遗传改良; 3）研究使用动物的HRFI来预测其CRFI的可能性。虽然该研究项目将使用奶牛作为模型，但该理论和方法将在其他行业的雌性育种群中具有广泛的应用。该研究计划将通过更好地了解饲料利用率，在农业科学领域实现重大知识进步。它将通过提高牛奶和肉类生产的饲料利用率，使加拿大和全球的乳制品和其他家畜行业受益匪浅。

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.