Integrative understanding and evaluation residual feed intake in dairy cattle

剩余采食量(RFI)是对饲料利用率的活重和产量的修正测量。它已被公认为牲畜饲料效率的可靠测量方法。RFI被定义为实际采食量与根据体重维持和生产水平的平均需要量预测的采食量之间的差值。肉用动物生长期间RFI的评估方法已在牛肉、猪和家禽中得到了很好的研究，但尚无一种方法可用于评估雌性种畜的RFI。这是因为奶牛等繁育母牛的多功能能量需求使衡量标准变得复杂，但肯定不会减少有用性。由于饲料反映了与牛奶生产和胚胎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要的经济意义。因此，RFI在繁育雌性中的研究应得到高度重视。这项拟议的研究将开发基于科学的方法，以奶牛为模型准确地评估繁殖母牛的RFI。我认为奶牛存在RFI的遗传差异，这可以用于饲料利用率的遗传改良。此外，从第一头哺乳母牛获得的RFI(HRFI)与其寿命RFI(CRFI)之间可能存在高度的遗传相关性，如果是这样的话，HRFI可以用来预测她的cRFI。这项拟议的研究旨在1)开发一种基于科学的创新方法来评估奶牛的RFI；2)识别个体奶牛在RFI上的遗传差异以进行遗传改良；以及3)研究使用动物的HRFI来预测其cRFI的可能性。尽管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母牛养殖群体中广泛应用。这项研究计划将通过更好地了解饲料利用，展示农业科学领域的重大知识进步。它将通过提高牛奶和肉类生产的饲料利用率，大大有利于加拿大和全球的乳制品和其他家畜行业。

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.