A comprehensive review of the estimation technology of feed intake and diet composition in grazing livestock

Forage intake by grazing livestock is one of the keys to understanding forage grazing system dynamics. It is confirmed that understanding the types of plant species selected by the animal and the contribution of each species to the total intake could give an insight into the nutritional status of the animal and predict their performance, thus providing an objective basis for various management decisions and offering a feasible range management strategy to optimize resource utilization. However, estimating intake and diet composition of freeranging livestock is difficult and expensive. The advanced technology and the improved methods have significantly improved our ability to collect grazing behavior data, but measurement of feed intake, diet composition and nutrient digestibility in freeranging animals remains a challenge in nutritional study because of the inherent errors associated with the methods that are used at present. In this review, we discussed the advantages and disadvantages, and more or less accuracy of those main methods (including imitation, preand postgrazing technique, acidinsoluble ash method, in vitro digestibility in combination of intraruminal chromic oxide method, nalkanes plant cuticular wax markers and near infrared reflectance spectroscopy) and also expounded a growing tendency to evaluate the feed intake and diet composition, consequently to supply information for further studies.