Residual Feed Intake towards Efficient Animal Production: A Paradigm Shift?

Modern methods of selection have contributed greatly to the genetically superior high yielding animals of current animal production systems [1]. While this being the case of the developed world, animal production in the tropics is constrained by the everlasting deficit in feed supply [2]. Therefore, a method based on lower feed intake without affecting mature weight and production will have a greater implication in agri-food industry. This was initially conceptualized in 1963 by Koch et al. [3], who introduced Residual Feed Intake (RFI), and defined it as the difference between actual intake and the expected requirements of feed for maintenance and body weight gain, in beef cattle. Assumption behind using RFI as a selection tool is that the biological processes regulating feed consumption and efficiency are similar in younger and older animals (as there exist high genetic correlation between postweaning intake and maturity) [4]. RFI is a moderately heritable trait in cattle (h2=0.25-0.48) which is independent of body size and production [5]. One approach for measuring RFI is by recording individual animal data on intake and growth for a minimum period of 35 days [5], while the second is by pre-screening for blood metabolites such as insulin like growth factor-1 followed by selection through RFI for increasing growth rate, feed efficiency and proportion of lean meat [4]. Expected dietary intake is estimated by means of a multiple regression equation of consumption, as determined by the metabolic live weight and weight gain [4,6].