Residual feed intake: a nutritional tool for genetic improvement

Abstract

The goal of this bibliographical study was to provide information about residual feed intake (RFI), a new criterion used in the selection of beef cattle for growth rate, food ingestion, and feed efficiency. RFI is calculated as the difference between real consumption and the quantity of food an animal is expected to eat based on its mean live weight and rate of weight gain. In studies of RFI, many speculations are made among researchers about the reliability of this criterion. However, there is a high genetic correlation with characteristics related to post-weaning consumption and maturity, indicating that the biological processes that regulate consumption and efficiency in young animals are similar to the processes that regulate consumption and efficiency in animals of greater age. In contrast to feed conversion, selection based on RFI seems to select for lower rates of consumption and lower animal maintenance requirements without changing adult weight or weight gain. Therefore, we conclude that the data indicate that there are extraordinary benefits to be gained from changing the goals of selection from increased weight gain to improved nutritional efficiency. Given the importance of animal production for economic development in Brazil choosing the best selection goals for livestock improvement is essential. To include an index of feed efficiency in future goals would be desirable, and RFI may play a part in this if economic methods of implementation can be developed.

Nutrient utilisation and methane emissions in Sahiwal calves differing in residual feed intake

“…This was in accordance with the expectation, as Group High RFI exhibited a higher DM intake and a greater manure production than Groups Low and Medium RFI. Because the N retention as percentage of N intake was significantly (p < 0.05) higher in Group Low RFI, this supports the hypothesis that animals with a low RFI are more efficient in N utilisation, which could be due to the lower protein degradation rate (Bezerra et al 2013). …”

“…Blood glucose concentration was not associated with RFI, as has been observed previously by Kelly et al (2010). Richardson et al (1996) demonstrated a significant increase of total plasma protein in high RFI steers compared with low RFI steers, and Theis (2002) found a significantly higher concentration of BUN among high RFI steers, which could be due to efficient protein deposition in low RFI animals (Bezerra et al (2013). Enzymes like ALT and AST, representing liver functional integrity, were within normal levels.…”

“…Further, the biological basis for high efficiency in Group Low RFI is thought to be due to better energy and protein metabolism (Karisa et al 2014), improved mitochondrial respiration rate (Kolath et al 2006), increased gene expression of gut microorganisms (Bezerra et al 2013) or hypothalamus (Perkins et al 2014) as observed for Angus-sired cattle. Altogether these factors could improve feed efficiency.…”

“…Therefore, residual feed intake (RFI) was introduced as an alternate measure of net feed efficiency, initially by Koch et al (1963). RFI is the difference between actual intake and the expected requirements of feed for maintenance and body weight gain and is independent of mature weight and average daily gain (ADG) (Nkrumah et al 2006;Lawrence et al 2013;Steyn et al 2014) and thus will be desirable as a nutritional tool for genetic improvement of the livestock (reviewed by Bezerra et al 2013). RFI, being moderately heritable (h 2 for cattle ranges from 0.25 to 0.49), has been studied as a selection method for feed efficiency in beef cattle (Kolath et al 2006;Nkrumah et al 2006;Hegarty et al 2007;Jones et al 2011;Perkins et al 2014), dairy cows (Lawrence et al 2013;Steyn et al 2014), Murrah buffaloes (Bisitha et al 2014), sheep (Muro-Reyes et al 2011Redden et al 2014), pigs (Grubbs et al 2013), chicken (Zhen-qiang et al 2014), rabbits (Larzul and de Rochambeau 2005) and minks (Hedemann and Damgaard 2012), although mechanisms underlying variation in RFI are poorly understood (Perkins et al 2014).…”

Potential of condensed tannins for the reduction of emissions of enteric methane and their effect on ruminant productivity

“…In this way, it has been predicted that emissions of CO 2 , CH 4 and N 2 O, will follow the same pattern of growth, as it was observed in 1996 when the world emissions of CH 4 reached 65,000 Gg (equivalents to CO 2 ) while in 2011 the emissions of CH 4 increased to 92,000 Gg 1 (FAOSTAT 2011). Due to this increase in the inventories of CH 4 , a series of strategies have been developed to decrease emissions of CH 4, among them: the search for more efficient breeds of livestock (Bezerra et al 2013), rumen defaunation with secondary metabolites (tannins and saponins), the use of various additives and inmunizations, the use of halogenated compounds and organic acids (Kumar et al 2014). However, the use of secondary metabolites (tannins and saponins) is one of the most appropiate method due to their abundance in tropical plants at a small cost.…”