Genetic variation of energy partitioning in laying hens: causes of variation in residual feed consumption

Abstract

When multiple linear regression of feed consumption on metabolic body weight (MBW), body weight gain (BWG) and egg mass production (EM) is calculated between or within strains of laying hens, a standard deviation of 47-180 kJ metabolizable energy (ME) per day remains unexplained by these effects. This unexplained fraction, called residual feed consumption (RFC), has a heritability of O-8O0/o. A survey of the literature was performed to quantify this unexplained variation between strains and among individuals within strains of laying hens with respect to some energy metabolism parameters independent of MBW, BWG and EM. Genetic differences in ability to metabolize gross feed energy are found to be of limited magnitude; the coefficient of variation is 1-3%. From calorimetric experiments, the ran e of heat production (HP) between strains is found to be 44-118 kJ kg-' s7' d-' ; variation among individuals within strains is of the same magnitude (standard deviation: 16-125 kJ kg-0.75 d-I). The range of maintenance requirements (ME,) is reported to be 41-113 kJ kg-0,75 d-'; standard deviation among individuals is 23-80 kJ kg-0.75 d-'. Variation of heat increment of production (constituting the difference between HP and ME,) seems to be small. The range of fasting heat roduction (FHP) between strains of laying hens appears to be 18-130 kJ kg-'qR d-l, whereas the standard deviation among individuals has again the same magnitude (22-51 kJ kg-0+75 d-' 1. It is concluded that variation of heat increment of maintenance (ME, -FHP) is small. The main component of HP variation and of RFC variation seems to be the variation of ME, : differences in physical activity, feathering density, basal metabolic rate, area of nude skin (comb, wattles, legs), body temperature and body composition. Net energy per g EM does not play an important role in variation of RFC.

Effects of ad libitum and restricted feeding on early production performance and body composition of Yorkshire pigs selected for reduced residual feed intake

“…RFI is calculated as observed minus expected feed intake for the pig's achieved rate of gain and BF (Koch et al, 1963;Luiting, 1990;Kennedy et al, 1993). In swine, RFI has been shown to be moderately heritable, with estimates ranging from 0.15 to 0.38 (Nguyen et al, 2005;Gilbert et al, 2007;Cai et al, 2008;Hoque et al, 2009).…”

“…The main biological factors that contribute to variation in RFI have been partially quantified in mice (McDonald et al, 2009), poultry (Luiting, 1990) and beef cattle (Richardson and Herd, 2004). As reviewed by Herd and Arthur (2008), in beef cattle, approximately 73% of the variation in RFI is accounted by factors that include activity, feed intake patterns, behavior, stress, digestibility, protein turnover and tissue metabolism.…”

Behaviour influences cholesterol plasma levels in a pig model

“…In animals, and farm animals, in particular, much research is directed to investigation of feed efficiency traits. A widely used estimate is that of 'residual feed intake (RFI)', which is defined as the feed that is consumed by an individual and its consumption as predicted from a model involving its maintenance and growth requirements (Luiting, 1990;Rauw et al, 2006a). Because of the complexity of measuring actual food intake in humans, this concept has never been applied to human research.…”

Modelling energy utilization for laying type Pullets

“…Besides, birds reared at 12ºC and fed 55% of ad libitum intake also showed negative energy retention, because maintenance requirements increased. the fact that greater energy costs for maintenance are needed for tissues with high protein levels, due to the permanent cell turnover, and that the maintenance of the fat tissue requires low energy, since it is virtually a metabolically inactive tissue (Luiting, 1990).…”