Relationship of Feed Efficiency to Carcass Composition and Metabolic Rate in Laying Birds

Abstract

From a population of SCWL laying hens, 100 birds were classified according to their efficiency of conversion of feed to egg mass. From these, 4 "efficient" and 3 "inefficient" birds were used in energy metabolism studies involving indirect calorimetry, while the remainder were used for carcass analysis. Birds maintaining a criteria of 13.5-15.5 kg egg/48 weeks and classified as efficient or inefficient with respect to feed conversion had comparable body weight gains and did not differ significantly (P<.05) in the protein or fat content of their carcasses. In terms of energy metabolism, efficient and inefficient birds (selected on the basis of similar body size and egg mass production) showed no significant (P<.05) difference in their ability to metabolize dietary energy. In metabolism chambers, however, inefficient birds produced significantly (P<.01) more heat under conditions of ad lib. feeding (.148 vs. .121 kcal/min/kg ) and starvation (.110 vs. .090 kcal/min/kg ). From a videotaped study of bird activity there was an indication that this difference in metabolic rate was related to bird movement since inefficient birds spent less time resting and more time standing and feeding than did the efficient birds.1978 Poultry Sci 57:735-739 735

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

“…There was also no indication of differences in feed waste between a cross from a commercial breeding programme and a cross with sires from a line which was selected over three generations for feed conversion rate. This is in agreement with the findings of Morrison and Leeson (1978) that feed waste did not influence variation of feed efficiency among individuals. Since feed waste can be substantially reduced through proper management (low feeding levels, choice of feeding system, choice of feed trough type, etc.…”

“…Calculations based on their data suggest that at least 95% of the variance of ME/GE among individuals is determined by feed consumption. However, in a comparison of two groups of hens which were extremely different with respect to feed consumption but were similar in production and body weight, Morrison and Leeson (1978) found only a very small difference in metabolizability in the expected direction (12.6 as against 12.7 kJ g-' feed, i.e. 53% of the standard Genetic variafion and residual feed consumption: P. Luiting deviation among individuals).…”

“…40-117 kJ kg-0.75 d-* ) i n a d libitum fed laying hens (MacLeod et al, 1982;Boshouwers and Nicaise, 1985;. Clear differences between strains and among individuals within strains have been found for physical activity levels (Farrell, 1975; Morrison and Leeson, 1978;Heil et al, 1982;MacLeod et al, 1982;Bentsen, 1983b;Damme, 1984;Katle et al, 1984;Mills et al, 1985;El-Sayed, 1988;. Movements made during feed consumption, standing, and preening, and especially during pre-ovipositional behaviour, seem to cause high absolute HP levels and large variation between animals (Table 4).…”

“…Yet, significant strain differences were found in these three experiments after correction for activity level and feathering score, which leads to a closer approximation of true BMR; therefore, their differences in Table 2 Table 2). Morrison and Leeson (1978) also measured FHP in their earlier mentioned high-low sampling study. The difference in FHP between their two groups was 89 kJ kg-0.75 d-' or 15% of the mean, and somewhat smaller than the difference in HPo 75.…”

Relationship between residual energy intake and the behaviour of growing pigs from three genetic lines

“…Noblet et al (1993) reported that the increase in energy expenditure induced by the standing posture may be estimated as 27.3 kJ·min − 1 kg BW − 0.75 . In addition, the standing posture has been associated with RMEI (Morrisson and Leeson, 1978) who found that birds selected for high RMEI were standing more often than those selected for low RMEI. Several behaviour traits were graphically close to postures measured during the growing period and thus, explained the same variation in RMEI.…”