Genetic Changes in Efficiency of Feed Utilization of Chicks Maintaining Body Weight Constant

Abstract

Selection based on individual feed conversion ratio was made for three generations in a chicken population previously selected for rate of growth and for one generation in a randombred population which had not been selected for rate of growth. Two sets of high (HL) and two sets of low (LL) feed conversion ratio lines were selected in each population: one set selected so that body weight was constant over generations (HLWK, LLWK), while in the other set (HLWV, LLWV) body weight was allowed to vary.In the three generations of selection in the chicken population the units of feed required for a unit of gain was increased .12 in the HLWV line over that of non-selected controls and .08 in the HLWK line. In the low feed conversion ratio lines the units of feed required for a unit of gain was decreased .11 in the LLWK line and .07 in the LLWV line. In both low lines more progress was made in females than in males. In the randombred stock, which had no previous selection for growth, as much progress in lowering the feed conversion ratio was made in one generation of selection as was made in three generations in the broiler population (decreased .12 in the LLWK and .13 in the LLWV) with no sex difference in response.The realized heritabilities for feed conversion for the lines selected from the broiler population were .20, .21, .33 and .26 for the LLWV, LLWK, HLWV, HLWK, respectively. In the lines selected from the randombred population the realized heritabilities were .56, .45, .35 and .31, respectively.The magnitude of the heritability values obtained indicate that even in lines previously selected for growth there is sufficient variation in efficiency of feed utilization to allow progress in selection without further change in body weight.

Evolution of the Modern Broiler and Feed Efficiency

“…In retrospect, this void is understandable because implementation of the laboratory experiments in a world of large numbers and multistage selection was lacking in both what and when to measure. Meanwhile, further evidence that feed efficiency responded to selection came from laboratories in the United States (39,40) and Australia (41). The public scientific base showed a heritable trait but not how it could be implemented.…”

Selection for food conversion in broilers: Predicted responses to selection for economic efficiency

“…The last set was derived from the results of Fox and Bohren (1954), Thomas et al (1958), Siegel (1962), Merritt (1966), Goto (1968), Kinney (1969), Wilson (1969), Pym (1971), Guill and Washburn (1974) and Pym and Nicholls (1979). The base population estimates of Pym and Nicholls were estimated by averaging over sexes, taking combined sire and dam component estimates for genetic variances and covariances.…”

“…However, there is evidence of substantial independent variation in food conversion efficiency not accounted for by variation in body weight (e.g. Guill and Washburn, 1974;Pym and Nicholls, 1979).…”

Genotype by environment interactions in relation to growth traits in slow growing chickens

“…The feed conversion ratio (FCR) may be improved by direct selection [10,24], especially in Label Rouge chickens, in which the feed conversion ratio is much higher than in broilers [8], ranging from 3.00 to 3.47 between 6 and 8 wk [17,25,28,30]. In Label Rouge production, animals are reared in extensive conditions.…”