title: Assessment of residual body weight gain and residual intake and body weight gain as feed efficiency traits in the turkey (Meleagris gallopavo).
abstract: BACKGROUND
  Since feed represents 70% of the total cost in poultry production systems, an animal's ability to convert feed is an important trait. In this study, residual feed intake (RFI) and residual body weight gain (RG), and their linear combination into residual feed intake and body weight gain (RIG) were studied to estimate their genetic parameters and analyze the potential differences in feed intake between the top ranked birds based on the criteria for each trait.
  
  
  METHODS
  Phenotypic and genetic analyses were completed on 8340 growing tom turkeys that were measured for feed intake and body weight gain over a four-week period from 16 to 20 weeks of age.
  
  
  RESULTS
  The heritabilities of RG and RIG were 0.19 ± 0.03 and 0.23 ± 0.03, respectively. Residual body weight gain had moderate genetic correlations with feed intake (-0.41) and body weight gain (0.43). All three linear combinations to form the RIG traits had genetic correlations ranging from -0.62 to -0.52 with feed intake, and slightly weaker, 0.22 to 0.34, with body weight gain. Sorted into three equal groups (low, medium, high) based on RG, the most efficient group (high) gained 0.62 and 1.70 kg more (P < 0.001) body weight than that of the medium and low groups, yet the feed intake for the high group was less (P < 0.05) than that of the medium group (19.52 vs. 19.75 kg). When separated into similar partitions, the high RIG group (most efficient) had both the lowest (P < 0.001) feed intake (18.86 vs. 19.57 and 20.41 kg) and the highest (P < 0.001) body weight gain (7.41 vs. 7.03 and 6.43 kg) relative to the medium and low groups, respectively.
  
  
  CONCLUSIONS
  The difference in feed intake between the top ranked birds based on different residual feed efficiency traits may be small when looking at the average individual, however, when extrapolated to the production level, the lower feed intake values could lead to significant savings in feed costs over time.
authors.affiliation: Centre for the Genetic Improvement of Livestock, Department of Animal and Poultry Science, University of Guelph, Guelph, ON, Canada. owillems@uoguelph.ca
authors.forename: Owen W
authors.initials: OW
authors.lastname: Willems
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Miller
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: Wood
mesh_terms: D000821:Animal Feed; D000818:Animals; D001835:Body Weight / Q000235:genetics*; D004032:Diet; D056726:Genetic Association Studies; D008297:Male; D010641:Phenotype; D019655:Quantitative Trait, Heritable; D013997:Time Factors; D014422:Turkeys / Q000235:genetics* / Q000254:growth & development*