title: Improving the efficiency of feed utilization in poultry by selection. 2. Genetic parameters of excretion traits and correlations with anatomy of the gastro-intestinal tract and digestive efficiency.
abstract: BACKGROUND
  Poultry production has been widely criticized for its negative environmental impact related to the quantity of manure produced and to its nitrogen and phosphorus content. In this study, we investigated which traits related to excretion could be used to select chickens for lower environmental pollution.The genetic parameters of several excretion traits were estimated on 630 chickens originating from 2 chicken lines divergently selected on apparent metabolisable energy corrected for zero nitrogen (AMEn) at constant body weight. The quantity of excreta relative to feed consumption (CDUDM), the nitrogen and phosphorus excreted, the nitrogen to phosphorus ratio and the water content of excreta were measured, and the consequences of such selection on performance and gastro-intestinal tract (GIT) characteristics estimated. The genetic correlations between excretion, GIT and performance traits were established.
  
  
  RESULTS
  Heritability estimates were high for CDUDM and the nitrogen excretion rate (0.30 and 0.29, respectively). The other excretion measurements showed low to moderate heritability estimates, ranging from 0.10 for excreta water content to 0.22 for the phosphorus excretion rate. Except for the excreta water content, the CDUDM was highly correlated with the excretion traits, ranging from -0.64 to -1.00. The genetic correlations between AMEn or CDUDM and the GIT characteristics were very similar and showed that a decrease in chicken excretion involves an increase in weight of the upper part of the GIT, and a decrease in the weight of the small intestine.
  
  
  CONCLUSIONS
  In order to limit the environmental impact of chicken production, AMEn and CDUDM seem to be more suitable criteria to include in selection schemes than feed efficiency traits.
authors.affiliation: INRA, UR83 Recherches Avicoles, F-37380, Nouzilly, France.
authors.forename: Hugues
authors.initials: H
authors.lastname: de Verdal
authors.forename: Agnès
authors.initials: A
authors.lastname: Narcy
authors.forename: Denis
authors.initials: D
authors.lastname: Bastianelli
authors.forename: Hervé
authors.initials: H
authors.lastname: Chapuis
authors.forename: Nathalie
authors.initials: N
authors.lastname: Même
authors.forename: Séverine
authors.initials: S
authors.lastname: Urvoix
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Le Bihan-Duval
authors.forename: Sandrine
authors.initials: S
authors.lastname: Mignon-Grasteau
mesh_terms: D000821:Animal Feed; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D003672:Defecation / Q000235:genetics*; D004063:Digestion / Q000235:genetics; D004787:Environmental Pollution; D005260:Female; D041981:Gastrointestinal Tract / Q000033:anatomy & histology*; D008297:Male; D008372:Manure; D009584:Nitrogen; D010758:Phosphorus; D011200:Poultry / Q000235:genetics*; D012641:Selection, Genetic
chemical_list: D008372:Manure; D010758:Phosphorus; D009584:Nitrogen