Herve Chapuis

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

BackgroundPoultry 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.ResultsHeritability 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.ConclusionIn 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.

Improving the efficiency of feed utilization in poultry by selection. 1. Genetic parameters of anatomy of the gastro-intestinal tract and digestive efficiency

BackgroundFeed costs represent about 70% of the costs of raising broilers. The main way to decrease these costs is to improve feed efficiency by modification of diet formulation, but one other possibility would be to use genetic selection. Understanding the genetic architecture of the gastro-intestinal tract (GIT) and the impact of the selection criterion on the GIT would be of particular interest. We therefore studied the genetic parameters of AMEn (Apparent metabolisable energy corrected for zero nitrogen balance), feed efficiency, and GIT traits in chickens.Genetic parameters were estimated for 630 broiler chickens of the eighth generation of a divergent selection experiment on AMEn. Birds were reared until 23 d of age and fed a wheat-based diet. The traits measured were body weight (BW), feed conversion ratio (FCR), AMEn, weights of crop, liver, gizzard and proventriculus, and weight, length and density of the duodenum, jejunum and ileum.ResultsThe heritability estimates of BW, FCR and AMEn were moderate. The heritability estimates were higher for the GIT characteristics except for the weights of the proventriculus and liver. Gizzard weight was negatively correlated with density (weight to length ratio) of duodenum, jejunum and ileum. Proventriculus and gizzard weights were more strongly correlated with AMEn than with FCR, which was not the case for intestine weight and density.ConclusionsGIT traits were largely dependent on genetics and that selecting on AMEn or FCR would modify them. Phenotypic observations carried out in the divergent lines selected on AMEn were consistent with estimated genetic correlations between AMEn and GIT traits.

Analysis of a slow-growing line reveals wide genetic variability of carcass and meat quality-related traits

BackgroundSlow-growing lines are widely used in France for the production of high quality free-range chickens. While such production is mainly dedicated to the whole carcass market, new prospects are opening up for the development of cuts and processed products. Whether the body composition and meat quality of slow-growing birds can be improved by selection has thus become an important issue. The genetic parameters of growth, body composition and breast meat quality traits were evaluated in relation to behaviour at slaughter in a large pedigree population including 1022 male and female slow-growing birds.ResultsThe heritability coefficients (h2) of body weight and body composition traits varied from 0.3 to 0.5. Abdominal fat percentage was genetically positively correlated with body weight but negatively correlated with breast muscle yield. The characteristics of the breast meat (i.e., post-mortem fall in pH, colour, drip loss, shear-force and lipid content) were all heritable, with h2 estimates ranging from 0.18 to 0.48. The rate and extent of the fall in pH were under different genetic control. Strong negative genetic correlations were found between the ultimate pH and the lightness, yellowness and drip loss of the meat. Wing flapping on the shackle line was significantly heritable and exhibited marked genetic correlations with the pH at 15 min post-slaughter and the redness of the meat. The genetic relationships between meat quality traits, body weight and body composition appeared slightly different between males and females.ConclusionThis study suggested that there are a number of important criteria for selection on carcass and breast meat quality in slow-growing birds. Selection for reduced abdominal fatness and increased breast muscle yield should be effective as both traits were found to be highly heritable and favourably correlated. Substantial improvement in meat quality could be achieved by selection on ultimate pH which was highly heritable and strongly correlated with the colour and water-holding capacity of the meat. Moreover, this study revealed for the first time that the behaviour at slaughter is partly genetically determined in the chicken.

Assessing the risk status of livestock breeds: a multi-indicator method applied to 178 French local breeds belonging to ten species

espanolLa clasificacion de las razas animales segun su nivel de peligro en cuanto a su desaparicion es un elemento de base para un sistema nacional de alerta y de monitoreo de los recursos geneticos. Un enfoque multicriterio ha sido desarrollado para establecer el nivel de peligro de una poblacion animal domestica. En total, se mantuvieron seis criterios: (i) el numero total de hembras reproductoras, (ii) la evolucion de este numero en los cincos ultimos anos, o las cincos generaciones, segun la especie; (iii) la proporcion de cruzamientos; (iv) el tamano efectivo de la poblacion, (v) la organizacion de los criadores y el apoyo tecnico; (vi) el contexto socio-economico. Con el proposito de facilitar la combinacion de estos criterios de tipo diferente, los valores observados fueron convertidos en una escala de 0 (ausencia de amenaza) a 5 (amenaza maxima), la correspondencia entre valores observados y notas siendo especifica por cada criterio. Para cada raza, las notas estan presentadas de forma grafica y una nota de sintesis esta calculada como la media de las seis notas. Este metodo ha sido aplicado a 178 razas locales francesas perteneciendo a diez diferentes especies: ganado, ovino, caprino, cerdo, caballo, asno, gallina, pavo, oca, pato comun. Asi se demostro que la mayoria de las razas locales francesas se pueden considerar como en peligro: todas las razas locales de equido y de cerdo, casi la totalidad de las razas locales de aves de corral, alrededor de 80% de las razas locales de ganado o caprinos y la mitad de razas locales de ovinos. Se discute el interes de este metodo para la definicion de estrategias de conservacion et la elaboracion de politicas publicas. EnglishBreed risk status assessment methods are key components of country-based early warning and response systems. In this study, a multiindicator method was developed to assess the risk status of livestock populations. Six indicators were used: (i) the current number of breeding females; (ii) the change in the number of breeding females over the last 5 years or generations (depending on the species); (iii) percentage of cross-breeding; (iv) effective population size; (v) breeders organization and technical support; and (vi) socio-economic context. To make these indicators comparable, observed values were converted into scores on a six-point scale (from 0 = no threat to 5 = maximum threat); a specific conversion method was used for each indicator. For each breed, the different scores were analysed graphically and an overall score was calculated by averaging the six separate indicator scores. This approach was applied to 178 French local breeds, belonging to ten different species: horse, donkey, goat, pig, chicken, turkey, goose and Pekin duck. A large percentage of local breeds were found to be at risk to be lost for farming, although the results were species dependent. All local equine and pig breeds, as well as almost all local poultry breeds appeared to be endangered. About 80 percent of local goat and cattle breeds, and half local sheep breeds were also found to be at risk. The usefulness of this method with regards to conservation strategies and public policy is discussed francaisLa classification des races animales selon leur statut vis-a-vis d’un risque de disparition est un element-clef d’un systeme national d’alerte et de suivi des ressources genetiques. Une approche multi-indicateurs a ete developpee pour etablir le degre de menace d’une population animale domestique. Au total, six indicateurs ont ete retenus : (i) le nombre total de femelles reproductrices, (ii) l’evolution de ce nombre dans les cinq dernieres annees, ou generations, selon l’espece ; (iii) la proportion de croisement ; (iv) la taille efficace de la population ; (v) l’organisation des eleveurs et l’appui technique ; (vi) le contexte socio-economique. Afin de faciliter la combinaison de ces indicateurs de nature differente, les valeurs observees sont converties sur une echelle de 0 (absence de menace) a 5 (menace maximale), la correspondance entre valeurs observees et notes etant specifique de chaque indicateur. Pour chaque race, les notes sont representees de facon graphique et une note de synthese est attribuee en calculant la simple moyenne des six notes. Cette methode a ete appliquee a 178 races locales francaises appartenant a dix especes differentes : cheval, âne, bovins, ovins, caprins, porc, poule, dinde, oie, canard commun. Il a ete ainsi montre que la plupart des races locales francaises peuvent etre considerees comme menacees : toutes les races locales d’equides et de porc, la quasi-totalite des races locales de volailles, environ 80% des races locales bovines ou caprines, et la moitie des races locales ovines. L’interet de cette methode pour la definition de strategies de conservation et l’elaboration de politiques publiques est discute.