Effet combiné de la génétique et de la nutrition sur la santé et le bien-être animal : impact sur les pododermatites de contact chez les volailles

Ce projet avait pour but d’étudier l’effet combiné (l’interaction) de la génétique et de la nutrition sur la santé et le bien-être du poulet de chair et de déterminer si la sélection génétique sur la capacité digestive pourrait permettre d’augmenter le taux des matières premières dites alternatives dans les aliments du poulet sans compromettre leur santé et bienêtre. Pour répondre à cette question 846 poulets de chair issus d’une expérience de sélection divergente pour une forte (D+) ou faible (D-) capacité digestive ont été élevés avec un régime classique ou alternatif. Le régime classique à base de maïs et de tourteau de soja était facile à digérer. Le régime alternatif incluait une variété de blé particulièrement difficile à digérer (Rialto) et du tourteau de colza. Pour chacun de ces quatre traitements expérimentaux, huit répétitions ont été effectuées. Afin d’évaluer globalement l’impact d’une stratégie combinant la sélection et la nutrition sur la durabilité, de nombreux indicateurs relevant des trois piliers de la durabilité ont été mesurés. Les résultats relevant du pilier économique montrent que les D+ présentent de meilleures performances que les D- quel que soit le régime. Ainsi, les D+ présentent un poids vif plus élevé (+1.5% sur maïs et +5.7% sur blé), un indice de consommation plus bas (-9.4% sur maïs et -24.1% sur blé), un moindre taux de mortalité cumulatif (-77 sur maïs et -78% sur blé) et un rendement de filet plus important (+8.32% sur maïs et 7.15% sur blé) que ceux des D- sur régime maïs et alternatif respectivement. Les résultats portant sur le pilier social montrent que la sélection pour la capacité digestive modifierait peu (comportement alimentaire) ou pas du tout (comportement exploratoire et social) les aspects comportementaux chez le poulet de chair. Les dermatites de contact, utilisées comme indicateurs du bien-être, sont également peu affectées par la sélection. Bien que la prévalence des pododermatites soit de 100% à 54 jours, la sévérité n’a pas dépassé 3.5 sur une échelle de 10 scores. De plus, la sévérité d’autres formes de dermatites comme les ampoules de bréchet et les brûlures tarsiennes était très faible. Quant aux aspects environnementaux, la sélection génétique sur la capacité digestive a permis de réduire non seulement la quantité de rejets produite par kg de poids vif (D+ vs D- -29% et - 43% sur régime maïs et alternatif respectivement) mais aussi la quantité d’azote rejetée dans l’environnement (D+ vs D- : à 7 jours : -18.3 et -54.5%, à 21 jours -22.3% et -51.6% d’azote ammoniacal dans la litière sur régime maïs et alternatif respectivement). En conclusion, la sélection génétique sur la capacité digestive s’avère un outil efficace pour l’amélioration des différents aspects de la durabilité des systèmes de production avicole

Possibility of improving broiler meat quality by genetic selection and interactions with rearing factors

Dans un contexte où la demande mondiale en viande de poulet ne cesse d’augmenter, les qualités technologique et sensorielle de cette viande sont devenues un enjeu majeur pour l’industrie. L’analyse de deux lignées de poulet divergentes pour le pH ultime (pHu) du filet confirme que la génétique est un déterminant majeur de ce caractère. Leur comparaison montre qu’augmenter le pHu du filet par sélection impacte le pHu d’autres muscles et améliore de nombreux critères dont le pouvoir de rétention d’eau, le rendement technologique et la tendreté de la viande. Si l’histologie et la composition biochimique du muscle ne sont pas affectées par la sélection, nos résultats suggèrent un lien défavorable entre un trop faible niveau des réserves énergétiques musculaires et l’incidence de défauts structuraux telle que les striations blanches. Par contre, aucun antagonisme génétique entre le pH ultime et les caractères de production (poids vif, rendement en viande et indice de consommation) n’a été observé.In a context where the global demand for chicken meat is increasing, technological and sensory qualities of this meat have become a major issue for the poultry industry. The analysis of two chicken lines divergent for ultimate pH (pHu) of breast fillets confirms that genetics is a major determinant of this trait. Between-lines comparison shows that increasing the pHu by selection changes the pHu of other muscles and improves many other quality criteria such as water-holding capacity, curing-cooking yield and meat tenderness. Although histology and biochemical composition of the muscle are not affected by the selection, our results suggest an unfavorable relationship between low muscle energy reserve and the incidence of structural defects such as white striping. On the contrary, no negative association between ultimate pH and production traits (body weight, meat yield and feed conversion ratio) was observed

Genetics and genomics of meat quality traits in poultry species

International audienc

Combined effect of divergent selection for breast muscle ultimate pH and dietary amino acids on chicken performance, physical activity and meat quality

Responses to changes in dietary Lys and other essential amino acid (AA) concentrations were evaluated in 480 male and female broilers originating from two lines divergently selected for high (pHu+) or low (pHu-) ultimate pH (pHu) of breast muscle. The two genetic lines were fed with two grower isoenergetic diets differing in both true digestible Lys (control=10.2 g/kg and experimental=7.0 g/kg) and amounts of other essential AA calculated in relation to Lys, which were sufficient for the control diet or in excess for the experimental diet. There were six repetitions per treatment. Birds were weighed individually at days 0, 21, 28 and 43. Feed consumption was recorded per pen and feed conversion was calculated over the growing period. The physical activity and walking ability of broilers were recorded during the whole rearing period. Breast and leg yield, and abdominal fat percentage were measured at 43 days of age, as were pHu, color, drip and cooking loss, Warner-Bratzler shear force, and curing-cooking yield of the breast Pectoralis major and pHu of the thigh Sartorius muscle. Divergent selection greatly affected most breast meat quality traits without significantly changing growth rate or feed efficiency. When subjected to a variation in dietary intake of AA, birds from the two genotypes responded in a similar way in terms of animal's growth, feed efficiency, body composition and meat quality traits. Although line and diet did not affect physical or feeding activities of the broilers, a significant effect of line-by-diet interaction was observed on gait score. Contrary to the pHu- birds, the walking ability of pHu+ birds was impaired when fed the control diet that favored growth and breast muscle development and limited storage of carbohydrate in muscle

Effect of reduced crude protein diets supplemented with free limiting amino acids on body weight, carcass yield, and breast meat quality in broiler chickens

ABSTRACT: This study investigated the effect of reducing dietary crude protein (CP) content in the grower and finisher diets of broiler chickens on breast meat quality, muscle protein functionality, growth, carcass yield, and meat yield. To achieve this, a total of 1,269 one-day-old male Ross 308 chicks were fed 1 of 3 diets replicated 9 times each in a randomized complete block design with 9 blocks. The diets included a control (20.4% and 19.5% CP in the grower and finisher phase, respectively), a diet with a 1.5% reduction (CP-1.5%) and a diet with a 3.0% reduction (CP-3.0%) in CP content in both the grower and finisher phases. At the end of the experiment, the reduced-CP diets had no impact on body weight, feed intake, or feed conversion ratio. However, reduced-CP diet resulted in reduced (P < 0.001) total nitrogen intake (−7.46 and −11.94% in CP-1.5% and CP-3.0%, respectively). Breast meat quality was assessed (n = 36 birds/group), and the experimental diets were associated with a slightly increased (P = 0.07) ultimate pH (5.75, 5.79, and 5.81 for the control, CP-1.5%, and CP-3.0%, respectively). Breast fillets from the CP-1.5% and CP-3.0% groups had lower yellowness (b*, P < 0.001) and lower cooking loss (CL, P < 0.001) values than the control. Moreover, the solubility, emulsion activity, and stability indices of the sarcoplasmic and myofibrillar fractions of muscle proteins were not influenced by the diets. CP-1.5% and CP-3.0% diets were associated with an increased (P < 0.001) breast yield (18.39, 19.21, and 19.61% for the control, CP-1.5%, and CP-3.0%, respectively) while leg yield remained unchanged. Additionally, breast meat nutritional properties including protein and lipid contents were not impacted by the experimental diets. In conclusion, the CP content in the grower and finisher diets of broiler chickens can be reduced by as much as 3.0% without detrimental effects on performance or on meat quality as long as birds' amino acid requirements are adequately met

The potential of in ovo-fed amino acids to alleviate the effects of heat stress on broiler chickens: effect on performance, body temperature, and oxidative status during the finisher phase

ABSTRACT: The aim of the current study was to investigate the potential of in ovo-fed amino acids (AA) to reduce the effects of heat stress on finishing broiler chickens. To achieve this, a total of 1,400 fertile hatching eggs were randomly distributed into 5 groups (n = 280/group) and injected with one of the following in ovo treatments on embryonic day 18: 52 µL of sterile diluent/egg (CTRL), CTRL + 1.0 mg of L-Leucine (T1), CTRL + 0.45 mg of leucine + 1.15 mg of methionine (T2), CTRL + 3.0 mg of methionine + 2.0 mg of cysteine (T3), and CTRL + 0.40 mg of leucine + 1.60 mg of methionine + 1.60 mg of cysteine (T4). After hatch, chicks were allocated according to a complete randomized block design comprising 2 thermal conditions: thermoneutral (24°C, 45% RH) and heat stress (34°C, 55–60% RH) with 5 pens/group/condition. The cyclical heat stress regimen (10 h/d) was then applied from d 29 to d 34. Compared to the CTRL group, T3 and T4 exhibited a higher BW during the starter phase (P < 0.001). T4 also had a lower feed conversion ratio (FCR) than CTRL during this same phase (P = 0.03). During the grower phase, males of all treatment groups consistently exhibited higher BW compared to the CTRL group, which was not observed among female birds (PSex × TRT = 0.005). During the finisher phase, the in ovo treatment effect on performance was not significant. However, heat-stressed birds from treatment group T3 and T4 exhibited lower facial temperatures (Pday × TRT < 0.001) as well as lower plasma (Pcondition x TRT = 0.039) and liver (Pcondition x TRT < 0.001) malonaldehyde concentrations compared to the CTRL group. In conclusion, in ovo-fed AA have the potential to modulate the effects of heat stress on finishing broiler chickens by limiting its detrimental consequences, including increased body temperature and oxidative damage

Impact de la sélection divergente pour le pH ultime du filet sur les performances en élevage et interaction avec l'alimentation

National audienc

Coancestry rate’s estimate of effective population size for genetic variability monitoring

Different methods and formulae have been suggested to estimate effective population size based on pedigree data. These methods vary in their sensitivity to various sources of bias related to heterogenous pedigree knowledge or pedigree structure. We propose here to adapt a pre-existing method estimating coancestry rate for the specific purpose of monitoring genetic variability within livestock and captive populations. Coancestry rate is computed by averaging coancestries between pairs of individuals corrected by their equivalent numbers of generations, while restricting pedigree information to a maximum number of generations. Simulation demonstrated that restricting the number of generations allows a much clearer observation of the impact of recent events on genetic variability. Restricting the number of generations for the calculation of coancestry also has less bias related to incomplete pedigree, although it may overestimate effective population size due to non-independence in family sizes across generations. This strategy was tested on the Norwegian Nordland Lyngen horse, the Colblood Trotter horse, the French Avranchin sheep, and Bresse chicken, illustrating the applications of the approach for the monitoring of genetic variability

Selecting broiler chickens for ultimate pH of breast muscle: Analysis of divergent selection experiment and phenotypic consequences on meat quality, growth, and body composition traits

Genetic parameters for ultimate pH of pectoralis major muscle (PM-pHu) and sartorius muscle (SART-pHu); color parameters L*, a*, b*; logarithm of drip loss (LogDL) of pectoralis major (PM) muscle; breast meat yield (BMY); thigh and drumstick yield (TY); abdominal fat percentage (AFP); and BW at 6 wk (BW6) were estimated in 2 lines of broiler chickens divergently selected for PM-pHu. Effects of selection on all the previous traits and on glycolytic potential, pectoralis major muscle pH at 15 min postmortem, curing-cooking yield (CCY), cooking loss (CL), and Warner-Bratzler shear force (WBSF) of the PM muscle were also analyzed after 5 generations. Strong genetic determinism of PM-pHu was observed, with estimated h(2) of 0.57 +/- 0.02. There was a significant positive genetic correlation (r(g)) between PM-pHu and SART-pHu (0.54 +/- 0.04), indicating that selection had a general rather than a specific effect on energy storage in skeletal muscles. The h(2) estimates of L*, a*, and b* parameters were 0.58 +/- 0.02, 0.39 +/- 0.02, and 0.48 +/- 0.02, respectively. Heritability estimates for TY, BMY, and AFP were 0.39 +/- 0.04, 0.52 +/- 0.01, and 0.71 +/- 0.02, respectively. Our results indicated different genetic control of LogDL and L* of the meat between the 2 lines; these traits had a strong r(g) with PM-pHu in the line selected for low ultimate pH (pHu) value (pHu-; -0.80 and -0.71, respectively), which was not observed in the line selected for high pHu value (pHu+; -0.04 and -0.29, respectively). A significant positive r(g) (0.21 +/- 0.04) was observed between PM-pHu and BMY but not between PM-pHu and BW6, AFP, or TY. Significant phenotypic differences were observed after 5 generations of selection between the 2 lines. The mean differences (P < 0.001) in pHu between the 2 lines were 0.42 and 0.21 pH units in the breast and thigh muscle, respectively. Breast meat in the pHu+ line exhibited lower L* (-5 units; P < 0.001), a* (-0.22 units; P < 0.001), b* (-1.53 units; P < 0.001), and drip loss (-1.6 units; P < 0.001) than in the pHu-line. Breast meat of the pHu+ line was also characterized by greater CCY (+6.1 units; P < 0.001), lower CL (-1.66 units; P < 0.01), and lower WBSF after cooking (-5.1 units; P < 0.001) compared to the pHu-line. This study highlighted that selection based on pHu can be effective in improving the processing ability of breast meat and reducing the incidence of meat quality defects without affecting chicken growth performance