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

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

National audienc

Genetic determinism of bone and mineral metabolism in meat-type chickens: A QTL mapping study

Skeletal integrity in meat-type chickens is affected by many factors including rapid growth rate, nutrition and genetics. To investigate the genetic basis of bone and mineral metabolism, a QTL detection study was conducted in an intercross between two lines of meat-type chickens divergently selected for their high (D+) or low (D−) digestive efficiency. Tibia size (length, diameter, volume) and ash content were determined at 3 weeks of age as well as phosphorus (P) retention and plasma concentration. Heritability of these traits and their genetic correlations with digestive efficiency were estimated. A QTL mapping study was performed using 3379 SNP markers.Tibia size, weight, ash content and breaking strength were highly heritable (0.42 to 0.61). Relative tibia diameter and volume as well as P retention were strongly and positively genetically correlated with digestive efficiency (0.57 to 0.80).A total of 35 QTL were identified (9 for tibia weight, 13 for tibia size, 5 for bone strength, 5 for bone mineralization, 2 for plasma P concentration and 1 for P retention). Six QTL were genome-wide significant, and 3 QTL for tibia relative volume, weight and ash weight on chromosome 6 were fixed, the positive allele coming from the D-line. For two QTL for ash content on chromosome 18 and relative tibia length on chromosome 26, the confidence intervals were small enough to identify potential candidate genes.These findings support the evidence of multiple genetic loci controlling bone and mineral metabolism. The identification of candidate genes may provide new perspectives in the understanding of bone regulation, even beyond avian species. Keywords: Chicken, QTL, Genetic parameters, Phosphorus, Environment, Bon

Fine mapping of QTL of carcass and meat quality traits in a chicken slow-growing line

Session 25. Free communications – molecular geneticsSession 25. Free communications – molecular geneticsabsen

Fine mapping of QTL for carcass and meat quality traits in a chicken slow-growing line

absen

Cartographie fine de QTL de qualité de la carcasse et de la viande dans une lignée de poulets à croissance lente

International audienceabsen

Cartographie fine de QTL de qualité de la carcasse et de la viande dans une lignée de poulets à croissance lente

International audienceabsen

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

Detection of QTL controlling feed efficiency and excretion in chickens fed a wheat-based diet

Background: Improving feed efficiency is a major goal in poultry production in order to reduce production costs, increase the possibility of using alternative feedstuffs and decrease the volume of manure. However, in spite of their economic and environmental impact, very few quantitative trait loci (QTL) have been reported on these traits. Thus, we undertook the detection of QTL on 820 meat-type chickens from a F2 cross between D- and D+ lines that were divergently selected on low or high digestive efficiency at 3 weeks of age. Birds were measured for growth between 0 and 23 days, feed intake and feed conversion ratio between 9 and 23 days, breast and abdominal fat yields at 23 days, and the anatomy of their digestive tract (density, relative weight and length of the duodenum, jejunum, ileum, and ratio of proventriculus to gizzard weight) was examined. To evaluate excretion traits, fresh and dry weight, water content, pH, nitrogen to phosphorus ratio from 0 to 23 days, and pH of gizzard and jejunum contents at 23 days were measured. A set of 3379 single nucleotide polymorphisms distributed on 28 Gallus gallus (GGA) autosomes, the Z chromosome and one unassigned linkage group was used for QTL detection. Results: Using the QTLMap software developed for linkage analyses by interval mapping, we detected 16 QTL for feed intake, 13 for feed efficiency, 49 for anatomy-related traits, seven for growth, six for body composition and ten for excretion. Nine of these QTL were genome-wide significant (four for feed intake on GGA1, one for feed efficiency on GGA2, and four for anatomy on GGA1, 2, 3 and 4). GGA16, 19, and 26 carried many QTL for different types of traits that co-localize at the same position. Conclusions: This study identified several QTL regions that are involved in the control of digestive efficiency in chicken. Further studies are needed to identify the genes that underlie these effects, and to validate these in other commercial populations and for different breeding environments