This study has assessed the association of single nucleotide polymorphisms (SNP) identified in the adipocyte fatty acid binding protein (A-FABP) and heart-type fatty acid binding protein (H-FABP) genes with the content of intramuscular fat (IMF) in a population of male Beijing-You chickens. A previously described SNP in the chicken A-FABP gene had a significant (P < 0.05) effect on IMF content. Chickens inheriting the homozygous BB genotype at A-FABP had a significantly higher content of IMF in thigh muscles and breast muscles than did those inheriting the AA and AB genotypes. A novel SNP, identified here, in the H-FABP gene was also significantly (P < 0.05) associated with IMF content in thigh and breast muscle. Chickens inheriting the genotypes of DD and CD had much higher content of IMF than those inheriting the homozygous genotype of CC. Markers at the A-FABP and H-FABP genes were associated with IMF content in the studied population. Chickens inheriting the BB genotype at A-FABP, along with the CD genotype at H-FABP, produced muscles with a much higher content of IMF when compared with all other genotypes. A weak interaction between A-FABP and H-FABP was detected (P < 0.09) for IMF content in the tested population. The statistical significance of interaction is tentative because of the limited number of observations for some genotypic combinations. Markers identified within the A-FABP and H-FABP genes are suitable for future use in identifying chickens with the genetic potential to produce more desirable muscle with higher IMF content, at least in the population of Beijing-You male chickens.

This study was conducted to estimate genetic parameters of meat quality-related traits by a MTDFREML procedure, using 1,069 purebred Beijing-You full-sib male chickens derived from the first 2 generations of divergent selection for the percentage of intramuscular fat (IMF) and selection for increased inosine-5'-monophosphate content (IMP) in breast meat. The results show that estimated heritability of IMP was moderate (0.23), and heritability of IMF was low (0.11). Other traits with high heritabilities, ranging between 0.56 and 0.79, were BW, abdominal fat weight (AFW), breast meat yield, ratio of breast meat yield to evisceration weight (BMP), leg muscle yield, comb weight, and ratio of comb weight to BW (CWP). Moderate heritabilities for the ratio of AFW to BW (AFP) and leg muscle yield to evisceration weight were estimated, 0.24 and 0.32, respectively. Lower significant phenotypic correlations of IMP with BMP and ratio of leg muscle weight to evisceration weight were discovered (P < 0.05), whereas IMF exhibited slightly positive, though significant, phenotypic correlations with BW (0.11) and AFP (0.27). Genetic correlations of IMP with BW and CWP were negative (-0.38 and -0.62, respectively), whereas a high positive genetic correlation was found between IMP and BMP (0.57). It was found that IMF had high genetic correlations with BW (0.75) and AFW (0.66) and moderate correlations with AFP (0.32) and CWP (0.40). A low positive genetic correlation was estimated between IMP and IMF (0.27). In conclusion, both IMP and IMF contents in chicken meat have the potential to be increased through genetic selection with little or no positive effect on BW. Furthermore, close managerial control of growth rate (and BW) will be needed to assure high quality of chicken meat so that increased IMP and IMF can be obtained with less abdominal fat deposited.

1. The association of single nucleotide polymorphisms identified within the ADSL (adenylosuccinate lyase deficiency) gene and GARS-AIRS-GART (glycinamide ribonucleotide synthetase-aminoimidazole ribonucleotide synthetase-glycinamide ribonucleotide transformylase) gene with the content of inosine 5'-monophosphate (IMP) was studied in a population of male Beijing-you (BJY) chickens slaughtered at 90 d of age. 2. A single nucleotide polymorphism in exon 2 of the ADSL gene had an effect on IMP content. Chickens inheriting the positive allele at ADSL, both homozygous and heterozygous genotypes, had a higher content of IMP in breast muscle than did individuals without it. 3. Similar results were obtained for the GARS-AIRS-GART gene. The marker at the 5' untranslated region (UTR) of the GARS-AIRS-GART gene was also significant for the IMP value. Chickens inheriting the genotypes with the positive allele at this locus had a much higher content of IMP than did those homozygous for the unfavourable one. 4. Interactions between ADSL and GARS-AIRS-GART were detected for such traits as body weight and muscle yields in the tested population. The two loci acted in an additive fashion. Because IMP is one of the most important flavour components in meat, markers developed at these two genes, as well as the combination genotypes, could be used as potential molecular markers for improving chicken quality.

1. The effects of nutrient density and lighting regime on oxidant status and immune function of broilers were investigated in a 2 x 4 experimental design (8 groups of 576 chickens). 2. There were two nutrient densities: high (H) starter diet AME 13.39 MJ/kg, 230 g crude protein (CP)/kg: finisher 13.39 MJ/kg, 197 g CP/kg CP) and low (L) starter AME 12.03 MJ/kg, 208 g CP/k; finisher 12.14 MJ/kg, 183 g CP/kg C. The 4 lighting regimes were continuous (CL) 23L:1D, 20L:4D (12L:2D:8L:2D), 16L:8D (12L:3D:2L:3D:2L:2D) and 12L:12D (9L:3D:1L:3D:1L:3D:1L:3D). Blood and lymphoid organs were collected at d 21 and 42 for assay of antioxidant indices and immunity. 3. Chickens fed low density diet had a higher Fabricius bursa weight (FBW). Low density diet tended (P = 0.089) to increase the a-Naphthylacetate esterase (ANAE) positive percentage response at 42 d. 4. The 12L:12D schedule decreased serum malondialdehyde compared with other regimes at 21 d. At 42 d, it was lower in the 12L:12D and 16L:8D groups than in CL and 20L:4D. There was a trend (P = 0.086) for greater superoxide dismutase activity in the 12L:12D and 16L:8D groups than under the CL and 20L:4D regimes at 42 d. ANAE positive percentage in 12L:12D group at 42 d was higher than in CL and 20L:4D groups. Plasma IgG in the 12L:12D group at 42 d was higher than in the CL group. 5. There was an interaction between nutrient density and lighting regime for FBW at 42 d. 6. These results demonstrate that low nutrient density and a 12L:12D schedule lighting schedule can enhance oxidant-antioxidant balance and the immune functions of broilers.

1. Changes resulting from divergent selection after 5 generations for intramuscular fat (IMF) content in breast muscle in a population of purebred Beijing-You chickens were investigated. Female chickens from lines selected-up (UL) and selected-down (DL) for 5 generations and random-bred controls (CL) were studied at 120 d of age. 2. In the UL, IMF in breast muscle (4.65%) was 1.38 times that in the DL (3.36%). The IMF content in leg muscle was also higher in UL compared to DL. 3. There were significant differences in growth, carcase traits and meat quality between the two selected lines. However, ultimate pH (pHu) was lower and lightness (L*) and yellowness (b*) were higher in breast muscles of UL birds compared to DL birds. Similar trends for pHu and L* value between UL and DL were observed in leg muscle. 4. Significant mRNA expression differences of the heart fatty acid-binding protein (H-FABP) gene between UL and DL were observed in breast muscle, and a negative correlation between expression of mRNA and IMF% in breast and leg muscles pointed to H-FABP as a potential selection candidate gene.