Studies On Inheritance And Candidate Genes Of Inosine-5'-Monophosphate And Intramuscular Fat Contents In Chicken Meat

Quality of chicken meat is becoming more and more important for meat-type chicken breeding and production. Two important quality attributes, IMP (inosine-5'-monophosphate) and IMF (intramuscular fat) contents, were studied in the thesis with regard to their evaluation, genetic parameters, and selection response in Beijing-You chickens. Meanwhile, the polymorphisms of two candidate genes AMPD1 (adenosine 5'-monophosphate deaminase) and A-FABP (adipocyte-fatty acid-binding proteins) were evaluated as potential genetic markers for the improvement of meat quality. The results were as follows.Results of sensory test showed that IMP played a major role in umami taste and different IMP contents resulted in different umami test owing to interaction between IMP and glutamine sodium. With the increasing of the storage temperature and time, the measuring values of IMP content decreased. IMP contents in breast muscle were maximal two hours after slaughtering at room temperature, and the value decreased by 16% and 55% after keeping 12 hours (P<0.01) and 24 hours (P<0.01), respectively. IMP content kept at 4C for 12 hours after slaughtering was equal to that one hour after slaughtering kept at room temperature. IMP content began to decrease a month later while kept at -15C (P<0.01). While comparing meat umami taste, it was better to use corrected values of IMP content based on IMP relatives. The value of IMP content varied when disposal liquid was frozen for IMP content.The IMP contents of Beijing-You chicken were 1.06-1.30 times of Arbor Acers(AA) broilers, and those of the breast muscle were 1.13-1.48 times of leg muscle, respectively. The males and females appeared a similar trend in IMP content. IMF content of Beijing-You chicken was significantly different from that of AA broiler. IMF content of breast meat was only 22%~36% of that of leg muscle. IMF content, unrelated to sex, varied with weight gain and increased with age in days. Genetic parameters of Beijing-You chicken were estimated. The results showed that heritabilities of IMP and IMF contents were 0.23 and 0.10 respectively. The genetic correlation between IMP and IMF contents was positive, and similar relation between IMF content and body weight was observed. IMP content, however, was negatively related with body weight. The results of selection trial for IMP and IMF (divergently delected) showed that the realized heritabilities of IMP and IMF contents were higher than estimated ones, and the realized genetic correlation of them were similar to estimated ones. The selection experiment demonstrated that the IMP and IMF contents could be increased through directional selection.The locus PB of candidate gene AMPD1 showed polymorphism in different chicken breeds, but the distribution of allele frequency was not related to meat flavor traits. Different genotypes of PB locus showed significant effects on IMP content, but the effects varied in different populations. More work are needed to verify the genetic effects of the gene. The chickens with genotype BB of locus P4 A-FABP gene had higher IMF content than those with other two genotypes (AA and AB). Genetic correlations between IMF content and abdominal fat ratio and comb ratio were generally positive. It was concludedthat this locus can be used as a useful marker of the selection for IMF content in chicken meat.The improvement of the measurement and calculation of IMP is important for research and practical application. Understanding the genetic parameters of the major traits related to meat quality is helping in designing efficient selective breeding program for quality chickens. At the same time, it is demonstrated in the thesis that candidate genes can be identified and used in the marker-assisted selection for meat flavor and other quality traits.