| As a local breed protected in Shaanxi Province,Lueyang black-bone has been selected systematically and scientifically for four consecutive years with the support of the local government.So far,the purification of diseases such as chicken pullorum has achieved remarkable results,and the growth performance,reproductive performance and population uniformity of meat breeding groups have been significantly improved.Based on the results of generation breeding,the breeding effect of Lueyang black-bone chicken was evaluated after four consecutive generations.The breeding effects of body weight traits of each generation were compared horizontally,and the growth curve of each generation was fitted,and its growth inflection point was determined.Moreover,the PCR-SSCP technique was used to scan the SNPs loci on all exons of the two genes(MSTN and KLF7),and the association between different genotypes and body weight of each week was analyzed.Furthermore,the expression of MSTN and KLF7 genes in breast muscle,leg muscle and other tissues of Lueyang black-bone chicken was analyzed by the q RT-PCR technique.To further improve the breeding effect,explore and develop the special feed for this breed of chickens.Taking the breeding group of P4 Lueyang black-bone chickens as the research object,360 chickens were selected and randomly divided into high and low addition groups and control group.1.0%,0.5%,0% biological enzymes were added,respectively.The effects of dietary supplemented biological enzymes on average daily gain,average daily feed intake,feed conversion rate,egg production and laying rate in feeding cycle,serum immunoglobulin and intestinal microflora of Lueyang black-bone chicken were analyzed.The results show that:(1)After four consecutive generations of breeding,the population weight traits of Luoyang black-bone chicken were significantly increased with the increase of generation(P< 0.05),and the population uniformity was significantly improved.(2)The age of inflection point of P4 generation rooster was 9.81 W,the body weight of inflection point was 1229.64 g,the maximum weekly gain was 198.71 g,the limit weight was 3342.51 g;the age of inflection point of hen was 8.95 W,the weight of inflection point was 841.29 g,the maximum weekly gain was 141.34 g,and the limit weight was 2286.87 g.(3)The c.233 A > G variation in exon 1 of MSTN was significantly correlated with4 W and 8W body weight(P < 0.05),while the variation site c.1022 C > T in exon 2 of KLF7 was weakly correlated with 16 W body weight(P = 0.052).(4)The expression of MSTN gene was significantly higher in breast and leg muscle of Lueyang black-bone chicken(P < 0.01),and the expression of KLF7 gene in liver and spleen was significantly higher than that in breast and leg muscle(P < 0.01).(5)The addition of biological enzyme significantly increased feed consumption,daily gain,feed conversion rate,egg laying rate(P < 0.01),IgA,IgG,IgM in serum(P <0.05),and changed the cecal microflora,Lawson and Rumen cocci were significantly lower than those in the control group,while Coprobacter was significantly higher than that in the control group(P < 0.05).The above results showed that the breeding effect of growth traits in Lueyang black-bone chicken was significant,and the population evenness was significantly improved;the growth rule was basically the same as that of other local breeds,and the inflection point weight,limit weight and growth rate had great advantages.The two selected SNP loci(MSTN:c.233 A > G,KLF7:c.1022 C > T)could be used as effective selection loci for body weight traits.In addition,dietary supplemented biological enzymes could significantly improve the growth performance,egg laying performance,immune level,and change their intestinal microflora.This study laid a scientific theoretical foundation for the breeding of Lueyang black-bone chicken and the formulation of nutrition standards and guided the development direction of Lueyang black-bone chicken industrialization. |
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