| China is the country that raises the most geese in the world.In recent years,the quantity of geese is about 600 million.The meat of goose was considered by the World Health Organization as the top of ’health food list’.Goose knob is formed after long-term breeding in chinese goose(Anser cygnodies).It is not only a symbol of the sexual maturity of geese,but also one of the important packaging traits that consumers concerned.Consumers have obvious consumption preference for geese with large knob.Therefore,the work that carry out research on knob trait formation has practical value to satisfy people’s consumption preference.Knob size mainly depends on the variety of geese,day age,but the differences in histology and anatomy of different varieties and different ages of knob is still unknown.The knob size and meat quality what traits have an impact,the size of the differences in the internal mechanism?This series of problems has not been reported so far.Based on the general survey of knobs size of major meat geese in China,this study studied the histological and anatomical characteristics of the growth and development rules of Yangzhou goose knobs of different days of age,and focused on the effects of knobs of different sizes on performance and meat quality as well as the molecular mechanism of the inherent differences.The aim of this study is to reveal the anatomical,histological and genetic basis of knobs of different sizes,so as to lay a theoretical basis for promoting genetic improvement of knobs of geese to meet people’s consumption preferences and increase consumption of meat geese.(1)Differences in morphology and histological anatomy of knobs among different goose breeds:knobs and beak size of six breeds including Shitou goose,Magang goose,Wanxi white goose,Zhedong white goose,Yangzhou goose and Sichuan white goose were measured,and histological and anatomical comparison was made between Yangzhou goose and Magang goose.The results showed as follows:Wanxi white goose knob was the largest,followed by Shitou goose,and significantly higher than other geese(P<0.01).The knobs of Yangzhou goose and Magang goose were dissected,and it was found that Magang goose was soft in texture,containing fresh adipose tissue mass and small bony protuberant.The knob of Yangzhou is hard,the outer layer is covered with cuticle,bony crest occupise most of the knob.In addition,histological analysis showed that the thickness of stratum corneum(Scn),stratum spinosum(Ss),stratum epidermis(Sr),stratum reticular(Sr)and stratum corium(Sci)of Magang geese were significantly lower than those of Yangzhou geese(P<0.01).(2)Morphological and anatomical changes of knobs of Yangzhou geese at different days of age:size,skin histology and anatomy of knobs of Yangzhou geese at 70,120,300 and 500 days of age were measured;The results show that knobs can be seen at about 100 days of age,and gradually develop with the increase of age,and the growth slows down after 300 days of age.Histological examination showed that the stratum comeum(Scn),stratum epidermis(Se),stratum reticular(Sr)and stratum corium(Sci)of knob skin were significantly thickened with age(P<0.01),while the stratum spinosum(Ss)had no significant change in different age.(3)Relationship between knob size of Yangzhou goose and performance and meat quality:Skin histology and anatomy of knob of Yangzhou Goose at 120 and 500 days of age with different sizes were observed.The results showed that:The results showed that the size of the knob had an effect on the length,height and depth of the bony crest,but had no obvious effect on the width of the bony crest(P<0.05),and there was a significant correlation between the size of knob and the size of bony crest(P<0.01),that is,the size of bony crest can play a decisive role in the size of knobs in Yangzhou geese.The histological differences of knobs of different sizes in Yangzhou geese at 120 days of age showed that the histological differences of small and small knobs were concentrated in the epidermis,and the stratum corneum spinous cell layer of large knobs in geese at 120 days of age was significantly higher than that of small knobs in geese(P<0.01),the epidermal layer was significantly larger than that of geese with knob(P<0.05).120-day-old Yangzhou goose was taken as the experimental object to analyze the relationship between knob size of Yangzhou goose and performance and meat quality.Knob size had significant effects on breast depth,leg muscle hydraulics and collagen content of Yangzhou geese(P<0.05).The larger the knob,the higher the muscle muscle hydraulics and collagen content.In addition,hormone levels of male and female geese with knob size were measured.The results showed that the larger the knob of female geese,the higher the levels of estrogen and growth hormone in the body,the larger the knob of male geese,the higher the levels of androgen and growth hormone in the body.(4)Comparison of knob sizes:High-throughput sequencing was performed on Yangzhou geese of different days of age(D70,D120,D300)and different knob size large(L)and small(S)groups at 300 days of age by RNA-seq,respectively.The results showed that a total of 82 different genes were involved in the growth and development of knobs at different days of age,of which 29 were up-regulated and 47 were down-regulated.A total of 415 genes were found to determine knob size,among which 357 genes were up-regulated and 58 genes were down-regulated.Further differential gene enrichment analysis showed that the pathways involved in knob development were mainly related to hormone,bone formation and mineralization,glycosaminoglycan,collagen and other chemical substances synthesis.Further differential gene enrichment analysis showed that 455 GO entries and 210 KEGG signaling pathways were enriched in GO and KEGG pathway analysis.Combined with the results of differential expression,timing analysis and WGCNA analysis,several key signaling pathways were revealed,including TGF-β signaling pathway,focal adhesion,MAPK signaling pathway,calcium signaling pathway,as well as candidate genes for knob trait differences such as BMP5,ALX1,IGFBP4,IGF1 and NPPC. |
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