Comparison Of Production Performance And Ovarian MRNA Expression In Two Crossbred Black-finned Hens

In order to select new egg-laying lines,two crosses were designed,the ortho(C3♂×C4♀)and the anticross(C4♂×C3♀),using the independently selected egg-laying lines C3 and C4 as parents,and their production performance indicators were measured and analysed.At 30 and 40 weeks,body weight,body size and egg quality of the crosses were measured;at 40 weeks,the crown shape,plumage colour,tibia colour and number of toes of the crosses were recorded by visual observation;the average egg production rate and number of eggs laid at 18-40 weeks were calculated for the crosses and fitted to the curve;at 42 weeks,transcriptome analysis of the ovarian tissues of the crosses was carried out and the main results were as follows:1.External characteristics: the plumage colour of both crosses was mainly black with a small amount of light black feathers;the crown type of both crosses was mainly single crown,with 80.44% and 85.53% single crown respectively;the tibia colour of crosses was mainly cyan,accounting for 86.8%,while the tibia colour of crosses was mainly black and white,accounting for 77.8%;the number of toes of both crosses was 5 toes or 4 toes.2.The average number of eggs laid at 40 weeks of age was 114.57 for the orthologue and 112.42 for the anticross,and the best results were obtained by fitting the Yang-Ning model(R2=0.996 for the orthologue and R2=0.995 for the anticross).Bertalanffy model with a fit of 0.999;the mean egg weight at 40 weeks of age was 51.60 g in the orthogonal and 53.99 g in the anticross;the egg shape index was 1.32 ± 0.05 and 1.31 ± 0.04respectively;the Hutchinson units were 72.51±6.36 and 72.94±6.1 respectively;the dead weight at 20-40 weeks of age in the orthogonal and anticross were 2.89% and 2.27%respectively.3.Body weight and size at laying: the mean body weight of the orthologs at 30 and 40 weeks of age was slightly but not significantly lower than that of the antis(P>0.05);the keel length,tibia circumference and tibia length of the orthologs were significantly higher than those of the antis(P<0.05 or P<0.01)4.Transcriptome analysis showed that a total of 542 differentially expressed genes were screened in 42-week-old forward and backward cross ovarian tissues.54 genes were up-regulated in forward cross CYP19A1,TMEM72 and PAX5 and 38 genes were down-regulated in FOXL2,LYPD2 and BMP6 compared with backward cross ovarian tissues;among them,the genes found to be related to ovarian reproductive performance in forward and backward crosses were FOXL2,CYP19A1,BMP6 and others.In summary,the two crosses of black-feathered hens were more similar in appearance and had similar adult body weights;the orthologue started laying slightly earlier,but the number of eggs laid and the average egg weight of the anticross were better than those of the orthologue.