| Water buffalo is mainly distributed in southern China,which has great crude feed tolerance,strong disease resistance,and high milk quality.These characters make buffalo to be the best dairy livestock that typically adapts to southern climate conditions.Compared with Holstein,the low milk production and reproduction performance of buffalo are two key issues restricting the development of dairy buffalo industry of China.Therefore,the fundamental approach is that to introduce great dairy buffalo breeds for genetic improvement of our local buffalo and produce a specialized dairy buffalo breed.However,due to the complexed population structure,unclear pedigree information and low fertility of our local buffalo,the traditional genetic hybrid breeding has progressed slowly.It is urgent to apply molecular breeding technologies to promote breeding process and improve breeding efficiency.Consequently,to investigate genetic structure of high milk production breed,to identify effective molecular markers affecting milk performance,and to evaluate buffalo genomic estimated breeding value,which will play important roles in the improvement of buffalo breeding industry using genome selection technology.During the introduction of buffalo breeds,the long-distance transport is inevitable.Many pieces of literature have pointed out that transport stress could influence the health and performance of animals,which seriously decrease the application efficiency of breeding animals.However,does transport stress have impacts on buffalo reproduction?If yes,whether the effects will be genetic or not?There are little studies to answer these questions.Hence,in the present study,we aimed to investigate the impacts of transport stress on the female reproduction and their offspring,to explore the molecular regulation mechanism of stress on female reproduction,and to detect the candidate anti-stress genes.These are significance for guiding breeds introduction and providing useful information to exploit new anti-stress technologies and select anti-stress buffalo for controlling or reducing the huge loss caused by transport stress.1.Genome-wide association study for milk production traits in water buffaloSix milk production traits including peak milk yield,total milk yield,fat yield,fat percentage,protein yield,and protein percentage were collected from 489 Italian Mediterranean water buffalo with 8434 lactation records.Genetic parameters and estimated breeding value were calculated by an animal model.Genotyping was conducted using the 90K Affymetrix Axiom?Buffalo SNP Array.After quality control,genome-wide association studies were performed between genomic makers and animal estimate breeding value to detect effective related markers,genes or regions.Furthermore,the haplotype association analyses were used to identify quantitative trait locus control of milk production.To explore feasibility of genomic selection in buffalo breeding industry,a five-fold cross validation was used to test the accuracy of genomic estimated breeding values(GEBV)and reliability of GEBV and estimated breeding values(EBV).The main findings were presented as below:(1)The average milk yield per lactation(270 days)of Italian Mediterranean buffalo is 2966 kg and the highest one is up to 5160 kg.The milk fat percentage and protein percentage were 8.3%and 4.7%,respectively.(2)The heritability of buffalo milk production traits was low and moderate(0.19-0.38).Positive genetic correlations(0.81-0.98)and phenotypic correlations(0.77-0.96)were obtained in peak milk yield,total milk yield,milk fat yield,and protein yield.Negative genetic correlation(-0.31--0.49)and phenotypic correlations(-0.10--0.28)were obtained in peak milk yield,total milk yield,milk fat and protein percentage.(3)After quality control,a total of 60387 SNPs distributed uniformly across bovine chromosomes with an average density of 23 SNPs/Mb.(4)With genome-wide association studies,26 suggestive SNPs(P?10-4)were detected to be associated with at least one of the six buffalo milk production traits.After false discovery rate(FDR)adjustment,four SNPs(AX-85148558,AX-85106096,AX-85073877,AX-85063131)were identified significantly(FDR?0.10)associated with milk fat yield and protein percentage.(5)Haplotype analyses showed that the 43.3-43.8 Mb region on chromosome 3 and66.5-67.0 Mb region on chromosome 14 could be two QTLs affecting milk production traits of buffalo.(6)Five most likely candidate genes including MFSD14A,SLC35A3,PALMD,RGS22,and VPS13B were identified to influence buffalo milk performance.(7)The reliability of GEBV for six milk production traits ranged from 0.06 to 0.22,and the correlation between EBV and GEBV was 0.23-0.35.The value of milk protein percentage and fat yield were higher than other buffalo milk producdtion traits.2.Effects and molecular mechanisms of transport stress on female reproductionIn this study,female BALB/c mice were used to investigate the effects of long-term(1000 km,on the ring road in Wuhan)transport stress on reproductive traits of individuals and female offspring including puberty onset,estrous cycle,follicular development,ovulation ability,litter size and milk production.We intended to compare the difference of reproductive performance for animals suffering transport stress in the different phrase(pre-puberty,puberty,and adult)and study whether transport stress had an effect on reproduction of female offspring.Moreover,the mouse gene expression chips were used to detect differentially expressed genes from hypothalamus,pituitary and ovary axis and to identify anti-stress genes related to female reproduction with gene function analyses.The main results were shown below:(1)Transportation stress has impacts on reproductive and milk production abilities of mice,and the influence degree and category are related to the physiological period of mice when stress occurs.Mice exposure to transport stress before puberty can promote the puberty onset,reduce estrus cycle,and affect follicular development the mature follicles decreased.While,mice exposure to transport stress in pubertal time could affect the milk production and reduce the weaning weight of offspring after sexual maturity.In adulthood,the transport stress could inhibit ovulation capacity,decrease ovulated oocytes,reduce litter size and affect milk production with a decrease of weaning weight of offspring.(2)Long-distance transport stress had no effect on the main reproductive traits of the female offspring including puberty onset,estrus cycle,follicular development,and ovulation.(3)In the hypothalamus,pituitary and ovarian tissues,comparations of differentially expressed genes between the control and stress groups were performed,respectively,and9 genes were detected to be enriched in the biological process of the Defense Response of Stress(GO:0006952).While,differentially expressed genes were compared between samples of high ovulated and low ovulated individuals,and 79 ones were enriched to the biological process as well.Combined these two analyses,eight anti-stress genes(Anapc1,Ccnb1,Huwe1,Ptgs2,Ereg,Rab14,Fabp4,and Ifna16)were identified from the hypothalamus-pituitary-ovary axis.Anapc1 and Ccnb1 genes join the signal pathway of progesterone-mediated oocyte maturation. |
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