| At present, the breeding work of the dairy cow is becoming a major factor which has restricted the development of the dairy industry in southern. DHI is the world’s most scientific and effective management tool for dairy production, also become an important reference for the breeding of dairy cattle. In recent years, Since the implementation of DHI in southern China, the southern region has accumulated a certain amount of performance measurement data, through the analysis of the DHI data, in order to understand and evaluate the applying effect of DHI system in southern China, also can provide scientific reference for the application and promotion of DHI system in southern.Meanwhile, in order to speed up the genetic breeding progress and shorten the breeding period of dairy in the south, molecular breeding has become one of the most effective methods, The mining and verification of functional genes of milk production traits is an important premise and foundation for molecular breeding in dairy cattle. In this study, The Mass ARRAY i PLEX genotyping technology will be used to detect the important candidate mutation loci on milk production traits in cows, using the correlation analysis for functional verification, expecting to dig into the candidate genes and function mutation locis which can make a real difference with milk production traits, provide basis on molecular marker-assisted selection in Holstein cows in Southern China.DHI data from a large dairy cow company in Guangdong Province were analyzed in this study, using the GLM procedure of SAS 9.2 to the ANOVA, with strict Bonferroni multiple comparison method to carry on the test of significance, at the same time, while using the least squares model to analyze the fixed effects which affecting the performance of production. Single locus regression analysis method was used to do association studies on the mass population though R language analysis software. The main results are asfollows:1. The calving years have a significant effect on lactation performance(P<0.01). Since2009, milk production was in a stable upward trend while the SCS was in a downward trend. The average milk yield increased from 6936.57Kg(22.59 kg / head ? Day) of 2009 to8356.50Kg(30.51 kg / head ? Day) of 2014, enhances 35%, has a significant difference(P<0.01); the percentage of milk fat increased from 3.3% to 3.9%, and the percentage of milk protein was not significantly improved; their ratio increased from 1.00 return to1.25(normal level range). Since DHI has participated, the production performance has been significantly improved.2. There have a significant effect on milk yield and milk composition in different seasons(P<0.01). The first lactation period has the highest milk yield, up to 30.17 kg / head ? Day.The third lactation period has the highest milk quality, fat percentage(4.009%), milk protein percentage(3.475%) and SCS(4.283).3. The effect of calving seasons and the parities all have reached to significant level on lactation performance(P<0.01). Calving in winter was the most favorable of the year calving and in summer the most disadvantaged. The milk yield, milk fat and milk protein in summer were lower than in other seasons, which milk fat is 3.597%, milk protein yield is3.190%; In terms of somatic cell score, Heat stress can make milk yield lower and SCS higher, the spring and summer in southern have the highest SCS, and there was a extremely significant difference with the other two seasons(P<0.01). In terms of parity, the milk yield of third parity is the highest, reached 8581.33 Kg. The milk fat percentage of the third parity is the highest(3.916%), milk protein percentage of the second parity is highest(3.257%).the SCS show an increasing trend with the parities increased.4. We have genotyped 90 SNPs in 295 Holstein cows, the results showed that: the average call rate of 98.39% and the SNPs polymorphisms rate of 98.82% which were genotyped successful, the average MAF value is 0.27. Using a single marker regression analysis method to do correlation analysis between five milk production traits and markers, there are45 SNPs have significantly affect on milk production traits, 17 of which are located onchromosome 14. In-depth analysis showed that 23 SNPs which affected with a variety of milk production traits, 22 SNPs which affected with only one trait. While the main genes which considered by most researchersare impact of milk production(DGAT, GHR,PPP1R16 A, TRAPPC9) is positioned in the experimental population of this study.5. Through the validation of DGAT1, GHR, TRAPPC9, ATP1A1 genes polymorphism in the group, we get the results that, rs109421300 loci of DGAT1 gene, rs110017379 loci of TRAPPC9 gene, the rs110256520 loci of ATP1A1 gene and rs61639260 loci of GHR gene can be considered as molecular markers applied to Holstein dairy cow marker assisted selection in Southern China. |
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