8458

7839

كارشناسي ارشد

علوم دامي

اصفهان: دانشگاه صنعتي اصفهان، دانشكده كشاورزي

1392

دوازده،74ص.: مصور،جدول،نمودار

ص.ع.به فارسي و انگليسي

سعيد انصاري مهياري، محمدعلي ادريس

مجيد خالداري، احمد رياسي

5/11/92

علي صادقي، محمد مهدي مجيدي

مهندسي كشاورزي

ID7839

به فارسي و انگليسي: قابل رويت در نسخه ديجيتالي

Abstract Fertility as a fundamental trait in dairy cattle breeding is under consideration for decades and gaining economic in the recent years In current study linear animal models were used to estimate co variance components heritabilities genetic and phenotypic correlations for reproduction traits for different milk production levels Estimated breeding values and phenotypic records were used to evaluate genetic and phenotypic trends Age at first service AFS and first calving AFC calving interval CI open days OD days to first service DFS interval between first and last insemination IFL conception rate CR insemination number per service INS and milk yield MY were studied Different levels of milk production were assigned as low production less than kg medium production greater than kg and less than kg and high production greater than kg A total number of records from first parity during to and a total number of records in secondary parity during to were used The data collected from Animal Breeding Center of Iran First fixed variables with significant effect on the traits were detected using fixed models Then according to the restricted maximum likelihood REML method different mixed models were considered to estimate genetic parameters Heritabilities for reproductive traits were below than Estimated heritability coefficient for milk production was The results showed strong genetic correlations between reproductive traits till The Maximum value of the correlations was related to CI and OD DFS and CR The minimum correlation was obtained between DFS and IFL Genetic and phenotypic correlations between reproductive traits and milk production at different levels indicated significantly high correlation between reproductive traits and milk production in all reproductive traits except IFL and DFS in low producing dairy cows compared to other milk production groups Estimated phenotypic and genetic trends for milk production and reproductive traits indicated that selection has been done to improve milk production Reproductive traits except calving interval has increased the trends while phenotypic trend of these traits was negative that showed environmental factors might be controlled Key words Milk production level reproductive traits genetic and phenotypic trends PDF created with pdfFactory trial version www pdffactory com

سعيد انصاري مهياري، محمدعلي ادريس

مجيد خالداري، احمد رياسي

علي صادقي، محمد مهدي مجيدي