7440

6946

كارشناسي ارشد

علوم دامي

اصفهان: دانشگاه صنعتي اصفهان، دانشكده كشاورزي

1391

دوازده، 56ص.: مصور، جدول

ص.ع. به فارسي و انگليسي

محمدعلي ادريس، سعيد انصاري مهياري

19/10/91

آقافخرميرلوحي، احمد رياسي

1396/09/22

كتابنامه

كشاورزي

مهندسي كشاورزي

ID6946

به فارسي و انگليسي: قابل رويت در نسخه ديجيتالي

Estimation Genetic and Phenotypic Trend for Age at First Calving and Calving Interval and the Factors Affecting Them for Isfahan Holstein Cows Reza Moradi Hajidavaloo reza iut84@yahoo com Date of Submission September 19 2012 Department of Animal Science Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisors M A Edriss S Ansari Mahyari edriss@cc iut ac ir Abstract The present study was conducted to evaluate genetic parameters and genetic and phenotypic trends in age at first calving calving interval in Isfahan Holstein cow herds Number of 224234 reproductive records related to 78228 cows used The analysis of data performed by using animal linear models and applying restricted maximum likelihood by DMU software Multiple trait we used to evaluate the genetic and phenotypic correlations between age at firs calving and first second and third calving interval traits The effect of age at firs calving average milk yield pregnancy days and open days for calving interval were used as covariate and others as fixed effect Also random effects included animal effect Heritability of age at first calving and calving interval in single trait analysis were 0 09 0 008 and 0 05 0 007 respectively and in multiple traits analysis were 0 05 0 001 and 0 02 0 002 and for first three calving interval were 0 068 0 008 0 038 0 008 and 0 029 0 01 respectively Positive genetic correlation between age at first calving and first 0 44 0 61 second 0 31 0 12 and third calving interval 0 17 0 19 proposed by selecting heifers with low age at firs calving can reduce calving interval In order to estimated analysis it was observed that all studied effects on age at first calving were significant P 0 0001 but calf sex had low significant P 0 0001 Also for calving interval except calf sex P 0 2621 others had high significant P 0 0001 Phenotype trend for age at first calving was negative favorable and significant P 0 0001 2 115 0 397 but for calving interval was positive and unfavorable and it tended to be significant P 0 0001 0 315 0 156 Genetic trend age at first calving was not similar to phenotype trend but was significant P 0 0001 0 087 0 0008 Also this trend for calving interval with opposite to phenotype heritability this trait was negative and significant P 0 05 0 56 0 025 Different between Phenotype and genetic calving interval with regard to low heritability can be resulted from inattention to environment and management factors for this trait Keywords Genetic and phenotypic trend Age at first calving Calving interval Holstein cows

محمدعلي ادريس، سعيد انصاري مهياري

آقافخرميرلوحي، احمد رياسي