برآورد پارامترهاي ژنتيكي صفات مرتبط با نرخ گيرايي در گله هاي گاو شيري هلشتاين

چكيده انگليسي :

Estimation of Genetic Parameters Related to Conception Rate in Holstein Dairy Herds Neda Nouri Naeini n nouri naeini@gmail com Date of Submission September 17 2012 Department of Animal Science Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisor M A Edriss edriss@cc iut ac ir Abstract Optimal reproductive performance of dairy cows formed the basis of economic herd lifetime Success or failure in each insemination as a practical measurement of cow fertility has been selected and considered as conception rate Evaluation of factors affecting fertility in cows and heifers identified them as much as possible which improve management and mating programs In the present study linear and threshold animal models was used to estimate co variance components heritability genetic and phenotypic correlations for production and reproduction traits related to conception rate in Isfahan Holstein dairy cows The traits were included age at first service AFS days to first service DFS conception rate CR insemination number per service INS success to first insemination SF open days OD calving interval CI days in milk DIM milk yield over 305 d lactation MY Because the conception rate in heifers and cows are different and also there are several limitations in reproductive traits therefore heifers and cows were analyzed separately Also when conception accrues in heifers there is no production therefore the correlation between production traits and conception rate was analyzed only in cows A total number of 83540 records from first parity during 1981 to 2010 and a total number of 170172 records in parity 2 to 6 during 1978 to 2008 were analyzed All data were collected from Vahdat Industrial Agriculturists and Dairymen Cooperative The fixed variables with significant effect on these traits were identified Bivariate linear models based on Restricted Maximum Likelihood REML method were considered to estimate genetic parameters As expected estimated heritabilities for reproductive traits were low below 0 1 The lowest and highest heritability of traits were related to SF 0 019 0 004 and INS 0 048 0 004 in heifers and SF 0 022 0 005 and OD 0 076 0 003 in cows respectively The estimated heritabilities were higher in continues traits OD CI than categorical and binary traits INS and SF The heritabilities for production traits were higher than reproduction traits 0 266 0 051 and 0 166 0 043 for MY and DIM respectively Strong genetic correlations were estimated between conception rate and fertility traits The maximum value of these coralations was related to SF that was estimated about 0 999 0 007 for heifers and 0 974 0 009 for cows that shows these traits have the same genetic factors and can replace each other in fertility index Genetic correlation between conception rate and production traits were estimated 0 688 0 050 for MY and 0 308 0 059 for DIM that showed the antagonistic correlation between these traits This study indicated that conception rate has a significant correlation with other fertility traits and highly affected by production traits Therefore to improve conception rate and reproductive performance fertility and production traits should be combined in selection index for breeding programs Keywords Genetic parameters Conception rate Reproductive performance Animal model Holstein dairy cows

نوري ناييني، ندا

برآورد پارامترهاي ژنتيكي صفات مرتبط با نرخ گيرايي در گله هاي گاو شيري هلشتاين

عملكرد توليد مثلي , مدل حيواني