Effect of age and parity as adjustment factors on estimation of variance components for some fertility traits in Holstein by using REML , ML , MIVQUE and TYPE1

	Effect of age and parity as adjustment factors on estimation of variance components for some fertility traits in Holstein by using REML , ML , MIVQUE and TYPE1
journal of kerbala university
Article 1, Volume 4, Issue 1, 2008, Pages 44-49 PDF (0 K)
Abstract
A total of 13817 records of calving interval and 13698 records of days open belonged to 4033 Holstein cows maintained at Nasr Dairy Cattle Station over period from 1990 to 2003 were analysed . The aim of the research is to make a comparsion between age and parity as adjusted factors for fertility ( calving interval and days open )and to study the effect of them on estimation of heritability for the fertility. General Linear Model (GLM) within the SAS program 2001 was used for comparison between the effect of age and parity on fertility after adjusting for each of them in addition to other fixed effects ( season , year of birth and sex of calf ) . Component of variance for the random effects in the employed mixed model were estimated by fourth methods REML , ML , MIVQUE , TYPE1 .The effect of age was high significant ( P < 0.01 ) on fertility whereas the effect of parity was significant ( P < 0.05 ) . All heritabilities estimated for fertility after adjusting for age using REML,ML.MIVQUE and TYPE1 were low ,being 0.064 , 0.058, 0.029 and 0.057 for calving interval and being 0.085 , 0.078 , 0.032 and 0.067 for days open , whereas the corresponding estimates of heritability of calving interval after adjusting for parity being 0.078 , 0.071 , 0.033 and 0.075 , and the estimates of heritability for days open were 0.102 , 0.095 , 0.037 and 0.083 respectively.

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