Effects of some factors on some productive characteristics of Friesian cattle in meddle Iraq

	Effects of some factors on some productive characteristics of Friesian cattle in meddle Iraq
Journal of Tikrit University For Agriculture Sciences
Article 1, Volume 11, Issue 1, 2011, Pages 245-255
Abstract
This work was carried out to analyze ( 731) records of 211 Friesian cows born and reared at Al-Is'haqi dairy cattle station for the period between 1993-2004. the study was conducted to investigate the effects of some non-genetic factors on the preceding which traits , and to estimate the genetic parameters of them ( heritability , genotypic and phenotypic correlations).General Linear Model (GLM) method of Statistical Analyses System(SAS) program is performed to estimate the fixed factors effects(season and parity) , together with the regression coefficients of the traits studied on the age at first calving . Milk yield (305 day) , lactation period and dry period were 2266.01 kg , 339. 44 days , 74.75 days , The heritability estimates were 0.38 , 0.17 , 0.11 , respectively . Highly significant effects (P<0.01) of season of calving and parity on milk yield (305-day) and non-significant on dry period. age at first calving was found to have no effect on all the traits studied. The study pointed there is a significant positive genotypic correlations (P<0.01) between milk yield (305day) and lactation period (0.10),At the same time the previous correlations was negative (P<0.01) dry period , was (- 0.04). While phenotypic correlation was significant between milk yield and lactation period , It was an negative and non-significant between milk yield and dry period . Negative correlation refers to the fact the gene of responsible of increase milk production has a relationship in decreasing reproductive characteristics of cattle ,This will leads to lengthening dry period ,the breeders, hence, become obliged to stop milking his cows.

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