Modeling of Some Dairy Performance Indices on Milk Somatic Cell Count in Holstein Dairy Cows

This study was conducted to evaluate the direct and the indirect standardized effects of some dairy performance parameters (days dry, lactation length, parity, total milk yield and 305-day milk yield) on the milk Somatic Cell Count (SCC) of Holstein cows throughout modeling of these variables with the path analysis technique. During studying 617 Holstein cows were enrolled in the experiment with the average Days in Milk (DIM) of 15±7.14 and still in the trial till the end of their lactation length. Milk samples were taken from each cow every three months; then, the fresh milk samples subjected to somatic cell counting via automatic cell counter. Other data of days dry, lactation length, parity, total and actual 305-day milk yields obtained from the dairy farm recording system (Dairycomp). After collection of all data, the data entered to AMOS software program version 24 to build a path model among days dry, lactation length, parity as independent variables and total, 305-day milk yields as intermediate transitional variables and milk SCC as a dependent variable. The study revealed that the SCC was directly affected by lactation length, total and 305-day milk yields, while it indirectly affected with total milk yield. Moreover, the overall standardized effect of the total milk yield on the milk SCC was week as a result of the negative direct effect -0.173 neutralized with another positive indirect one 0.229.