Abstract:

The purpose of this paper was to determine the direct, indirect and total effect of age of calving (AC), year of calving (YC), calving season (SC) and lactation length (LL) on 305-day milk yield (305-DMY) in Jersey cows using path analysis. The data used included 1717 lactation yield records of 617 Jersey cows calving from 2002 to 2012 on the Samsun Karakoy State Farm in Turkey. The results showed that AC, YC, SC and LL had statistically important effects on the 305-day milk yield f the Jersey cows. The results further indicated that the direct and total effects of LL on 305-day milk yield were higher than the effect of AC, YC and SC, although the indirect effect of AC on 305-day milk yield was the highest. As a consequence, to facilitate increasing milk yield per cow, the use of the lactation length provides some useful knowledge for management and the genetic evaluation of Jersey cows.

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