GENETIC ANALYSIS OF PERFORMANCE TRAITS OF JERSEY COWS IN SUB-TEMPERATE ENVIRONMENT OF HIMACHAL PRADESH, INDIA

The evaluation of  production performance of Jersey cows were essential for their genetic improvement in sub-temperate region. The present investigation was conducted on  439 records of 196 Jersey cows maintained at Dairy farm, Himachal Pradesh Krishi Vishvavidyalaya, Palampur for 25 years (1984-2008) .  The production traits   considered for the present study were 305 days lactation milk yield, peak yield, lactation  length, average milk yield per day of lactation length and average milk yield per calving interval. Heritability, genetic and phenotypic correlation coefficients were estimated for these traits. Periods showed highly significant effect of periods on these  traits while season and parity had highly significant effect except in 305day lactation milk yield and lactation length. These production traits showed significantly higher values in winter seasons except peak yield and lactation length which showed higher values in  summer and rainy season respectively. These traits did not showed a consistent trend in different periods. In third lactation these traits showed better performance except lactation length which is higher in second lactation. The heritability estimates of these traits  were found very low except 305 day lactation milk yield and peak yield .  The genetic associations among these traits were  positive and high except association of lactation length with other traits which were negative and low..The  phenotypic associations were observed low to high and negative  except LMY×MY, LMY×AMY/LL and LMY ×AMY/CI.