DEVELOPMENT OF SELECTION CRITERIA FOR JERSEY AND JERSEY CROSSBRED COWS USING PRINCIPAL COMPONENT ANALYSIS
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Date
2011-06-29
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Divison of Animal Genetics and Breeding, Sher-e-Kashmir University of Agricultural Sciences and Technology of Jammu
Abstract
Records on 196 Jersey and 265 Jersey crossbred cows maintained at Dairy farm, Himachal Pradesh Krishi Vishvavidyalaya, Palampur for 25 years (1984-2008) and 29 years (1981-2008) were analyzed for the effects of non-genetic factors viz., season of calving, period of calving, age group of cows and parity of cows on pre-calving, post-calving and production traits. Heritability and genetic and phenotypic correlation coefficients were also estimated for these traits. The overall least squares means estimated in this study for pre-calving traits were 40.54±0.67 months and 20.43±0.20 kg for age at first calving and birth weight, post-calving traits were 182.05±8.17 days, 462.33±8.18 days and 86.91±4.94 days for service period, calving interval and dry period and for 305day milk yield, lactation milk yield, lactation length, peak yield, average milk yield per day of lactation length and average milk yield per day of calving interval were 2089.81±29.46 kg, 2539.57±48.37 kg, 376.49±7.24 days, 12.08±0.16 kg, 6.52±0.10 kg and 5.65±0.09 kg respectively in Jersey cows and corresponding estimates were 40.61±0.53 months, 23.01±0.21 kg for pre-calving traits, 144.95±6.45 days, 427.87±6.51 days and 87.64±4.18 days for post-calving traits and 2104.14±38.79 kg, 2354.41±49.62 kg, 340.99±5.91 days, 11.25±0.19 kg, 7.14±0.12 kg, and 5.63±0.11 kg for production traits in Jersey crossbred cows. Pre-calving and post calving traits were significantly influenced by period of calving and effect of parity was also significantly affecting most of the post calving and production traits in Jersey and Jersey crossbred cows whereas, effect of age group was significant on service period, lactation milk yield and average milk yield per day of calving interval in second lactation, 305day lactation milk yield and lactation milk yield in third lactation of Jersey cows. Impact of parity was significant on service period, calving interval and most of the production traits in Jersey and Jersey crossbred cows. The heritability estimates for first lactation traits were consistently higher than heritability estimates computed from pooled over lactation records in Jersey and Jersey crossbred cattle. The heritability estimates were low to moderate (0.021±0.154 for service period to 0.266±0.219 for dry period) for post-calving reproductive traits and low to high (0.043±0.074 for average milk yield per day of calving interval to 0.557±0.282 for average milk yield per day of lactation length) for production traits in Jersey and low to moderate (0.035±0.056 for dry period to 0.319±0.227 for service period) and low to high (0.053±0.061 for average milk yield per day of calving interval to 0.915±0.341 for peak yield) for corresponding traits in Jersey crossbred cattle. The phenotypic and genetic associations among post-calving reproductive traits were significant positive and negative and high positive genetic and phenotypic associations were observed for production traits in Jersey cattle. The genetic and phenotypic correlation coefficients were low to moderate (0.035±0.056 for dry period to 0.319±0.227 for service period) for post-calving reproductive traits and low to high (0.053±0.061for average milk yield per day of calving interval to 0.915±0.341 for peak yield) in Jersey crossbred cows. The moderate to high heritability estimates of 305day milk yield, lactation milk yield and peak yield (0.185, 0.088 and 0.109 in Jersey and 0.121, 0.202 and 0.610 in Jersey crossbred cattle) and positive correlations of these traits with production efficiency traits indicate that these traits can be utilized as reliable tools for selection of dairy cows. Low heritability for calving interval and lactation length indicates that the length of these traits is much influenced by management and husbandry practices, which can be improved by better management practices. Principal component analysis is a better tool for selection of dairy cows as maximum variation in dependent variable is explained with reduction of data and better predictions of 305day milk yield and lactation milk yield is possible with more than seventy percent precision by utilizing principal component analysis technique.
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COW, JERSEY COW