Correlations Among Some Characteristics of Lactation Curve and Environmental Factors of Friesian Cows Raised Under the Conditions of the Jordan Valley
2003
Tabbaa, M.J, | Al-Atiyyat.R.M. (Jordan Univ., Amman (Jordan) Faculty of Agriculture)
Data for 242 full lactation records of 103 Friesian cows belonging to a herd raised at the Jordan Valley, were employed to calculate simple correlation among the characteristics of lactation curve and environmental factors. Correlations between average daily milk and peak yield, total milk yield, milk after peak and lactation number were 0.86, 0.78, 0.61 and 0.40, respectively. Correlations of peak yield with total milk yield, milk up to peak, milk after peak and persistency were 0.75, 0.40, 0.62 and 0.27, respectively. Friesian cows could be selected on the basis of peak yield as well as total milk yield. The correlation between peak yield and slope of milk production was -0.23, while the correlation between peak yield and time to peak was -0.09. The correlation between total milk yield and milk up to peak was moderate (0.40). Whereas the correlation between total milk yield and milk up to peak was moderate (0.40). Whereas the correlation between total milk yield and milk after peak was 0.93. Small negative correlation was obtained between total milk yield and persistency (-0.17). The correlation between total milk yield and lactation number was 0.29. Friesian cows with long time to peak produced more amount of milk up to peak. In addition, age at first calving was not correlated with the characteristics of lactation curve. The correlations between the month of calving and average daily milk yield, peak yield, total milk yield, milk up to peak and persistency were negatively correlated and ranged from-0.19 to 0.09. Also, the correlation between the year of calving and average daily milk yield, peak yield, milk up to peak and persistency were negatively correlated and range from -0.18 to -0.14. These results indicate the importance of environmental factors in determining the characteristics of lactation curve
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