The aim of this study was to evaluate phenotypic relationships between physiological blood markers tested in dairy heifers during the first 18 months after birth and their subsequent reproductive and productive performance, as well as length of life. The study was conducted on 104 heifers born between 1985-1988 as a result of the crossing of native Black-and-White cattle with the Holstein-Friesian breed. All animals were born, reared and managed until the end of their lives at the same farm. Blood samples were taken according to the following schedule: 2, 21, 42, 90, 200, 440 and 540 days after birth. The whole blood was assayed for glucose and haemoglobin concentrations and haematocrite number, whereas blood serum was assayed for concentrations of urea, total cholesterol, total protein, albumins, and immunoglobulins, as well as AspAT and AlAT activities. Pearson correlations between physiological blood markers and efficiency traits were calculated at the first stage of statistical evaluation of the data. These correlations were low, not exceeding the value of 0.4. There-after a multiple polynomial regression analysis was undertaken, which remarkably increased the predictive value of physiological blood markers. The largest values of the multiple correlation coefficient (Rm) were found for the first calving interval and average lifetime calving interval (Rm 0.93 and 0.80, respectively), followed by pooled fat and protein yield at the first lactation, and milk yield and pooled fat and protein yield per day of life (Rm from 0.66 to 0.76). The Rm value for other dependant variables (age at first calving, length of life, lifetime milk yield, lifetime fat and protein yield) ranged from 0.44 to 0.58. Based on the results of the regression analysis it was determined that glucose, immunoglobulins, urea and the haematocrite number have the highest association with efficiency traits, whereas 2, 21, 90 and 540 days after birth appear to be appropriate ages for testing.
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.