Comparison of Milk Yield Prediction by Two and Three Test Day Records in Pleven Blackhead Dairy Sheep
G. DIMOV1, D. GEORGIEV2 and G. GETOV2
1 Institute of Animal Science, BG – 2232 Kostinbrod, Bulgaria
2 District Breeding Center, BG – 5800 Pleven, Bulgaria
DIMOV, G., D. GEORGIEV and G. GETOV, 1999. Comparison of milk yield prediction by two and three test day records in Pleven Blackhead dairy sheep. Bulg. J. Agric. Sci., 5: 761-768
Study on 805 first and 556 second lactations of Pleven Blackhead ewes compared three methods for shortcut prediction of lactation yield – average of first three test days with interval of 30 days, average of the two most informative test days among all 7 or 8 and regression on two test days. Two test days in milking only period were sufficient for prediction of lactation yield with accuracy of 66-69%. Smallest prediction error (MSE) was found for regression approach. Weighted average of two or three test days gave underestimation (with 4 – 6 l) of normal lactation yield. Prediction with actual lactation period was more accurate compared to fixed 200 days period. For practical application was recommended the following variant: I=L (0.3+0.4K3+0.3K5).
Key words: dairy sheep, prediction, accuracy, test day yield
Abbreviations: MSE – mean square error, DEV – deviation of predicted from actual yield