engleski

Analysis of the relationships between first three lactations of Holstein cows

The objective of this study was to evaluate relationship between milk yield in the first three lactations regarding to levels of milk yield in first lactation and levels of age at first calving. The data used in this study were 5, 743 lactataion yields collected from 1995 to 2003. All cows finished the first three lactations. Mean value of milk yield in the first lactation was 5, 283 kg, 6, 035 kg in the second and 6, 338 kg in the third one. The milk yield estimation coefficients between the first and second lactation was 1.164, between first and third was 1.231, and 1.079 between the second and third. The levels of milk yield in the first lactation highly significant influenced the value of estimation coefficient between first three lactations, while the age at first calving influenced less significantly. Determination coefficient (R square) values for models used in prediction ranged from 0.348 to 0.396.

Holstein breed ; lactation ; milk yield ; estimation coefficients ; statistical models

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