Abstract
In the analysis, records of Black and White cows in Slovenia with lactation length more than 200 days and known length of previous and present calving interval (CI) in the period between 1986 and 1997, were included. The number of analysed records for milk yield and fat yield and content in standard lactation were 49 807 and for protein yield and content 39 802. Effects of year of calving, calving season, successive lactation, previous and present CI and interaction between previous and present CI were included in the model as fixed effects. The milk yield increased for 561 kg from present CI less than 340 days to CI from 401 to 460 days. Fat and protein yield increased for 22.3 kg and 17.0 kg with the same increased CI. The effect of previous CI amounted 50 % of the effect of present CI. The effect of CI on fat and protein content was less pronounced. Milk yield per day of present CI decreased for 2.6 kg, if present CI increased from less than 340 days to more than 460 days, and increased for 0.9 kg if previous CI increased from less than 340 days to more than 460 days.
Published Version
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