The Portuguese dairy cattle associations estimate cumulative lactation yields for milk and milk components by the Test Interval Method (TIM, Sargent, 1968). The Portuguese National milk data set is relatively small with an average of about 90 000 new lactations (L) records added per year. However, National genetic evaluations use only yields from terminated L with 210 or more days-in-milk (DIM), extended to 305-d if necessary, using pre-calculated factors (Gama et al., 2000). All L with less than 210-d are excluded from the genetic analysis, representing each year 11 % to 14 % of all terminated L (ANABLE, 1999). On top of this number, it is also necessary to add all L still in progress at the moment of data retrieval for analysis. At the end of the year 2000, for example, there were in the first three L, 61,000 cows in milk (30 % of all terminated L in that year) that were also excluded from any analysis. In a relatively small data set as this, any information that may be added to the evaluation would be an important contribution to improve the reliability of the predicted breeding values.
Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume 2002. Session 1, , 1.57, 2002
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