The First Lactation Yield as a Basis for Selection as Compared with the Second and Third Lactations

In an earlier publication (Johansson and Hansson, 1940) it was shown that under the management conditions of the Red-and-White Cattle in Sweden the dam-daughter correlation was considerably higher for the first lactation yield than for the second, and it was also somewhat higher than that for the third lactation. The second lactation yield was found to be much more sensitive to variations in length of the preceding calving interval, or dry period, than was the yield in the later lactations, and probably it is also more sensitive to environmental influences. The yield during the first lactation is influenced by the age and the nutritional state of the cow at calving, but here no preceding dry period enters in as a variable. It was concluded that a preliminary evaluation of the production capacity of the cow can safely be based on her first lactation yield. Furthermore it was suggested that even when records are available for two or more lactations of a cow, the record for the second lactation should not be considered.