Effectiveness of the Components of Lactation in Selecting for Milk Production in Hariana Cattle

First-lactation milk yields of 521 Hariana cows were analyzed.Period of calving (each 5 years except the fourth one, which was 4 years) significantly affected persistency, peak yield, lactation length, and yield.Persistency was also significantly affected by season of calving, tteritabiiities by paternal half-sister correlations were 0.01, 0.49, 0.21, and 0.40 for persistency, peak yield, lactation length, and yield.Persistency was phentoypieally correlated positively with lactation length and lactation yield only. Peak yield and lactation length had large positive correlations with lactation yield.Genetically, peak yield and lactation length were positively correlated with lactation yield.Peak yield and persistency were negatively associated both phenotypically and genetically.Comparatively, selection for peak yield would lead to a large correlated increase in lactation yield in these animals.But selection for either the fifth monthly production or the first three monthly cumulative production is expected to lead to a better result.