The data on period of birth, age at first calving, 305 days milk yield and sire of cow were
considered as the factors affecting the productive herd life and longevity in Sahiwal herd at NDRI,
Karnal. The data were classified and analyzed by applying Least Squares Technique. The overall
mean for productive herd life (PHL) and longevity were recorded as 1418 ± 89.40, 2547.85 ± 89.43
days, respectively. No significant effect of period of birth of cow, age at first calving (AFC) and sire
of the cow was observed. However, 305 days first lactation milk yield (FLMY) affected highly
significantly the PHL and longevity. The heritability estimates were 0.17 ± 0.22 and 0.09 ± 0.20 for
PHL and longevity, respectively.