Effect of some factors on cow longevity

Abstract. Longevity (lifespan, length of productive life, number of calvings) was analysed in 25 231 cows that first calved in 1988 and 2000 in the Pomerania and Kujawy regions in Poland. GLM procedures of the SAS package were used in the statistical calculations. Longevity of cows that first calved in 2000 was found to improve in relation to that of cows that were first milked in 1988. The lifespan and length of productive life increased the most (by about 1 year) in herds of up to 20 cows, in herds with the lowest production level (by about 0.85 years), in herds of cows that first calved before 24 months of age up (by about 1 year) and in herds of cows that yielded 4 000–7 000 kg milk as first calvers (by about 0.5 years). Shortening the length of productive life in cows culled for low milk production (by 0.3 years) is probably one of the reasons for considerable production progress attained in cows in recent years. Age of cows at first calving and first lactation milk yield were significantly correlated to cow longevity.