Longevity, length of productive life and lifetime performance of German Brown Part 1: Systematic effects on longevity and length of productive life of German Brown cows

摘要

Data of 524,190 German Brown cows born between 1990 and 2001 was used to analyse the length of life, length of productive life and number of calvings. Date of birth, date of culling and milk production data were available for all cows. Analysis of variance with a mixed linear model was employed to analyse the effects of Brown-Swiss proportion, relative and absolute herd production level, age at first calving, year of birth, month of birth, herd and sire. On average, length of life was 6.15 years and length of productive life 3.46 years with 3.51 calvings. The average Brown-Swiss level was 67.1%. The relative herd production level followed by absolute herd production level and year of birth had the most significant effects on length of life, length of productive life and number of calvings. Differences up to one standard deviation of the relative herd production were associated with least-squares (LS) means of 4.84 and 7.55 years of length of life as well as 2.15 and 4.85 years of length of productive life. A higher absolute herd production level had been found as correlated with a longer length of life and productive life. The younger the birth cohort the lower were LS means for length of life, length of productive life and number of calvings. Cows with a Brown-Swiss proportion of 41-50% achieved the longest length of life and productive life and the highest numbers of calvings. Cows with a young age at first calving had a lower length of life and productive life. A reduction of intraherd-variation of milk production of cows and no higher increase of Brown-Swiss proportion above 70-80% should contribute to a longer length of life and productive life of the German Brown population.