ADSA Southern Branch Symposium: Dairy Cattle Longevity Revisited-Trends, Economics, and Opportunities

摘要

Dairy cattle longevity averages approximately 3 years after first calving,despite improvements in genetics and cow comfort over the past severaldecades. The natural life span of cattle is about 20 yr. In some parts ofWestern agriculture, there is a strong push to extend dairy cattle longevity.Our objectives are to first explore economic and environmentalincentives for increasing average dairy cattle longevity and then discussdeterrents to increasing longevity. The vast majority of culling decisions,and by extension of dairy cattle longevity, are driven by economicdecision-making. Younger herds capitalize on genetic progress but havefewer efficient mature cows and greater replacement costs. There is alsoa growing interest in the use of beef semen in dairy cattle, which does notadd to the supply of dairy heifers. High premiums for crossbred calvessuggest a greater marginal value of extending dairy cattle longevity.Extending dairy cattle longevity might also decrease the environmentalfootprint of milk production. Historically, models focused on optimizingculling decisions for individual cows, while assuming an unlimitedsupply of heifers, found optimal cull rates of approximately 30%. Thissuggests a slightly longer longevity than is currently observed. However,cow performance has changed and the average findings of these modelsmay no longer be optimal. Some consider a short longevity a result ofunavoidable forced culling and a welfare issue. Management and housingmay affect longevity by improving health care and cow comfort. Onthe other hand, this short longevity is also driven by an abundance ofreplacement dairy heifers now available through the use of sexed semenand good reproduction. The dairy community should reevaluate howmany dairy heifers are needed, which animals should be the dams, andwhat to do with animals that do not need to supply replacements. Geneticselection, cow comfort, and health care will increase the ability of cattleto avoid culling for forced reasons. These topics are interdependent andwill drive future changes in dairy cattle longevity.