Influence of production, reproduction, morphology, and health traits on true and functional longevity in French Holstein cows

摘要

In the long term, resilient animals are able to maintaintheir normal biological processes when confrontedwith environmental perturbations, reducing their riskof being culled. Therefore, longevity can be proposedas an indicator of long-term resilience. Decisions toremove a given dairy cow from the herd are mainlyrelated to low milk production (i.e., voluntary culling)or to reasons other than production (i.e., involuntaryculling). The aptitude of animals to delay any culling isdefined as true longevity (TL), whereas functional longevity(FL) is the ability to avoid involuntary culling.The aim of the study was to investigate the influenceof production, reproduction, morphology, and healthtraits on TL and FL, to identify risk factors for culling.Data included 278,217 lactations from 122,461 HolsteinFriesian cows reared in 640 herds. The length of productivelife, calculated as the time between first calvingand culling, or censoring, was used as the measure oflongevity. Survival analysis was performed using proportionalhazards models assuming a piecewise Weibulldistribution of the baseline hazard function, with orwithout adjustment for milk production to evaluateFL and TL. Insemination status, calving ease, mastitis,somatic cell count, displaced abomasum, and udderdepth had significant relationships with TL and FL.Differences in estimates of relative risk between TL andFL showed that milk production often influenced cullingdecisions: farmers are more prone to cull animalswith low production even when they had good othercharacteristics. The culling risk factors identified in thepresent study can be used to study resilience in dairycattle and to improve genetic evaluations of functionalor total longevity.