Invited review: Lying time and the welfare of dairy cows

摘要

Adequate time lying down is often considered animportant aspect of dairy cow welfare. We examinewhat is known about cows’ motivation to lie downand the consequences for health and other indicatorsof biological function when this behavior is thwarted.We review the environmental and animal-based factorsthat affect lying time in the context of animal welfare.Our objective is to review the research into the timethat dairy cows spend lying down and to critically examinethe evidence for the link with animal welfare.Cows can be highly motivated to lie down. They showrebound lying behavior after periods of forced standingand will sacrifice other activities, such as feeding, tolie down for an adequate amount of time. They willwork, by pushing levers or weighted gates, to lie downand show possible indicators of frustration when lyingbehavior is thwarted. Some evidence suggests that riskof lameness is increased in environments that provideunfavorable conditions for cows to lie down and wherecows are forced to stand. Lameness itself can result inlonger lying times, whereas mastitis reduces it. Cowbasedfactors such as reproductive status, age, andmilk production influence lying time, but the welfareimplications of these differences are unknown. Lowerlying times are reported in pasture-based systems, drylots, and bedded packs (9 h/d) compared with tiestallsand freestalls (10 to 12 h/d) in cross-farm research.Unfavorable conditions, including too few lying stallsfor the number of cows, hard or wet lying surfaces,inadequate bedding, stalls that are too small or poorlydesigned, heat, and rain all reduce lying time. Timeconstraints, such as feeding or milking, can influencelying time. However, more information is needed aboutthe implications of mediating factors such as the effectof the standing surface (concrete, pasture, or othersurfaces) and cow behavior while standing (e.g., beingrestrained, walking, grazing) to understand the effectof low lying times on animal welfare. Many factorscontribute to the difficulty of finding a valid thresholdfor daily lying time to use in the assessment of animalwelfare. Although higher lying times often correspondwith cow comfort, and lower lying times are seen inunfavorable conditions, exceptions occur, namely whencows lie down for longer because of disease or whenthey spend more time standing because of estrus orparturition, or to engage in other behaviors. In conclusion,lying behavior is important to dairy cattle, butcaution and a full understanding of the context and thecharacter of the animals in question is needed beforedrawing firm conclusions about animal welfare frommeasures of lying time.