General resilience in dairy cows: A review

Dairy farming is deeply affected by climate change, especially by rising temperatures and heat waves, poorer availability of quality food and water, and the spread of new diseases and pests outside their original ecological niche. Their impact can be mitigated not only by changes in technologies, management and treatment, but also by breeding and selection of more resilient cows. General resilience encompasses the animal's capacity to cope with environmental, social and disease challenges. It is described as the capacity of the animal to be minimally affected by a disturbance or to rapidly return to the physiological, behavioural, cognitive, health, affective and production states that pertained before exposure to a disturbance. As disturbances can be of different natures, general resilience is a composite trait consisting of different resilience types according to the nature of the disturbance. Resilience can be quantified through time series data that capture fluctuations in the daily performance. Recent studies have worked with deviations in the daily milk yield and daily live weight from optimal performance or have focused on the assessment of the daily activity in terms of the daily step count. To observe the duration and magnitude of the response to perturbance, two indicators were suggested: the autocorrelation (rauto) and the natural logarithm of deviations (LnVar). Based on the daily milk yield deviations, both indicators have shown sufficient genetic variabilities with the estimated heritability ~0.1 for rauto and ~0.2 for LnVar. Low values of both indicators were genetically related to better udder health, better hoof health, better longevity, better fertility, higher body condition score, less ketosis but also lower milk yield level. The selection for improved resilience could benefit from the use of genomic information as several genes and biological pathways associated with disease resilience and resilience to heat stress have already been identified. The presented results suggest that the integration of resilience into the cattle breeding programmes would improve the capacity of the dairy industry to cope with global climate change.