Largescale analysis of chronic stress in dairy cows using hair cortisol and blood fructosamine  (general introduction)

English. editorial reviewed

English. Stress in dairy herds can come from many sources. When stress becomes chronic due to long duration and inability of animals to adapt, it can affect the emotional state, health, immunity, fertility and milk production of cows. It therefore has a negative impact on the welfare, economy and social acceptability of dairy farms. Knowing the practices that influence chronic stress would allow proposing strategies to improve animal welfare on farms. The study aims to better understand the relationship between two chronic stress biomarkers and potential explanatory variables related to production, management, health and housing. From a past research, two molecules were identified as biomarkers of chronic stress: capillary cortisol and blood fructosamine. Based on 1,372 ELISA measurements of hair cortisol and blood fructosamine, we studied their variability from 23 qualitative and quantitative features related to the herd management practices collected in 77 farms from 5 different countries (Austria, Belgium, France, Germany, and Luxembourg). The qualitative variables included information on cow diet type, management and housing system. The quantitative features included information on cow characteristics, milk composition, housing conditions, udder health, body condition score, and lameness. Principal components analysis and multivariate regressions highlighted the differences in cortisol and fructosamine results between farms, and relate them to the different herd management practices implemented on each farm. Preliminary results show that there may be multiple sources of stress, but that cortisol and fructosamine levels appear to be strongly influenced by overcrowding. These first and subsequent results could help to identify sources of chronic stress and provide useful guidance to dairy farmers to improve animal welfare.