PSV-23 Physiological status evolution of veal calves after reception period

Abstract Veal calves have to deal with several stressors early in life, such as transport and commingling with animals of unknown health histories from multiple different origins; making the reception a possible critical period where animals should adapt to all these challenges. The aim of this study was to evaluate the evolution of the physiological status of veal calves after farm reception. Dairy beef calves [n = 84; body weight (BW) = 44.3 ± 3.05 kg, BVD-free] coming from auction market were followed during the 8 wk after farm arrival. On farm arrival animals were housed individually until d 39 when animals were grouped in pens of 4 calves. Animals (n = 24) were blood sampled on d 1 (day of arrival), on d 7, on d 37, and on d 41 (48 h before and after grouping animal) to analyze biomarkers related to immune system (MILLIPLEX MAP Kit), energy status (BHBA) and gut integrity (citrulline, lactulose and mannitol). Data were analyzed by unpaired t-test (normally distributed data) or by non-parametric Mann-Whitney test (data not normally distributed). After the first week of adaptation (d 7 vs d 1), animals showed a general activation of the immune system increasing serum concentration of interleukin (IL) 8 (P < 0.001), interferon (INF) γ (P < 0.001), tumor necrosis factor (TNF) α (P < 0.01), IL10 (P < 0.001), macrophage Inflammatory Protein (MIP) 1α (P < 0.05), IP10 (P < 0.001), monocyte chemoattractant protein (MCP) 1 (P < 0.01), and IL1β (P < 0.15). In parallel animals reduced the mobilization of fat, evidenced by a decrease in the concentration of BHBA (P < 0.001), and displayed changes in gut permeability reducing lactulose and mannitol concentrations (related to paracellular and transcellular transport, respectively; P < 0.001). On the other hand, after the grouping challenge on d 39 (comparing d 41 vs d 37), calves experienced a certain immunosuppression indicated by the reduction of IL10 (P < 0.001), IP10 (P < 0.01), MIP1β (P < 0.01), Vascular endothelial growth factor (VEGF) α (P < 0.05), and MCP1 (P < 0.15). Moreover, after the mixing challenge, animals tended to increase the mannitol concentration (P < 0.001) in serum. From this trial, we can conclude that the stress experienced by veal calves in situations like transport and/or mixing, has a direct impact on their immune system. The observed immunosuppression may increase their predisposition to experience health issues. Further research should be conducted in calves to develop strategies able to boost their immune system and increase their resilience in front of the challenges occurring wk 1 in a fattening farm.