Nutritional and environmental stressors in dairy cows inflammatory markers

Introduction. Dairy cows are continuously exposed to nutritional and environmental stressors, such as acidotic diets and changing in housing systems[1]. The aim of this research was to explore the effects of nutritional (acidotic diet) and environmental (change in stall system) stressors on inflammatory markers in high producing dairy cows. Animals, material and methods. 24 lactating homogenous Holstein cows were enrolled in 3 consecutive groups, and fed a standard diet (46:54 F:C and 23% starch) in a free stall barn during a baseline period (BS, 28d). Cows were then moved to a tie stall and fed an acidotic diet (25:75 F:C and 35% starch) during a challenge period (CH, 28d), mimicking the stress caused by a nutritional and housing change. Rumination time (RT) and reticular pH (rPH) were recorded continuously during both periods. Blood was sampled 4 times: one right before the beginning of CH (0d, BS period), and 3 times in CH period to evaluate the acute (7d), mid acute (14d) and chronic (28d) response (CH period). Hematologic, biochemical parameters were determined in each time point, and immunological profile on 0, 7 and 28d. Mixed model procedure was used for data analysis; time point, group and interactions were used as fixed effects, animal as random effect, and sampling as repeated structure. Significant effects were than compared between time points with a T-student test. Result and discussion. RT decreased during the challenge period (-89 min/d, P<.01). Daily average rPH was not changed, but in CH, area with pH < 5.8 and 5.5 increased (+9.63 and +2.62 AUC pH 5.8 and 5.5 respectively, P<.01). Blood analysis revealed an acute, mid acute and chronic phase response of the organism following the stressors event (table 1). In acute phase (7d) Il-6, serum amiloid A (SAA), ceruloplasmin (Cp) and Reactive Oxygen Metabolites (ROM) increased significantly. In mid acute phase (14d) paraoxonase (PON), Ferric Reducing Ability of Plasma (FRAP), and gamma glutamil transferase (GGT) changed significantly. Finally, in chronic phase (28d) albumin (Alb) significantly decreased. Others analysed parameters did not change. Table 1. Markers of inflammatory status. Parameter 0d 7d 14d 28d SEM P IL-6, pg/ml 1803.71B 2277.04A - 1716.04B 441.18 <.05 SAA, µg/ml 65.34c 147.17ab 190.49a 141.12abc 31.64 <.05 Cp, μmol/L 1.97C 2.27B 2.51A 2.54A 0.11 <.01 ROM, mg H2O2/100 ml 14.12C 16.17B 17.57A 16.91AB 0.55 <.01 PON, U/ml 90.45BC 87.32C 96.27A 94.74AB 4.33 <.01 FRAP, µmol/L 170.42A 160.80AB 155.90B 154.31B 7.04 0.01 GGT, U/L 25.06D 26.75CD 28.65BC 31.83A 1.70 <.01 Alb, g/L 36.68ABC 36.12CD 36.57BC 35.48D 0.51 <.01 Conclusion. These results showed that an abrupt dietary change, increasing the content of concentrates, and the change in housing stall system, had a massive effect in animal homeostasis and inflammatory response. The most responsive markers after abiotic stressors in our study were: Il-6, SAA, Cp, Alb, ROM in acute; PON, FRAP and GGT in mid acute and Alb in chronic phase. We suggest that these markers could be used as indicator of inflammation in high producing dairy cows. References. [1] Humer et al. (2018) J. Dairy Sci. 101:872–888