Effect of an immunomodulatory feed additive on markers of immunity in pasture‐fed dairy cows

BackgroundInfectious diseases in dairy cows often follow a time of nutritional or physiological stress and the subsequent altered immune system function. This study aimed to determine if the immunomodulatory effects of a feed additive previously observed in experimental animals and housed cattle fed total mixed rations could be reproduced in pasture‐fed dairy cattle under Australian conditions.MethodsThe study included 34 pasture‐fed dairy cattle given the treatment (n = 17) or placebo (bentonite, n = 17) for an acclimation period of 15 days followed by 60 days of supplementation. Blood tests were taken pre‐trial and then 30, 60 and 90 days after acclimation. Blood samples were extracted and preserved in Trizol and analysed for immune markers.ResultsPasture‐fed dairy cows in the treatment group had significantly higher levels of the immune markers interleukin‐8R and L‐selectin in comparison with placebo‐fed cows at 60 days after the start of supplementation.ConclusionThe immunomodulatory effects of the additive observed in the current study and the associated enhanced neutrophil function demonstrated by other studies suggest a role in decreasing the rates of mastitis and other infectious diseases of dairy cattle, particularly during times of nutritional or physiological stress.