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

Abstract

Background: Infectious 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. Methods: The 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. Results: Pasture-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. Conclusion: The 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.