Effect of Lactic Acid Bacteria (Probiotics) on Local and Systemic Immune Responses in Cattle

Abstract

The purpose of this study was to investigate effect of probiotics as dietary supplement in three to four month-old Holstein calves on their local and systemic immune responses. Probiotic bacteria are microorganisms that have beneficial effects on the physiology and pathology of their host animals. Their effects on intestinal microflora may play a role in improving animal health. One of their putative effects is the modulation of the immune function. Probiotics have been shown to affect the innate and both the cellular and the humoral arms of the immune system. In this study, Lactobacillus acidophilus was administered orally to six calves daily for 35 days at the rate of 109 colony-forming units per animal. Five other calves were not given the bacteria and served as controls. I observed that there was no significant difference observed in phagocytic activity of immune cells isolated from animals fed on probiotics and the controls. ELISA measurements of serum IgA concentrations of animals fed on probiotics and their controls showed no significant difference. Pro-inflammatory cytokine gene assay, by semi-quantitative RT-PCR also yielded result of no significant difference between the two groups of animals suggesting that the probiotic did not have effect on their regulation. Therefore, I concluded that, at the rate of feeding healthy 3 to 4- month old calves with at least 109 colony-forming units of bacteria, no key immunological function is enhanced. Either the bacteria had difficulty in establishing and colonizing the gastrointestinal tract, or the numbers of bacteria fed to the animals were low such that no microfloral balance was created leading to no beneficial effects being conferred to the animals.