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Calves are born with a fully developed but still naïve immune system and are thus vulnerable to high rates of morbidity and mortality. The best defence to ensure calves health and survival is ingestion of colostrum, containing large amounts of maternal immunoglobulins, leukocytes and cytokines. Besides adequate colostrum intake properly used antibiotics can provide much protection for the bovine neonate. However, increased antibiotic scrutiny and in particular consumer demand for organic products have prompted investigations of natural immunomodulators for enhancing calf health. In this context plant-based immunomodulators, such as Morinda citrifolia (noni) reportedly having a broad range of immunomodulatory effects, are of noteworthy interest.
The objective of this study was to evaluate the effects of feeding noni fruit puree on the immune system of neonatal calves during the first two weeks of life. For this purpose 18 newborn Holstein Friesian bull calves were acquired in pairs from local dairies. All calves had received 3.785 l (1 gal.) of pooled colostrum by 12 hrs of age. Adequate passive transfer was confirmed at 24 hrs of age. After arrival at the Veterinary Medical Teaching Hospital of the University of Wisconsin in Madison calves were divided randomly into two groups. Group 1 comprised of control calves, while Group 2 received 30 ml (1 oz) of noni puree twice daily in milk replacer. Day 0 samples were obtained before the first feeding of puree between 36 and 48 hrs of age. Peripheral blood mononuclear cells (PBMC) were collected and isolated from each calf on days 0, 3, 7 and 14.
To measure lymphocyte proliferation, a mitogen induced lymphocyte blastogenesis test (LBT) was performed. Mitogen induced activation of CD4+, CD8+ and γδ TCR+ T cells was evaluated by measuring the up-regulation of the surface protein CD25, which is part of the IL-2 receptor, on these cells with two-color flow cytometry. For both tests Concanavalin A (Con A) and Phytohemagglutinin (PHA) were used as global mitogens. Bactericidal assays were performed to estimate the percent killing of E. coli and Staph. epidermidis. EDTA anti-coagulated blood was collected from each calf on days 0, 3, 7, and 14.
Results of flow cytometry showed a significant increase in percent CD25 expression on CD4+ and CD8+ T cells on day 3 of the study or approximately 5 days postpartum in response to Con A stimulation. The LBT did not show significant differences between the two groups in response to either mitogen. The bactericidal assay revealed an effect of noni on bactericidal activity against E. coli. Noni puree-fed calves had significantly increased E. coli bacterial killing when compared to controls on day 14. Differences were not significant on days 0, 3 and 7, but did increase over time. There was no significant difference between groups for Staph. epidermidis killing. This immunomodulatory effect may be of high interest for the production animal industry in the future to enhance calves health within the first two weeks of life since antibiotic use becomes more restricted. Additional clinical trials are warranted to investigate the clinical application of noni puree in promoting calf health.