The effect of probiotics in a milk replacer on leukocyte differential counts, phenotype, and function in neonatal dairy calves

Authors: EICHER, SUSAN - Retired ARS Employee; KRITSHEVSKY, JANICE - Purdue University; BRYAN, KEITH - Chr Hansen Inc; Chitko-Mckown, Carol

Submitted to: Microorganisms
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/19/2023
Publication Date: 10/24/2023
Citation: Eicher, S.D., Kritshevsky, J.E., Bryan, K.A., Chitko-Mckown, C.G. 2023. The effect of probiotics in a milk replacer on leukocyte differential counts, phenotype, and function in neonatal dairy calves. Microorganisms. 11(11). Article 2620. https://doi.org/10.3390/microorganisms11112620.
DOI: https://doi.org/10.3390/microorganisms11112620

Interpretive Summary: Probiotics are microorganisms that are beneficial to health. Most are provided orally in foodstuffs or supplements and aid in digestion. However, due to the connection between the oral cavity and the respiratory system, they may contribute to immunity throughout the body by affecting the immune system through the oral mucosa. Our objectives were to determine changes in performance and blood immune cell populations as well as lung immune cells in dairy calves fed probiotics in milk replacer and dry rations from birth to weaning. We observed that performance traits did not differ between the two treatment groups. Peripheral blood cell populations varied by time and day between treatments. Only a subpopulation of animals (5 from each treatment) had lung immune cells collected. Possibly due to the small sample size, no differences were found between the treatments for immune receptors and proteins expressed by lung immune cells. Probiotics provided orally appear to affect peripheral blood immune cells and function, however their affect of overall calf health remains to be determined.

Technical Abstract: Probiotics have been investigated for many health benefits; however few studies have been performed to determine the effects of oral probiotics on peripheral blood and respiratory immune cells in cattle. Our objectives were to determine changes in health and growth status, differential blood cell counts and function, and blood and lung cell function using flow cytometry and PCR in dairy calves fed a milk replacer with (PRO, N=10) or without (CON, N=10) the addition of probiotics to the milk replacer and dry rations from birth to weaning. Performance and clinical scores were not different between the treatment groups. Treatment-by-day interactions for peripheral blood leukocyte populations differed in cell number and percentages. A greater percentage of leukocytes expressed the cell surface markers CD3, CD4, CD8, CD11b and CD205 on d 21 in CON animals. Lung lavages were performed on five animals from each treatment group on d 52. There were no differences between treatment groups for the expression of cytokines and Toll-Like Receptors as measured by Polymerase Chain Reaction, possibly due to the small sample size. Oral probiotics appear to affect peripheral blood immune cells and function. Their effect on overall calf health remains to be determined.