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Cooling dairy calves pre- and postnatally increases circulating serotonin and modulates immune function.

M. G. Marrero


Cooling dairy calves pre- and postnatally increases circulating serotonin and modulates immune function.
M. G. Marrero*, B. Dado-Senn, S. L. Field, J. Laporta. University of Florida Gainesville, FL.

Heat stress suppresses dairy calves' ability to develop optimum immune responses predisposing them to increased morbidity and mortality. We investigated the effects of providing heat stress abatement across pre- and postnatal periods on dairy calf immune system development. We hypothesized that pre-weaned calves receiving heat stress abatement will have increased humoral immunity and circulating serotonin (5-HT, an immunomodulator). To test this, calves born to heat stressed (HS) or cooled (CL) dams during late gestation (~46 d) were then exposed to postnatal HS or CL environments (56 d) resulting in 2 treatments: HSHS and CLCL; n = 6/group. Postnatal CL was achieved using fans providing wind speed ≥2 m/s. All calves were fed 4 L pooled colostrum at birth. Blood samples were collected weekly (d0 to 56) to measure leukocyte populations, 5-HT and IgG concentrations. On d47 a 24h in vitro LPS-challenge (0, 0.5, 1.0, 5.0 μg/mL dose) was performed. On d0, 21 and 42 blood was collected using Tempus RNA tubes for gene expression analysis of heat shock proteins (HSP70 and HSP72), transforming growth factor β (TGFB), toll-like receptors 2 and 4 (TLR2 and TLR4), interferon gamma (IFNG), T-cell transcription factors (GATA3, FoxP3, TBX21 and RORcy), 5-HT receptors 2A and 2B, 5-HT transporter (SERT) and tryptophan hydroxylase (TPH1). Data were analyzed using mix-model ANOVAs with treatment, day and interaction as fixed effects and ID as random. CLCL calves had greater TPH1 expression at birth (P = 0.005) and greater circulating 5-HT (P = 0.04), however, both groups had greater 5-HT concentrations after LPS-challenge in vitro (P = 0.01). Although there were no differences in neutrophil, monocyte and lymphocyte counts (P > 0.11), CLCL calves had greater gene expression of HSP70, FoxP3, TBX21, TGFB, TLR4 and 5-HT2A (P < 0.04). Notably, there was a treatment by day interaction whereby IgG concentrations were higher in the CLCL calves from d35 and thereafter (P = 0.01). Heat stress abatement increases circulating serotonin and has the potential to improve adaptive and humoral immune development in pre-weaned dairy calves.

Keywords: serotonin, immunology, heat stress.

Biography: Marcela Marrero, currently a 3rd year Ph.D. student researching dairy calves immune system priming through serotonin's precursor 5-hydroxytryptopgan supplementation. Originally from Puerto Rico. Have a masters from the university of Puerto Rico specializing in mastitis. Had the opportunity to be one of the William H. Miner Institute summer interns in 2013.