Physiological Adaptations in the GI Tract Detected By a Fecal RNA Method and Blood Inflammatory Biomarkers in Neonatal Dairy Calves Undergoing a Mild Diarrhea

Diarrhea is a major cause of morbidity and mortality in dairy calves less than one month old. Exfoliated gastrointestinal epithelial (EGE) cells isolated from fecal samples of neonatal dairy calves could be used to study transcriptional changes in the GI tract due to nutrition or physiological adaptations to diarrhea. Eight newborn Jersey male calves were used from birth to 5 wk of age and housed in individual pens at the Oregon State University Dairy Center. After birth, calves received 1.9 L of colostrum from their respective dams. Calves had ad-libitum access to water and starter grain and were fed twice daily a total of 5.6 L whole milk. Blood samples were collected weekly for inflammatory profiling from wk 0 to wk 5. Fecal score (FS) was recorded daily throughout the experiment. Fresh fecal samples were collected weekly for RNA isolation from EGE for RT-qPCR analysis. Data were analyzed using the PROC MIXED procedure of SAS. Orthogonal contrasts were used to evaluate linear or quadratic effects over time. Statistical significance and tendencies were declared at P < 0.05 and P ≤ 0.15, respectively. Fecal score increased over time (P < 0.01), with a maximal (2.6 ± 0.3) score at wk 2. The blood inflammatory biomarkers, ceruloplasmin and haptoglobin had a time effect (P ≤ 0.05), that was reflected in a positive quadratic effect (P ≤ 0.04) over time. A trend (P = 0.10) for a time effect on IL-6 was observed, which was explained by a positive quadratic effect (P = 0.01) over time. The concentration of serum amyloid A decreased (P < 0.01) over time. The mRNA expression of proinflammatory related genes TLR4, TNFA, IL8, and IL1B had a time effect (P < 0.01), where a positive quadratic effect (P = 0.05) was observed for all. A trend for a time effect was observed for NFKB1 expression (P = 0.07), where this expression increased linearly (P = 0.04) over time. A time effect (P ≤ 0.04) was observed for the cell membrane transporters, SLC5A1 and AQP3, where both genes expressed a negative quadratic effect (P ≤ 0.05) over time. Overall, these data provide evidence for the use of the fecal RNA method as a tool to evaluate transcriptomic changes in the GI tract of dairy calves experiencing not only scours but also such method could shed light in the molecular adaptations of the GI tract to dietary effects.