The effects of intramammary cephalosporin antibiotic treatment at dry off on peripheral blood and milk mononuclear cell mitochondrial enzyme activity in Holstein cows
Cephalosporin antibiotics are commonly used at dry off to treat and prevent intramammary infections (IMI). Research in murine and other mammalian cell types showed that cephalosporin antibiotics negatively affect mitochondrial respiratory chain activity, which impacts cellular function. The objective of this study was to evaluate the effects of intramammary (IM) cephalosporin (Cefitiofur Hydrochloride and Cephapirin Benzathine) antibiotic treatment administered at dry off on peripheral blood mononuclear cell (PBMC) and milk mononuclear cell (MMC) mitochondrial enzyme activity 4 h prior to dry off (TPT1), 7 d post dry (TPT2), and between 55 – 75 DIM in the subsequent lactation (TPT3). Thirty-seven Holstein cows from a commercial dairy were enrolled at TPT1 and assigned to 1 of 4 treatments: 1) Low SCC control (LCON), 2) High SCC Control (HCON), 3) High SCC Ceftiofur Hydrochloride (CH), (Spectramast DC; Zoetis Inc., Kalamazoo, MI), and 4) High SCC Cephapirin Benzathine (CB), (ToMorrow; Boehringer Ingelheim Vetmedica Inc., St. Joseph, MO). Control treatments received no antibiotics. Low and high SCC cows were defined as < 100,000 cells/mL (low), and > 200,000 cells/mL (high) at TPT1. Whole blood and milk samples were collected at TPT1, TPT2, and TPT3. Enzyme activities of citrate synthase (CS), complex I (CI), complex IV (CIV), and ATP synthase were performed on crude mitochondrial extracts using kits from Abcam (Cambridge, MA). An index representing the ratio of electron transport activity to ATP synthase activity (OXPHOS) was calculated from the sum of CI and CIV enzyme activities divided by ATP synthase enzyme activity. Data were analyzed by REML ANOVA with repeated measures in R (Version 4.0.4). The PBMC CIV enzyme activity was highest at TPT1 in the LCON treatment compared with the HCON, CH, and CB treatments, but was not different at TPT2 and TPT3, indicating that PBMC CIV enzyme activity was influenced by IMI. The PBMC and MMC CS, CI, ATP synthase and OXPHOS changed with time. These data indicate that MMC and PBMC mitochondrial enzyme activities and OXPHOS were not influenced by cephalosporin treatment. The time related changes in OXPHOS and enzyme activities were likely influenced by diet composition, milk production, oxidative stress, and fetal growth.