Effect of weaning strategies on biosynthesis of oxylipids in Holstein dairy calves.

The aim of this study was to determine the effect of the weaning calves at 2 ages (early vs. late) and 2 weaning paces (abrupt over 3 d vs. gradual over 14 d) on plasma oxylipids. Seventy-one dairy calves (38.8 ± 4.4 kg, BW ± SD), blocked by sex and BW at birth, were randomly assigned in a 2 × 2 factorial arrangement of treatments. The factors were weaning age (early: 6-7 wk vs. late: 8-9 wk) and weaning pace (abrupt: 3 weaning steps over 2 d vs. gradual: 7 weaning steps over 14 d), generating 4 treatment groups: early-abrupt, early-gradual, late-abrupt, and late-gradual. Blood samples were collected from the jugular vein 1 d preweaning, and one day postweaning. Oxylipids concentration was measured by liquid chromatography-tandem MS. Fatty acid profile (including nonesterified fatty acids) was also assessed. Weaning pace, age, pace × age, BW at birth, and sex were included as fixed effect and cohort was included as random effect in the model. Linoleic acid derivatives 13- oxooctadecadienoic (OxoODE) and 9-OxoODE had a greater concentration in calves abruptly weaned when compared with those for gradually weaned calves. Calves weaned gradually showed a greater concentration of 9-hydroxyoctadecadienoic (HODE), 13-HODE, 12,13-dihydroxyoctadecenoic (DiHOME), 9,10-DiHOME, all linoleic acid-derived compared with that for abruptly weaned calves. Anti-inflammatory oxylipid 17,18-dihydroxyeicosatrienoic, an eicosapentaenoic acid derivative, was greater in calves abruptly weaned compared with those gradually weaned. Overall, the pace of weaning affected the plasma concentration of oxylipids, demonstrating that weaning pace affects the oxylipids status involved in inflammation in dairy calves.