Interaction among energy status, and retinoid status in periparturient dairy cows: production, milk retinoid, and metabolic response
An objective of this study was to determine the effect of feeding various amounts of dietary vitamin A (0 or 110 IU/kg BW), crude protein (12.5% or 16%), and an ionophore (monensin at 0 or 400 mg/d per head) on performance measures, retinoid metabolism, immune system, and metabolic response. Multiparous Holstein dairy cows (n = 80) were studied from day -35 to +21 relative to expected parturition, in a complete randomized block design with a 2 × 2 × 2 factorial arrangement of treatments. Milk samples were obtained at the 1st, 2nd, 3rd milking, and every 3 d thereafter, and processed for components, somatic cell count (SCC), retinol, α-tocopherol, and β-carotene. Serum samples were collected on d -35, -7, +3, +9, +21 and processed for NEFA, BHBA, haptaglobin, and thiobarbituric acid reactive species (TBARS). Peripheral blood mononuclear cells (PBMC) were also isolated on d +7. Real time qPCR gene analysis for intercellular adhesion molecule (ICAM-1), interleukin (IL) 1β and 6, and tumor necrosis factor-α (TNF-α) were performed on PBMC. Significance of treatments was declared at P ≤ 0.05. Results indicated vitamin A reduced (P = 0.05) milk SCC with no effect on milk yield or composition, DM intake both pre- and postpartum. An effect of CP × monensin on milk retinol concentration was observed (2.19, 1.72, 2.12, and 2.35 ± 0.16 µg/mL for low CP + monensin, low CP – monensin, high CP + monensin, and high CP – monensin, respectively; P = 0.03 ), but no differences in milk α-tocopherol and β-carotene were found. Furthermore, serum haptoglobin was lower (P = 0.03) with greater dietary CP. Also, cows that received monensin had lower (P = 0.013) serum haptoglobin postpartum compared with the prepartum concentrations observed. No differences in serum NEFA, BHBA, or TBARS were detected. Cows that received greater CP had increased gene expression of TNF-α (P = 0.04) in PBMC, but not effect on gene expression of ICAM-1, IL-1β, and IL-6 was found. Overall, these observations show that dietary vitamin A, monensin and protein affect retinol and SCC in milk without affecting performance measures. Further studies are needed to fully understand the retinoid metabolism in the transition dairy cow.
Keywords: transition cows, retinoids, gene expression