Effects of Chromium-Niacin Supplementation on Production and Metabolic Performance in Transition Dairy Cows

The objective of this study was to investigate the effects of chromium-niacin (CrNi) supplementation on production parameters, blood metabolites, antioxidant status and serum metabolite profile in transition dairy cows. A total of 28 multiparous Holstein dairy cows were included in the study. The experimental design included two treatments: a control group and a CrNi group, with each cow in the CrNi group receiving 8 mg chromium and 6 g niacin per day. The results showed that CrNi supplementation improved postpartum dry matter intake (DMI), which was higher in the CrNi group (21.02 vs. 19.74 kg/d; P = 0.09). Milk yield was significantly increased by 1.99 kg/d in the CrNi group (39.55 vs. 37.56 kg/d; P = 0.04). Somatic cell count (SCC) was numerically lower in the CrNi group (217 vs. 414 × 10³ cells/mL; P = 0.08), indicating a possible improvement in udder health. Milk protein, fat, lactose and solids-not-fat percentages and yields were not significantly affected by the treatment. Body condition score (BCS) remained similar between groups. No treatment differences were found in serum calcium, BHB, NEFA, alanine aminotransferase (ALT), aspartate aminotransferase (AST), urea, glucose, insulin, bilirubin, total protein, albumin, malondialdehyde (MDA) or total antioxidant capacity (TAC). Serum triglyceride levels were affected by CrNi (P = 0.06), with a significant treatment × time interaction (P < 0.05). Metabolomics analysis revealed that 42 metabolites were significantly altered by CrNi supplementation, with 21 metabolites upregulated, particularly those involved in lipid metabolism and microbial co-metabolism. In particular, DG (i-15:0/8:0/0:0) and Vanillic acid 4-O-sulfate were strongly upregulated, indicating increased lipid mobilization. Conversely, 21 metabolites were downregulated, including L-Threonine and Gabexate, indicating suppression of certain metabolic pathways, including anti-inflammatory processes. These results suggest that CrNi supplementation may contribute to improved production performance and metabolic health in transition dairy cows.