Supplementation of herbal plants differently modulated metabolic profile, insulin sensitivity, and oxidative stress in transition dairy cows fed various extruded oil seeds

The study investigated the effects of a mixture of herbal plants (HM) and two sources of unsaturated fatty acids (FA), extruded linseed (LS) and soybean (SB), on metabolic profile, insulin sensitivity, and oxidative status of transition dairy cows. Thirty-two prepartum Holstein cows, blocked by parity and calving day, were randomly assigned to 1 of 4 treatments, in a 2 × 2 factorial design, starting from 25 days before the expected calving date to 26 days postpartum. The supplementation rates of HM were 150 and 170 g/animal/day at pre- and postpartum, respectively. Blood samples were analyzed for metabolites on day 7.15 ± 1.70 prepartum and on days 1 and 21 postpartum. An intravenous glucose tolerance test (IV-GTT) was conducted on day 25 postpartum. Data showed that cows supplemented with HM had lower serum concentration of NEFA (0.395 vs. 0.602 ± 0.044 mmol/L; P < 0.01) and NEFA to insulin ratio (P < 0.01) postpartum. Compared to animals fed SB-based diets, cows fed the LS-based diet had greater serum glucose concentration during prepartum (80.7 vs. 71.3 ± 3.32 mg/dL; P = 0.06) and postpartum period (86.3 vs. 73.5 ± 3.35 mg/dL; P = 0.01), as well as lower NEFA (0.425 vs. 0.572 ± 0.044 mmol/L; P = 0.03) and insulin to glucose ratio (P < 0.01) postpartum. Revised quantitative insulin-sensitivity check index revealed that supplementing HM in LS-based diet improved insulin sensitivity (0.45 vs. 0.41 ± 0.013; P = 0.03) prepartum, whereas after parturition, the HM addition was effective for both oil seeds (0.40 vs. 0.37 ± 0.008; P = 0.06) in enhancing insulin sensitivity. Result of IV-GTT indicated that cows fed LS-based diets had higher basal glucose concentration (63.7 vs. 55.7 ± 2.37; mg/dL; P = 0.02) and lower glucose area under the curve (995.8 vs. 1529.5 ± 100.7; mg/dL × 45 min; P < 0.01). Supplementing HM resulted in greater total antioxidant capacity prepartum (0.55 vs. 0.48 ± 0.017 nmol/L; P = 0.01) and lower malondialdehyde concentration at prepartum (1.03 vs. 1.96 ± 0.140 μmol/L; P < 0.01) and postpartum (1.32 vs. 1.88 ± 0.178 μmol/L; P = 0.04). Although feeding LS ameliorated insulin resistance, this feeding strategy lowered total antioxidant capacity prepartum (0. 48 vs. 0.55 ± 0.017 nmol/L; P < 0.01) and increased malondialdehyde concentration postpartum more than the SB diet (1.91 vs. 1.28 ± 0.172 μmol/L; P = 0.02). Overall, both HM supplementation and LS feeding improved metabolic profile and insulin response following glucose infusion, although feeding of LS-based diets induced an increased oxidative stress.