Effect of flax meal supplementation on oxidative stress and metabolic status of early lactation dairy cows infused with flax oil in the abomasum

The addition of flax oil (FO) to the diet of high-yielding dairy cows is a good strategy to improve the energy balance during early lactation. Although polyunsaturated fatty acids have numerous healthy attributes, they are easily oxidized and promote oxidative stress. In this project, we tested if the inclusion of natural antioxidants, flax meal (FM) rich in plant lignans, in cow’s diet could decrease oxidative stress and optimize the potential of FO as a source of energy. This experiment was conducted using twenty (20) multiparous high-yielding Holstein cows fitted with ruminal cannulas. Cows were assigned to two dietary treatments: (1) 250 g flax oil/d infused in the abomasum (n = 10, FO) and (2) FO + 15% flax meal (FM) in the dry matter (n = 10, FMFO). Treatments were administered over a 21 d (d) period from d 7 to d 28 post calving. Plasma and urine samples were collected on d 7 (before treatment initiation), 14, 21, 28 (end of treatment) and 49 (for carryover effect) to evaluate systemic oxidative damage to proteins (carbonyls) and DNA (8-hydroxy-2’-deoxyguanosine), and to determine the enzymatic activity of the antioxidants glutathione peroxidase (GPx) and superoxide dismutase (SOD), and diet had no effect (P > 0.05). Biopsies were taken from the liver and mammary gland tissue on d 7, 28, and 49 to measure the activity and mRNA expression of antioxidants and evaluate energy production in the form of adenosine triphosphate (ATP), and diet had no effect (P > 0.05) on activity of GPx and SOD. The mRNA expression of SOD1 in mammary tissue was lowered by the addition of FM to the diet (P < 0.01). In the liver, SOD1 mRNA levels remained stable throughout the experimental period in the FMFO group while it was higher on d 49 in cows infused with FO (interaction treatment × day, P < 0.05). Analysis of hepatic levels of ATP revealed that the addition of FM suppressed the increase in energy production observed on d 49 in the FO group (interaction treatment × day, P < 0.05). Infusion of FO in the abomasum decreased the level of proteins carbonyls in mammary gland tissue from d 7 to d 49, and this effect was counteracted by the addition of FM (interaction treatment × day, P < 0.05). Taken altogether, these results suggest that the oxidative status of early lactating cows infused with FO is not significantly affected by the addition of FM to the diet.