Mammary gene expression and activity of antioxidant enzymes and oxidative indicators in the blood, milk, mammary tissue and ruminal fluid of dairy cows fed flax meal

Abstract

The effects of flax meal (FM) on the activity of antioxidant enzymes (superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase (CAT)) in the blood, mammary tissue and ruminal fluid, and oxidative stress indicators (thiobarbituric acid-reactive substances (TBARS) and 1,1-diphenyl-2-picrylhydrazyl-scavenging activity) in the milk, plasma and ruminal fluid of dairy cows were determined. The mRNA abundance of the antioxidant enzymes and oxidative stress-related genes was assessed in mammary tissue. A total of eight Holstein cows were used in a double 4 £ 4 Latin square design. There were four treatments in the diet: control with no FM (CON) or 5 % FM (5FM), 10 % FM (10FM) and 15 % FM (15FM). There was an interaction between treatment and time for plasma GPx and CAT activities. Cows supplemented with FM had a linear reduction in TBARS at 2 h after feeding, and there was no treatment effect at 0, 4 and 6 h after feeding. TBARS production decreased in the milk of cows fed the 5FM and 10FM diets. There was a linear increase in nuclear factor (erythroid-derived 2)-like 2 (NFE2L2) mRNA abundance in mammary tissue with FM supplementation. A linear trend for increased mRNA abundance of the CAT gene was observed with higher concentrations of FM. The mRNA abundance of CAT, GPx1, GPx3, SOD1, SOD2, SOD3 and nuclear factor of k light polypeptide gene enhancer in B-cells (NFKB) genes was not affected by the treatment. These findings suggest that FM supplementation can improve the oxidative status of Holstein cows as suggested by decreased TBARS production in ruminal fluid 2 h post-feeding and increased NFE2L2/nuclear factor-E2-related factor 2 (Nrf2) mRNA abundance in mammary tissue.Key words: Catalase: 1,1-Diphenyl-2-picrylhydrazyl: Glutathione peroxidase: Superoxide dismutase: Thiobarbituric acid-reactive substances High-yielding dairy cows are prone to oxidative stress due to intensive metabolic demands for maintenance and production. This condition can be exacerbated under certain environmental, physiological and dietary factors (1,2) . Although lipid supplementation of ruminant diets with n-3 PUFA is a strategy to improve the nutritional quality of dairy products, this approach could increase the risk of plasma peroxidation with deleterious consequences on animal health (3) . Peroxidation results from oxidative metabolism, which is essential for the survival of cells. However, a side effect of this phenomenon is the production of free radicals and other reactive oxygen species that can cause oxidative damage (2) . Normally, the body is protected by a wide range of antioxidant systems working in concert with intracellular enzymes such as superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase (CAT), which remove superoxides and peroxides before they react with metal catalysts to form more reactive compounds (4) . Lactation performance and antioxidant status of cows fed oxidised fat are enhanced when antioxidants are included in the diet (5) , which may be due to the scavenging of peroxides a...

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