Reevaluation of vitamin E supplementation of dairy cows: bioavailability, animal health and milk quality

Abstract

Although vitamin E has been known as an essential nutrient for almost 80 years, we are far from a complete understanding of all the aspects related to bioavailability and its effects on health and milk quality in dairy cows. Vitamin E is a generic descriptor for two families of lipid-soluble compounds, the tocopherols and the tocotrienols, of which a-tocopherol has the highest biological activity. Commercially available a-tocopherol supplements for dairy cows contain either the natural RRR form or the synthetic (all-rac) form, which contains all the eight possible stereoisomers (four possessing the 2R and four possessing the 2S configuration) in equimolar amounts. Recent data clearly suggest that an almost complete discrimination against the 2S isomers occurs in dairy cows. Thus, 1 g of the all-rac form is essentially equivalent to 0.5 g of the RRR form. With respect to the effect of vitamin E supplementation of dairy cows on health and milk quality, the majority of published studies suggests that vitamin E supplementation at the level 1000 to 4000 IU/cow per day during the dry period reduces both the frequency of intramammary infection and that of clinical mastitis and improves milk quality, as shown by a reduction in the levels of somatic cell count (SCC)/ml in milk, decreased plasmin activity and increased oxidative stability of milk. However, a recent study from the Netherlands suggested that vitamin E supplementation at the 3000 IU/cow per day level during the dry period when combined with high levels of plasma vitamin E at dry-off (.14.5 mmol/l) increases the incidence of mastitis. Data from previously unpublished survey studies and those from published vitamin E feeding trials, in which high levels of blood vitamin E were observed, were reanalyzed. All farms selected for the analysis implemented oral administration of vitamin E at the 3000 IU/cow per day level throughout or during the late dry period (4 weeks before the expected day of parturition). Dairy cows were divided into three groups, depending on blood a-tocopherol levels at dry-off: high (.6.25 mg/ml), medium (between 6.25 and 4.25 mg/ml) and low (,4.25 mg/ml). Data indicate that there were no differences in the incidence of mastitis and in the level of SCC/ml of milk between the three groups. Thus, supplementation of 3000 IU vitamin E/cow per day in the late dry period remains recommended because it is generally associated with decreased risk of mastitis. Conditional or opposite effects have not been repeated and require further research before changing recommendations for vitamin E supplementation.

Oxidative stress index (OSi) as a new tool to assess redox status in dairy cattle during the transition period

“…Therefore, we are measuring the cumulative capacity of the antioxidant defense against a particular oxidant aggression (how the animal has been accumulating and disposing its antioxidants reserves to specific, predictable and expected situations such as delivery and early lactation), rather than measure the short-term antioxidants at the time of sampling. The prepartum period is characterized by a depleted antioxidant status and, consequently, OS (Bernabucci et al, 2002 and, and therefore these cows were supplemented with a vitamin complex before parturition, which is a recommended practice to minimize the risk of postpartum diseases (Politis, 2012). This fact prevents us from getting the clear picture of the natural cycle of OSi; however, on the other hand, it shows the oxidative status that might be observed in dairy cows in commercial farms.…”

Investigation into omocysteine, vitamin E and malondialdehyde as indicators of successful artificial insemination in synchronized buffalo cows (Bubalus bubalis)

“…It may therefore seem surprising that VitE supplements are routinely recommended to counteract the detrimental effect of ROS in dairy herds. Since the real antioxidant need might well vary with the individual, a standard dose may not always be suitable (Politis, 2012;Dimri et al, 2013), particularly in the dry period.…”

Review: In vivo and postmortem effects of feed antioxidants in livestock: a review of the implications on authorization of antioxidant feed additives

“…More importantly, SSC is one of the significant factors that determine milk price as it is considered as a gauge for the hygienic quality of milk. A review by Politis (2012) suggested that dietary vitamin E can improve milk quality either by directly enhancing the oxidative stability of milk or by indirectly reducing the level of SSC and plasmin activity in milk. Dietary antioxidants including vitamin E, Se and other trace minerals could reduce the occurrence of intramammary infection and thus decrease the SSC in milk (Baldi et al, 2000;Politis et al, 2004;Machado et al, 2013).…”