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A randomized, controlled field trial with dairy cows demonstrated an adverse effect of vitamin E supplementation during the dry period on mastitis incidence in early lactation. This study was conducted on farms with historically high rates of mastitis to investigate the benefit of vitamin E supplementation on udder health; however, the outcome showed an adverse effect. The aim of the study was to evaluate whether daily supplementation of 3,000 IU of vitamin E to dairy cows during the dry period could improve udder health in commercial herds with a high incidence of mastitis. On 5 dairy farms, dry cows were randomly divided into 2 experimental groups: a high and a low group. Both groups received a dry cow mineral mix providing 3,000 or 135 IU of vitamin E/cow per day, respectively, between dry-off and calving for a mean period of 8 wk. Providing 3,000 IU of vitamin E exceeds NRC standards, but this amount has been used in previous studies. The experiment, as well as the majority of the statistical analysis, were carried out blinded. Blood was sampled 3 times before calving and on calving day. Serum was analyzed for vitamin E and cholesterol. Vitamin E and the vitamin E:cholesterol ratio were analyzed as dependent variables in mixed models and Student's t-tests to study trends in time and differences between groups. Relative risk calculation and survival analysis were used to study the effect of supplementation on mastitis incidence in the first 3 mo of lactation. The results showed that vitamin E supplements increased both absolute vitamin E and the ratio of vitamin E to cholesterol in blood. In the high group, significantly more subclinical and clinical cases occurred, showing the same trend on all farms. In this study, an initial vitamin E level at dry off above 14.5 μmol/L was a risk factor for clinical mastitis, suggesting that the vitamin E status at the start of the dry period is important. It is recommended to work out exactly at what threshold vitamin E is harmful for udder health before new trials with high dosages of vitamin E are started. Additionally, further research is required to investigate the mechanism by which vitamin E affects udder health., (Copyright © 2010 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

The aim of this study was to evaluate, retrospectively, which physiological states influenced the effect of vitamin E supplements during the dry period on the level of oxidative stress at 2 wk antepartum. Furthermore the effect of oxidative stress at 2 wk antepartum on the risk of clinical mastitis in early lactation was investigated. Cows experience oxidative stress around calving. Vitamin E is able to decrease oxidative stress by scavenging free radicals. Normally, vitamin E radicals formed when vitamin E reacts with free radicals are regenerated by a network of other antioxidants, termed the "vitamin E regeneration system" (VERS). In case of vitamin E supplementation, VERS should be sufficient to regenerate formed vitamin E radicals; if not, oxidative stress might increase instead of decrease. Additionally, the level of oxidative stress and vitamin E might be important physiological states to evaluate before supplementation. In a clinical trial, 296 cows on 5 farms were randomly divided into 2 groups, supplemented with a mineral mix between dry off and calving that supplied 3,000 or 135 IU/d, respectively. Blood samples collected at dry off and 2 wk antepartum were analyzed for vitamin E, reactive oxygen metabolites, ferric-reducing ability of plasma, glutathione peroxidase, and malondialdehyde. Cows were allocated retrospectively into 8 subgroups based on the level of oxidative stress, vitamin E, and VERS status at dry off. To evaluate whether differences in physiological states at dry off influenced the effect of vitamin E supplementation on the level of oxidative stress, group effects (supplemented vs. control) were studied with Student's t-test for all 8 subgroup at 2 wk antepartum. Differences in physiological states at dry off influenced the effect of vitamin E supplements. In 2 insufficient VERS subgroups, the supplemented group had higher levels of free radicals at 2 wk antepartum compared with the control group. Relative risk calculation was used to study the effect of oxidative stress at 2 wk antepartum on the incidence of mastitis in the first 100 d of lactation. Higher levels of oxidative stress at 2 wk antepartum were related to higher risk of clinical mastitis. In conclusion, not every dry cow responded well to high vitamin E supplementation. This subgroup analysis provides a possible explanation for the unexpected adverse effects observed in the clinical trial., (Copyright © 2010 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

The objective of this study was to investigate the effect of vitamin E supplementation on oxidative status in blood, liver, milk, and ovarian follicular fluid in periparturient heifers. Vitamin E supplementation started 8 wk before calving and continued until 8 wk postpartum. Grass silage was the main forage fed during the experiment. In addition, supplemented heifers (n=9) received 3,000I U of vitamin E daily on a carrier food; control heifers (n=9) consumed only the carrier food. Blood samples and liver biopsies were taken frequently throughout the study and ovarian follicular fluid was sampled at 8 wk postpartum. Body condition score was scored weekly and milk yield was measured daily. A marker of oxidative damage, determinable reactive oxygen metabolites (d-ROM), and a set of antioxidants were measured in blood, liver, milk, and ovarian follicular fluid. Control heifers had a low vitamin E status, and selenium status was marginal in control and supplemented heifers. Vitamin E supplementation increased vitamin E concentrations in blood, liver, and ovarian follicular fluid and increased triacylglycerol in liver. Serum d-ROM were not reduced by vitamin E supplementation. Superoxide dismutase and glutathione peroxidase activity in red blood cells and liver and glutathione peroxidase activity in ovarian follicular fluid were not affected by vitamin E supplementation and they were not increased around calving. Protein thiol groups and ratio of reduced glutathione to oxidized glutathione were also not increased around calving. These results suggest that heifers around calving experience a low level of oxidative processes. This might be caused by lower than expected milk production attributed to a low forage intake. Serum d-ROM were negatively correlated with protein thiol groups and positively correlated with the activity of glutathione peroxidase in red blood cells, oxidized glutathione, and the ratio of reduced glutathione and oxidized glutathione in serum. The lack of treatment effects allowed estimation of the effects of body condition 4 wk before calving and the loss of body condition on markers of lipid peroxidation and antioxidants. A trend that a body condition of >or=3 might result in more oxidative damage measured by serum d-ROM was observed, but fatter heifers had a significantly higher ratio of reduced glutathione to oxidized glutathione., (Copyright (c) 2010 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

The effect of oral vitamin E supplementation during the dry period on serum biomarkers of oxidative status was evaluated in an observational field study. Ninety-eight cows were selected from 26 herds in the Netherlands. On 15 farms dry cows were supplemented with a dry-cow mineral mix containing 1000 IU vitamin E (vitamin E+ group, n = 52), and on 11 other farms dry cows did not receive the supplement (control group, n = 48). A blood sample was taken from all cows between 0 and 28 days before calving. Serum levels of alpha-tocopherol, cholesterol, triacylglycerol, superoxide dismutase (SOD), glutathione peroxidase (GSHpx), uric acid, albumin, protein sulphydryl oxidation level, reactive oxygen metabolites (ROM), iron, the ferric reducing ability (FRAP), and malondialdehyde (MDA) were measured. Alpha-tocopherol levels were significantly higher in the vitamin E+ group, as was the alpha-tocopherol:cholesterol ratio. MDA levels were significantly lower in the vitamin E+ group, suggesting that levels of lipid peroxidation were lower with vitamin E supplementation. In conclusion, vitamin E supplementation increases alpha-tocopherol and lowers MDA serum levels.

This study investigated the relationship between oxidative damage and the effect of vitamin E supplementation in blood, milk, and liver tissue in 16 periparturient heifers. The question is whether measurements of oxidative and vitamin E status in blood of a periparturient cow are representative of the total body, given that blood concentrations of both vitamin E and oxidative stress products change around this period. The daily vitamin E intake of the vitamin E-supplemented Holstein-Friesian heifers (n = 8) was 3,000 international units and was started 2 mo before calving; the control heifers (n = 8) were not supplemented. Oxidative damage was determined on the basis of malondialdehyde (MDA) concentrations. Blood was sampled 9 times before calving, on calving day, and twice after calving. Liver biopsies were taken at wk -5, -1, and 2 relative to calving day. Milk was obtained from all heifers immediately after calving, the first 2 milkings and on d 3, 7, and 14 at 0600 h. Serum and liver tissue were analyzed for vitamin E, cholesterol, and MDA; and milk samples were analyzed for vitamin E, MDA, fat, protein, and somatic cell count. The results showed that vitamin E supplements increased both absolute vitamin E concentrations and the ratio of vitamin E to cholesterol in blood and liver tissue. Absolute vitamin E concentration in milk tended to be greater in supplemented cows. Based on the increased MDA blood concentrations at calving, it seems that dairy heifers experience oxidative stress. The effect of vitamin E on MDA differs between the blood, liver, and mammary gland. Vitamin E supplementation could not prevent the increase in blood MDA at calving, but the significantly lower MDA blood concentrations of supplemented cows in the 2 wk after calving suggest that vitamin E has a role in recovery from parturition-related oxidative stress. Vitamin E supplementation reduced oxidative damage in liver, whereas no obvious effect was found on milk MDA concentrations. A strong relationship was found between blood and liver vitamin E and the ratio of vitamin E to cholesterol. Concentrations of MDA in blood and milk were also strongly related. The results show that the relationship between oxidative damage and vitamin E differs within blood, liver tissue, and milk. This implies that oxidative and vitamin E status calculated on the basis of blood values alone should be interpreted with caution and cannot be extrapolated to the whole animal.

Abstract: This study aimed at estimating the Schmallenberg virus (SBV) seroprevalence in dairy heifers, non-dairy adult cattle, sheep and goats in the Netherlands after cessation of SBV transmission at the end of 2011. Archived serum samples from ruminants submitted to the GD Animal Health Service for monitoring purposes between November 2011 and March 2012 were selected and tested for presence of SBV-specific antibodies using an in-house ELISA. Animal seroprevalences were estimated at 63.4% in dairy heifers, 98.5% in adult non-dairy cattle, 89.0% in sheep and 50.8% in goats. Multivariable analyses were carried out to describe the relationship between potential risk factors and the ELISA outcome S/P%. The overall SBV seroprevalence in ruminants and ruminant herds in the Netherlands at the end of 2011 was high, with considerable differences between species and farm types. No gradient spatial pattern in final seroprevalence could be detected and therefore no suggestions about the site of introduction and spread of SBV in the Netherlands in 2011 could be made. In dairy heifers, it was shown that S/P% increased with age. In sheep, S/P% was lower in animals located in the coastal area. Whether herds were located near the German border did not affect the S/P% in sheep nor in dairy heifers. An attempt was made to gain insight in the spatiotemporal introduction of SBV in the Netherlands in 2011, by testing sheep serum samples from 2011. A seroprevalence of about 2% was found in samples from April, June and July 2011, but the ELISA positive samples could not be confirmed in a virus neutralization test. A clear increase in seroprevalence started at August 2011. From mid-August 2011 onwards, seropositive samples were confirmed positive by virus neutralization testing. This indicated the start of the epidemic, but without a clear spatial pattern. [Copyright &y& Elsevier]