Selenium supplementation and selenium status of dairy cows fed diets based on grass, grass silage or maize silage

Selenium concentration and glutathione peroxidase (GSH-Px) activity in serum of cows at different stages of lactation

The aim of the study was to evaluate the activity of glutathione peroxidase (GSH-Px) and the concentration of selenium in Holstein-Friesian cows at different stages of lactation. Selenium was determined spectrofluorimetrically and GSH-Px activity using a Sigma CGP1 Glutathione Peroxidase Cellular Activity Assay kit. Mean serum selenium concentration was highest in early-lactation multiparous cows (0.18 μg/ml) and the lowest in dry cows (0.111 μg/ml). In early lactation, serum selenium concentration was significantly (P ≤ 0.01) higher in multiparous cows than in cows from the other groups. Mean GSH-Px activity in the serum of dry cows was over twice lower than in late-lactation cows (P ≤ 0.01) and over four times lower than in first-calving heifers and multiparous cows in early lactation (P ≤ 0.01). The coefficients of Spearman's rank correlation between GSH-Px activity and selenium concentration in the cows at different stages of lactation were not significant. A significant (P ≤ 0.01) mean positive correlation (0.46) was found between GSH-Px activity and serum selenium concentration for all the cows analysed together. The highest Se concentration and GSH-Px activity found in the serum of cows during the first stage of lactation may suggest that the generation of reactive oxygen species and their derivatives was higher during this period compared to the other stages, thus placing the cows at a greater risk of oxidative stress. It is therefore essential to give particular attention during this period to meeting the cows' requirement for selenium and other feed components that increase, directly or indirectly, the capacity of the body's antioxidant system.

Relationship between selenium and selected heavy metals concentration in serum of cattle from a non-polluted area

The present study was undertaken to evaluate the concentration of selenium and selected heavy metals and their possible relationship in serum of 25 healthy lactating cows (Montbéliarde) reared in a non-polluted area, in the western part of Poland. Cadmium, lead, copper, and zinc concentrations were determined by inductively coupled plasma-atomic emission spectrometry and Se concentration was determined fluorimetrically. The content of Se, Zn, and Cu was 0.083 ± 0.026, 0.629 ± 0.413, and 0.152 ± 0.042 μg/mL, respectively. The presence of the Cd and Pb was found in all serum samples. The mean concentration of these metals was 0.0009 ± 0.0008 and 0.018 ± 0.016 μg/mL, respectively. Analysis of correlations between Se and toxic metals showed a negative and significant (P < 0.05) relationship between selenium concentration and lead and cadmium concentration in the serum of the animals studied, with correlation coefficients of r = -0.595 and r = -0.618, respectively. For copper and zinc, this relationship was also negative but not significant (r = -0.255 and r = -0.203). Our study demonstrated that the level of toxic metals decreased as serum selenium concentration increased. It seems necessary to conduct further research on the interactions between these elements in blood, serum, and target organs concomitantly with the determination of their intake.

W, Cobuci J. Efeito da suplementação com diferentes níveis de selênio orgânico e inorgânico na produção e na composição do leite e no sangue de vacas em lactação

Avaliaram-se o efeito da suplementação de selênio, na dieta ofertada aos animais, sobre a concentração do mineral no sangue e no leite e as alterações nas características físico-químicas, contagem de células somáticas (CCS) e produção de leite. O experimento durou 63 dias, dos quais os primeiros 21 foram pré-experimental. Foram utilizadas 32 vacas em lactação da raça Jersey, as quais apresentavam, ao início, peso corporal de 402,5+58,4kg, escore de condição corporal de 3,19+0,31, produção de leite de 10,4+2,1kg e número de dias em lactação de 141,4+69,3. Os tratamentos foram: sem suplementação (grupo-controle); com suplementação de selênio inorgânico 0,3 (dieta-padrão + 0,3mg selenito de sódio/kg de concentrado - SI0,3); com suplementação com selênio orgânico 0,3 (dieta-padrão + 0,3mg seleniometionina/kg de concentrado - SO0,3) e com suplementação de selênio orgânico 0,6 (dieta-padrão + 0,6mg seleniometionina/kg de concentrado - SO0,6). As quantidades totais de selênio das dietas foram, respectivamente, 2,38; 4,18; 4,18 e 5,98mg/dia para os tratamentos controle, SI0,3, SO0,3 e SO0,6. O delineamento experimental foi o completamente ao acaso. O número de dias em lactação e os valores obtidos no início do experimento foram usados como covariáveis. Foram realizadas avaliações da produção de leite, do peso, da condição corporal, da composição do leite e do sangue nos dias 0, 14, 28 e 42 do período experimental. Entre os tratamentos, não foram detectadas alterações quanto à produção de leite, peso, condição corporal, características físico-químicas e microbiológicas do leite, e perfil bioquímico do sangue, exceto em relação à concentração de selênio no sangue entre o tratamento-controle e os tratamentos suplementados. Não houve diferenças quanto aos teores de selênio no sangue entre as fontes de selênio e as doses. Os teores de selênio no sangue evoluíram distintamente durante o experimento conforme a dose e a fonte. A suplementação com selênio não alterou os demais componentes do leite e do sangue.

Developing selenium-enriched animal feed and biofuel from canola planted for managing Se-laden drainage waters in the westside of central California

We studied the reuse of selenium (Se)-laden effluent for producing canola (Brassica napus) and subsequent bioproducts in central California. Canola was irrigated with poor quality waters [electrical conductivity (EC) of approximately 5 dS m(-1) sulfate-salinity, 5 mg B L(-1), and 0.25 mg Se L(-1)]. Typical seed yields were 2.2 metric tons ha(-1). Seeds were processed for their oil, and transesterified to produce ASTM-quality biodiesel (BD) blends. The resulting Se-enriched seed cake meal (containing approximately 2 mg Se kg(-1) DM) was used in a dairy feed trial. Seventy-two Jersey and Holstein cows, 36 respectively, were fed Se-enriched canola meal as 6.2% of their daily feed ration for five weeks. Blood and milk samples were collected weekly and analyzed for total Se. This study showed that Se-enriched canola meal did not significantly increase total blood Se content in either cow breed. Milk Se concentrations did, however, significantly increase to safe levels of 59 microg Se L(-1) and 52 microg Se L(-1) in Jersey and Holstein cows, respectively. The production of BD 20 biofuels and Se-enriched feed meal from canola irrigated with poor quality waters may help sustain similar phytomanagement strategies under Se-rich conditions.

Short-term effects of selenium supplementation of cows' feed on the content and distribution of selenium, copper and zinc in bovine milk, whey and blood plasma

The effect of selenium supplementation of feed on the Se content in bovine milk, whey and plasma, and on the distribution of Se, Zn and Cu in whey and plasma was investigated. In a cross-over study two groups of cows were given a basal feed with 0·16 ppm selenite (approx. 3 mg Se/d) with or without 25 mg yeast Se/d for 2 weeks. In the supplemented group the Se content increased 10-fold in milk, 10-fold in whey and 2-fold in plasma, and after the cessation of the supplementation, selenium in milk decreased with a calculated half-life of 3·5 d. In another experiment, two groups of cows were given either 100 mg yeast Se/d for 1 week or only the basal feed. The increase in Se content in both whole and defatted milk was 40–50-fold, and in whey it was approx. 20-fold. Size-exclusion chromatography of whey using inductively coupled plasma mass spectrometry for detection showed that supplementation increased the proportion of Se in the β-lactoglobulin-α-lactalbumin fraction. Distribution of Cu and Zn was essentially unaffected. In plasma, supplementation increased the Se content in all major Se fractions like selenoprotein P, albumin and low-molecular-weight compounds, but the distribution profiles of Zn and Cu underwent no major changes. The study showed for the first time the rapid kinetics of the Se increase and decrease in milk after the initiation and cessation of supplementation, respectively, and the preferential appearance of Se in the β-lactoglobulin-α-lactalbumin fraction of whey. Milk highly enriched in selenium will be a useful tool for different research purposes.

Blood selenium associated with health and fertility in Norwegian dairy herds

A survey of blood selenium (Se) concentrations in Norwegian Red heifers and dry period cows was conducted to reveal possible association to management, feeding, health and fertility. Selenium contents were determined in 254 herd blood samples consisting of pooled samples from individual non-lactating animals from herds in 5 counties. The Se concentrations showed a normal distribution with mean 0.09 μg Se/g blood, with a standard deviation (SD) of 0.05, and ranged from 0.02 to 0.23 μg/g, with 50 % of the samples being between 0.06 and 0.11 μg/g. The herds with Se concentrations below 0.06 μg/g were smaller (21.4 ± 8.7 cow-years) than those with Se levels above 0.11 μg/g (27.5 ± 14.1 cow-years) (P < 0.01), but there were no differences in milk yield, incidence of replacement, proportion of animal culling, amount of concentrate or grass silage as percentage of energy consumption between the groups. Treatment registration records showed a tendency that more animals in the low Se herds were treated for all the diseases included in this investigation (64.8 animals per 100 cow-years) than those in the high Se herds (57.5 per 100 cow-years), while no such differences were revealed for individual disorders. There was, however, a significant difference in bulk milk somatic cell counts (BMSCC) between low and high Se herds, their values being 137 000 and 155 000 cells/ml, respectively. This difference was significantly influenced by herd size. Furthermore, a total of 4 916 lactations were analyzed from individual health and fertility recordings, including 2 934 first lactations and 1 982 later lactations. The present study revealed a reduced incidence of disease treatment with increased Se concentrations from 0.02 to 0.23 μg Se/g blood. In this regard, there seemed to be an optimum of 0.10 to 0.15 μg Se/g for all types of mastitis treatments summarized, and for treatment of retained placenta. Thus, herd Se concentrations below and above these values was connected with increased probability for sum mastitis and retained placenta, reflecting the effect of the quadratic term of Se. The cow (composite) milk somatic cell count (SCC) was lower in lactations from low Se herds than in high Se herds with a marked SCC increase in the Se concentration interval from 0.11–0.13 μg/g blood. In conclusion, heifers and dry period cows in Norway are low in blood Se content and there seems to be a positive association between increased blood Se concentration pre partum and decreased incidence of mastitis, ovarian cysts and anoestrus/silent oestrus post partum.