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The aim of this trial was to determine whether the selenium status of suckling calves could be improved by supplementing their dams' diet with organic Se instead of sodium selenite. A herd of 103 Hereford cows, which were on grass paddocks all year round, was divided into two groups. Both groups had free access to a mineral supplement that contained 30 mg of Se/kg; for one group the source of the Se was a Se yeast product, and for the other group the source was sodium selenite. The basal feed contained .02 mg of Se/kg DM. During the trial, the mean daily consumption of the mineral supplement was approximately 110 g/cow. The calving season started in the middle of March and ended in the middle of May. Blood samples were taken from 11 cows and their calves in the yeast group and from nine in the selenite group at the end of April and again at the beginning of June, and milk samples were taken at the same times. At both samplings, the concentration of Se in whole blood and the activity of glutathione peroxidase (GSH-Px) in the erythrocytes of the cows and calves in the yeast group were higher than in the samples from the animals in the selenite group. The same pattern was seen for plasma, except for the cows at the first sampling. The mean concentrations of Se in whole blood from calves in the yeast and selenite groups were 130 and 84 microg/L, respectively, and plasma concentrations were 48 and 34 microg/ L, respectively. Mean Se concentration in the milk from the yeast group (17.3 microg/L) was higher than that in milk from the selenite group (12.7 microg/L). There were significant correlations (r = .59 to .68) between the concentrations of Se in the cow's milk or cow's whole blood compared with Se concentrations in the calves whole blood and plasma or with the erythrocyte GSH-Px activity of the calves. The Se status of the calves in the selenite group was considered to be marginal, but the status of the calves in the yeast group was considered to be adequate. Supplementation of the suckler cows' diet with organic Se in the form of Se yeast rather than sodium selenite improved the Se status of their calves when the Se was mixed into a mineral supplement containing 30 mg of Se/kg. In practice, such supplementation would probably eliminate the risk of nutritional muscular degeneration in suckling calves.

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The Se concentration in maternal and cord whole blood and plasma was determined spectrofluorimetrically in: (1) 42 women at term and (2) 46 at preterm parturients, and in the placenta. The glutathione peroxidase (GSH-Px) activity was measured in red cells and plasma in maternal and cord blood of both groups. The Se concentrations and GSH-Px activities of the above-mentioned groups were compared with those of non-pregnant women. Whole blood and plasma Se concentration of parturients at term did not differ significantly from those of non-pregnant women (72.3 versus 80.3 ng ml-1 whole blood and 48.7 versus 56.2 ng ml-1 plasma). In preterm parturients, however, Se concentrations were significantly lower (61.1 ng ml-1 whole blood and 39.2 ng ml-1 plasma) when compared with term parturients. The Se levels in cord blood and plasma were similar to their mothers' Se concentrations. No difference was observed in placenta Se levels (130 ng g-1 wet weight in both groups). The same was true for glutathione (GSH): the concentration in maternal and cord blood of term and preterm parturients did not differ and varied from 2.43 to 2.50 mmol l-1 red cells. Red cell GSH-Px activities were similar in maternal and cord blood of both term and preterm groups and ranged from 14.3 to 15.7 U g-1 Hb. The plasma enzyme activity in the maternal blood of preterm parturients was significantly (p < 0.05) lower than that of mothers at term delivery. The GSH-Px activity in the plasma of cord blood was significantly (p < 0.001) lower in the preterm than in the term group. It is suggested that low Se levels in the blood of women at preterm delivery, as shown here, may be one of the causes of retinopathy and respiratory distress syndrome in preterm infants.