Acta Veterinaria Scandinavica 2007, 49:1 http://www.actavetscand.com/content/49/1/1 In Fig. 2, the development in mean plasma vit E, mean plasma Se and mean body weight is shown for each herd. Analysed litter by litter, the fall in plasma vit E from day - 1 to day 4 was statistically significant by student's t-test (paired analysis) in 10 of the 15 litters in herds 2 to 6, but not in any of the litters in herd 1. The rise in plasma Se from day -1 to day 4 was statistically significant in 16 of the 18 litters studied. The average daily weight gain in all pigs from day -1 to day 18 was 384 g/day, with standard deviation 147 g/day and range 147 to 753 g/day. Throughout the study, mean body weight in herd 1 was significantly higher than in all the other herds. Results of the variance component analysis are shown in Table 2, with and without herd 1 included. In the 6 sows analyzed, the mean whole blood Se concen- tration at day -1 was 0.20 µg/g, and the average ratio plasma Se/blood Se was 1.07. In the 12 weanling pigs, the average ratio plasma Se/blood Se was calculated for each sampling day, and varied between 0.83 and 0.91. There was a strong correlation between plasma Se and blood Se in the weanling pigs (r = 0.90, p < 0.0001), but much weaker correlation in the sows (r = 0.49, n.s.). Discussion The mean plasma concentration of vit E in piglets at day - 1 in this study was 2.6 µg/ml, or about 65% of the mean plasma level in their sows. This relative ratio between pig- let and sow plasma levels at weaning is in line with find- ings in the feeding study of Håkansson et al. [2]. The plasma vit E level at day -1 was highly variable, both in sows and in their piglets (Fig. 1), but there was not statis- tically significant correlation between plasma vit E in the sows and in their piglets. This seems surprising, but is compatible with the finding of Håkansson et al. [2] that plasma vit E levels in piglets, both at 3 days and 5 weeks of age, were primarily correlated to the vit E levels in colostrum. The observed fall in plasma vit E after weaning is in line with the results reported by several authors [2,3,6,16]. The regression model analysis did not show any significant differences in plasma vit E between the three sampling days after weaning. The apparent turn in the mean plasma vit E level around day 8 (Table 1) may therefore be fortu- itous, or it may reflect a real trend that could not be con- firmed statistically due to the limited size of the study. Håkansson et al. [2] found a similar reversion, with a rise in plasma vit E levels from one week to four weeks after weaning. The fall in plasma vit E from day -1 to day 4 was confirmed in 5 of the 6 herds in this study. In herd 1, how- ever, the mean vit E level changed very little after weaning (Fig. 2). In this herd, the piglets were uncommonly old (48 days) and well developed at weaning, as reflected in their bodyweights. Possibly, these pigs had already started eating some of the sow's feed, and may have been "half- weaned" already at day -1. However, the possibility that the difference may also reflect age-related physiological changes in vit E absorption cannot be excluded. In herds 2–6 the average weaning age was 34.9 days. The average weaning age in the entire In-gris litter recording system in the same year was 35.0 days [13]. When herd 1 was excluded, differences between litters contributed more to the total variation of plasma vit E at weaning in the variance component analysis than the herd differences did (Table 2). This indicates a certain effect of the sows on piglet plasma vit E levels, in spite of the lack of correlation between litter and sow plasma lev- els at weaning. In the variation of the change in plasma vit E from day -1 to day 4, however, the litter effect was smaller than the effect of herds, even with herd 1 excluded. This may imply that feeding and management factors in the herds influence the size of the fall in plasma vit E after weaning more strongly than they influence the plasma level at weaning. The mean plasma Se concentration of the piglets at day -1 was 0.08 µg/g, or 36% of the mean plasma Se in the sows. This result is quite similar to that observed by Mahan & Moxon [10] with sows fed a diet supplemented with 0.1 mg Se/kg. The individual variation in plasma Se concen- trations at weaning was much smaller than for vit E (Fig. 1). This may partially explain the lack of significant corre- lation between plasma Se in the sows and their litters. The significant rise in plasma Se from day -1 to day 4, and the further, more limited rise throughout the observation period, are in line with the findings of Mahan & Moxon [10] in weaned pigs fed a diet supplemented with 0.3 mg Se/kg. As for vit E, the individual variation between the pigs dominated over litter or herd effects both in the regression model and in the variance component analysis. For the Se variables, however, the contribution to the total variation was more evenly distributed between herd and litter effects, though litter effects were somewhat more important when herd 1 was excluded (Table 2). The analysis of whole blood Se in a number of samples was done to control for possible variation between plasma and whole blood Se concentration. Because of the high amount of glutathione peroxidase in erythrocytes, analysis of Se in whole blood is relevant to Se status [17], and may differ from the plasma values. In this study, the correlation between whole blood and plasma Se was very high in the piglets, but weaker in the sows. There is no general agreement in the literature on limits between adequate, marginal and deficient plasma levels in pigs, neither for vit E nor for Se. In Norway, the Page 5 of 9 (page number not for citation purposes)