page 3

Each soil sample comprised a representative sample drawn from a mix of approximately 20 slices of dry soil dug with a stainless steel trowel and taken at equal spacings along a W shape spanning an area of approximately five acres; the area being representative of the region grazed/cropped by the TSE affected mammals under study.
Each slice was drawn from the top soil to a depth of 6 inches, if possible, taking care to avoid inclusion of root material/surface organic matter and drawing of samples near gateways, roadsides, animal dung, disturbed/excavated or polluted terrain, etcThe 20 slices were put into plastic bags and mixed together into an even homogenate, from which a further sample of no more than 300 g was drawn and placed into a small cardboard box which was sealed, labelled and dispatched to the UK Laboratories of Natural Resources Management (NRM), Coopers Bridge, Braziers Lane, Bracknell, Berkshire, RG42 6NS. Soil samples were laid out on drying trays after arriving at the laboratory and dried in forced air flow cabinets for 12-18 h until dry. The temperature was maintained below 32° for this period and the air was constantly dehumidified. Any solid rock granules were removed from samples before being ground to pass a 2 mm mesh using a hammer mill. The mill was flushed between samples using a small portion of the next sample. Samples required for total mineral analysis were subsequently ground to pass a 0.5 mm mesh. Samples were then presented for analysis - the analytical procedures for each mineral are described on Table 3, which were conducted in accord with the standard analysis procedure of the Ministry of Agriculture, Fisheries and Food. Each plant tissue sample comprised a 200g sample representing tissue collected from approximately 10 pickings taken at equal spacings in a W shape across an area of approx five acres which was representative of the region grazed/cropped by the TSE mammals under study. Each picking involved taking tissue (leaves, stem and flowerheads) from the upper half of the plant, and involved species of grasses, plants and/or shrubs that commprised the overall dietary intake of the mammals under study according to local intelligence. Samples were picked dry and away from roadsides, gateways, animal manure, polluted or disturbed terrain, whilst care was taken to avoid the inclusion of any root material or soil. The tissue was packed into plastic bags which were lightly sealed, labelled accordingly and dispatched to the laboratories of NRM.
Samples were thoroughly washed with deionised water, in a plastic sieve, on arrival at NRM Ltd. After removal of all roots and soil, the samples were spread evenly on a drying tray and dried in a 90 degree C oven to constant weight, and then ground by a Christy Norris mill. A small portion of the sample was used to flush the mill, before collection of the ground material. The samples were then prepared for analysis by dry ashing for non-volatile elements and wet digestion in aqua/regia for volatile elements (e.e. selenium, etc).
The analytical procedures for each mineral is listed on Table 1, and these were carried out in accord with MAFF's standard analysis method.

RESULTS: HIGH LEVELS OF MN CATION FOUND IN TSE ASSOCIATED FOODCHAINS

1. Icelandic scrapie cluster

The scrapie endemic valleys in North Central/Eastern Iceland where sheep have suffered from a high incidence of scrapie for many decades demonstrated a consistent two and a half fold greater concentration of the divalent cation, manganese, in herbage at 200 mg/kg dry basis in relation to the 80 mg/kg average level found in the regions where scrapie has never been recorded (Table 1) (Fig.2).
This could be part related to the higher intensity of precipitation/snow cover (e.g., perhaps linked to the eco-impact of the annual snow thaw run off) recorded in the scrapie endemic regions (personal communication; S. Sigurdarson) in combination with the high organic matter content of the peat soils which favours increased waterlogging and soil acidity, rendering Mn more freely available for plant uptake (31, p. 14/15/166).
Furthermore, the snow cover and short daylight interval of the Icelandic winters could favour an increased amount of Mn in herbage tissue in line with the recorded effects of shade on increasing the Mn content of leaves (65).

Table 1 Analyses of herbage samples drawn from farms in the scrapie-endemic and scrapie-free regions of Iceland on 30/8/98 to 25/9/98; in mg/kg dry basis, unless marked % w/w dry basis

2 Vidivellir	1.56	0.20	1.26	0.19	0.57	89	2.4	0.05	118	32.7	2.68	0.018	0.15
3 Desjarmyri	2.35	0.28	1.40	0.24	0.39	228	3.4	0.32	599	47.6	0.56	0.032	0.40
4 Hrafnabjorg	3.15	0.36	1.63	0.24	0.44	107	5.0	0.06	164	27.8	0.41	0.012	0.28
5 Hofsa	2.64	0.30	1.33	0.18	0.41	144	4.7	0.12	389	34.0	0.73	0.055	0.32
6 Ingvarir (M)	1.88	0.21	1.17	0.17	0.40	297	3.5	0.05	942	32.9	1.07	0.051	0.59
7 Ingvarir (L)	2.85	0.29	0.90	0.31	0.90	145	4.3	0.35	132	17.5	3.29	0.029	1.61
8 Ingvarir (H)	1.06	0.10	0.81	0.12	0.26	277	1.2	0.01	151	18.2	0.48	0.010	0.25
9 pvera (M)	3.53	0.37	2.47	0.24	0.47	275	5.9	0.10	611	44.7	0.92	0.037	0.58
9 pvera (L)	1.62	0.17	1.05	0.20	0.60	245	2.3	0.02	213	31.6	0.62	0.110	0.42
11 pvera (H)	1.61	0.10	0.75	0.16	0.40	127	2.3	0.01	846	21.9	0.64	0.002	0.95
12 Atlastadir	1.58	0.20	0.94	0.21	0.46	310	3.0	0.03	192	20.7	0.17	0.011	0.13
13 Vigdisarstadir	3.30	0.32	0.58	0.34	0.51	210	6.5	0.24	271	28.3	1.26	0.010	0.46
Av scrapie	2.26	0.24	1.24	0.22	0.50	200	3.4	0.10	373	30.5	0.99	0.032	0.50
Category	mean	low	mean	low	mean	high	very low	very low	mean	low	mean low	very low	high

Scrapie-free
14 Hjalp	1.73	0.21	1.18	0.29	0.84	89	2.3	0.03	303	34.4	0.51	0.077	0.40
15 Holmar	1.81	0.24	1.21	0.14	0.28	67	3.8	0.10	1285	24.2	2.20	0.021	0.76
16 Kvisker	2.10	0.25	1.62	0.38	0.77	100	3.2	0.08	98	122.3	0.86	0.030	0.16
17 Modruvellir	3.47	0.33	2.36	0.25	0.37	76	6.2	0.00	89	23.9	0.64	0.010	0.09
18 Modruvellir	2.52	0.28	2.34	0.17	0.31	69	6.2	0.01	61	14.2	0.38	0.010	0.23
19 Brakandi	1.90	0.18	1.71	0.17	0.33	96	2.1	0.00	85	16.4	1.26	0.020	0.14
20 Skriduklaustur	2.27	0.28	2.09	0.23	0.65	67	4.1	0.02	131	37.2	2.06	0.010	0.56
Av Sc-free	2.26	0.25	1.79	0.23	0.50	80	4.0	0.03	293	39.0	1.13	0.025	0.33
Category	mean	low	mean	low	mean	mean	low	very low	mean	low	mean	very low	high

Scrapie ?? in scrapie-endemic zone
21 Sakka	3.41	0.35	1.88	0.23	0.48	179	6.1	0.11	417	48.5	1.88	0.020	0.43
22 Brautarholl	2.28	0.26	1.35	0.21	0.52	235	3.3	0.06	93	23.0	0.84	0.010	0.11
23 Barka	2.85	0.34	1.65	0.20	0.39	135	3.6	0.02	153	33.1	0.84	0.023	0.10
Av Sc??	2.85	0.31	1.62	0.21	0.46	183	4.3	0.06	221	34.8	1.18	0.017	0.21
Category	mean	mean	mean	low	mean	high	low	very low	mean	low	mean	very low	high
Levels of Al/S/V/Ni/Cr/F/As/Cd/Pb/Sn were normal on all farms tested.

Fig. 2 Map of Iceland depicting sample sites and main scrapie endemic region (hatched). Numbered sample sites correspond to numbering of farms on Table 1.

Fig. 3 Map of Larimer County in Colorado Depicting location of sample sites across CWD endemic cluster region and where CWD affected cervidae have been found (58). Numbered sample sites correspond to numbering of locations on Table 3. Shaded circles represent CWD affected deer. Hatched circles represent CWD affected elk.

The recent fall in scrapie incidence in the scrapie-endemic regions must be partly due to the sharp decline in the total number of 'TSE susceptible' sheep due to the Icelandic government's scrapie slaughter policies (60. The fall could also be due to the virtual universal switch over from feeding hay to silage as winter fodder over the last ten years in Iceland. Various analytical studies have demonstrated increasing concentrations of Mn in the seed heads of grasses during the maturation process (31), confirming the fact that manganese concentrations are higher in hay than in silage (69); simply because it is customary to harvest grass for hay at a more advanced stage of maturity than the younger flowering stage required for the silage harvest. Hidiroglou et al. (66) measured serum Mn levels in different batches of cattle fed hay or silage, and concluded that the bioavailability of Mn is much greater in hay than in silage.


Copyright © Mark Purdey & Equofax 2002-2008 Comments and feedback to the webmaster		Design by Equofax Last updated 09-Feb-2007

2 Vidivellir

1.56

0.20

1.26

0.19

0.57

89

2.4

0.05

118

32.7

2.68

0.018

0.15

3 Desjarmyri

2.35

0.28

1.40

0.24

0.39

228

3.4

0.32

599

47.6

0.56

0.032

0.40

4 Hrafnabjorg

3.15

0.36

1.63

0.24

0.44

107

5.0

0.06

164

27.8

0.41

0.012

0.28

5 Hofsa

2.64

0.30

1.33

0.18

0.41

144

4.7

0.12

389

34.0

0.73

0.055

0.32

6 Ingvarir (M)

1.88

0.21

1.17

0.17

0.40

297

3.5

0.05

942

32.9

1.07

0.051

0.59

7 Ingvarir (L)

2.85

0.29

0.90

0.31

0.90

145

4.3

0.35

132