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Volume 67, 1938
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An Iodine Survey of New Zealand Live Stock. Part IV. Sheep of the Marlborough, Nelson and Westland Districts and Review of the South Island.

[Read before Wellington Philosophical Society, September 22, 1937; received by the Editor, October 7, 1937; issued separately, March, 1938.]

This paper completes the iodine survey of the animal thyroids from the South Island of New Zealand, previous results being published by Mason (1933) and Mason and Waters (1936). The same method has been used throughout the series.

By taking thyroid glands from lambs slaughtered at freezing works and then obtaining further information from the owner it has been possible to obtain sufficient glands numerically to get a sample fully representing a flock and sufficient samples to represent a district. This could not be done otherwise since taking the thyroid necessitates the death of the animal and large numbers of glands are required because in the size and iodine content of the gland considerable variation is possible between individual animals.

As described in previous papers the information collected from the owners of the animals included exact location of farm, soil description, feeding and licks supplied. The wide variations found to occur in glands from the same farm even when taken in the same season has prevented any detailed attempt to correlate iodine content of the thyroid with any of the data collected. Such anomalies do not necessarily indicate that the method of estimating iodine supply is faulty but are most likely due to seasonal variations in iodine content of the glands and in the animals' food supply. Possibly this is further confused by the age of the animals since one draft may consist of young animals while a subsequent draft may include also older lambs which have been slower to reach the standard required by the buyer for the freezing works. Unfortunately no record was taken of the age of lambs slaughtered. By taking a large number of samples it is claimed that results have been obtained which are reasonably representative of each area. All animals used were bred and reared on the areas mentioned and had only food grown on that area.

In the results now presented soil descriptions, geology, and type of country have been confined to a general description of each area surveyed. In this it is hoped that the aim of the investigation as indicated by the title of this paper is still being kept and that the results differentiate between the areas where iodine is available to grazing animals in sufficient quantity and the areas where the supply of iodine is such that the health of the animals may be affected and under adverse conditions sporadic cases of goitre and loss of lambs may occur.

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In previous papers results were tabulated in the naturally bounded areas from which the samples were taken. This procedure was followed here except that results are given for groups of farms instead of individual holdings. Each group is usually a small farming district in which the farms are located on similar country and worked under similar conditions. The groups are given names that will show their location and the extent of the area represented.

The average values for each group are an indication of the status of that area in regard to iodine supply. However, an average may be very misleading, so advantage has been taken of the limited range of the iodine values found to demonstrate further the “spread” or distribution of the samples between certain iodine percentage groups. The first group, less than .10 per cent. iodine, gives the number of samples found to be definitely deficient in iodine. This figure has been considered by Marine and Lenhardt to be the critical value or minimum percentage of iodine below which the gland cannot function normally. The second group, .10 to .19 per cent., contains those samples that are low. The third group, .20 to .29 per cent., comprises samples that must be regarded as satisfactory for New Zealand. The fourth and fifth groups contain samples high and exceptionally high for New Zealand lambs, though even the highest would probably be an average value for Australian stock. The tables, then, indicate the average value for each group of farms and demonstrate the extent to which the average is representative and whence it is derived. Ideally, where conditions are fixed within narrow limits, the large majority of samples would fall into one group with odd samples in the adjoining groups. This is demonstrated in Table III, Wataroa area. Figures shown in Table II, Collingwood area, indicate that conditions here are varied and that the area cannot be adequately represented by an average. In the last column in each table, averge figures are given for the dry weight of the glands, which follow in a general way the accepted rule that the size of the gland varies inversely with the percentage of iodine. All iodine percentages are calculated on the dry weight.

Marlborough.

This district comprises the north-eastern portion of the South Island. To the southwest the country is mountainous so that the chief sheep raising areas are on the lower foothills near the coast and the valleys of the Wairau and Awatere Rivers.

Sounds Area and Adjacent Farms.

Sheep are raised on scattered farms on the hillsides and islands of the area, which is a maze of drowned river valleys, backed by hills, mainly of greywacke and schist. The average yearly rainfall is from 40 to 80 inches. The average figures are good and with the exception of Queen Charlotte Sound are distributed about the third group.

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Table I. Marlborough.
Classification of Samples. Average for Area.
Farming Areas. V. Low. Low. Fair. High. V. High. Iodine per cent. dry weight. Dry weight per gland grams.
up to .09 .10 to .19 .20 to .29 .30 to .39 .40 and over.
Sounds:
D'Urville Id. 1 .29 .84
Rai Valley 2 .24 .74
Havelock Subn. 1 1 .25 .97
Keneperu Sd. 1 1 2 1 .34 .49
Q. Charlotte Sd. 1 1 .17 .92
Pt. Underwood 1 .24 1.02
Koromiko 1 1 1 .24 .83
Totals and Mean 1 3 7 4 1 .25 .83
Wairau River: Upper Valley 3 1 .18 .96
Kaituna 1 2 .24 .85
Tuamarina 1 2 3 1 .20 .83
Spring Creek 2 1 1 .25 .48
Blenheim 1 2 1 .15 .89
Totals and Mean 3 9 6 2 2 .20 .76
Awatere River: Jordan 2 2 1 .15 .91
Marama 1 2 7 2 2 .26 .73
Dashwood 1 2 .31 .58
Totals and Mean 3 4 9 4 2 .24 .78
East Coast: Grassmere 4 2 .42 .60
Ward 1 2 2 .31 .97
Totals and Mean 1 2 4 4 .37 .77
Wharanui 3 .05 1.17
Kaikoura 4 5 1 .13 .88
Totals and Mean 7 5 1 .11 .98

Wairau River Valley.

This river rises in greywacke mountains and the samples are mainly from farms on alluvium from this and from the schist and Tertiary formations of the lower reaches. The rainfall is below 40 inches over most of the area. With the exception of Tuamarina and Kaituna, the samples of the areas and the totals for the district fall in the second group. The average for the area is only fair and the samples are very varied. Blenheim is uniformly low and one sample contained only .03 per cent. iodine. Several of the lower samples were taken from salty river flats right on the coast.

Awatere River Valley.

This valley resembles the Wairau Valley. Most of the farming is on papa formation round Marama and the average iodine content of the glands is fair. Higher up the valley round Jordan the average value drops to one half and a greater proportion of the samples are classed as deficient.

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East Coast.

This district is on a mixed geological formation and the average rainfall is 30 to 40 inches. The most noticeable feature of the figures is the low value obtained from Wharanui. This area is to the south of the others and is more hilly. The samples from the rest of the district are particularly high in iodine. One sample from Grassmere, not included above, was from lick-fed stock and showed 60 per cent. iodine. Kaikoura is a coastal district much further south on a small alluvial plain at the foot of greywacke mountains. The rainfall is about 50 inches. The samples are low in iodine and resemble those of the adjoining North Canterbury district.

The Marlborough area is mainly well supplied with iodine with the exception of the portion from Wharanui southwards and round Blenheim and the upper Awatere Valley.

Nelson.

This province at the northern end of the island is mountainous and of very varied geological formation. Sheep farming is practised on the coast of Golden Bay, on the coastal plains and river valleys of Tasman Bay and on the upper valleys of the Buller River and its tributary, the Inangahua River.

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Table II. Nelson.
Classification of Samples. Average for Area.
Farming Areas. V. Low. Low. Fair. High. V. High. Iodine per cent. dry weight. Dry weight per gland grams.
up to .09 .10 to .19 .20 to .29 .30 to .39 .40 and over.
Golden Bay:
Collingwood 1 1 1 1 3 .33 .60
Takaka 1 4 .21 .47
  Totals and mean 2 1 5 1 3 .28 .55
Tasman Bay:
Moutere 2 3 2 .33 .47
Richmond 4 4 1 .22 .61
Whakapuaka 1 .32 .47
Thorpe 2 3 1 .22 .46
Spring Grove 2 3 2 .25 .63
Wakefield 3 4 2 .23 .61
Motupiko 5 1 1 .20 .56
  Totals and mean 16 17 11 2 .24 .56
Buller Valley:
Glenhope 1 1 .21 .55
Howard 1 1 2 1 .20 .50
Gowan 2 1 .19 .49
Owen R. 1 3 .12 .89
Tutaki 2 3 2 .16 .56
Matakitaki 3 2 .11 .86
Matiri 1 3 .11 .80
Murchison 1 2 .09 .83
Maruia 4 5 .10 .91
Inangahua 1 .12 .53
Reefton 4 2 .10 .89
  Totals and mean 17 25 6 1 .14 .75
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Golden Bay.

These samples are from hilly country mostly of papa and limestone formation. The annual rainfall is about 80 inches. The average value for the area is good although samples were received in each group

Tasman Bay.

This is a more closely settled area and a larger number of samples was available. The geology of the district is complicated and the soil types very numerous. The rainfall varies from 40 to 70 inches. It is notable that no glands occur in the first group. From Moutere better glands including two exceptionally high glands were received. The distribution in the district is close to the average value, .25 per cent., which is fair. In the Motupiko area, although the average value .20 per cent. is fair, most of the glands were below this figure so that the area must be regarded as less satisfactory than the rest of the district. This area is at the head of the Motueka River and is adjacent to the Buller area.

Buller Valley.

The Buller is a large river which rises in schist formation, flows through Miocene country upon which most of the farms are situated and a belt of granite in the Maruia Valley area. The rainfall is about 80 inches.

The glands from this district give an average iodine content of .14 per cent. on the dry weight, which is roughly half that for the rest of the Nelson district. It is noticeable that the distribution is shifted towards the columns to the left of the table. One third of the glands were below the critical value. Most of the glands come into the second group and from Matakitaki downwards no glands were received containing more than .19 per cent. iodine.

One sample taken at Four Rivers, Murchison, was just above the critical value. Since this sample was taken, two greatly enlarged lobes of pig thyroid were received from the same farm. Upon arrival the larger lobe weighed 216 grams, dry weight 29 grams, iodine in dry weight .009 per cent. The smaller lobe weighed 41 grams wet, 7 grams dry, iodine .010 per cent. A sample of clay said to be greedily sought after by stock was received from Owen River, above Murchison. On analysis this clay was found to contain 2,600 gamas iodine per 100 grams. This is roughly 10 times as much iodine as is usual in North Island soils low in iodine and is equivalent to a lick containing one ounce of potassium iodide to the ton. Two samples of thyroids from Lake Rotoiti are included in the Howard area results. The first was from lambs reared at the foot of the lake and the dry glands weighed .56 grams and contained .20 per cent. iodine. The second sample, from the head of the lake, weighed .72 grams per gland and contained .09 per cent. of iodine. The owner stated that the lambs from the head of the lake were always the better lambs. It seems that the rapid growth of these lambs has resulted in depletion of the iodine of the thyroid and therefore it is desirable that larger supplies should be made available so that the iodine may rapidly be replaced in the gland.

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The Nelson district therefore is divisible into two distinct parts. The northern portion is well supplied with iodine. Motupiko and the Buller Valley, however, are definitely low in iodine and goitre is to be expected to occur.

Westland.

This is a narrow province where the land rises steeply to the Southern Alps and most of the farms are located on flats and river valleys of alluvium derived from the schistose formations of this side of the mountains. The prevailing wind is north-westerly and there is heavy precipitation which varies from 80 inches in the Grey Valley to 150 inches in the south.

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Table III. Westland.
Classification of Samples. Average for Area.
Farming Areas. V. Low. Low. Fair. High. V. High. Iodine per cent. dry weight. Dry weight per gland grams.
up to .09 .10 to .19 .20 to .29 .30 to .39 .40 and over.
Grey Valley:
Ikamatua 4 6 1 1 .14 .88
Kopara 3 7 1 .13 .89
Totara Flat 9 5 .08 1.28
Ngahere 4 1 .16 .92
  Totals and mean 16 22 3 1 .12 1.06
Coastal Plains:
Kumara 2 1 .18 .83
Koiterangi 3 11 3 .15 1.01
Ross 7 2 .16 .88
Harihari 9 6 .18 .74
Wataroa 3 23 3 2 .16 .85
Waiho 1 4 .13 .95
Waiheka 5 7 .11 .86
Bruce Bay 1 .19 1.34
Okuru 2 .27 1.07
  Totals and mean 12 64 17 2 .16 0.88

Grey Valley

This is a wide river valley of mixed alluvium derived from schist, greywacke and granite of the surrounding mountains. A large number of glands were received from this district and enlarged glands have been reported from time to time.

Again the distribution is well towards the left as few of the samples were above .19 per cent. iodine. The samples from Totara Flat may be subdivided further. Four samples from the western bank contained between .10 and .19, average .12 per cent. iodine. Ten samples from the eastern bank averaged .07 per cent. iodine, one being .15 per cent. and the rest between .04 and .07 per cent. The eastern bank is the alluvial flat between the Grey River and its tributary the Ahaura River. In no other area surveyed have samples been predominantly so low.

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The Grey Valley is probably in greater need of iodine than any other district in the island.

Coastal Plains.

Down this coast sheep farming is practised usually on plains and river flats in well-defined areas. In the past the country has been heavily bushed and is usually still rough pasture. The rainfall is high and amounts to 150 inches a year in parts.

The results from the area are remarkably uniform. In all 95 samples were analysed, 93 of which were between .09 and .31 per cent. iodine and 74 between .09 and .19 per cent. One sample, not tabulated, from Ross was from a farm described as being entirely old mining tailings. This sample gave the remarkable figure of .50 per cent. iodine which is highest in the district and comparable with the highest of the Nelson samples. As would be expected, the dry weight .48 grams was the lowest in the district. Five samples included in those from Koiterangi were taken from one farm where iodised licks were used. These samples were slightly lower in iodine and larger than other samples from this area.

Westland, especially the Grey Valley, must be classed as an area low in iodine where outbreaks of goitre may be expected.

Graphical Presentation of Results.

As in the paper by Mason and Waters (1936) the results are presented in a cumulative distribution-diagram as used by Sykes (1934) and described by him as follows:—

“This is a modification of the ogive (Fisher, 1927), in which the scale is so adapted that a normal distribution results in a straight line. A complete explanation of this type of graph is given by Dufton (1930). The points are obtained by taking the percentage of the samples as ordinates, which lie on or below the different values shown as abscissae. The more nearly normal the distribution is, the more nearly straight will be the curve drawn through these points, the more upright the curve, the closer the limits of variation, and if on one diagram two or more curves are drawn the nearer they lie the more nearly identical are the results they represent. If they lie distinct from one another there is a significant difference in the results.

“The value on the curve, corresponding to the 50 per cent. mark, is the median, half the samples having more and half less than this value. If the distribution is normal, then this value will also be the mean or average. The chief advantage of this type of presentation over the more familiar histogram lies in the greater facility with which several sets of figures can be represented in one diagram.”

Results from all three provinces are shown in Figure 1.

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Fig. 1.

Marlborough.

The curve is based on 73 samples and does not include the Kaikoura results. The flat form of the curve indicates a wide variation in conditions, some areas being very high while others are low in iodine. Twelve per cent. of the samples are shown to be over .4 per cent. iodine and the same percentage below .10 per cent.

Kaikoura.

The curve representing 10 samples from this district shows the resemblance between this and the Grey Valley areas.

Nelson.

As described above the samples from the northern part of the district are noticeably higher than those from the Buller Valley. The two areas are shown separately. The curve for 58 samples from Nelson resembles that for Marlborough, but is rather more upright,

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as there is less variation between the samples. Five per cent. of the samples are below .10 per cent. and 5 per cent. above .4 per cent. iodine.

Buller Valley.

This curve (49 samples) clearly shows the difference between this area and the rest of Nelson. Forty per cent. of the samples are below .10 per cent. and 90 per cent. below .22 per cent. iodine. The curve may be taken as typical of country where the available iodine is low.

Westland.

The results for the Grey Valley and the rest of the district are shown separately.

The curve for Westland (95 samples) is more vertical than the Nelson curve and shows the greater uniformity of the samples. Approximately 15 per cent. of the glands are below .10 per cent. iodine and these are mostly about .09 per cent. Ninety per cent. of the samples are below .24 per cent. iodine. The curve resembles those for the Buller and Grey Valleys. The Grey Valley curve is seen to be similar to the Buller Valley curve but with lower iodine values throughout. Ten samples from Totara Flat have been plotted to show how low this area is in iodine and to demonstrate the type of curve to be obtained when a small uniform area is sampled. Ninetenths of the samples contain from .05 to .07 per cent. iodine, giving a nearly vertical curve for that range.

Summary.

The Marlborough district is mainly well supplied with iodine with the exception of that portion south of Ward, an area round Blenheim and the Upper Awatere Valley.

The northern part of the Nelson district is well supplied with iodine. The area round Motupiko and more especially the Buller Valley area are definitely low in iodine.

Westland district as a whole is low in iodine, while the Grey Valley is very low.

These areas may be arranged in descending order of iodine content as follows:—Marlborough, Nelson, Westland, Buller Valley, Grey Valley.

Review of Results from the South Island.

In Figure 2 these are presented in a cumulative distributiondiagram. As many of the curves were nearly identical some have been omitted and only sufficient shown to represent the general characteristics of all districts.

The Otago results form a flat curve which indicates wide variations in the district. About 8 per cent. of the glands are deficient. This percentage is higher than that for Nelson and almost identical

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Picture icon

Fig. 2.

with that for Canterbury. On the other hand 20 per cent. of the samples contained over 0.4 per cent. iodine—a greater proportion of high samples than to be found in other districts. The Nelson curve is slightly more vertical showing less variation in Nelson than in Otago samples and fewer glands are extremely high or low. The Marlborough curve is similar to that for Nelson and would lie between the Nelson and Otago curves. Banks Peninsula, a small uniform district, gives a curve similar to, but still more vertical than that for Nelson. These areas may all be classed together and are broadly all satisfactory in regard to iodine supply.

Canterbury in the incidence of low samples resembles Otago, but the absence of samples of high iodine content produces a more vertical curve. This curve represents all samples produced on alluvium under conditions of low rainfall. The area is an intermediate one which is low in iodine yet few glands are markedly deficient.

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Westland, Southland and the Grey Valley in this order are progressively lower in iodine and are typical districts where outbreaks of goitre are liable to occur. Actually while Westland gives a slightly higher proportion of deficient samples than Otago, only five samples containing more than .25 per cent. iodine are found in Westland, whereas in Otago 50 per cent. of the samples are above this figure. The Buller Valley curve closely resembles that for Southland, while Kaikoura may be classed with the Grey Valley. Totara Flat is an extreme example of an area low in iodine.

These areas as grouped above have been suitably marked on an outline map of the South Island, Figure 3.

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Fig. 3.

Conclusions.

Otago, Marlborough, Nelson and Banks Peninsula are high and are approximately equal in iodine status.

Canterbury is lower in iodine than these areas just mentioned.

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Westland, Southland, Buller Valley and Grey Valley are areas deficient in iodine and where occasional outbreaks of goitre are to be expected.

Summary.

An iodine survey has been made of the South Island of New Zealand based upon the iodine content of thyroid glands taken from lambs killed for export.

The island has been divided into naturally bounded areas and these have been classified according to iodine status. This has been shown on a map.

The author wishes to thank Mr. B. C. Aston, late Chief Chemist, Department of Agriculture, under whose direction this work was commenced and performed, for helpful advice and criticism. Thanks also are due to Mr R. E. R. Grimmett, Chief Agricultural Chemist, Department of Agriculture, for advice in the later stages of the work, and the officers of the Live-stock Division of the Department, who arranged the collection of samples and data.

References.

Mason, Ethelwyn M., 1933. An Iodine Survey of New Zealand Live-stock, Part I. Sheep and Lamb Thyroids from Otago and Southland, Trans. N.Z. Inst., vol. 63, pp. 373–388.

Mason, Ethelwyn M., and Waters, D. F., 1936. An Iodine Survey of New Zealand Live-stock, Part III. Sheep of the Canterbury District, Trans. Roy. Soc. N.Z., vol. 66, pp. 143–177.

Sykes, P. H., 1934. An Iodine Survey of New Zealand Live-stock, Part II. Sheep of the Wairarapa District, Trans. Roy. Soc. N.Z., vol. 64, pp. 17–34.