An Iodine Survey of New Zealand Live-stock. Part I. Sheep and Lamb Thyroids From Otago and Southland.

Transactions and Proceedings of the Royal Society of New Zealand, Volume 63, 1934, Page 373

An Iodine Survey of New Zealand Live-stock. Part I. Sheep and Lamb Thyroids From Otago and Southland. By Ethelwyn Mason. [Received by Editor, January, 1933; issued separately, June, 1933.] The existence of endemic goitre in New Zealand has long been recognised, and a great deal of work has been done in tracing its geographical distribution. Investigations of this nature in other countries, notably Switzerland and the United States of America, have justified the conclusion that one of the primary causes of simple goitre is a deficiency of iodine, hence the work carried out in this country, where there are a number of areas very low in iodine, would be expected to throw considerable light on the problem. In a general survey of New Zealand, C. E. Hercus, W. N. Benson, and C. L. Carter (1925) examined a large number of school children for thyroid enlargement, and made iodine analyses of soils and water samples collected throughout the country as representatively as possible. They concluded that, generally, the incidence of the disease is inversely proportional to the amount of iodine in the soil, and considered that the investigation fully sustained the hypothesis that goitre is caused by a deficiency of iodine. In a more detailed investigation of some of the North Island districts the work was continued by R. A. Shore and R. L. Andrew. They also found that, with the exception of certain anomalies, a general relation existed between the incidence of goitre and low soil iodine. The occurrence of goitre in wild and domestic animals, with an occasional outbreak of “cretinism” among lambs from certain districts, has shown the need for an investigation into the problem from an agricultural viewpoint. As plant iodine is dependent not on the total iodine in the soil, but on the “available” iodine, it is reasonable to suppose that the nature and type of soil would exert a definite influence on the iodine content of pasture, hence on the iodine intake of herbivorous animals. As the most important factor affecting the iodine of the thyroid gland is the iodine intake (Orr and Leitch), analyses of thyroid glands would be expected to reveal a deficiency of

intake. Accordingly B. W. Simpson (1930) during a visit to New Zealand from the Rowett Research Institute made a brief survey of the iodine content of sheep and lamb thyroids collected throughout New Zealand. She found an enormous variation in the percentage of iodine in the glands, and showed that a deficiency was nearly always associated with enlarged glands. She concluded that the iodine content of thyroids of lambs born and bred on definite areas gave a fair indication of the amount of iodine available on these areas, and that systematic advisory work on iodine feeding could be based on such analytical data, but that, however, more data and more widespread investigations were required. Similar work in Australia has shown a relatively small variation in the iodine content of thyroids from sheep, with no indications of thyroid enlargement. The authors conclude that so far as they have investigated there is no trace of an iodine deficiency in Australia (Dawbarn and Farr, 1932). This paper embodies results from part of a more extended survey of New Zealand. The districts of Otago and Southland have been studied in considerable detail. No definite system of classification other than that of geographical distribution has as yet been adopted, for it is considered that as data accumulate, some natural basis of systematic classification such as geological formation may present itself. The effects of geomorphology, climate, soil, and manurial treatment are considered, and their possible influences on the available iodine in soil. Sampling: All samples from Otago and Southland were obtained through the District Superintendent at Dunedin by the meat inspectors at the various freezing works throughout the country. Information as to the history of sheep and type of country where they were raised was obtained by the local stock inspectors and veterinarians. The glands were wrapped in greaseproof paper (sprinkled with a little 10 per cent. formalin solution during the hottest part of the summer), packed tightly in small tins, and forwarded to the laboratory. There they were dissected free from fat and tissue, dried to constant weight in a water-oven, treated with a 10 per cent, solution of caustic potash, made up to a given volume, and stored for analysis. Owing to the difficulty in obtaining whole glands from “butcher” killed sheep, samples were sometimes more or less mutilated, hence a short preliminary investigation was made to determine the distribution of iodine throughout the gland, and the possible effect of mutilation on the percentage of iodine. Eleven glands, both normal and slightly enlarged, were selected at random from sheep, and carefully dissected free from fat and tissue. These were then cut in pieces both transversely and horizontally, and the pieces analysed separately. The isthmus generally

contained a slightly smaller percentage of iodine, whereas in the remainder of the gland iodine was very evenly distributed. The results justified the assumption that a loss of a small portion of a gland would not significantly affect the whole percentage of iodine. Badly mutilated glands were discarded. Table I. Sample. Fresh Wgt. Grams. % Iodine. Total Iodine Grams. Remarks. 1 1.727 w0.119 0.0021 Right lobe. 0.166 0.091 0.00015 Isthmus. 1.610 0.123 0.0020 Left lobe. 3.503 0.119 0.0042 Whole gland. 2 2.196 0.163 0.0036 Right lobe. 0.148 0.118 0.00016 Isthmus. 2.218 0.168 0.0037 Left lobe. 4.562 0.164 0.0075 Whole gland. 3 2.284 0.144 0.0033 Right lobe. 2.508 0.146 0.0037 Left lobe. 4.792 0.145 0.0069 Whole gland. 4 3.536 0.162 0.0058 Right lobe. 0.065 0.108 0.0007 Isthmus. 3.776 0.175 0.0065 Left lobe. 7.377 0.167 0.0133 Whole gland. 5 2.242 0.156 0.0035 Right lobe. 0.337 0.156 0.00053 Isthmus. 2.683 0.153 0.0041 Left lobe. 5.262 0.155 0.0082 Whole gland. 6 4.815 0.054 0.0026 Right lobe. 0.104 0.057 0.0006 Isthmus. 4.012 0.058 0.0023 Left lobe. 8.931 0.056 0.0050 Whole gland. 7 3.069 0.101 0.0031 Right lobe. 0.367 0.083 0.0003 Isthmus. 3.071 0.101 0.0031 Left lobe. 6.507 0.100 0.0065 Whole gland. 8 1.591 0.111 0.0018 Right lobe, long. section. 1.620 0.132 0.0022 0.190 0.089 0.0002 Isthmus. 1.866 0.123 0.0023 Left lobe, long. section. 1.621 0.139 0.0023 6.888 0.125 0.0087 Whole gland.

9 2.153 0.092 0.0020 Right lobe, long. section. 1.651 0.098 0.0016 0.107 0.073 0.00008 Isthmus. 2.181 0.095 0.0021 Left lobe, long. section. 1.276 0.076 0.0010 7.368 0.092 0.0067 Whole gland. 10 0.860 0.126 0.0011 Right lobe, transverse section. 0.994 0.124 0.0012 0.149 0.129 0.0002 Isthmus. 1.289 0.132 0.0017 Left lobe, transverse section. 1.183 0.130 0.0015 4.474 0.129 0.0058 Whole gland. 11 0.547 0.068 0.0004 Right lobe, transverse section. 0.721 0.083 0.0006 0.048 0.034 0.00002 Isthmus. 0.551 0.080 0.0004 Left lobe, transverse section. 1.181 0.083 0.0010 3.048 0.079 0.0024 Whole gland. A composite sample was taken from each flock investigated, in order to minimise as far as possible individual variation. Wherever individual glands showed a definite abnormality as regards size or texture they were treated separately. Analyses of glands were made, with slight modifications, by the method of von Fellenberg as described by Leitch and Henderson (1926). The percentage of iodine is calculated both on the fresh and dry weight basis. The weights of glands given in the tables represent in each case the average weight of one gland from the given samples. In Fig. I are the samples listed in the following tables, and arranged in order of increasing percentage of iodine, calculated on the fresh gland basis. The same order of the samples is kept throughout Figs. I-IV, so that the variation of other properties with the percentage of iodine on the fresh weight can be illustrated diagramatically. The arrows in Figs. III and IV indicate much enlarged glands, the weights of which fall outside the diagram. Throughout this paper, unless stated to the contrary, weight and percentage of iodine refer to that of the fresh glands. Moisture: The samples examined have an average moisture content of about 74 per cent. The actual variation of moisture was from 61.2 per cent. to 87.8 per cent., and the weights of glands examined ranged from 1 to 90 grams, of which one gland weighing 90.6 grams had a moisture content of 73.8 per cent., and one weighing 1.04 grams had 73.2 per cent, moisture.

The distribution curve for the percentage moisture in the glands is practically symmetrical. A general increase in moisture due to the pathological condition of the samples may have occurred, causing the curve to shift as a whole towards the right. This can only be proved by comparison with a similar curve for glands from a district where there are no goitrous tendencies. At present, however, the available data are insufficient for such a comparison. The Influence of Sex: Samples of glands from ewes and wethers were obtained from 30 different districts. The variation appeared to be due to chance, as the number of glands in each sample was too

small to be representative. Dawbarn and Farr for similar reasons are not able to form any definite conclusions regarding the influence of sex other than that the differences were not marked. Variations observed, however, were comparatively small, and would therefore be entirely obscured by abnormalities due to an jodine deficiency. The Influence of Age: In all the samples examined, glands from sheep are appreciably heavier than those from lambs with the same percentage iodine, hence are not strictly comparable, as they would thus tend to raise the average weight for a given percentage of iodine. This is true for both normal and deficient glands (see Figs. III and IV). The number of glands examined from sheep, however, was relatively small. The Variation of Weight with the Iodine Content (Figs. III and IV): The line drawn through B represents the critical percentage of iodine (0.03 per cent.), so that the glands between A and B are deficient in iodine. The increase in weight with the fall in the percentage of iodine is negligible until this value is reached, where the increase takes place much more rapidly. The two anomalous glands weighing 8.77 and 6.99 grams respectively can be explained on the assumption that the iodine available to these animals as licks has had the effect of increasing the quantity of iodine in the gland without producing a proportional decrease in size. With these two exceptions, of 100 specimens from uniodised lambs containing 0.03 per cent. of iodine and over, only three weighed as much as 4.5 grams, the greater number weighing between 2 and 4 grams. Of 44 similar samples containing less than 0.03 per cent. iodine only one weighed as little as 2 grams, the greater number ranging between 3 and 6 grams. Ten weighed over 6 grams. Of these, five were typical goitres, one weighing 90.6 grams. Glands from sheep show the same general variations as those from lambs. Iodine Feeding: Among glands analysed, 24 samples were from lambs and sheep which had had access to iodised licks. These glands ranged in weight from 2 to 50 grams, with an iodine content of 0.138 per cent, to 0.006 per cent. With the exception of the two anomalies mentioned above the weights of the glands fall approximately into line with those from animals which have not had access to iodine. This may be caused either by the failure to take the lick or by insufficient iodine in lick. This latter may be due to the incorporation of insufficient iodine when mixing, to the loss of iodine through decomposition of the iodide and subsequent volatilisation, or to the

leaching action of the rain. It is, however, impossible to base definite conclusions on these figures, as information regarding the amount of iodine ingested cannot be obtained. An interesting case occurred at Ruakura (in the North Island) in which a gland weighing 350 grams containing 0.006 per cent. of iodine was obtained from a young bull. The brother of this bull, which also had an enlarged gland, was dosed with potassium iodide. Two months later his gland was obtained and analysed. It weighed 202 grams, and contained 0.057 per cent. of iodine. Work carried out in Australia by Dawbarn and Farr on the supplementary feeding of iodine to sheep shows that the iodine content of glands from sheep which had had access to iodised licks was only slightly greater than that of glands from sheep with no licks, and that there was no correlation between the proportion of iodine in licks and the increase in the proportion of iodine in the thyroid gland. This is probably due, however, to the exceptionally high iodine content of the glands in the normal state. Relationship Between the Nature of the Soil and its Iodine Content: In their paper entitled “Endemic Goitre in New Zealand,” published 1925, Hercus, Benson, and Carter discuss in some detail the quantities of iodine occurring in various types of soils and the variation with soil origin. In a general summary they conclude that soils with the least iodine are of a sandy nature, with little clay or iron in the ferric state. They are usually pale in colour unless darkened by the presence of ferrous minerals, ironsand, or carbonaceous matter. Soils of the last type are not invariably low in iodine, as the plant-remains in them may contain a good deal of this element. The soils which contain most iodine are in general the fertile brown or red loamy soils. They find that iodine is relatively abundant in soils derived from igneous rocks, most noteworthy in basic volcanic rocks (basalts and andesites) and in siliceous plutonic rocks (granite). It is not very marked in basic plutonic rocks, and there are very small amounts in siliceous volcanic rocks. It occurs in moderate amounts in those sedimentary rocks (greywackes), in which material was derived from igneous rocks with but little chemical alteration, but is greatly diminished during the metamorphic processes by which the greywackes are recrystallised to form mica schists. In marine sandstones and greenstones the quantities are small, and only minute amounts occur in grey clays. In the gravel of rivers, etc., iodine is generally deficient, though it may be accumulated in plant remains. Usually the deep weathering of rock allows a thorough leaching of its debris, producing residual clay which may contain but little iodine. On the other hand, it may be accumulated in clay

colloids, if such are present, and in humus, the remains of organisms, and thus becomes fairly abundant in the soil. They therefore conclude that it is not possible to make a definite correlation between the amount of iodine in the soil and its geological origin. As plant iodine is dependent not on the total iodine in the soil, but on the available iodine, it might be expected to vary with the nature of the soil. For instance, clay and peat, though themselves rich in iodine, give up no iodine to the water in which they are suspended, whereas water rapidly dissolves iodine from shell, grit, and sand. Von Fellenberg (Iodine in Nutrition, Orr and Leitch) has shown that iodine is more readily absorbed by plants from an acid soil than from an alkaline. For the purposes of discussion the results have been listed in order as the farms occur up the river valleys and other naturally bounded areas. Fig. VI, which is a geological sketch map of Southland and Otago, also gives the approximate positions of the farms sampled. Soil descriptions are based on data collected by field officers, and not on laboratory analyses. Table II. Waiau River. No. Date. Fresh Wgt. Grams. Dry Wgt. Grams. % I. Fresh. % I. Dry. % Moisture. No. of Lobes. Place. 115A 16/5/32 5.475 1.319 .029 .120 75.9 6 Te Tua 115B 16/5/32 3.603 .893 .050 .201 75.2 8 " 99 25/5/32 18.721 3.201 .003 .018 82.9 2 Clifden 99B 25/5/32 4.744 1.069 .008 .035 77.6 2 " 99C 25/5/32 2.032 .471 .044 .191 76.8 2 " 99D 25/5/32 7.138 1.570 .004 .019 78.0 6 " 122A 26/5/32 2.520 .652 .039 .150 74.1 7 Fairfax 122B 26/5/32 2.313 .576 .043 .174 75.1 8 " 96 4/5/32 1.650 .391 .019 .081 76.3 10 Mt. Linton, Nightcaps Aparima River. 108A 19/3/32 2.559 .728 .045 .157 71.5 6 Otahuti 108B 19/3/32 1.358 .404 .055 .175 70.2 7 " 109 19/3/32 3.514 .868 .024 .098 75.3 9 Drummond 114A 16/5/32 2.510 .640 .039 .153 74.5 7 Aparima 114B 16/5/32 3.198 .798 .035 .138 75.0 9 " These farms up the Waiau River are on light soils of an open nature, such as sandstones, which, combined with a comparatively high rainfall—40 to 50 inches—would undoubtedly be subjected to a fairly thorough leaching action, hence low in soluble iodine. The

99 series are from a flock with undoubted goitrous tendencies, and are a particularly good illustration of the direct relationship of increase in weight of gland with decrease in percentage of iodine. In this series also the percentages of moisture increase directly with the weight. Superphosphate is used as a topdressing on this farm. The other samples in the table are from farms which have been dressed with lime and superphosphate. In the Aparima district there are samples from three farms only. These farms are all on a heavier type of soil, clay and loam, and although they have approximately the same rainfall as the Waiau River, they do not suffer such a drastic leaching action. Lime and superphosphate are used for topdressing. The glands are not deficient in iodine, and, as far as can be told from the number of samples, show no tendency towards enlargement. Table III. New River. Lab. No. Date. Fresh Wgt. Grams. Dry Wgt. Grams. % I. Fresh. % I. Dry. % Moisture. No. of Lobes. Place. 67A 27/5/32 4.571 1.224 .027 .099 73.2 12 Balfour 67B 27/5/32 3.302 .878 .033 .125 73.4 10 " 106A 1/3/32 2.991 .773 .020 .077 74.2 10 Five Rivers 106B 1/3/32 1.724 .488 .045 .160 71.7 5 " 97A 4/5/32 2.088 .546 .092 .351 73.9 7 Mossburn 97B 4/5/32 1.596 .417 .060 .228 73.9 10 " 111A 20/4/32 6.233 1.256 .014 .070 79.8 6 Oporo 111B 20/4/32 3.932 .896 .030 .132 77.2 7 " * Access to iodised licks.113A 20/4/32 2.901 .651 .026 .114 77.6 8 Lochiel *113B 20/4/32 2.674 .662 .022 .090 75.2 9 " *89A 8/4/32 4.663 1.074 .025 .108 76.9 6 Winton *89B 8/4/32 3.552 .822 .022 .094 76.8 6 " 98A 9/5/32 3.271 .766 .020 .087 76.6 12 Central Bush 98B 9/5/32 5.787 1.233 .011 .054 78.7 8 " *112A 20/4/32 3.324 .790 .019 .079 76.2 8 South Hillend *112B 20/4/32 3.353 .712 .011 .052 78.8 6 " 100A 25/5/32 2.937 .744 .025 .100 74.7 10 Konana 100B 25/5/32 1.783 .476 .049 .185 73.3 6 " The land in this district is mainly flat, with some river-flat, composed of loams and clays derived from river alluvium. It is subjected to a fairly heavy rainfall—30 to 50 inches. Topdressing is mainly superphosphate and lime. It appears from the analyses of glands that iodine is not available in sufficient quantities, though there is no marked tendency to thyroid enlargement. Nos. 113, 112, and 89 are exceptional, as iodine was available to these lambs without having the effect of increasing the percentage of iodine in the thyroid. It is quite possible, however, that these lambs were slaughtered before they had learned to take a lick.

Table IV. Mataura River. Lab. No. Date. Fresh Wgt. Grams. Dry Wgt. Grams. % I. Fresh. % I. Dry. % Moisture. No. of Lobes. Place. 110A 19/3/32 2.245 .536 .041 .171 76.1 6 Fortrose 110B 19/3/32 4.538 1.100 .042 .177 75.8 5 " 57 12/5/32 7.938 1.573 .003 .013 80.2 10 Mataura Is. * Access to iodised licks.54 9/5/32 2.706 .725 .060 .223 73.2 4 Glenham 66A 21/5/32 3.917 1.044 .041 .152 73.3 4 " 66B 21/5/32 3.692 .935 .031 .122 74.7 8 " 47A 19/4/32 4.774 1.064 .016 .073 77.7 6 Wyndham 47B 19/4/32 5.976 1.281 .012 .054 78.6 2 " *50A 22/4/32 3.357 .914 .028 .104 72.8 4 " *50B 22/4/32 4.480 1.252 .020 .070 72.0 4 " *93A 23/4/32 3.454 .837 .018 .074 75.8 6 " *93B 23/4/32 3.212 .804 .019 .075 75.0 7 " *61A 20/5/32 2.977 .786 .056 .213 73.6 6 Mataura *61B 20/5/32 3.002 .867 .076 .262 71.1 10 " 60A 16/5/32 3.393 .929 .050 .182 72.6 14 Waimumu 60B 16/5/32 4.622 1.158 .027 .107 75.0 8 " *65A 21/5/32 3.156 .755 .023 .098 76.1 8 " *65B 21/5/32 2.800 .703 .026 .104 74.9 6 " 69A 30/5/32 4.158 1.044 .033 .131 75.0 7 Otukarama 69B 30/5/32 2.898 .705 .031 .127 75.7 2 " 70 30/5/32 5.902 1.500 .025 .099 74.6 9 Willowbank *71A 30/5/32 5.922 1.385 .018 .079 76.6 6 Gore *71B 30/5/32 2.265 .561 .032 .127 75.2 4 " 52A 22/4/32 3.412 .838 .022 .090 75.4 6 " 52B 22/4/32 4.229 1.014 .033 .136 76.0 2 " 49 19/4/32 4.841 1.083 .020 .088 77.6 6 Mandeville 56 12/5/32 3.722 .868 .013 .055 76.7 4 Otama 64A 21/5/32 3.206 .766 .050 .209 76.1 6 Riversdale 64B 21/5/32 2.841 .697 .034 .138 75.5 8 " 59 12/5/32 7.763 1.706 .006 .028 78.0 4 Otamita 63A 21/5/32 2.510 .668 .086 .322 73.4 8 Balfour 63B 21/5/32 2.197 .597 .087 .322 72.8 12 " 53A 6/5/32 2.064 .527 .038 .147 74.5 6 " 53B 6/5/32 2.878 .713 .034 .135 75.2 8 " 53C 6/5/32 2.180 .542 .045 .182 75.1 3 " 51A 22/4/32 1.908 .527 .057 .205 72.4 4 " 51B 22/4/32 2.184 .601 .063 .229 72.5 2 " With the exceptions of 51, 53, and 63 (Balfour) the samples are from farms with soils ranging from light sandy loams to medium clay loams, which have mostly been topdressed with lime and superphosphate, but 59, 60, 61, 64, 69 have had in addition some guano. With the exception of 59, these samples have all a higher average percentage of iodine, which may in some measure be due to the extra iodine put into the soil by the guano. The samples from Balfour have all a higher iodine content, but they are also from farms where the soil is of a heavier type. The country as a whole is rolling to hilly; 47 is flat, 52 and 57 are on river flats. The rainfall for this district ranges from 25 to 40 inches.

Table V. Lake Wakatipu. Lab. No. Date. Fresh Wgt. Grams Dry Wgt. Grams. % I. Fresh. % I. Dry. % Moisture. No. of Lobes. Place. 107A 1/3/32 1.709 .493 .208 .096 71.1 6 Crown Tce. 107B 1/3/32 4.666 1.264 .029 .109 72.8 6 Arrowtown 87 15/3/32 5.644 1.461 .032 .123 74.1 12 Queenstown The samples are from high rocky country, typical mica schist. This is apparently a border-line district, where a change in conditions such as, for instance, a particularly wet season, might cause an outbreak of goitre. The glands are all from sheep. The number of samples is, however, too small to justify definite conclusions. Table VI. Clutha River Lab. No. Date. Fresh Wgt. Grams. Dry Wgt. Grams. % I. Fresh. % I. Dry % Moisture. No. of Lobes. Place. 73A 30/1/32 2.160 .447 .037 .177 79.3 14 Glenomaru 73B 30/1/32 2.940 .598 .017 .082 79.7 13 " * Access to iodised licks.74 30/1/32 51.104 12.911 .006 .024 74.7 2 Sterling 84 6/4/32 4.378 .996 .031 .137 77.2 20 Romahapa 72 13/1/32 2.821 .726 .030 .107 74.2 25 Clinton 92 23/4/32 3.665 .958 .037 .140 73.8 22 Wangaloa † Full-grown sheep.*83 5/2/32 8.770 2.247 .069 .268 74.4 12 Milton *79 5/5/32 4.263 1.076 .037 .145 74.6 18 Greenfield, Clutha Valley 80 9/5/32 3.393 .892 .037 .142 73.7 24 Tuapeka 81A 9/5/32 2.772 .710 .047 .184 74.4 27 Awamungu 81B 9/5/32 15.342 2.930 .016 .082 80.9 2 Clutha Valley 55A 9/5/32 2.294 .556 .051 .209 75.8 8 Waipahi 55B 9/5/32 2.109 .548 .065 .249 74.0 8 " 82 30/5/32 3.164 .778 .035 .143 75.4 12 Clydevale 58A 12/5/32 3.007 .816 .033 .123 72.8 16 Kaiwera 58B 12/5/32 2.012 .530 .030 .112 73.6 4 " 76 19/4/32 3.132 .786 .058 .231 74.9 23 Clydevale 48 19/4/32 3.222 .820 .055 .217 74.6 6 Maitland 77 21/4/32 4.444 1.092 .012 .048 75.4 40 Clydevale 62A 20/5/32 2.682 .722 .049 .185 73.1 8 Waikaka 62B 20/5/32 3.905 1.044 .045 .167 73.3 6 " 75 15/4/32 4.116 .650 .013 .041 84.2 33 Edievale 78 23/4/32 4.542 1.071 .020 .085 76.4 18 " *91 19/4/32 3.573 .985 .066 .241 72.4 22 Miller's Flat 90 13/4/32 3.880 .474 .020 .082 87.8 23 Teviot All the glands from this district, which come from farms where the soil is a heavy clay or loam, have a percentage of iodine just above the critical value, with the exception of 77 (Clydevale). Although the percentage of iodine in these glands is low, they show no signs of enlargement. Most of the topdressing is done with superphosphate and lime; 82, 84, and 89 have used guano as well. Numbers 73, 74, 75, 79, and 90 are from farms where the soil is light and sandy. With the exception of 79 and 91, where iodised licks have been used, the percentage of iodine in these glands is well below the critical value. Number 74 has also had an iodised lick, but this sample consists of one gland only, which is a typical goitre. The rainfall in the Clutha basin is 20 to 30 inches.

Table VII. Upper Taieri and Maniototo Plains Lab. No. Date. Fresh Wgt. Grams. Dry Wgt Grams. % I. Fresh. % I. Dry. % Moisture No of Lobes. Place. * Access to iodised licks.5 17/2/32 1.997 .556 .081 .292 72.2 22 Middlemarch 86 29/2/32 3.316 .992 .0.16 .201 72.2 19 Sutton 1 15/1/32 4.685 1.205 .010 .062 74.3 54 Middlemarch -21 21/4/32 3.063 .819 .031 .117 73.3 22 Ngapara 4 12/2/32 1.805 .514 .160 .562 71.5 20 Dunback 3 12/2/32 3.677 1.068 .124 .427 70.9 22 Kokonga † Full-grown sheep. 103 15/2/32 9.299 2.333 .026 .105 74.9 12 " *18 15/4/32 3.589 1.066 .117 .395 70.3 20 " † 15A 14/4/32 4.116 1.176 .073 .256 71.4 22 " 15B 14/4/32 1.640 .465 .130 .460 71.6 20 " 6 25/2/32 1.428 .413 .131 .454 71.1 23 Ranfuily † 7 26/2/32 4.999 1.419 .085 .300 71.6 20 " † 33 18/5/32 5.034 1.631 .118 .365 67.6 12 " 20A 20/4/32 2.552 .702 .052 .187 72.5 19 " 20B 23/4/32 1.276 .412 .118 .356 67.7 18 " †20C 23/4/32 5.148 1.476 .085 .297 71.3 20 " 17 15/4/32 2.407 .642 .046 .173 73.3 16 " 38 23/5/32 3.195 .740 .026 .111 76.8 12 " 10 15/4/32 3.813 1.030 .033 .122 73.0 16 Waipiata †27A 13/5/32 3.945 1.155 .108 .369 70.7 22 Wedderburn 27B 13/5/32 1.870 .524 .091 .323 72.0 20 " †9 29/2/32 5.161 1.775 .070 .204 65.6 16 Waipiata †30 13/5/32 4.571 1.142 .055 .218 75.0 18 " 14 13/4/32 3.766 1.112 .146 .494 70.6 20 " 9A 29/2/32 1.710 .478 .090 .338 72.0 14 " †26 6/5/32 5.063 1.453 .081 .284 71.2 18 Hyde 101 26/5/32 2.596 .673 .060 .233 74.1 12 Paerau The soils in this district are mainly alluvial, silt and loam with underlying subsoil of gravel and clay. There are some schist outcrops. This is a district with a very low rainfall (15–25 inches) and a very high rate of evaporation (32 inches). In summer, conditions usually approximate to those of drought. Dawbarn and Farr found that glands collected from sheep under drought conditions contained approximately double the percentage of iodine found in glands from the same localities during a good season. They suggest that this is due to a decreased demand for thyroid hormone owing to the low nutritive level of the sheep and the associated lowering of their basal metabolism. The increased iodine content of glands from the Maniototo district as compared with those from Southland may be due to reasons such as these, but more probably to the fact that in the soils comparatively large amounts of soluble matter (including soluble iodine salts) are deposited as the ground-water is evaporated from the surface or transpired by plants. Throughout the Maniototo Plains occur small basin-like depressions in which crystalline salt deposits are exuded from the ground. These contain as much as 9000 γ iodine per kgm.,* γ =10−6 gm. and are readily eaten by the sheep. These soils are in direct contrast to those of Southland, where the heavier and well-distributed rainfall promotes a constant leaching, and where saline accumulations are not known to occur.

Table VIII. Manuherikia and Ida Valleys. Lab No. Date. Fresh Wgt. Grams Dry Wgt. Grams. % I. Fresh. % I. Dry. % Moisture. No. of Lobes. Place. 10 29/2/32 1.892 .541 .139 .436 71.4 20 Omakau 105 12/5/32 1.341 .367 .058 .214 72.6 24 " 88 15/3/32 1.468 .403 .092 .335 72.6 28 Lauder 85 13/2/32 2.611 .584 .058 .259 77.6 22 " 104 9/4/32 3.698 .945 .033 .127 74.4 22 Poolburn 22 21/4/32 2.378 .622 .045 .170 73.8 20 Lauder 94 2/5/32 2.256 .588 .068 .261 74.0 20 Ida Valley 8 13/4/32 4.681 1.149 .010 .042 76.4 20 " Manuherikia Valley is a depression stretching south-west, mainly determined by two great faults, one along the east side of Dunstan Range and the other along the west side of Raggedy Range. The surface of the valley is covered with terrace-gravels, except where inliers of schist or of Tertiary beds are exposed or where hills of greywacke conglomerate rise above the terraces. Ida Valley is similarly determined by two faults, but terraces are not so conspicuous as they are in the other basins, the higher ground of the floor sloping down gradually to the flood-plains of the Poolburn and the Idaburn. The Manuherikia Valley is one of the driest districts in Central Otago, with an average rainfall of about 15 inches. Thyroid glands from these valleys contain a relatively high average of iodine, and there appears to be no tendency to thyroid enlargement. Table IX. East Coast—Palmerston To Oamaru. Lab. No. Date. Fresh Wgt. Grams. Dry Wgt. Grams. % I. Fresh. % I. Dry. % Moisture. No. of Lobes. Place † Full-grown sheep.2 5/2/31 3.851 1.307 .087 .256 66.1 24 Waikouaiti 41 27/5/32 2.287 .623 .084 .308 72.7 12 Dunback 42 27/5/32 2.618 .660 .034 .135 74.8 14 " 44 30/5/32 2.509 .869 .106 .306 65.3 12 Kartigi †13B 18/3/32 5.704 1.485 .073 .280 74.0 18 Moeraki Est., Hampden 13A 18/3/32 4.004 1.027 .044 .171 74.7 20 " * Access to iodised licks.34 20/5/32 2.944 .790 .047 .174 73.2 12 Reay Farm, Hubert 13C 23/4/32 4.126 1.094 .103 .388 73.5 16 Hampden 13D 23/4/32 3.862 .947 .041 .166 75.5 24 " *28 13/5/32 4.041 1.168 .108 .373 71.1 20 Maruakoa 40 26/5/32 2.665 .789 .100 .337 70.4 12 Maruakoa †36 23/5/32 6.665 1.856 .044 .159 72.2 12 Tapui 39 26/5/32 3.269 .851 .031 .118 74.0 12 Maruakoa 45 31/5/32 3.310 .831 .039 .155 74.9 12 Tokaiaki 23 23/4/32 2.754 .716 .068 .262 74.0 24 Weston 19 19/4/32 1.887 .532 .079 .280 71.8 20 Ngapara 35 20/5/32 3.452 .975 .059 .208 71.8 12 Pakopino *18C 16/5/32 6.990 2.033 .108 .370 70.9 10 Oamaru Waitaki River. 12 18/3/32 2.297 .580 .071 .280 74.7 16 Waitaki 11 18/3/32 4.665 1.115 .021 .087 76.1 20 Duntroon †37 23/5/32 5.231 1.477 .075 .264 71.8 12 Kurow

The soils in this area are very varied, being on the whole light and good, with some alluvial schist and clay. The country is from hilly to rough and rocky. Less attention is paid to topdressing than in Southland, small amounts of superphosphate or lime being used occasionally. The rainfall is relatively low (20–30 inches), and the percentage of iodine in the glands well above the critical value. There is no indication of any tendency to thyroid enlargement in this area. Fig. VII. Note.—In Fig. VII, percentage of iodine is that calculated on the fresh weight basis, and the samples are those listed in the preceding tables. Glands from animals which have had access to iodised licks have been excluded. Under Southland are included the samples listed in Tables II, III, IV, V, and VI, and under Otago are those from Tables VII, VIII, and IX.

The curve for the Otago samples, apart from a jaggedness which is probably due to an insufficient number of samples, shows a fairly symmetrical distribution. Contrasting sharply with this is the curve for the Southland samples, which is decidedly skew in respect to the normal. This curve indicates clearly the relatively low iodine content of thyroid glands from sheep in Southland. Summary and Conclusion. A large number of samples of thyroid glands from sheep and lambs from Otago and Southland, New Zealand, have been collected, weighed, and analysed for iodine. The results have been classified according to district and listed in tables. The relative effects of age, sex, and moisture on the percentage of iodine in the glands have been studied, but the data are as yet too scanty for the successful application of statistical methods, hence apparent variations may be due to chance only. From a study of the weight of the gland and its percentage iodine, it has been shown that there is an inverse relationship, which is, however, almost negligible until the percentage of iodine has fallen below a certain critical value (0.03% fresh weight). Below this value the weight of the gland increases fairly rapidly, with a decrease in the percentage of iodine. Spontaneous enlargement of the glands may occur where the percentage of iodine is less than 0.03; these glands sometimes increase in weight fiftyfold. No such enlargement has been observed in any district where the percentage of iodine is above the critical value. It occurs usually in individual cases in flocks where the average percentage of iodine in the glands is below 0.03, though occasionally the whole flock is affected. One case occurred at Wanaka (Hopkirk and Dayus, 1930) where there was an outbreak of congenital goitre among the lambs, all of which were born very weak, with much enlarged thyroids, while many were hairless or deformed. If the lambs survived three days, cures were usually effected by treatment with tincture of iodine. Salt licks containing 3 ounces potassium iodide per cwt. of salt have successfully prevented further trouble. No explanation is offered of the phenomenon of a sudden outbreak of goitre, either in individual cases or in whole flocks, but there is undoubtedly some factor which affects the mechanism that controls cell proliferation and colloid storage, and throws it out of adjustment when the iodine in the gland is below a certain value. Circumstances under which a deficiency is likely to occur are to some extent dependent on soil and climatic conditions. Light and sandy soils, accompanied by more or less heavy rainfall, facilitate the leaching of soluble salts, whereas the presence of heavy clays and loams or of good clay or rock substrata inhibits this effect. In the semi-arid districts, where evaporation takes place rapidly, soluble salts are deposited in the soil where they are available for plant assimilation. In some districts these salts are exuded from small basin-like depressions in the ground, as salt incrustations which are directly available to stock. Hercus and others (1931) have found as much as 9000 γ iodine per kgm. in these deposits. Thyroid glands of sheep from these districts are rarely deficient in iodine.

Old river flats are generally well leached, hence deficient in iodine. From the data given in this paper it would appear that iodine feeding, with the exception of one or two cases, has little or no effect on the iodine content of the glands of sheep. As the total iodine of the thyroid can be increased by feeding iodides (Orr and Leitch, 1929), it follows that the sheep in question are not receiving an adequate amount. Therefore either they are not eating the lick in sufficient quantities or the iodides have been lost by leaching, decomposition, or some other means. At least one case has been reported in which the potassium iodide has decomposed and free iodine has volatilised in considerable quantities. Potassium iodide is not stable under acid conditions, and there-fore might be attacked by the carbon dioxide of the air or by traces of phosphoric acid in the salt. Inclusion of small amounts of lime or sodium carbonate should prevent its decomposition. Potassium iodide is also a very soluble salt, and thus might be easily leached away if the licks were exposed unprotected in the fields. Work is required on the efficacy of potassium biniodate in salt licks in raising the iodine content of thyroid glands, as this compound is considerably less soluble, and is more stable to acids. Goitre is liable to occur in most of the Southland districts, so that the incorporation of iodides in salt licks as a preventive measure is to be advised. Roughly, most of the country north of Dunedin and Alexandra, with the exception of the Lake districts, is free from the effects of an iodine deficiency, so that the use of iodised licks is only necessary in exceptional cases. Until quite recently salt licks containing about 3 ozs. of potassium iodide per cwt. have been in fairly general use in New Zealand. Such large amounts of iodine have a therapeutic value in deficient areas, but it is doubtful whether they are necessary in general licks for preventive purposes. Experimental work with iodised licks under farming conditions is now in progress in some of the Southland districts. The author wishes to express her indebtedness to Mr B. C. Aston for his valuable constructive criticisms throughout the work, to Mr C. V. S. Dayus and his field officers for the time and trouble they have spent in obtaining samples, together with the information concerning each. References. Orr and Leitch. Iodine and Nutrition. Medical Research Council. 1929. H. T. Ferrar. Soils of Irrigation Areas in Central Otago. C. E. Hercus, W. N. Benson, and C. L. Carter. Endemic Goitre in New Zealand and its Relation to Soil Iodine. J. of Hygiene, XXIV, Nos. 3 and 4, 1925. C. E. Hercus, H. A. Aitken, H. M. S. Thomson, and G. H. Cox. J. of Hygiene. Vol. XXXI, 4, 494. R. A. Shore and R. L. andrew. Goitre in School Children, 1929. M. C. Dawbarn and F. C. Farr. Australian J. of Exptl. Biol. and Med. Science, X. 1932. B. W. Simpson. N.Z. Journal of Agriculture. XLI, No. 5., p. 306. Leitch and Henderson. Biochem. J., Vol. XX, No. 5, 1926. C. S. M. Hopkirk, C. V. Dayus, B. W. Simpson, and R. E. R. Grimmett. N.Z. Journ Agric., XL., No. 4, 226.