Iranian Journal of Veterinary Research, University, Vol. 11, No. 1, Ser. No. 30, 2010

Short Paper

Selenium and iodine status of sheep in the ,

Talebian Masoudi, A. R.1*; Azizi, F.2 and Zahedipour, H.1

1Agriculture and Natural Resource Research Center of Markazi Province, Arak, Iran; 2Research Institute for Endocrine Sciences, Shahid Beheshti University (M.C), , Iran

*Correspondence: A. R. Talebian Masoudi, Agriculture and Natural Resource Research Center of Markazi Province, Arak, Iran. E-mail: [email protected]

(Received 21 Oct 2008; revised version 11 Jul 2009; accepted 18 Jul 2009)

Summary

The aim of this study was to provide preliminary quantitative information on selenium and iodine status of sheep in Markazi province, Iran. Selenium and iodine status of grazing sheep were measured for 57 different flocks in 14 regions over one year. The districts were selected to represent major sheep growing areas in the province. Blood samples were collected from 2 to 3-year-old ewes during summer, autumn and winter. Samples were analyzed for blood glutathione peroxidase (GSHpx) activity and plasma inorganic iodine. There were significant differences between regions and seasonal differences in terms of blood GSHpx activity and plasma inorganic iodine concentration (P<0.01). Low levels of GSHpx activity (<60 IU/gHb) and plasma inorganic iodine (<5 µg/dl) in some regions or some seasons indicated the need for dietary supplementation of these minerals.

Key words: Sheep, Nutrition, Mineral, Selenium, Iodine

Introduction of insufficient iodine intake (Bobek, 1998). A primary reason for determining the Living organisms depend on minerals selenium (Se) and iodine (I) status of an for proper function and structure. Mineral animal is to establish whether that animal is imbalances (deficiencies or excesses) in being adequately nourished with Se and soils and forages have long been held iodine. responsible for the low production and Markazi province (Fig. 1) has about 1.4 reproductive problems of the grazing million head of sheep. Sheep production ruminants (McDowell and Arthington, systems in this province vary between 2005). Selenium is an essential constituent regions and seasons, with similar patterns in of glutathione peroxidase (GSHpx) that aids all regions. Sheep feeding is based mainly in protecting cellular and subcellular on existing natural resources obtained membranes from oxidative damage (Rotruck directly by grazing. Breeding ewes run on et al., 1973). The only known role of iodine pasture during spring with feed supplements is in the synthesis of thyroid hormone. in winter. In Markazi province, like other Selenium deficiency depresses the activities provinces in Iran, grazing livestock often do of type I and type II, 5'-iodothyronine not receive mineral supplements. Mineral deiodinase in animal tissues and may supplementation, if any, is limited to exaggerate the iodine deficiency through common salt. impairing the conversion of It has been reported that trace element tetraiodothyronine (T4) to triiodothyronine imbalances, along with poor husbandry and (T3) (Yuming et al., 1995). Iodine inadequate diets, frequently contribute to concentrations lower than 100 µg/L in cattle sub-clinical deficiencies in grazing and small ruminants were reported as a sign ruminants (Conrad et al., 1980). This is

78

Iranian Journal of Veterinary Research, Shiraz University, Vol. 11, No. 1, Ser. No. 30, 2010 particularly true in small holder grazing determination of selenium dependent areas where there is no supplementation. GSHpx activity, and the plasma was frozen Despite some reports of deficiencies of at -20°C for plasma inorganic iodine minerals in sheep, there are no published analysis. The GSHpx activity was data on the incidence or severity of mineral determined in whole blood by a coupled deficiency in Markazi province. enzyme assay using a commercially On the basis of clinical reports (Anon., available kit (Ransel, Randox, UK) and the 2003) the deficiencies of selenium/vitamin E activity was expressed as units per gram and iodine in this province is probable. haemoglobin. This method is based on that The purposes of this study were to of Paglia and Valentine (1967), in which investigate: glutathione peroxidase catalyses the 1) The selenium and iodine status of grazing oxidation of glutathione by cumene sheep feeding on pasture or locally grown hydroperoxide. In the presence of feedstuffs. glutathione reductase and NADPH the 2) The seasonal changes in mineral status to oxidized glutathione is immediately identify when supplementation is required. converted to the reduced form with a 3) The different geographical regions to concomitant oxidation of NADPH to identify where it is necessary to provide NADP+. The decrease in absorbance at 340 supplements. nm is measured (Paglia and Valentine, 1967). Iodine was measured by the ceric- Materials and Methods arsenic redox reaction (Benotti and Benotti, 1963; Benotti et al., 1965). Whole serum Animals was analyzed to obtain total serum iodine Samples were collected from 57 (TI) concentrations, and perchloric acid different flocks within 14 regions in Markazi precipitates of serum were analyzed to province during three seasons. Sites were determine the protein-bound iodine (PBI) chosen to represent the main sheep- concentration. The formula for calculating producing regions in the province. Sampling the plasma inorganic iodine (PII) is as periods for selenium status were October follows: PII = TI - PBI (Vought et al., 1963). (before the breeding season) 2005, February 2006 (late gestation) and June 2006 (end of Data analysis grazing season), and for iodine status were The data were analyzed (Snedecor and October 2005 and February 2006, Cochran, 1980) by the general linear models corresponding to the start and end of the (GLM) procedure of the SAS system (SAS grazing season and feeding stages in each Institute Inc., 1987). Differences among region. The numbers of sheep flocks in each means were tested using the Duncan’s new site were chosen proportionate to the multiple range test (Duncan, 1955). A p- number of sheep in that site and 5-7 ewes value less than 0.05 was considered as were sampled in each selected flock statistically significant. depending on flock size. The sheep sampled The geographical locations of the were young ewes during their second sampling points were recorded with global pregnancy and lactation (2 to 3-year-old). positioning system (GPS). The distribution Samples of 285 sheep were obtained for point maps of selenium and iodine status of each of the sampling periods. sheep were created from point measurements using moving average Blood samples interpolation technique in ILWIS academic After puncture of v. jugularis, blood software (Figs. 2 and 3). samples were collected in heparinized test tubes. Each sample was divided into two Results portions: fresh whole blood and plasma. To obtain plasma, a portion of each sample was Results of GSHpx activity and iodine centrifuged at 3000 rpm for 20 min. Whole status of sheep for various regions are blood was utilized immediately for presented in Table 1. There were marked

79

Iranian Journal of Veterinary Research, Shiraz University, Vol. 11, No. 1, Ser. No. 30, 2010

Fig. 3: Iodine status of sheep in Markazi province, Iran

Table 1: GSHpx activity (Mean ± SD) and

plasma inorganic iodine (Mean ± SD) of sheep Fig. 1: The location of Markazi province in in 14 regions of Markazi province Iran GSHpx activity plasma inorganic District (IU/gHb) iodine (µg/dl) 95.88a ± 24.86 5.70de ± 5.19 95.08a ± 24.46 8.25cd ± 8.56 Nobaran 93.36a ± 19.59 10.67bcd ± 9.11 92.82a ± 22.91 15.64b ± 16.34 78.86b ± 18.34 11.80bcd ± 14.64 Khomein 75.25bc ± 20.36 11.16bcd ± 13.73 Farahan 73.49bc ± 22.35 12.07bcd ± 10.89 69.79bcd ± 7.64 33.15a ± 8.73 Arak 66.99cd ± 27.57 12.75bc ± 12.38 66.06cd ± 29.68 1.68e ± 6.39 Mahalat 65.27cd ± 15.57 10.67bcd ± 13.87 Tureh 61.42d ± 27.34 1.38e ± 1.97 46.42e ± 13.35 12.69bc ± 10.21 Hendudar 44.36e ± 16.20 5.51de ± 10.94 Means with different superscripts in each column are significantly different (P<0.01)

deficient in iodine (5-10 µg/dl). Figures 2 and 3 represent the selenium and iodine status distribution of sheep in Markazi

province, respectively. The lowest selenium Fig. 2: Selenium status of sheep in Markazi status was seen in sheep in the highland province, Iran areas of the southeast region, while sheep in the lower rainfall areas in the northwest differences between regions in blood GSHpx areas had marginal selenium status. activity and plasma inorganic iodine. On the There were significant differences in basis of the critical reported values (Andrés GSHpx activity and iodine between different et al., 1997; Bobek, 1998), two regions seasons (P<0.01). Seasonal differences could be classified as low in selenium (<60 (P<0.01) were found for GSHpx activity IU/g Hb), twelve as marginally deficient in with higher GSHpx activity in autumn and selenium (60-100 IU/g Hb), two as deficient winter in comparison with summer (Table in iodine (<5 µg/dl) and five as marginally 2), and interactions of season by district

80

Iranian Journal of Veterinary Research, Shiraz University, Vol. 11, No. 1, Ser. No. 30, 2010 were significant (P<0.01). Lower GSHpx link soil-plant-animal applies also to activity was seen in the highland areas of the selenium and iodine (Campbell et al., 1995; southeast regions in the summer season than Groce et al., 1995; Kamada et al., 2000). in northwest regions in the same season. According to other studies (Stevens et The PII concentration in autumn was al., 1985), there may be wide variations in found to be significantly higher (P<0.01) the serum selenium concentrations and compared with that in winter (Table 3). glutathione peroxidase activities in livestock grazing forages even within the same Table 2: GSHpx activity (Mean ± SD) of sheep geographical area. Seasonal patterns in the in different seasons in Markazi province selenium and iodine status of sheep are well Season Variable recognized. McDowell et al. (1989) reported Winter Summer Autumn seasonal fluctuations in soil selenium levels, GSHpx activity 77.26a 55.85b 73.34a (IU/g Hb) ±33.93 ±19.21 ±23.03 higher in the dry season and lower in the wet Means with different superscripts in each row are season. Our findings are in agreement with significantly different (P<0.01) other reports that indicate seasonal fluctuations in the GSHpx activity of sheep Table 3: Plasma inorganic iodine (Mean ± SD) with lower levels during spring-early of sheep in different seasons in Markazi summer than in winter (Caple et al., 1980; province Andrés et al., 1999). Season Variable Also, mineral requirements are highly Winter Autumn b a dependent on the level of productivity. The Plasma inorganic iodine 3.83 14.17 reported results show the selenium status of (µg/dl) ±6.89 ±13.08 Means with different superscripts in each row are sheep approximately 60 days before significantly different (P<0.01) sampling time, as current blood concentrations of GSHpx reflect the Discussion selenium intake of the animal at the time the present circulating erythrocytes were Markazi is a province with relatively formed. Thus, the minimum of GSHpx large climatic, geographical and vegetation belongs to the late winter and beginning of differences so that the mineral status of spring which is coincident with late grazing livestock is likely to differ largely gestation, lambing and lactation when the among regions. Analysis of the samples selenium requirement of sheep is raised. indicated that sheep in some regions of Also, this period is concurrent with end of Markazi province have low intakes of feeding of storage, and inferior quality hay selenium/vitamin E or iodine during some or straw with low tocopherol content. The seasons. increasing requirements of sheep in Natural intake of selenium or iodine by selenium/vitamin E in late gestation and ruminants depends primarily on the lactation (NRC, 2007), and low intake of geographical position, or more specifically, these nutrients in this period cause seasonal on mineral concentration in soil. Many differences in selenium status as shown in naturally occurring deficiencies in grazing this study. Adverse weather conditions, cold livestock can be related to soil and rain may also increase the characteristics (Andrés et al., 1997; selenium/vitamin E requirements of sheep McDowell, 2003). and adversely affect selenium status. This Mineral deficiencies result most often may explain the lower selenium status of when animals are confined within a given sheep in the highlands area of the southeast area and are thus closely dependent upon the regions with the relatively harsh weather in structure of the soil and the plant life in a the winter in comparison with the northwest very limited space (McDowell, 2003). The regions in the same season. soil-plant-animal system is a complex It is clear that sheep in major regions of system which has not been investigated Markazi province must be able to survive adequately in developing countries. The and produce with a 7-month period of low general and well-documented principle of quality forages between June and October. the control of trace element intake by the This period of low feed availability is

81

Iranian Journal of Veterinary Research, Shiraz University, Vol. 11, No. 1, Ser. No. 30, 2010 concurrent with the weaning of lambs and iodine by partial automation. Clin. Chem., 9: drying the ewes till early gestation with no 408-416. major detrimental effects on productivity. Benotti, J; Benotti, N; Pino, S and Gardyna, H The severity of these problems changes with (1965). Determination of total iodine in urine, location and seasons. In some regions, both stool, diets, and tissue. Clin. Chem., 11: 932- 936. selenium and iodine status were low. Bobek, S (1998). Profilaktyka jodowa u Hendudar is of particular interest as zwierzat. Met. Wet., 54: 80-86. selenium deficiency may be exacerbated at Campbell, JR; Jim, GK; Booker, CW and iodine deficiency (Donald et al., 1993). Guichon, PT (1995). A survey of the Based on experiences with mineral selenium status of beef cows in Alberta. Can. supplements in other areas of the world, the Vet. J., 36: 698-702. low mineral status would be expected to Caple, LW; Andrewartha, KA; Edwards, SJA limit production of sheep. and Halpin, CG (1980). An examination of In summary, this survey suggests that the selenium nutrition of sheep in Victoria. deficiencies of selenium and iodine may be Aust. Vet. J., 56: 160-167. Conrad, JH; Sousa, JC; Mendes, MO; Blue, WG occurring in sheep flocks in parts of Markazi and McDowell, LR (1980). Iron, manganese, province. However, the results need to be sodium and zinc interrelationships in a interpreted with caution because critical tropical soil, plant and animal system. In: values derived from foreign breeds applied Verde, LS and Fernandez, A (Eds.), to native sheep breeds and the preliminary Proceedings of fourth world conference on nature of the survey can give only a very animal production. Buenos Aires, Argentina. crude guide to the seasonal and geographical PP: 38-53. distribution of deficiency. Information is Donald, GE; Langlands, JP; Bowles, JE and required on the interrelationship of minerals Smith, AJ (1993). Subclinical selenium among soil, plant and animals and more insufficiency 4. Effects of selenium, iodine, and thiocyanate supplementation of grazing studies are now needed to determine if ewes on their selenium and iodine status, and mineral deficiencies are limiting grazing on the status and growth of their lambs. Aust. sheep production. Mineral supplementation J. Exp. Agri., 33: 411-416. studies are needed to evaluate the cost- Duncan, DB (1955). Multiple range and multiple benefit relationship of providing supplement F tests. Biometrics. 11: 1-42. minerals. Groce, AW; Taylor, CE; Pettry, DE and Kerr, LA (1995). Levels of selenium and other Acknowledgements essential minerals in forages, bovine blood and serum relative to soil type. Vet. Clin. Nutr., 2: 146-152. The authors wish to thank Dr. Hedayati, Kamada, H; Nishimura, K; Krongyuti, P; who assisted in the sample analysis and Dr. Sukkasame, P; Phoengpong, N and Faisal Awawdeh for manuscript correction. Intramanee, S (2000). Selenium status of soil, herbage and beef cattle in southern Thailand. References Asian-Aust. J. Anim. Sci., 13: 757-760. McDowell, LR (2003). Minerals in animal and Andrés, S; Jiménez, A; Maňé, MC; Sánchez, J human nutrition. 2nd Edn., New York, and Barrera, R (1997). Relationships between Elsevier. P: 29. some soil parameters and the blood McDowell, LR and Arthington, JD (2005). glutathione peroxidase activity of grazing Mineral for grazing ruminants in tropical sheep. Vet. Rec., 141: 267-268. regions. 4th Edn., Florida, University of Andrés, S; Maňé, MC; Sánchez, J; Barrera, R Florida. P: 1. and Jiménez, A (1999). Temporal variations McDowell, LR; Salih, Y; Hentges, JF; Mason, RM and Wilcox, CJ (1989). Effect of mineral in blood glutathione peroxidase (GSHPx) activity in sheep at Pasture in a supplementation on tissue mineral Mediterranean Area. Vet. J., 157: 186-188. concentrations of grazing Brahman cattle II. Anon. (2003). White muscle disease in sheep and Trace Minerals Inst. J. Anim. Sci., 4: 6-13. goats of Markazi province. Markazi Province NRC (2007). Nutrient requirements of small Veterinary Administration. Vet. Reports. ruminants: sheep, goats, cervids and new Benotti, J and Benotti, N (1963). Protein-bound world camelids. 1st Edn., Washington, D.C., iodine, total iodine and butanol-extractable The National Academies Press, P: 135.

82

Iranian Journal of Veterinary Research, Shiraz University, Vol. 11, No. 1, Ser. No. 30, 2010

Paglia, DE and Valentine, WN (1967). Studies concentrations and glutathione peroxidase on the quantitative and qualitative activities in cattle grazing forages of various characterization of erythrocyte glutathione selenium concentrations. Am. J. Vet. Res., peroxidase. J. Lab. Clin. Med., 70: 158-169. 46: 1556-1560. Rotruck, JT; Pope, AL; Ganther, HE; Swanson, Vought, RL; London, WT; Lutwak, L and AB; Hafeman, DG and Hoekstra, WG (1973). Dublin, TD (1963). Reliability of estimates of Selenium: biochemical role as a component serum inorganic iodine and daily fecal and of glutathione peroxidase. Science. 179: 588- urinary iodine excretion from single casual 590. specimens. J. Clin. Endocrinol. Metab., 23: SAS Institute Inc. (1987). SAS/STAT Guide for 1218-1228. Personal Computers. Version 6 Edition. SAS Yuming, G; Zhiwei, L and Yuping, Z (1995). Institute Inc., Cary, NC. Selenium, iodine and thyroid hormone Snedecor, GW and Cochran, WG (1980). metabolism. Proceedings of a workshop on Statistical methods. 7th Edn., Ames, Iowa, mineral problems in sheep in northern China Iowa State University Press. and other regions of Asia. Beijing, China, 25- Stevens, JB; Olson, WG; Kraemer, R and 30 Sep., P: 52. Archambeau, J (1985). Serum selenium

83