Effect of various iodine supplementations, rapeseed meal application and two different iodine species on the iodine status and iodine excretion of dairy cows

The aim of the present study was to investigate the impact of various feed iodine supplementations up to the permitted maximum level in the EU, the effect of applying rapeseed meal (RSM) compared to a glucosinolate (GSL) free ration and the impact of two different iodine species (iodide, iodate) on milk, urinary, faecal and blood serum iodine as well as on T₃ and T₄ levels of blood. The results of the milk iodine are not completely shown but partly discussed in this paper. The study was conducted with 32 dairy cows, divided into 4 groups with 8 animals each. In two groups the cows were fed distillers dried grains with solubles (DDGS) as main protein source (16.5% of ration DM), in the other groups rapeseed meal (3.5 mmol GSL/kg) was applied. In each case half of the animals received feed with iodine in the form of potassium iodide, the other half as calcium iodate. Iodine supplementations of 0, 0.5, 1, 2, 3, 4 and 5 mg/kg DM were tested in consecutive periods of 21 days each. The supplementary iodine increased iodine contents of serum, urine and faeces. RSM application resulted in consistently higher iodine contents in the mentioned matrices just displaying significant differences at high supplementation levels. When feeding DDGS, at high iodine supplementations iodide caused higher serum and faecal iodine than iodate. Besides, the iodine species showed no consistent impact on the tested parameters. At the highest tested iodine supplementation (5 mg/kg DM) in the experimental groups (DDGS/iodide, DDGS/iodate, RSM/iodide, RSM/iodate) the iodine concentration of serum amounted to 234, 157, 334 and 361 µg/l, of urine to 1134, 1020, 2341 and 2513 µg/l and of faeces to 673, 354, 715 and 790 µg/kg fresh matter. At the same supplementation level T₄ was significantly lowered. No impact was shown for the RSM application and the iodine species on T₃ and T₄. The results of the present study indicate that high iodine intakes not only cause strong increases in milk and urinary iodine but also lead to a considerable rise of iodine excretion via faeces. RSM in feed causes a shift of iodine normally excreted via milk to an excretion via urine and faeces accompanied by higher serum iodine.     

Ozone disinfection of eggs from gilthead seabream Sparus aurata, sea bass Dicentrarchus labrax, red porgy, and common dentex Dentex dentex

The risk of fish pathogen transmission via eggs can be reduced by disinfection in ozonated seawater. The aim of this study was to determine the suitable conditions for ozone disinfection of the eggs of gilthead seabream Sparus aurata, sea bass Dicentrarchus labrax, red porgy Pagrus pagrus, and common dentex Dentex dentex. The eggs were disinfected with a concentration (C) of 0.5 mg of ozone/L of water at four different exposure times (T = 2, 4, 8, and 16 min). The hatching rate was determined in triplicate for each treatment. Bacterial colonies were counted on tryptic soy agar and thiosulfate-citrate-bile salts-sucrose agar. At the end of the experiment, bacterial load and hatching rate were assessed together to determine the optimal ozone treatment values, which were estimated in CT units (i.e., C [= 0.5 mg/L] x T [min]). Optimal values were CT 2-4 (T = 4-8 min; 18 degrees C) for gilthead seabream and red porgy, CT 2 (T = 4 min; 18 degrees C) for common dentex, and CT 4 (T = 8 min; 15 degrees C) for sea bass.     

一种复方聚维酮碘凝胶有效碘稳定性研究

制备复方聚维酮碘凝胶,研究一种对复方聚维酮碘凝胶中有效碘含量影响相对较小的配方。采用正交试验法筛选复方聚维酮碘凝胶的最佳配方;以各温度项下有效碘质量浓度的自然对数（lgC）对时间（t）做线性回归分析,得到直线方程,推算出贮存期。结果表明,制备的凝胶剂均匀细腻,筛选出复方聚维酮碘凝胶最佳配方为：100 g复方聚维酮碘凝胶中氢氧化钠0.075g,4%聚维酮碘3.75 g,碘酸钾0.50 g,丙二醇10 g。各温度条件下加热时间与有效碘质量浓度对数变化线性关系良好,25℃时贮存期为799 d。     

The Impact of Egg Ozonation on Hatching Success,Larval Growth,and Survival of Atlantic Cod,Atlantic Salmon,and Rainbow Trout

The direct exposure of fish eggs to ozonated water has generated interest as a means of ensuring pathogen-free eggs without the use of harsh chemicals. However, there are numerous knowledge gaps, including safe contact times, exposure levels, and potential long-term effects on aquaculture species in both freshwater and seawater. The effect of different ozone (O₃) doses (0.5–1.0, 1.5–2.0, and 2.5–3.0 mg of O₃/L for 90 s) on recently fertilized eggs of Atlantic Cod Gadus morhua and eyed eggs of Atlantic Salmon Salmo salar and Rainbow Trout Oncorhynchus mykiss was evaluated in comparison with the effects of two commercial disinfectants: Perosan (0.004 mg/L) and Ovadine (100 mg/L). The impact of ozone application was evaluated based on hatching success, larval nucleic acid concentration, larval growth, and survival. Overall, results indicated that ozonation of Atlantic Cod eggs at a dose less than 3.0 mg/L for 90 s produced no negative effect on the larvae up to 30 d posthatch. Furthermore, ozonation of Atlantic Salmon and Rainbow Trout eggs generated no negative effect on the larvae, based on monitoring until 85% yolk sac re-absorption (16 d posthatch).

Received May 6, 2014; accepted October 24, 2014     

Impact of iodine supplementation of dairy cows on milk production and iodine concentrations in milk

AIM: To determine the effect of iodine supplementation on milk production and iodine concentrations in milk for pasture-fed, seasonally calving dairy cows. METHODS: The study was run over two consecutive seasons on the same dairy farm. In Trial One, 294 Friesian dairy cows were either untreated or injected intramuscularly three times with iodised oil (2,370 mg iodine/dose) at the start of lactation (Day 1) and at about 100-day intervals thereafter. Iodine concentrations in milk were determined prior to each injection on Days 1, 98 and 210, and milk, fat and protein yields measured on Days 43, 98, 176 and 238. In Trial Two, 234 Friesian dairy cows were either untreated or injected intramuscularly with iodised oil (2,370 mg iodine/dose) in early lactation (Day 1) and 99 days later. Iodine concentrations in milk were determined prior to treatment on Days 1, 55 and 161. Serum thyroxine (T4) and triiodothyronine (T3) concentrations were determined in the latter two samples and milk, protein and fat yields were determined on Days 25, 119, 182 and 221. In both trials, pasture was sampled at 1- or 3-monthly intervals and iodine concentrations in herbage measured. RESULTS: Iodine concentrations in pasture averaged 0.24 mg/kg dry matter (DM) in both seasons and varied little over the experimental period. Iodine concentrations in milk from unsupplemented cows were <20 microg/L in both trials. Three iodine injections at about 100-day intervals increased iodine concentrations in milk to 58 microg/L for at least 98 days after each treatment. Two iodine injections at about 100-day intervals raised milk iodine concentrations to 160 microg/L and 211 microg/L at least 55 days after each treatment, but had no effect on serum thyroid hormone concentrations. Iodine supplementation had no significant effect on milk, milkfat or milk protein yield. CONCLUSIONS: Pastures in New Zealand that contained 0.24 mg iodine/kg DM appeared to provide an adequate iodine intake for dairy cows. Intramuscular injections of iodine resulted in significant increases in iodine concentrations in milk. CLINICAL SIGNIFICANCE: Increasing iodine concentrations in milk via intramuscular injection of iodine could provide a method for significantly increasing iodine intakes of humans, in particular, children.     

Ozone Disinfection of Eggs from Gilthead Seabream Sparus aurata,Sea Bass Dicentrarchus labrax,Red Porgy,and Common Dentex Dentex dentex

Abstract

The risk of fish pathogen transmission via eggs can be reduced by disinfection in ozonated seawater. The aim of this study was to determine the suitable conditions for ozone disinfection of the eggs of gilthead seabream Sparus aurata, sea bass Dicentrarchus labrax, red porgy Pagrus pagrus, and common dentex Dentex dentex. The eggs were disinfected with a concentration (C) of 0.5 mg of ozone/L of water at four different exposure times (T = 2, 4, 8, and 16 min). The hatching rate was determined in triplicate for each treatment. Bacterial colonies were counted on tryptic soy agar and thiosulfate–citrate–bile salts–sucrose agar. At the end of the experiment, bacterial load and hatching rate were assessed together to determine the optimal ozone treatment values, which were estimated in CT units (i.e., C [= 0.5 mg/L] × T [min]). Optimal values were CT 2–4 (T = 4–8 min; 18°C) for gilthead seabream and red porgy, CT 2 (T = 4 min; 18°C) for common dentex, and CT 4 (T = 8 min; 15°C) for sea bass.

Received April 12, 2011; accepted February 2, 2012     

Nitrate-induced goiter in captive whitespotted bamboo sharks Chilosryllium plagiosum

Elasmobranch susceptibility to goiter formation in captive environments has been well documented. Until recently, most public aquariums operated under the belief that the etiology of goiter in elasmobranchs was nutritional and specifically caused by insufficient dietary iodine. Recent studies have demonstrated that high environmental nitrate (NO3-N) inhibits the ability of the thyroid gland to utilize available iodide, resulting in thyroid gland overstimulation by thyroid stimulating hormone and ultimately leading to the development of goiter. The objective of this study was to evaluate the effects of high environmental nitrate concentrations on thyroid function in juvenile whitespotted bamboo sharks Chiloscyllium plagiosum. In July 2008, five juveniles (80-150 g) were exposed to a low-nitrate environment (NO3-N concentration < 1 mg/L of water) and five were exposed to an elevated-nitrate environment (NO3-N = 70 mg/L) for 29 d in a flow-through natural seawater system. Nitrate exposure did not affect growth rates (e.g., weight, length, and condition factor) and did not alter free plasma thyroxine concentrations during the 29-d experimental period. However, histological examination of thyroid glands from sharks exposed to elevated nitrate revealed the development of diffuse hyperplastic goiter. With increasing restrictions on water use, most modern aquaria operate as recirculating systems, which results in higher and more chronic nitrate exposure for captive animals. Goiter is one of the most common health problems in captive elasmobranchs, and this study suggests that nitrate exposure is an important factor in the etiology of this disease.     

Effects of supplementary iodine on the performance and egg traits of laying hens

1. This experiment was carried out to determine the effects of dietary iodine supplementation on the performance and egg traits of laying hens. A total of 600 SHSY type brown layers aged 21 weeks of age were chosen at random from a large flock. They were randomly distributed into 30 pens at 20 hens per pen. Each treatment comprised 6 replicates of 20 layers in groups of 5 birds. The diets were supplemented with 0, 3, 6, 12 and 24 mg/kg iodine as calcium iodate. The experimental period lasted 30 weeks. 2. There were no significant differences among the groups in body weight, food consumption, egg production, food consumption per kg eggs, eggshell index, eggshell breaking strength, shell thickness or egg yolk index. 3. Supplementation of the diet with 12 mg/kg iodine increased food consumption per dozen eggs compared to the groups fed on diets supplemented with 0 and 6 mg/kg iodine. 4. Egg weight was less in groups fed on diets supplemented with 12 and 24 mg/kg iodine than in the group receiving no iodine supplementation. 5. Iodine supplementation to provide 12 and 24 mg/kg reduced egg albumen index and egg Haugh units. 6. There were no significant differences among the groups in egg cholesterol and egg yolk cholesterol contents. 7. The iodine concentrations in egg yolk, egg albumen and whole egg increased with increased iodine supplementation. 8. As a result, the 3 and 6 mg/kg iodine supplementation of diet could be used to enrich the eggs with iodine without any adverse effect on performance and egg traits.     

Nitrate-Induced Goiter in Captive Whitespotted Bamboo Sharks Chiloscyllium plagiosum

Abstract

Elasmobranch susceptibility to goiter formation in captive environments has been well documented. Until recently, most public aquariums operated under the belief that the etiology of goiter in elasmobranchs was nutritional and specifically caused by insufficient dietary iodine. Recent studies have demonstrated that high environmental nitrate (NO₃-N) inhibits the ability of the thyroid gland to utilize available iodide, resulting in thyroid gland overstimulation by thyroid stimulating hormone and ultimately leading to the development of goiter. The objective of this study was to evaluate the effects of high environmental nitrate concentrations on thyroid function in juvenile whitespotted bamboo sharks Chiloscyllium plagiosum. In July 2008, five juveniles (80–150 g) were exposed to a low-nitrate environment (NO₃-N concentration < 1 mg/L of water) and five were exposed to an elevated-nitrate environment (NO₃-N = 70 mg/L) for 29 d in a flow-through natural seawater system. Nitrate exposure did not affect growth rates (e.g., weight, length, and condition factor) and did not alter free plasma thyroxine concentrations during the 29-d experimental period. However, histological examination of thyroid glands from sharks exposed to elevated nitrate revealed the development of diffuse hyperplastic goiter. With increasing restrictions on water use, most modern aquaria operate as recirculating systems, which results in higher and more chronic nitrate exposure for captive animals. Goiter is one of the most common health problems in captive elasmobranchs, and this study suggests that nitrate exposure is an important factor in the etiology of this disease.

Received August 4, 2010; accepted February 22, 2011     

Comparative Uptake of Orally Administered Difloxacin in Atlantic Salmon in Freshwater and Seawater

Abstract

Fluoroquinolones are synthetic antibacterials with potential use for treatment of fish diseases. This study examined the comparative uptake of difloxacin, administered as a single oral gavage, by juvenile Atlantic salmon Salmo salar in freshwater and in seawater. In separate freshwater and seawater experiments with fish of the same spawning cohort, the concentration of difloxacin in plasma and fillets was determined at 1, 2, 4, 8, 12, 18, 24, and 48 h after the fish received the dose. Although plasma difloxacin concentration began to plateau in the freshwater fish at about 24 h, the highest average, 1,195 ng/mL, was in fish sampled at 48 h; thus, the plasma levels continued to rise through the end of the test. A similar pattern was observed in fillets from fish held in freshwater, but the peak average fillet concentration at 48 h was 4,737 ng/g. Contrastingly, in the seawater study, the average peak plasma concentration of 678 ng/mL was observed at 8 h after gavage and the peak average fillet concentration of 924 ng/g was observed at 18 h. Although difloxacin concentrations were higher in the freshwater-held fish than in the seawateradapted fish, the results suggest that difloxacin could be efficacious in treating bacterial diseases of Atlantic salmon in both freshwater and seawater.     

Commercial diet induced hypothyroidism due to high iodine. A histological and radiological analysis.

A number of puppies of the School Hospital of the Faculty of Veterinary Science-UBA showed bone changes. Measurement of the iodine content of the commercial diet showed a significant increase in its content. Iodine excess causes alterations in thyroid function and morphology, and its hormones have a direct action on bone formation. Three groups of puppies were fed on different diets: a home-prepared diet, a commercial diet (containing 5.6 mg potassium iodide/kg dry food), and a home-prepared diet supplemented with 5.6 mg potassium iodide/kg dry food. Groups B and C developed hypothyroidism. A significant decrease (p<0.05) in the styloid apophyseal surface was found in groups B and C vs. A, determined by radiography. Histologically, the hypertrophied cartilage was shorter in groups B and C than in group A (p<0.0001). The present results suggest that commercial diets with a high iodine content may cause hypothyroidism and changes in bone metabolism.     

Effects of chlorine, iodine, and quaternary ammonium compound disinfectants on several exotic disease viruses

The effects of three representative disinfectants, chlorine (sodium hypochlorite), iodine (potassium tetraglicine triiodide), and quaternary ammonium compound (didecyldimethylammonium chloride), on several exotic disease viruses were examined. The viruses used were four enveloped viruses (vesicular stomatitis virus, African swine fever virus, equine viral arteritis virus, and porcine reproductive and respiratory syndrome virus) and two non-enveloped viruses (swine vesicular disease virus (SVDV) and African horse sickness virus (AHSV)). Chlorine was effective against all viruses except SVDV at concentrations of 0.03% to 0.0075%, and a dose response was observed. Iodine was very effective against all viruses at concentrations of 0.015% to 0.0075%, but a dose response was not observed. Quaternary ammonium compound was very effective in low concentration of 0.003% against four enveloped viruses and AHSV, but it was only effective against SVDV with 0.05% NaOH. Electron microscopic observation revealed the probable mechanism of each disinfectant. Chlorine caused complete degeneration of the viral particles and also destroyed the nucleic acid of the viruses. Iodine destroyed mainly the inner components including nucleic acid of the viruses. Quaternary ammonium compound induced detachment of the envelope of the enveloped viruses and formation of micelle in non-enveloped viruses. According to these results, chlorine and iodine disinfectants were quite effective against most of the viruses used at adequately high concentration. The effective concentration of quaternary ammonium compound was the lowest among the disinfectants examined.     

饲粮碘含量对牦牛体外瘤胃发酵的影响

本试验旨在研究饲粮碘含量对牦牛体外瘤胃发酵的影响。以碘化钾作为添加形式,以牦牛饲粮为底物进行体外发酵,底物碘含量分别为0.1、0.3、0.5、0.7、0.9 mg/kg,共发酵48 h。发酵结束测定总产气量、瘤胃发酵特性指标及消化酶活力。结果表明:当底物碘含量为0.3 mg/kg时,发酵液微生物蛋白质(M CP)、乙酸(C2)、丙酸(C3)、丁酸(C4)、异戊酸(i-C5)、戊酸(C5)、总挥发性脂肪酸(TVFA)浓度以及淀粉酶(AMS)、脂肪酶(LPS)、胰蛋白酶(TYS)活力均达到最大值,分别为3.694 g/L、56.286 mmol/L、28.906 mmol/L、9.507 mmol/L、1.552 mmol/L、0.919 mmol/L、97.769 mmol/L、1.567 U/mL、0.453 U/mL、60.787 U/mL;当碘含量为0.5 mg/kg时,干物质消化率(DMD)达到最大值,为69.39%,显著高于其他处理(P0.05);在碘含量为0.7 mg/kg时,发酵液纤维素酶(CLS)活力达到最大值,为79.956 U/mL,发酵液乙酸/丙酸最低,为1.636。综合各项指标得出,在体外条件下,在底物碘含量为0.3~0.7 mg/kg时,牦牛体外瘤胃发酵处较高水平。     

Transmission of Loma salmonae (Microsporea) to chinook salmon in sea water.

Transmission studies were conducted to determine if Loma salmonae was transmissible in sea water. Transmission of L. salmonae to chinook salmon (Oncorhynchus tshawytscha) held in sea water was achieved by exposing fish to macerated, infected gill tissue. Fish were exposed in seawater in a flow-through aquarium, and the infection was detected as soon as 5 wk after exposure. Heavily infected fish exhibited numerous xenomas in the branchial arteries, central venous sinusoids, and within the blood channels of the lamellae. The pathological changes were similar to those seen in pen-reared salmon with L. salmonae infections. The infection was not observed in Atlantic salmon (Salmo salar), Pacific herring (Clupea pallasi, family Clupeidae), or shiner perch (Cymatogaster aggregata, family Embiotocidae), experimentally exposed using identical methods. This study suggests that L. salmonae is transmissible to chinook salmon in seawater netpens. Fish farmers and fish health specialists should consider this possibility when developing and implementing strategies to control the infection.     

臭氧水防治草莓白粉病的效果评价

以草莓白粉病为研究对象,通过不同浓度的臭氧水以及臭氧水与枯草芽孢杆菌协同防治来评价防治效果。结果表明,采用1.0-1.5 mg·L-1的臭氧水每 2 d喷雾 1 次,连续使用,对草莓白粉病具有一定的防治效果,臭氧水与枯草芽孢杆菌1000倍液协同使用,对草莓白粉病的防治效果与常规化防效果相当,第 2 次处理后 14 d的防效达139.44%,持效期明显延长。因此在草莓生产中白粉病预防可以间隔3-5d单独使用1.0-1.5mg·L-1浓度的臭氧水;治疗白粉病可以与枯草芽孢杆菌协同使用,间隔5-7d喷施1.0-1.5mg·L-1浓度的臭氧水,待臭氧水风干以后再喷1000倍液的枯草芽孢杆菌,此方法可有效降低化学农药的使用量,具有较高推广价值。     

Evaluation of bithionol as a bath treatment for amoebic gill disease caused by Neoparamoeba spp

This study examined the toxicity of bithionol to Atlantic salmon Salmo salar and rainbow trout Oncorhynchus mykiss in fresh- and seawater and the efficacy of bithionol as a 1h seawater bath treatment for amoebic gill disease (AGD). To examine toxicity, fish were bathed for 1, 3 and 6h in bithionol, an anti-protozoal at 0, 1, 5, 10, 25 and 35mgL(-1) with toxicity determined by time to morbidity. Efficacy was examined by bathing AGD-affected Atlantic salmon and rainbow trout for 1h at bithionol concentrations of 1-25mgL(-1). Efficacy was determined by examining gill amoeba counts and identifying percent lesioned gill filaments at 1 and 24h after bath exposure to bithionol. For both species, bithionol was determined to be toxic at 25 and 35mgL(-1) exhibiting median lethal times (LT50s) ranging from 21 to 84min. Morbidity occurred in the 5 and 10mgL(-1) treatments, however, due to sampling regime there were not enough fish available to calculate LT50s. Only bithionol at 1mgL(-1) was considered non-toxic with no signs of morbidity. Bithionol was more toxic in seawater than freshwater and had no acute effects on gill Na+/K+ ATPase and succinic dehydrogenase, or plasma osmolality and chloride concentration. Bithionol at 1mgL(-1) reduced percent lesioned gill filaments in Atlantic salmon and rainbow trout by 33 and 27 per cent, respectively, compared to the seawater control. Similarly, numbers of amoeba were reduced by 33 and 43 per cent for Atlantic salmon and rainbow trout, respectively, when compared to the seawater control. Furthermore, bithionol reduced percent lesioned gill filaments as much as did the current industry standard of freshwater. This study demonstrated that a 1h seawater bath containing 1mgL(-1) bithionol could be an improvement to the current method of treatment for AGD-affected Atlantic salmon and rainbow trout.     

不同浓度海水灌溉对香根草生长的影响

模拟香根草在海边滩涂湿地上的生长环境,采用不同盐分浓度的海水浇灌移栽后的香根草,试验结果显示,不同浓度海水灌溉会影响香根草移栽后的成活率及其地上部和地下部器官的生长发育。不同浓度海水对香根草移栽后的成活率影响显著,0倍海水浓度处理香根草成活率1009,6,而2倍海水浓度处理移栽香根草则全部死亡,并且供试的4个处理,随着海水浓度升高抑制香根草生长发育的效应增强,0倍海水浓度灌溉对香根草生长发育没有抑制作用,0．5倍海水浓度和1倍海水浓度香根草生长受轻微影响,且两者之间没有显著差异,但2倍海水浓度浇灌香根草地上部的分蘖、绿叶数、株高、茎叶干重和地下部的最大根长、一级根条数、根体积、根干重及根茎比等性状指标都显著受到抑制。     

Supplementation of algae to the diet of pigs: a new possibility to improve the iodine content in the meat

Meat products with a higher iodine content can be produced through feeding animals with a diet supplemented with inorganic iodine salts or with algae containing high iodine. This may help to improve daily iodine intake and to control iodine deficiency disorders (IDD) in man. In the present study a total of 40 crossbred pigs (Deutsche Landrasse × Piétrain) with an average body weight of 17 kg were allotted to either a control group, to two groups receiving potassium iodide (KI) at different concentrations (5 or 8 mg iodine per kg of feed) or to two groups receiving the algae Laminaria digitata containing the same amount of iodine. After pigs were fed with iodine-supplemented diets for 3 months, it was found that compared to the control group the iodine content increased by up to 45% in fresh muscle, by 213% in adipose tissue, by 124% in the heart, by 207% in the liver and by 127% in the kidneys. There was a significant (p < 0.01) higher concentration of serum thyroxine (T₄) and a lower concentration of serum triiodothyronine (T₃) in those iodine-supplemented groups. The iodine content of urine from all iodine-supplemented groups was also greatly increased. Furthermore, it was shown that the supplementation of algae into feed could increase daily body weight gain by 10% (p > 0.05). It is suggested that the carry-over of iodine through feeding pigs with an algae-supplemented feed could be beneficial to both the control of IDD and the improvement of pig production.     

Toxicological effects and recovery of the corneal epithelium in Cyprinus carpio communis Linn. exposed to monocrotophos: an scanning electron microscope study

This study was conducted based on the evidence of fish habitats in North India being affected by organophosphate pesticides draining from agricultural fields into bodies of water, especially during the rainy season. Various tissues of fish such as scales, gills ovaries, kidney, and liver have been studied from the toxicological point of view, but the toxicological effects of aquatic pollutants on fish cornea have not been investigated to date. We conducted comparative toxicological studies on the cornea of Cyprinus carpio communis using two sublethal (0.038 and 0.126 ppm) concentrations of monocrotophos pesticide for 30 days. Corneas from all the groups were evaluated by a scanning electron microscope. The fish exposed to the monocrotophos pesticide developed corneal necrosis due to the formation of crystalloid‐like structures, thinning and shrinkage of microridges on the corneal epithelium. After 30 days, fish from the monocrotophos‐treated tank were transferred to normal environmental conditions. After 60 days under natural condition, epithelial cells did not fully recover. In conclusion, exposure to monocrotophos induces irreversible changes in the cornea of C. carpio communis. As fish and mammalian visual systems share many similarities, the reported finding may offer useful insights for further toxicological and ophthalmological studies in humans.     

Effect of dietary vitamin E on cortisol and glucose responses to handling stress in juvenile beluga Huso huso

An 8-week feeding experiment was conducted to investigate the effect of dietary vitamin E on the physiological response to handling stress in juvenile beluga Huso huso. Fish were fed six experimental diets supplemented with 0, 25, 50,100, 200, or 400 mg Dl-all-rac-alpha-tocopherol acetate/kg diet. At the end of the experiment, the fish in each tank were subjected to acute handling and air exposure stress. Cortisol and glucose were measured as the primary hormonal and secondary metabolic responses to the stressors, both before and 3 h after application of the stressors. The growth parameters and feed utilization rates were significantly lower in fish fed the diet not supplemented with vitamin E than in fish fed diets supplemented with vitamin E. Cortisol concentration was not affected by dietary treatment but glucose concentration was. Fish fed vitamin E at 0, 25, 100, and 400 mg/kg diet had higher concentrations of glucose than those fed vitamin E at 50 and 200 mg/kg. However, fish fed diets with 50 and 200 mg/kg exhibited higher growth rates. These results indicate that dietary vitamin E has some effect on plasma glucose but no effect on plasma cortisol. In general, when the stressors were applied to belugas, the glucose and cortisol responses were relatively low. This may be due to higher resistance and lower physiological responses to these types of stressors by this species or by chondrosteans in general.