Subclinical thiamine deficiency results in failed reproduction in Arctic foxes

Thiamine deficiency can result in life-threatening physiological and neurological complications. While a thiamine-deficient diet may result in the onset of such symptoms, the presence of thiaminase - an enzyme that breaks down thiamine - is very often the cause. In such instances, thiaminase counteracts the bioavailability and uptake of thiamine, even when food-thiamine levels are adequate. Here, we report on a case of failed reproduction in seven Arctic fox (Vulpes lagopus) breeding pairs kept at a captive breeding facility, including the presentation of severe thiamine deficiency symptoms in two male foxes. Symptoms included ataxia, obtundation, truncal sway, star-gazing and visual impairment. Blood tests were inconclusive, yet symptoms resolved following treatment with a series of thiamine hydrochloride injections, thereby verifying the diagnosis. A fish-dominated feed, which for the first time had been frozen for a prolonged period, was identified as the likely source of thiaminase and subsequent deterioration in the animals' health. Symptoms in the two males arose during the annual mating period. All seven breeding pairs at the captive breeding station failed to reproduce - a phenomenon never recorded during the captive breeding facility's preceding 17-year operation. Relating our findings to peer-reviewed literature, the second part of this case report assesses how thiamine deficiency (due to thiaminase activity) likely resulted in subclinical effects that impaired the production of reproduction hormones, and thereby led to a complete breeding failure. While previous work has highlighted the potentially lethal effects of thiamine deficiency in farmed foxes, this is, to our knowledge the first study showing how subclinical effects in both males and females may inhibit reproduction in foxes in general, but specifically Arctic foxes. The findings from our case report are not only relevant for captive breeding facilities, but for the welfare and management of captive carnivorous animals in general.

Establishment of a reference interval for thiamine concentrations in healthy dogs and evaluation of the prevalence of absolute thiamine deficiency in critically ill dogs with and without sepsis using high-performance liquid chromatography

OBJECTIVE

To determine the normal reference interval (RI) for thiamine concentrations in healthy dogs and investigate the prevalence of thiamine deficiency in critically ill dogs with and without sepsis.

DESIGN

Prospective, observational, multicenter study, conducted between 2019 and 2021.

SETTING

Two veterinary university teaching hospitals.

ANIMALS

A total of 109 dogs were enrolled into 3 groups: 40 healthy dogs, 33 dogs with suspected or confirmed sepsis and evidence of tissue hypoperfusion (Doppler blood pressure ≤90 mm Hg or plasma lactate ≥3 mmol/L), and 36 dogs with other critical illnesses and evidence of tissue hypoperfusion.

INTERVENTIONS

For each dog, CBC, serum biochemistry, plasma lactate concentration, whole-blood thiamine concentration, blood pressure, vital parameters, Acute Patient Physiologic and Laboratory Evaluation (APPLE)fast score, and clinical outcomes were recorded, alongside basic patient parameters and dietary history. Whole-blood thiamine pyrophosphate (TPP) concentrations were measured using high-performance liquid chromatography.

MEASUREMENTS AND MAIN RESULTS

The RI for whole-blood TPP in healthy dogs was 70.9-135.3 μg/L. Median TPP concentrations were significantly lower in septic dogs compared to healthy controls (P = 0.036). No significant difference in median TPP concentrations was found between septic dogs and nonseptic critically ill dogs, or between healthy dogs and nonseptic critically ill dogs. TPP concentrations were below the normal RI in 27.3% of septic dogs, compared to 19.4% of nonseptic critically ill dogs (P = 0.57). No correlations were found between TPP concentrations and lactate concentrations, age, body condition scores, time since last meal, RBC count, serum alanine aminotransferase, APPLEfast scores, or patient outcomes.

CONCLUSIONS

TPP concentrations were significantly lower in septic dogs compared to healthy controls, with an absolute thiamine deficiency found in 27.3% of septic dogs. The established TPP RI allows for further investigation of thiamine deficiency in critically ill dogs.

Severe thiamine deficiency in eastern Baltic cod (Gadus morhua)

The eastern Baltic cod (Gadus morhua) population has been decreasing in the Baltic Sea for at least 30 years. Condition indices of the Baltic cod have decreased, and previous studies have suggested that this might be due to overfishing, predation, lower dissolved oxygen or changes in salinity. However, numerous studies from the Baltic Sea have demonstrated an ongoing thiamine deficiency in several animal classes, both invertebrates and vertebrates. The thiamine status of the eastern Baltic cod was investigated to determine if thiamine deficiency might be a factor in ongoing population declines. Thiamine concentrations were determined by chemical analyses of thiamine, thiamine monophosphate and thiamine diphosphate (combined SumT) in the liver using high performance liquid chromatography. Biochemical analyses measured the activity of the thiamine diphosphate-dependent enzyme transketolase to determine the proportion of apoenzymes in both liver and brain tissue. These biochemical analyses showed that 77% of the cod were thiamine deficient in the liver, of which 13% had a severe thiamine deficiency (i.e. 25% transketolase enzymes lacked thiamine diphosphate). The brain tissue of 77% of the cod showed thiamine deficiency, of which 64% showed severe thiamine deficiency. The thiamine deficiency biomarkers were investigated to find correlations to different biological parameters, such as length, weight, otolith weight, age (annuli counting) and different organ weights. The results suggested that thiamine deficiency increased with age. The SumT concentration ranged between 2.4–24 nmol/g in the liver, where the specimens with heavier otoliths had lower values of SumT (P = 0.0031). Of the cod sampled, only 2% of the specimens had a Fulton’s condition factor indicating a healthy specimen, and 49% had a condition factor below 0.8, indicating poor health status. These results, showing a severe thiamine deficiency in eastern Baltic cod from the only known area where spawning presently occurs for this species, are of grave concern.

Thiamine Levels in Muscle and Eggs of Adult Pacific Salmon from the Fraser River, British Columbia

Multiple species and stocks of Pacific salmon Oncorhynchus spp. have experienced large declines in the number of returning adults over a wide region of the Pacific Northwest due to poor marine survival (low smolt-to-adult survival rates). One possible explanation for reduced survival is thiamine deficiency. Thiamine (vitamin B₁ ) is an essential vitamin with an integral role in many metabolic processes, and thiamine deficiency is an important cause of salmonid mortality in the Baltic Sea and in the Laurentian Great Lakes. To assess this possibility, we (1) compared muscle thiamine content over time in a holding experiment using Fraser River (British Columbia) Sockeye Salmon O. nerka to establish whether adults that died during the holding period had lower thiamine levels than survivors, (2) measured infectious loads of multiple pathogens in held fish, and (3) measured egg thiamine content from four species of Pacific salmon collected on Fraser River spawning grounds. Chinook Salmon O. tshawytscha had the lowest egg thiamine, followed by Sockeye Salmon; however, egg thiamine concentrations were above levels known to cause overt fry mortality. Thiamine vitamers in the muscle of Fraser River adult Sockeye Salmon shifted over a 13-d holding period, with a precipitous decline in thiamine pyrophosphate (the active form of thiamine used in enzyme reactions) in surviving fish. Survivors also carried lower loads of Flavobacterium psychrophilum than fish that died during in the holding period. Although there is no evidence of thiamine deficiency in the adults studied, questions remain about possible thiamine metabolism-fish pathogen relationships that influence survival.

Expression of Thiaminase in Zebrafish (Danio rerio) is Lethal and Has Implications for Use as a Biocontainment Strategy in Aquaculture and Invasive Species

As the world increasingly relies on aquaculture operations to meet rising seafood demands, reliable biocontainment measures for farmed fish stocks are desired to minimize ecological impacts arising from interactions of cultured fish with wild populations. One possible biocontainment strategy is to induce a dietary dependence on a vitamin, such as thiamine (vitamin B1), required for survival. Fish expressing thiaminase (an enzyme that degrades thiamine) within a confined aquaculture facility could receive supplemental thiamine to allow survival and normal growth, whereas escapees lacking this dietary rescue would die from thiamine deficiency. To test the concept and efficacy of such a dietary dependency system (for potential future use in larger aquaculture species), we expressed thiaminase in zebrafish as a test model. We drove the expression of thiaminase under the strong ubiquitous and constitutive control of the CMV promoter which resulted in non-viable fish, indicating that the thiaminase sequence kills fish. However, the CMV promoter is too strong to allow conditional survival since the lethality could not be rescued by exogenous thiamine provided as a supplement to typical food. In addition, microinjection of 0.5 pg of thiaminase mRNA in zebrafish embryos at the one-cell stage resulted in 50% larval mortality at 5 days post-fertilization (dpf), which was partially rescued by thiamine supplementation. Evaluating the efficacy of biocontainment strategies helps assess which methods can reliably prevent ecological impacts arising from breaches in physical containment systems that release engineered organisms to nature, and consequently provides critical information for use in regulatory risk assessment processes.

Thiamin deficiency induces impaired fish gill immune responses, tight junction protein expression and antioxidant capacity: Roles of the NF-κB, TOR, p38 MAPK and Nrf2 signaling molecules

In this study, we investigate the effects of dietary thiamin deficiency on immune responses, tight junctions, antioxidant capacity and related signaling molecules in the gills of young grass carp (Ctenopharyngodon idella). Fish were fed diets that contained 0.12-2.04 mg thiamin kg(-1) for 8 weeks. We found that dietary thiamin deficiency resulted in reduced complement 3 content, lysozyme and acid phosphatase activities, mRNA levels of hepcidin, liver-expressed antimicrobial peptides 2, transforming growth factor (TGF)-β1, interleukin (IL)-10, inhibitor protein-κBα (IκBα), ribosomal S6 protein kinase 1 and target of rapamycin (TOR) and increased expression of interferon-γ2, tumor necrosis factor-α, TGF-β2, IL-1β, IL-8, IκB kinases (IKKβ and IKKγ) and nuclear factor-κB p65 (NF-κB p65). Our findings showed that thiamin deficiency reduced the immune status of fish gills. Furthermore, thiamin deficiency resulted in reduced mRNA transcript levels of claudin b, claudin 3, claudin 12, zonula occludens 1 (ZO-1) and occludin and increased mRNA transcript levels of claudin 15a, myosin light-chain kinase (MLCK) and p38 mitogen-activated protein kinase (p38 MAPK) in fish gill tissues. These data suggested that thiamin deficiency disrupted tight junction-mediated fish gill barrier function. Additionally, reactive oxygen species, malondialdehyde and protein carbonyl levels and both the activities and expression levels of Cu/Zn superoxide dismutase, catalase, glutathione peroxidase, glutathione-S-transferases and glutathione reductase, as well as NF-E2-related factor 2 gene expression in fish gills, were lower in fish fed a thiamin-deficient diet. By contrast, thiamin deficiency increased levels of Kelch-like-ECH-associated protein 1a (Keap1a) and Keap1b mRNA transcript expression in fish gills. Taken together, our findings indicated that thiamin deficiency impaired fish gill health by effects on the expression of genes encoding cytokines, tight junction proteins, antioxidant enzymes, NF-κB p65, MLCK and Nrf2.

In vitro immune functions in thiamine-replete and -depleted lake trout (Salvelinus namaycush)

In this study we examined the impacts of in vivo thiamine deficiency on lake trout leukocyte function measured in vitro. When compared outside the context of individual-specific thiamine concentrations no significant differences were observed in leukocyte bactericidal activity or in concanavalin A (Con A), and phytohemagglutinin-P (PHA-P) stimulated leukocyte proliferation. Placing immune functions into context with the ratio of in vivo liver thiamine monophosphate (TMP--biologically inactive form) to thiamine pyrophosphate (TPP--biologically active form) proved to be the best indicator of thiamine depletion impacts as determined using regression modeling. These observed relationships indicated differential effects on the immune measures with bactericidal activity exhibiting an inverse relationship with TMP to TPP ratios, Con A stimulated mitogenesis exhibiting a positive relationship with TMP to TPP ratios and PHA-P stimulated mitogenesis exhibiting no significant relationships. In addition, these relationships showed considerable complexity which included the consistent observation of a thiamine-replete subgroup with characteristics similar to those seen in the leukocytes from thiamine-depleted fish. When considered together, our observations indicate that lake trout leukocytes experience cell-type specific impacts as well as an altered physiologic environment when confronted with a thiamine-limited state.

Impact of thiamine deficiency on T-cell dependent and T-cell independent antibody production in lake trout

Lake trout Salvelinus namaycush on thiamine-replete and thiamine-depleted diets were evaluated for the effects of thiamine status on in vivo responses to the T-dependent antigen trinitophenol (TNP)-keyhole limpet hemocyanin (TNP-KLH), the T-independent antigen trinitrophenol-lipolysaccaharide (TNP-LPS), or Dulbecco's phosphate-buffered saline (DPBS; negative control fish). Plasma antibody concentrations were evaluated for possible differences in total anti-TNP activity as well as differences in response kinetics. Associations between anti-TNP activity and muscle and liver thiamine concentrations as well as ratios of muscle-to-liver thiamine to anti-TNP activity were also examined. Thiamine-depleted lake trout that were injected with TNP-LPS exhibited significantly more anti-TNP activity than thiamine-replete fish. The depleted fish injected with TNP-LPS also exhibited significantly different response kinetics relative to thiamine-replete lake trout. No differences in activity or kinetics were observed between the thiamine-replete and -depleted fish injected with TNP-KLH or in the DPBS negative controls. Anti-TNP activity in thiamine-depleted lake trout injected with TNP-KLH was positively associated with muscle thiamine pyrophosphate (thiamine diphosphate; TPP) concentration. A negative association was observed between the ratio of muscle-to-liver TPP and T-independent responses. No significant associations between anti-TNP activity and tissue thiamine concentration were observed in the thiamine-replete fish. We demonstrated that thiamine deficiency leads to alterations in both T-dependent and T-independent immune responses in lake trout.

[Measurement of thiamine concentration in the cat using high pressure liquid chromatography]

OBJECTIVE

Thiamine deficiency in cats frequently leads to a dysfunction of the central nervous system including vestibular signs with fatal outcome in untreated cases. The aim of the present study was to directly measure thiamine concentrations using high pressure liquid chromatography (HPLC) in feline blood samples and to evaluate values in healthy and diseased cats.

MATERIAL AND METHODS

Blood samples (1 ml EDTA-whole blood) from 193 cats were analysed for total thiamine and thiamine diphosphate using HPLC. For the interpretation of the results cats were retrospectively assigned to six groups: A) healthy cats, B) cats with diseases of the gastrointestinal tract, C) cats with different traumas not affecting the gastrointestinal tract, D) cats with inappetence, cats with central vestibular signs and normal (E) or low values of thiamine (F), respectively.

RESULTS

In animals of group F no obvious cause for the vestibular signs was found and spontaneous recovery after thiamine application occurred in three cats. Therefore thiamine deficiency was a highly likely clinical diagnosis. Total thiamine concentration (mean 48.2 µg/l, standard deviation ± 22.6) of group F significantly differered from the other groups (group A-D: p<0.01, group E: p<0.001). Comparable results were obtained for thiamine diphosphate. However, low total thiamine values were also found in cats with inappetence without any neurological signs.

CONCLUSION AND CLINICAL RELEVANCE

In the present study a method for direct measurement of thiamine formerly established for ruminants was evaluated for cats. A more accurate and objective clinical diagnosis of thiamine deficiency is feasible in cats with values less than 50 µg/l and typical clinical signs. In animals with values of total thiamine levels between 50-70 µg/l a prophylactic substitution of thiamine can be discussed.

Thiamine status of feedlot cattle fed a high-concentrate diet

As thiamine status of ruminants is adversely affected by rumen acidity, this study investigated whether or not thiamine deficiency occurs in feedlot cattle fed a high concentrate diet. Fifty 1- to 2-year-old feedlot cattle fed a high concentrate diet (75% barley) for at least 3 mo (high concentrate diet group) and 15 healthy feedlot cattle of similar ages (control group) that were fed a low concentrate diet (30% barley) were used. Rumen fluid samples were obtained by rumenocentesis and their pH was determined with a portable pH meter. Blood samples taken from all animals from a jugular vein were used to determine erythrocyte transketolase enzyme activity, and hence thiamine pyrophosphate (TPP) effect. Odor and mean pH values of ruminal fluid samples from the high concentrate diet and control group were acidic (pH 5.3) and aromatic (pH 6.1), respectively. The mean TPP effect % in the high concentrate diet group (47.2 ± 3.2) was significantly higher than in the control group (19.53 ± 2.5) (P < 0.001). The study provides evidence of a TPP effect in feedlot cattle fed a high concentrate diet.

Thiamine deficiency in a cat: resolution of MRI abnormalities following thiamine supplementation

Thiamine (vitamin B₁) is an essential component of a number of metabolic pathways and thiamine deficiency results in a progressive encephalopathy in both humans and animals. Confirming thiamine deficiency is problematic and relies on demonstrating reduced red blood cells transketolase activity, or indirect methods including urinary organic acid analysis and dietary analysis. The characteristic and selective vulnerability of different brain regions in carnivores has been demonstrated by magnetic resonance (MR) imaging in the dog and cat as an aid to diagnosis. A 2-year-old, female, domestic shorthair cat was presented with an acute onset of seizures and ataxia. MR imaging was consistent with thiamine deficiency and supplementation resulted in a progressive clinical improvement. Repeated MR imaging 4 days after starting thiamine supplementation revealed near complete resolution of the MR abnormalities. Repeated MR imaging following appropriate therapy may be useful to further confirm thiamine deficiency.

Thiamine deficiency effects on the vision and foraging ability of lake trout fry

The exact causes of the historical recruitment failures of Great Lakes lake trout Salvelinus namaycush are unknown. Thiamine deficiency has been associated with neurological abnormalities in lake trout that lead to early mortality syndrome (EMS) in salmonine swim-up fry, and EMS-related mortality at the swim-up stage is a factor that contributes to the reproductive failure of lake trout populations in the Great Lakes. The potential for adverse effects of thiamine deficiency beyond the swim-up stage is unknown. We investigated the effects of low egg thiamine on behavioral functions in young, post-swim-up lake trout fry. The behavioral endpoints included visual acuity and prey capture rates in the same groups of lake trout fry from each family. Low-thiamine eggs were produced by feeding lake trout broodstock diets entailing thiaminase activity. The thiamine content of the spawned eggs ranged from 0.3 to 26.1 nmol/g. Both visual acuity and prey capture rates were affected by the thiamine content of the eggs. The visual acuity of lake trout was severely affected by low egg thiamine, mainly at thiamine concentrations below the threshold of 0.8 nmol/g but also at higher concentrations in field-collected eggs. Feeding was also reduced with low egg thiamine content. The reduction of prey capture rates was dramatic below 0.8 nmol/g and less dramatic, but still significant, in a portion of the families with egg thiamine concentrations of less than 5.0 nmol/g from both laboratory and field samples. Approximately one-third of the latter families had reduced feeding rates. Deficits in visual acuity may be part of the mechanism leading to decreased feeding rates in these fry. The effects of low egg thiamine on both of the behavioral endpoints studied increase the risk of low recruitment rates in Great Lakes lake trout populations.

Effects of vitamin B1 (thiamine) deficiency in lake trout alevins and preventive treatments

The objectives of this study were to examine the effect of thiamine immersion of fish from a population known for compromised survival as a result of early mortality syndrome (EMS) and to investigate the cause-response relationship between thiamine concentration and lesions in tissues in swim-up-stage lake trout Salvelinus namaycush alevins. Lake trout eggs from 14 fish from Lake Michigan were artificially fertilized and the progeny divided into two groups based on the thiamine concentration (low [< 0.73 nmol/g] or high [> 0.85 nmol/g]) in the unfertilized eggs. Progeny were treated or not with a thiamine solution (2,000 mg/L for 2 h) at hatching or the swim-up stage. The survival of progeny in control groups at the swim-up stage correlated with thiamine concentration. The low thiamine-treated groups had significantly higher survival between the swim-up stage (812.0 degree-days) and 16 d after swim-up (963.3 degree-days) than the control groups; the survival of the high thiamine-treated groups did not differ between treated and control fish, regardless of the treatment at hatching and the swim-up stage. Control alevins that had low thiamine levels showed EMS, which resulted in 94.9-100% mortality 16 d after the swim-up stage. No pathological changes were observed in the brain, olfactory lobe, eye, liver, or muscle in alevins of high thiamine-treated group. Glycogen deposits in the liver of alevins from the low control group were variable, no glycogen being observed in the hepatocytes of 7 of the 24 fish. We demonstrate that thiamine treatment at swim-up enhances the survival of EMS-affected lake trout relative to treatment at hatching.

Gizzard shad thiaminase activity and its effect on the thiamine status of captive American alligators Alligator mississippiensis

Adult mortality and low egg hatch rate were observed among American alligators Alligator mississippiensis in Lake Griffin, Florida, between 1998 and 2003. Previous studies show that the alligator mortality is due to neurological impairment associated with thiamine (vitamin Bt) deficiency. This study determined the rate of thiaminase activity in gizzard shad Dorosoma cepedianum, a fish often eaten by alligators, and examined the thiamine status of captive adult alligators fed only gizzard shad. We found that the thiaminase activity of gizzard shad in Lake Griffin is 16,409 +/- 2,121 pmol/g/min (mean +/- 2SEs). This high rate of thiaminase activity was present in most months and across a wide range of shad sizes. Seven alligators were captured in the wild from Lake Griffin and Lake Woodruff, held in captivity, and fed gizzard shad. We monitored blood and muscle thiamine levels throughout the experiment and liver thiamine at the end. Over a period of 6-12 months, all of the alligators maintained weight but blood and muscle thiamine levels decreased to 25-50% of the original (healthy) values. Three animals with the greatest reduction in thiamine died, demonstrating mobility impairment and neural histopathology similar to those seen in wild alligators in Lake Griffin. Two alligators were fed shad for 10 months but then treated with thiamine. These animals showed a reduction in thiamine while eating shad, but treatment restored their thiamine levels to the initial values, which were comparable to those of normal wild Lake Griffin alligators. We demonstrated that thiamine deficiency can be induced by a diet of gizzard shad and cause neurological signs and death in alligators in captivity. We conclude that the thiaminase activity in gizzard shad is high enough to cause thiamine deficiency in wild alligators when shad are a major part of their diet.

Evaluating the effect of stressors on thiaminase activity in alewife

No consistent explanation has been found for the variability in the thiaminase activity of alewives Alosa pseudoharengus despite the role of alewife thiaminase in large-scale salmonine mortality in the Laurentian Great Lakes. We conducted experiments to evaluate the effect of two stressors, reduced salt content in the water and food limitation, on alewife thiaminase activity. Alewives were subjected to treatments in replicated tanks in which conductivity was lowered (< 100 microS/cm) for 8 d and feeding was limited for 39 d. Circulating white blood cells, plasma cortisol, plasma glucose, and whole-body thiaminase were measured in individual alewives to assess their response to these experimental treatments. Alewives from the controls had significantly larger numbers of circulating white blood cells than those in the salt-reduced and food-limited treatments (24,000 and 19,000 cells/microL and 11,000 and 9,000 cells/microL for alewives from the two control and salt-reduced treatment tanks, respectively, and 34,000 and 30,000 cells/microL and 21,000 and 16,000 cells/microL for alewives from the two control and food-limited treatment tanks). No significant differences in alewife thiaminase activity were found between treatment fish and their controls. The mean thiaminase activity in the alewives studied increased from 6,900 to 16,000 pmol x g(-1) x min(-1) from the time of their collection in Cayuga Lake to the start of laboratory experiments 1.5-2.5 years later; the latter value was more than twice that of previously reported levels of thiaminase activity from alewives collected in the wild. These data suggest that the variability in alewife thiaminase is not related to stress from salt reduction or food limitation, but laboratory holding conditions significantly increased thiaminase through a mechanism not evaluated by our experimental treatments.

Effectiveness and retention of thiamine and its analogs administered to steelhead and landlocked Atlantic salmon

We investigated the feasibility of enhancing the reproduction of steelhead Oncorhynchus mykiss and landlocked Atlantic salmon Salmo salar in lakes where the consumption of alewives Alosa pseudoharengus and other forage fishes containing thiaminase can cause them to become thiamine deficient and thereby reduce the survival of their fry. We evaluated feeding fingerling steelhead excess thiamine hydrochloride (THC1) for 1 or 2 weeks or equimolar amounts of thiamine mononitrate, thiamine-tetrahydrofurfuryl-disulfide, benfotiamine, or dibenzoyl thiamine (DBT). We found minimal internal reserves of thiamine after 6 months. We also compared the ability of injections of thiamine and its analogs to prevent mortality in thiamine-deficient steelhead and Atlantic salmon sac fry and found all forms to be effective, although benfotiamine was the least effective on an equimolar basis. Further, we injected yearling steelhead and found that DBT was tolerated at approximately 11,200 nmol/g of body weight, about 10 times more than thiamine in any other form. When yearling steelhead were injected with near-maximal doses of thiamine hydrochloride and several analogs and then fed a thiamine-deficient diet, DBT was retained for approximately 2 years--in contrast to other forms, which were retained for less than about 6 months. Therefore, these results suggest that neither feeding nor injecting young hatchery salmonids with DBT is likely to enhance their reproduction for more than 2 years after stocking. However, injecting DBT in nearly mature fish (either cultured fish from hatcheries or wild fish captured in lakes) may provide them with enough thiamine to successfully spawn within 2 years even though they consume mainly thiaminase-containing forage fishes.

[Thiamine and its derivates in cattle blood measured by HPLC in healthy animals, in patients suffering from CCN and in their cohorts]

The aim of this project was to develop a routine method to measure thiamine and its derivates in blood, to detect the need of vitamin B1-supply in cattle faster and more precise than until now using the transketolase test. For that, thiamine and its derivates (thiaminediphosphate = TDP,-monophosphate = TMP) were analysed in cattle blood by HPLC technique with post-column derivatization. Moreover, the levels in healthy cattle were compared with those in herds with single CCN cases. EDTA-blood-stored up to 10 days by 6 or 20 degrees C- was the most appropriate substrate. Sensitivitiy and specifity were significantly better than (TT, sum of all fractions): 1.95% and 2.10%; thiamine and TMP: 7.02% and 9.17%. The lowest concentration, which could be measured, was 0.5 ng/ml. 72 samples could be analysed daily. In the blood of 280 healthy calves and cows (group A), 201 clinically unsuspicious animals out of stocks with single cases of CCN (group B) and 12 patients with clinical obvious CCN (group C), thiamine and its phosphates were measured and the means calculated (ng/ml). After this, the thiamine status is characterized by (ng/ml): (A) thiamine 13.5 (4.61-28.8),TDP 51.0 (33.1-82.2), TMP 8.79 (2.23-18.1),TT 73.3 (44.6-114); (B) thiamine 8.73 (0.00-20.0), TDP 43.5 (15.5-75.7),TMP 6.15 (0.00-16.6), TT 59.4 (18.7-96.5); (C) thiamine 3.85 (0.00-1 1.5), TDP 14.5 (0.00-28.3), TMP 1.27 (0.00-4.87), TTP 19.6 (4.92-35.9). So, HPLC with post-column derivatization offers a precise, automatically working method for a fast diagnose of thiamine deficiency. The lowest critical value of TT is 40 ng/ml for healthy animals in the blood. The sample (EDTA-blood) can be posted simply at temperatures up to 20 degrees C. In comparison to other measuring methods, this HPLC-technique enables an early recognition of the risk to come down with CCN in endangered cattle herds.

M74 syndrome in Baltic salmon and the possible role of oxidative stresses in its development: present knowledge and perspectives for future studies

Baltic salmon suffer from maternally transmitted yolk-sac fry mortality syndrome--M74. The incidence of M74 varies considerably on a year to year basis. In the 1990s the mortalities were 50-80% but in 2003-2005, below 10%. Before death, M74-affected fry have several typical symptoms. M74-eggs are characterized by low thiamine and carotenoid content, and affected fry show signs of oxidative stress. Although M74 is associated with thiamine deficiency and the symptoms of the fry can be alleviated with thiamine, the underlying causes of the syndrome have remained a mystery. We have studied the symptoms of M74 at the molecular level by investigating the global gene expression patterns using cDNA microarray and have quantified the changes in transcriptional regulation in M74-affected and healthy yolk-sac fry. Our and previous results suggest that M74 in Baltic salmon yolk-sac fry results from oxidative stresses disturbing several different developmental molecular pathways. Because the M74 syndrome is of maternal origin, factors in the Baltic Sea during salmon feeding and migration, i.e., the chemical composition of food, may be decisive in the development of M74. The possible mechanisms by which oxidative stresses may develop in adult salmon are discussed in the review.

Presumed primary thiamine deficiency in a young African lion (Panthera leo)

A 1-yr-old intact male African lion (Panthera leo) fed only beef muscle meat was evaluated for episodes of hypermetric ataxia, generalized weakness and tonic-clonic front limb movements. A hemogram, biochemical profile, blood lead, electrocardiogram, survey radiographs, and brain computed tomography were normal. Cerebral spinal fluid analyses suggested mild inflammation. Acetylcholine receptor antibody and serologic tests for all infectious agents tested were negative. Clinical signs resolved completely 9 days after instituting oral thiamine (3 mg/kg/day) and a completely nutritional diet. This lion's pretreatment thiamine blood value (11 nmol/L) was markedly lower than that of a healthy lion (191 nmol/L) and a proposed reference range for adult African lions (160-350 nmol/L). The lion remained clinically normal 2 yr later when his blood thiamine value was 340 nmol/L. African lions can develop clinical primary thiamine deficiency and may respond favorably when thiamine treatment and adequate diet are instituted prior to irreversible neuronal necrosis.

Thiamine deficiency in dogs due to the feeding of sulphite preserved meat

A 6-year-old dog, a 4-year-old dog and three 7-week-old puppies were diagnosed with thiamine deficiency caused by feeding sulphite treated meat. The 6-year-old dog presented with a history of inappetence, weight loss and vomiting that rapidly progressed to signs of multifocal intracranial disease including mental dullness, paresis, seizures, spontaneous nystagmus and strabismus. Thiamine pyrophosphate effect was elevated at 58% and magnetic resonance imaging revealed bilaterally symmetrical hyperintensity of the caudate nucleus and rostral colliculi. The dog recovered with thiamine supplementation. The 4-year-old dog and three 7-week-old puppies also presented with rapidly progressive multifocal central nervous system signs including ataxia, paresis, increased muscle tone, seizures, nystagmus and exophthalmos. The 4-year-old dog made a rapid recovery with thiamine supplementation. Euthanasia and necropsy of a puppy revealed malacia of multiple brainstem nuclei and oedema of the cerebral cortex. These findings were consistent with thiamine deficiency.

Inflammatory cerebrospinal fluid analysis in cats: clinical diagnosis and outcome

The medical records of 62 cats with clinical signs of central nervous system disease and accompanying inflammatory cerebrospinal fluid (CSF) analysis were examined retrospectively to determine if signalment, clinical signs, CSF analysis and ancillary testing could accurately predict the type of central nervous system disease that was present. An inflammatory CSF was defined as one in which a total nucleated cell count was greater than 5 cells/μl or one in which the total nucleated cell count was normal but the nucleated cell differential count was abnormal. Sex, degree of CSF inflammation, neuroanatomical location and systemic signs provided little contributory information to the final diagnosis. In 63% of the cases a presumptive diagnosis could be made based on a combination of clinical signs, clinicopathological data and ancillary diagnostic tests. CSF analysis alone was useful only in the diagnosis of cats with feline infectious peritonitis, Cryptococcus species infection, lymphoma and trauma. Overall, despite extensive diagnostic evaluation, a specific diagnosis could not be made in 37% of cats. The prognosis for cats with inflammatory CSF was poor with 77% of cats surviving less than 1 year.

A degenerative encephalomyelopathy in 7 Kuvasz puppies

Seven Kuvasz puppies from 2 same-parentage litters developed weakness and ataxia. Six necropsied dogs had lesions in caudate nucleus, cerebellar nuclei and folia, and spinal cord. Lesions seen were felt to be familial or due to the effects of an amprolium-induced thiamine deficiency on the developing brains of these puppies.

Polioencephalomalacia in adult sheep grazing pastures with prostrate pigweed

Polioencephalomalacia was diagnosed in 2 animals from different farms. In apparently healthy animals from same farms, fecal thiaminase and a significant reduction in erythrocyte trans-ketolase activity was observed. The presence of thiaminase in Amaranthus blitoides could have contributed to the development of polioencephalomalacia in sheep grazing on natural pastures.

Organochlorine Pesticides and Thiamine in Eggs of Largemouth Bass and American Alligators and Their Relationship with Early Life-stage Mortality

Thiamine deficiency has been linked to early mortality syndrome in salmonids in the Great Lakes. This study was conducted to compare thiamine concentrations in American alligators (Alligator mississippiensis) and Florida largemouth bass (Micropterus salmoides floridanus) eggs from sites with high embryo mortality and high exposure to organochlorine pesticides (OCPs) (Lakes Apopka and Griffin, and Emeralda Marsh, Florida, USA) to those from sites that have historically exhibited low embryo mortality and low OCPs (Lakes Woodruff and Orange, Florida). During June-July 2000, 20 alligator clutches were collected from these sites, artificially incubated, and monitored for embryo mortality. Thiamine and OCPs were measured in one egg/clutch. During February 2002, 10 adult female bass were collected from Emeralda Marsh and Lake Woodruff and mature ovaries analyzed for thiamine and OCP concentrations. Although ovaries from the Emeralda Marsh bass contained almost 1,000-fold more OCPs compared with the reference site, Lake Woodruff, there were no differences in thiamine concentrations between sites (11,710 vs. 11,857 pmol/g). In contrast, alligator eggs from the reference site had five times the amount of thiamine compared with the contaminated sites (3,123 vs. 617 pmol/g). Similarly, clutches with >55% hatch rates had significantly higher concentrations of thiamine compared with clutches with <54% hatch rates (1,119 vs. 201 pmol/g). These results suggest that thiamine deficiency might be playing an important role in alligator embryo survival but not in reproductive failure and recruitment of largemouth bass. The cause(s) of this thiamine deficiency are unknown but might be related to differences in the nutritional value of prey items across the sites studied and/or to the presence of high concentration of contaminants in eggs.

Polioencephalomalacia in captive harbour seals (Phoca vitulina)

In a colony of 11 harbour seals (Phoca vitulina Linné 1758) two episodes of central nervous disorders occurred within 2 years causing fatalities in seven adult animals. Clinical signs comprised dyspnoea, anorexia, apathy, incoordination and lateral recumbency. Vitamin B complex therapy was successful once. Pathomorphological examination of seven carcasses revealed acute and subacute malacia of the cerebellar grey matter. Additional acute malacic lesions located in the cerebral cortices and basal ganglia were observed. Mesencephalic nuclei were less severely affected and displayed acute changes. Despite intense search for environmental toxins and infectious agents, the cause of the fatalities remained undetermined. However, the type and pattern of the lesions are most suggestive of a thiamine deficiency.

Physiological, biochemical and morphological studies of Baltic salmon yolk-sac fry with an experimental thiamine deficiency: relations to the M74 syndrome

Sea-run Baltic salmon (Salmo salar) populations are suffering from the M74 syndrome, a reproduction disorder affecting both broodfish and their progeny. The syndrome is usually manifested during the middle part of the yolk-sac fry stage and has been shown to be associated with a thiamine (vitamin B(1)) deficiency. Development of the disease is reversible by thiamine treatments of broodfish or progeny. This study aimed at investigating the ability of the thiamine antagonist pyrithiamine, administered by microinjections 3 days after hatch, to cause M74-like signs i.e. typical clinical symptoms, high mortality rates and histopathological changes. Furthermore, the effects of pyrithiamine on hepatic activities of the thiamine-dependent enzyme transketolase (TK), the glucose-6-phosphate dehydrogenase (G6PDH) and the cytochrome P4501A (CYP1A) were evaluated. Six family groups with differing thiamine status were sampled on three occasions during the yolk-sac fry stage. All pyrithiamine exposed groups, with the exception of the one with the highest thiamine concentration, showed M74-like symptoms and suffered from high mortality. Enzyme activities were not different in pyrithiamine groups as compared with controls. However, the TK-activities were strongly associated with the thiamine concentrations. The G6PDH-activity demonstrated small variations with the highest activities in the M74-groups. The [TK]/[G6PDH]-ratios were considerably lower in the M74-groups than in the healthy controls, indicating an imbalance between the oxidative and the non-oxidative part of the pentose-phosphate shunt due to a deficit in thiamine. The pyrithiamine-injections induced several M74-like symptoms including incoordination, lethargy, whitened liver and yolk-sac precipitates. They also caused high mortality rates, in addition to lowered glycogen levels and increased prevalence of necrotic brain cells. Moreover, the study demonstrates that the TK, G6PDH and CYP1A-activities are associated with the thiamine content.

Maternal blood, egg and larval thiamin levels correlate with larval survival in landlocked Atlantic salmon

A link was previously established between the Cayuga syndrome, a condition causing 100% mortality in larval landlocked Atlantic salmon, Salmo salar, in several of New York's Finger Lakes, and a maternal diet of alewife, Alosa pseudoharengus, a non-native thiaminase-rich Clupeid fish. We evaluated salmon larvae viability relative to maternal thiamin status, and investigated the putative link of the Cayuga syndrome to an alewife diet in fish from the geographic regions outside the Finger Lakes/lower Great Lakes watersheds. We identified Cayuga syndrome in Atlantic salmon from Otsego Lake in the Susquehanna River watershed and from Green Pond in New York's Adirondack Mountains. In both systems alewife represent the major component of the diet for the salmon. Thiamin levels in the maternal blood of Otsego salmon with syndrome-negative progeny were three- to four-fold greater than those Otsego females whose progeny exhibited 100% mortality. Thiamin levels in eggs and larvae were directly related to thiamin levels in maternal blood in both syndrome-positive and syndrome-negative stocks. Thiamin bath treatments of syndrome-afflicted larvae eliminated mortality regardless of their lake stock of origin. Maternal blood levels of approximately 0.31 nmol thiamin pyrophosphate/g or 0.44 nmol total thiamin/g appear necessary to achieve egg threshold levels of approximately 0.8 and 1.1 nmol/g unphosphorylated and total thiamin, respectively; these egg thiamin levels should prevent significant syndrome-related mortality in landlocked Atlantic salmon larvae. These results confirm the role of thiamin in the etiology of the Cayuga syndrome and support the dietary link of this naturally occurring thiamin deficiency to the thiaminase-rich alewife.

Amprolium-induced cerebrocortical necrosis (CCN) in dromedary racing camels

Amprolium was successfully used to induce cerebrocortical necrosis (CCN) in dromedary racing camels, only when they were fed on a barley diet. Camels which were fed on hay ad libitum did not suffer form CCN, although their thiamine pyrophosphate (TPP) reached similar levels as in camels fed on barley. The reason for this phenomenon is discussed. Five camels which suffered from CCN had TPP values of 80-115% and were euthanized on humane grounds when they were in lateral recumbency. Pathohistological investigations revealed a polioencephalomalacia of the dorsal cerebral cortex with oedema and status spongiosus. Cerebral autofluorescence was observed under ultraviolet light. The major clinicopathological changes were a slight anemia and a decreased potassium value whereas glucose, muscle enzymes, leucocyte counts and differential counts were elevated. A TPP effect of 12% was found during this study in healthy dromedary racing camels and symptoms were observed when TPP values reached 80-115%. The test is now being widely used during the camel racing season.

Evaluation of ruminal sulfide concentrations and seasonal outbreaks of polioencephalomalacia in beef cattle in a feedlot

OBJECTIVES

To measure concentrations of thiamine in blood and sulfide in ruminal fluid in cattle with polioencephalomalacia (PEM) and to evaluate temporal associations between PEM and risk factors.

DESIGN

Epidemiologic analysis.

SAMPLE POPULATION

14 steers with acute signs of PEM, 26 clinically normal steers and records of all cattle in a feedlot for the past 6 years.

PROCEDURES

Concentrations of thiamine in blood and sulfide in ruminal fluid were measured. Values were compared between healthy steers that had been in the feedlot for 3 weeks or 2 months. Records were used to estimate the incidence of PEM and the time when cattle were at greatest risk of developing PEM.

RESULTS

Thiamine concentrations in steers with PEM were within reference ranges. Healthy steers had significantly greater sulfide concentrations 3 weeks after entering the feedlot, when the incidence of PEM was greatest, than 2 months after entering the feedlot, when risk of developing PEM was low. Thiamine concentrations were within reference ranges at these times. Annually recurrent outbreaks of PEM during the summer began after initiating use of a water well containing a high content of sulfate.

CLINICAL IMPLICATIONS

Excessive ruminal sulfide production is an important factor in the pathogenesis of PEM, without concurrent thiamine deficiency. Most cases of PEM developed between 15 and 30 days after introduction to a high-sulfur diet. When water is an important source of dietary sulfur, risk of PEM may increase during hot weather.

Thiamine deficiency in a cat associated with the preservation of 'pet meat' with sulphur dioxide

A cat with allergic dermatitis was fed a diet of fresh meat and a multi-vitamin supplement for 38 days to exclude food allergy as a cause of its dermatopathy. The cat died as a result of acute thiamine deficiency, which was caused by inactivation of thiamine by the preservative, sulphur dioxide. The continuing undeclared usage of sulphites in the Australian pet food industry is discussed.

Polioencephalomalacia induced with amprolium in buffalo calves--clinicopathologic findings

Polioencephalomalacia was induced in eight buffalo calves, 6-12 months old, by drenching amprolium (300 mg/kg body weight per day) for 29-55 days. Four buffalo calves of the same age group were drenched with tap water only and served as control. Blood samples were collected at different intervals during amprolium administration until the onset of clinical signs. Cerebrospinal fluid was also collected prior to amprolium administration and at the onset of clinical signs. A significant progressive decrease in erythrocyte transketolase (TK) activity and an increase in the percent of thiamine pyrophosphate (TPP) effect were observed in amprolium-fed calves during amprolium administration until the onset of clinical signs. There was a significant increase in blood lactate and blood pyruvate concentrations and a significant decrease in lactate/pyruvate ratio at the onset of clinical signs. Serum electrolyte (Na, Ca, P, Mg) concentrations showed no significant changes. However, the serum potassium concentration had decreased significantly at the onset of signs. The cerebrospinal fluid analyses revealed a significant increase in lactate and pyruvate concentrations and lactate/pyruvate ratio in amprolium-fed calves. The electrolytes (Na, K, Ca, P and Mg) of cerebrospinal fluid did not show any change. It is concluded that oral administration of amprolium (300 mg/kg body weight daily) for 4-6 weeks produces biochemical changes characteristic of polioencephalomalacia in buffalo calves.

Hypokalaemic episodic polymyopathy in cats fed a vegetarian diet

A previously undocumented hypokalaemic condition with a cyclical nature, comprising acute bouts of polymyopathy followed by spontaneous recoveries, is described in the cat. Cats being fed a high protein vegetarian diet developed recurrent episodes of polymyopathy, characterised by ventroflexion of the head and neck, stiff forelimb gait, lateral head-resting and generalised muscle weakness. Plasma potassium concentrations (mean +/- standard deviation) were reduced from 3.28 +/- 0.33 mmol/l at the beginning of the experiment to 2.45 +/- 0.24 mmol/l during bouts of myopathy. This hypokalaemia was associated with increased creatine kinase activities indicative of muscle damage, and decreased urinary potassium concentrations, and was caused by insufficient dietary potassium. Cats that received the same diet supplemented with potassium did not develop hypokalaemic polymyopathy. Spontaneous recoveries of affected cats were not associated consistently with increases in plasma potassium concentrations. Plasma taurine concentrations decreased and glutamic acid increased markedly in all cats fed the experimental diet. There was no evidence of thiamin deficiency associated with the high glutamic acid intake. Veterinarians should be aware that hypokalaemic cats, and in particular those on potassium-deficient diets, may show cyclical disease with episodes of polymyopathy recurring after periods of spontaneous clinical recovery. This condition in cats may be a useful animal model for familial hypokalaemic periodic paralysis in humans.

Thiamin deficiency in a colony of cats

Twenty-eight cats belonging to a cat rescue society developed clinical signs consistent with thiamin deficiency after being fed a proprietary canned food containing inadequate amounts of the vitamin. Five of the cats died but the others recovered after appropriate therapy. The diagnosis was based on clinical signs, histopathological findings, food analysis and response to treatment.

Efficacy of lateral ventricular injection of epinephrine, cyproheptadine, or adenosine triphosphate on feed intake in thiamin-deficient turkeys

In previous work, thiamin deficiency (TD) resulted in decreased brain levels of adenosine triphosphate (ATP) and epinephrine, but serotonin (5-HT) was increased in the turkey. The goal of the present study was to determine whether the introduction of calculated levels of epinephrine, ATP, or cyproheptadine into the lateral ventricle could affect feed intake of TD birds. Adenosine triphosphate, epinephrine, and cyproheptadine (5-HT antagonist) were injected into the lateral ventricle of TD and control birds. These injections did not alter feed intake in the control birds. Cyproheptadine and ATP decreased feed intake in the 1st h in the TD birds as compared with sham-injected TD birds (P less than .05), but epinephrine had no effect. The results indicate replacement or inhibition of a single altered neurochemical does not increase short-term feed intake in TD birds.

The effect of thiamin deficiency on amino acids in the brain, liver, and plasma of the turkey

The present study was conducted to determine the effect of thiamin deficiency (TD) on amino acids in brain, liver, and plasma. Twenty-seven 1-wk-old female turkeys were assigned to TD or control groups. Experimental birds were fed a TD diet; control birds received the same diet with thiamin at levels recommended by the National Research Council. Chromatographic analysis at 12 days of age found altered levels of amino acids in selected brain areas and liver of TD birds. Proline was increased in the TD archistriatum and liver. Leucine was elevated in the TD hypothalamus, medulla-pons, midbrain thalamus, and cerebellum. Threonine was lower in the hippocampus, but was increased in the liver of TD birds. Glutamine declined in the TD hippocampus, but glutamate increased in the TD liver only. Urea decreased and valine increased in the TD medulla-pons. Aspartic acid and serine decreased in the TD liver. These results indicate that dietary TD does alter amino acids in these tissues.

Vitamin deficiencies in cattle

Deficiencies of vitamins A, D, K, E and thiamin can cause severe limitations in beef production. In particular, vitamin A and E can be common causes of lost profit, secondary to limitations of reproductive and growth potential. Prolonged dry periods will reduce available A and E in pasture forage, as can ensiling and prolonged storage of harvested feedstuffs. Polioencephalomalacia is a thiamin responsive disorder, associated with high concentrate feeding and lush pastures. Antimetabolites, such as amprolium, will cause thiamine deficiency when fed in excess. Recent information has shown improved performance with supplemental beta carotene and niacin. The positive responses in reproductive performance, noted with cattle fed supplemental beta carotene, was independent of vitamin A. Supplementation of vitamins above National Research Council recommendations can be justified. However, proper evaluation of feed and animal status, and documentation of a response to supplementation is necessary before diagnosing deficiencies of specific nutrients.

Thiamin deficiency in cats and dogs associated with feeding meat preserved with sulphur dioxide

Thiamin deficiency was diagnosed in cats and dogs being fed fresh minced meat, which contained sulphur dioxide as a preservative and less than 0.5 mg/kg thiamin. Thiamin in the meat and in added dietary ingredients, including a supplementary vitamin mixture, was destroyed by the sulphur dioxide.

Visual-evoked potentials and electroretinograms in ruminants with thiamine-responsive polioencephalomalacia or suspected listeriosis

Electrodiagnostic visual testing (electroretinogram [ERG] and visual-evoked potential [VEP]) was performed on 5 ruminants (3 lambs, 1 kid, and 1 steer) with thiamine-responsive polioencephalomalacia (PEM) and on 2 sheep with listeriosis. The lambs and kid had typical clinical signs of PEM, especially blindness. In these animals, the ERG was normal but the VEP was abnormal. Follow-up recordings in the kid and 1 lamb indicated an improvement in VEP recordings accompanying a gradual return of vision after thiamine treatment. Possible subtle changes in VEP peak latencies could not be assessed because of lack of normative VEP data for sheep and goats. All animals had complete return of vision (owner-assessed). The steer did not have signs of blindness, and the ERG and VEP were normal. Changes in VEP accompanying permanent PEM blindness are not known. One sheep with suspected listeriosis had lack of menace response and palpebral and corneal reflexes, but had intact vision. The ERG and VEP were normal. The second sheep with suspected listeriosis had intact menace response and vision, but became acutely blind and died; the ERG was normal, but VEP amplitudes were depressed.

Thiamine deficiency in sheep exported live by sea

Three shipments of sheep being exported live by sea were examined to determine their thiamine status. Measurements were made of thiamine concentration in liver and ruminal contents, transketolase activity in erythrocytes and thiaminase activity in ruminal liquor. Sheep that died or were clinically ill and euthanased had significantly lower hepatic and ruminal thiamine concentrations than clinically healthy control sheep. A high proportion had thiamine concentrations comparable to those found in sheep that die with polioencephalomalacia. Thiamine concentrations decreased with increasing time that sheep were in pre-embarkation feedlots and on board ship. Destruction of thiamine in the rumen by thiaminase was not a significant factor. Erythrocyte transketolase activities indicated that many of the sheep that arrived in the Middle East without signs of clinical disease were also in a state of thiamine insufficiency.

Comparison of three methods of thiamine supplementation by measurement of urinary thiamine excretion in sheep

The relative efficacy of thiamine supplementation to sheep by injection, subcutaneous implant and orally administered protected thiamine bolus was compared in two experiments using a grass and hay ration and a ration containing bracken rhizomes to induce thiamine deficiency. In both experiments, urinary excretion of thiamine was significantly higher in supplemented sheep than in the controls, and in sheep supplemented by injection than in sheep supplemented by implant or protected boluses. Thiamine excretion was lower in sheep fed the ration containing bracken rhizomes than in sheep fed the grass ration.

Comparison of transketolase activity and thiamin pyrophosphate levels in erythrocytes and liver of rainbow trout (Salmo gairdneri) as indicators of thiamin status

Yearling rainbow trout (Salmo gairdneri) were fed a purified diet with and without thiamin supplementation for 30 wk, at which time overt signs of thiamin deficiency appeared in the deficient group. Overt signs of thiamin deficiency were anorexia, darkening and ataxia. Death rapidly followed the development of overt thiamin deficiency. Transketolase activity and thiamin pyrophosphate levels were measured monthly in erythrocyte and liver samples. Significant differences in erythrocyte transketolase activity between fish fed the thiamin-deficient and control diets were measured after 24 wk of feeding. No significant difference in liver transketolase activity was found between trout fed diets with or without thiamin supplementation. Thiamin pyrophosphate levels were significantly lower in erythrocytes and liver of fish fed the thiamin-deficient diet after 16 wk of feeding. Thiamin pyrophosphate levels in erythrocytes and liver were found to be a more sensitive indicator of thiamin status of rainbow trout than erythrocyte or liver transketolase activity.

Influence of thiamin supplements on furazolidone-induced cardiomyopathy in turkey poults

Furazolidone (700 ppm) was fed to turkey poults from 2 to 5 weeks of age. The drug produced a cardiomyopathy and reduced the feed intake and growth of the birds. Thiamin was concurrently injected into the furazolidone-fed poults to determine whether the vitamin would prevent or reduce the severity of the cardiotoxic effect of the drug. Supplemental injections of thiamin had no significant effect on feed consumption or growth of the birds nor did they protect the heart against the cardiotoxicity. The conclusion is that furazolidone-induced cardiomyopathy is not caused by a thiamin deficiency.