Monitoring blood glucose levels in female mink during the reproductive cycle: 1. Prevention of hyperglycemia during the nursing period.

Nursing sickness, the largest cause of death in female adult mink, is a metabolic disorder characterized by hyperglycemia. The impacts of body condition, dietary supplements, and reproductive status on the blood glucose concentration in female mink during the reproductive cycle were investigated. Mink dams on 3 farms were assigned to receive either herring oil (HerO) or chromium picolinate (CrPic) or to be in a control group, receiving only the basal diet, for 6 wk at the onset of lactation. Hyperglycemia was observed throughout the reproductive cycle. Significant differences in blood glucose levels were observed between farms, emphasizing the importance of herd genetics and of animal management and feeding practices in glycemic regulation. Female mink exhibiting hyperglycemia early in the reproductive cycle tended to remain hyperglycemic and to have poorer health and fewer kits. Glucose levels > 7 mmol/L can be considered critical in this regard. Supplementing the diet with CrPic reduced the blood glucose concentration. Results from this study suggest that a diet containing high-quality n-3 polyunsaturated fatty acids, high levels of carbohydrate, and CrPic supplementation may help the nursing mink dam maintain a normal blood glucose concentration during lactation.

Endocrine and metabolic alterations in the mink (Mustela vison) due to chronic phytoestrogen exposure.

Phytoestrogens are natural components of plant-based food items with beneficial health effects. The aim of the present study was to investigate the chronic effects of dietary phytoestrogens, genistein (8 mg kg(-1) day(-1)) and beta-sitosterol (50 mg kg(-1) day(-1)), on the weight regulation of the mink (Mustela vison). The parental generation was exposed from August 2002 to May-June 2003 to either beta-sitosterol or genistein, while the kits were exposed through gestation and lactation. Food consumption and body masses were monitored monthly. Plasma lipid, glucose, total protein and hormone (ghrelin, leptin, triiodothyronine and thyroxine) concentrations were measured from the parents in August 2002, January 2003 and at the end of the experiment in May-June 2003 when the kits were 21 days of age. Relative food intake was higher in the beta-sitosterol-exposed minks than in the control or genistein minks in September 2002. Plasma leptin and total protein concentrations were lower in the beta-sitosterol kits compared to the control kits. Furthermore, plasma ghrelin levels and liver phosphorylase activities of the mink kits were higher due to genistein exposure. In mink kits, exposure to both phytoestrogens reduced the plasma thyroxine concentrations. The kidney glycogen concentrations and the muscle phosphorylase activities of phytoestrogen-treated adult minks were elevated. The results of this study suggest that minks are sensitive to perinatal phytoestrogen exposure.

A diet rich in phosphatidylethanolamine increases plasma homocysteine in mink: a comparison with a soybean oil diet.

The effects of high dietary levels of phosphatidylethanolamine (PE) on plasma concentrations of homocysteine (tHcy) have not previously been studied. Eighteen mink (Mustela vison) studied were fed one of three diets during a 25 d period in a parallel-group design. The compared diets had 0, 17 and 67 % extracted lipids from natural gas-utilising bacteria (LNGB), which were rich in PE. The group with 0 % LNGB was fed a diet of 100 % soyabean oil (SB diet). Phospholipids are the main lipid components in LNGB and Methylococcus capsulatus is the main bacteria (90 %). The fasting plasma concentration of tHcy was significantly higher when the mink consumed the diet with 67 % LNGB than when they consumed the SB diet (P=0.039). A significantly lower glutathione peroxidase activity was observed in mink consuming the 17 % LNGB diet or the 67 % LNGB diet than was observed in mink fed the SB diet. The lack of significant differences in the level of plasma PE due to the diets indicates that most of the PE from the 67 % LNGB diet was converted to phosphatidylcholine (PC) in the liver. It has previously been hypothesised that phosphatidylethanolamine N-methyltransferase is an important source of tHcy. The present results indicate that plasma tHcy is at least partly regulated by phospholipid methylation from PE to PC. This methylation reaction is a regulator of physiological importance.

Effects of gender, diet, exogenous melatonin and subchronic PCB exposure on plasma immunoglobulin G in mink.

Effects of different fish-based diets (freshwater smelt, Baltic herring, marine herring/cod offal or their mixtures), gender, beta-glucan supplement, exogenous melatonin, and PCB exposure (Aroclor 1242((R)), 1 mg per animal per day in feed) on plasma immunoglobulin G (IgG) in the mink (Mustela vison) were studied. The aims of the study were to find out whether plasma IgG of the mink is affected by the subchronic PCB exposure, and whether biological, nutritional and hormonal effects are large enough to mask the possible IgG response. The concentration of IgG was determined using enzyme-linked immunosorbent assay (ELISA). Sexual dimorphism was detected, the males having higher levels of plasma IgG. In addition, melatonin tended to decrease IgG in females but not males. Diet also affected the humoral immune arm; the mixed-fish diets caused an unfavorable ratio of the oxidation products of lipids vs. vitamin E in liver, and resulted in low IgG concentration in plasma. In males fed Baltic herring, the beta-glucan supplement also lowered IgG levels. The PCBs failed to affect the plasma IgG of the smelt-fed female mink, and IgG concentration was not correlated with increased hepatic EROD activity or with the decreased total retinol in the liver of exposed mink. It is concluded that hormonal/seasonal and dietary factors affect the plasma IgG levels to such an extent that possible change in plasma IgG level due to PCBs in wild populations of mink is difficult to detect without a large amount of reference data.

Effect of folic acid supplementation on folate status and formate oxidation rate in mink (Mustela vision).

We investigated the folate-dependent toxicity of formate to mink to better understand the use of formic acid in fur animal feeds. Folic acid supplementation (0, 1, 5, 10, and 20 mg/kg of DM) in the feed of weanling mink for 4 wk resulted in hepatic tetrahydrofolate (H4folate) concentrations of 3.94, 8.51, 9.15, 10.4, and 15.0 nmol/g, respectively (SE 1.03). Oxidation tests in metabolic chambers, preceeding a single injection of sodium [14C]formate (500 mg/kg BW), showed that the nonsupplemented mink oxidized formate into CO2 at a rate 37% less than that of the supplemented mink. The oxidation rate increased with supplementation level and was maximal, 54.2 mEq.kg1.h1 (SE 3.0), at 10 mg of folate/kg; at the highest level of supplementation (20 mg/kg), CO2 production tended to be lower. Concentration of hepatic 14C increased with the hepatic H4folate, and its accumulation continued after the highest point of oxidation. These observations indicate that mink oxidize formate readily but at a slightly lower rate than do rats. However, if extra folate is not supplemented in the feed during the period of early intensive growth, hepatic H4folate level may decline to the levels found in humans and monkeys, which are susceptible to formate accumulation. Average daily weight gain improved with each increase in supplementation of folic acid; however, only the differences between the nonsupplemented diet and the two highest levels of the vitamin reached statistical significance (P < .05).

Effects of supplemental dietary sodium chloride and restricted drinking water on mink.

Thirty-six male mink were fed diets that contained 0, 1, 2 or 4% supplemental salt (sodium chloride) and were given drinking water ad libitum for 7 d. Three mink on each diet were then placed on ad libitum, 50% ad libitum or 25% ad libitum drinking water for the next 14 d. Ad libitum water consumption was directly proportional to the salt content of the diets. Feed consumption was inversely related to the level of dietary salt, although water restriction had a greater effect in reducing feed consumption than did the supplemental salt. The clinical signs of salt toxicity-water restriction observed were increased thirst, mild dehydration, decreased feed consumption, decreased body weight, rough coat, crusty nose and eyes, irritability in the early stage, and lethargy in the later stages. In general, serum and urinary sodium and chloride ion concentrations increased with increasing dietary salt concentrations. Expressed as a percent of brain weight, liver, spleen, kidney and heart weights of mink fed supplemental salt were less than the control weights. Adrenal gland weights increased in response to water restriction. Brain sodium concentrations were not affected by salt supplementation when drinking water was provided ad libitum. However, restricting drinking water generally resulted in increased brain sodium concentrations. Mild to moderate micro- or macrovesicular vacuolar changes were observed in the livers of some mink fed each level of dietary salt, but were especially prominent in the mink restricted in drinking water.

Plasma thyroxine concentration in non-pregnant and lactating mink, and effect of dietary rapeseed oil in the reproduction period.

Effect of dietary rapeseed oil from 00-varieties of rapeseed (0, 1.5% or 3% respectively in the wet compounded diets) on plasma thyroxine (T4), reproductive performance and kit weight gain during lactation was investigated with 3 groups of each 20 mink females. Plasma T4, which has not previously been reported for female mink, was significantly lower in lactating than in non-pregnant females. Unlike in an earlier experiment with growing male mink, it was not affected by dietary rapeseed oil. Reproductive performance, female weight development, feed consumption, and kit weight gain was normal in all treatment groups and there were no significant effects of the experimental treatment.

Feeding supplemental iodine to adult mink; effect on thyroid hormones in adult and offspring.

We fed adult mink diets containing supplemental iodine, from 0 to 320 ppm, for one or seven months prior to breeding. Blood samples collected from the adults and their offspring (kits) at 4 wk post-partum were assayed for total thyroxine (T4), triiodothyronine (T3), reverse T3 (rT3), and T4-binding indices. As expected T4 concentrations of the adult and kit mink varied inversely with the level of supplemental iodine. In addition, T3 and rT3 concentrations decreased gradually in kits from the long-term experiment in response to the increased dietary iodine of the dams. T3 concentrations of kits from dams fed iodine short-term decreased markedly while rT3 concentrations were elevated greatly in response to increased dietary iodine of the dam. These decreases in hormone levels are due to serum iodine blocking the thyroid uptake of iodine and subsequent decrease of hormone synthesis. Excess iodine may also block the effect of thyroid stimulating hormone. The T4-binding indices of the adults, in general, were depressed, while the T4-binding indices of the kits were more variable. These effects are probably due to fluctuations in thyroglobulin.

[Morphology and biochemistry of blood of various mustelids. 4. Determination of various metabolites in the arterial plasma of mink--principles of the preparation of standard values for laboratory diagnosis in farm mink (Mustela vison Schreber, 1777)]. / Beiträge zur Morphologie und Biochemie des Blutes einiger Musteliden. 4. Mitteilung: Zur Bestimmung einiger Stoffwechselprodukte im arteriellen Nerzplasma--Grundlagen zur Erstellung labordiagnostischer Arbeitswerte für den Farmnerz (Mustela vison Schreber, 1777).

An account is first given of latest knowledge on how to determine clinico-diagnostic applicability of certain metabolites in mink plasma and serum. Then, statistically treated results obtained from analysis of levels of total protein, albumin, creatinine, urea, total cholesterin, triglyceride, and total bilirubin are tabulated and discussed, with due consideration being given to sexual dimorphism, following determination of those values from arterial plasma of 118 male and 124 female minks, aged between six and seven months and kept under anaesthesia. The following preliminary findings are somewhat worth mentioning: (a) Total cholesterin concentrations in plasma of females were found to be higher than those recorded from the males tested. However, no sex-related differences were established for any of the other parameters. (b) Creatinine, urea, and total cholesterin followed simple normal distribution. However, plasma protein concentrations exhibited no Gaussian distribution until all individual data had been logarithmically transformed. (c) In a complementary model experiment, in which the above plasma data were determined from nine male ferrets, aged between six and seven months, evidence was produced to differentiated effects of neuroleptanalgesia on metabolite concentrations.

Hypervitaminosis D in fur-bearing animals.

Investigations concerning the effect on fur-bearing animals of large doses of vitamin D3 were carried out. The material comprised 62 animals in all--10 silver foxes, 17 blue foxes and 35 mink (Table II). Daily doses of 5 IU vitamin D3/g body weight for two months did not produce clinical symptoms in the foxes. However, a short while after the dose was increased to 10 IU, the animals showed loss of appetite, had difficulty in moving, were apathetic and developed dark coloured faeces. Analysis of blood serum showed markedly raised calcium values (Table III). Calcium deposits were demonstrated in the kidneys and in some cases also in the musculature, gastric mucosa, bronchi and the larger blood vessels. No abnormal signs were shown by 30 mink which received 0.6--0.7 IU vitamin D3/g body weight for five months. PM findings were normal.