Ovarian steroidogenesis inhibition by constant photothermal conditions is caused by a lack of gonadotropin stimulation in Eurasian perch

In fish, the reasons for the inhibition of reproduction by constant photothermal conditions of rearing are far from clear. In an in vivo experiment, two groups of females reared under natural (4-28 degrees C) or constant photothermal conditions (20-22 degrees C, photoperiod 12/12) were investigated for gonad development, sex-steroids (testosterone-T, 17-beta-estradiol-E2 and 11 Keto-Testosterone-11KT) dynamics and brain aromatase activity in January, February and March. Two days before each sampling date, a group of females reared under constant conditions was injected with HCG (Human Chorionic Gonadotropin: 100 Ul/kg) and evaluated for the same parameters. In addition, in vitro ovarian steroidogenesis capacity for each female was determined with or without stimulation by HCG and/or IGF-1 (insulin-like Growth Factor-1). The results indicate that vitellogenesis stage is the limit ovarian stage never reached in females submitted to constant photothermal conditions. This was associated with gonadogenesis delay and low levels of circulating sex-steroids (T, E2 and 11KT). Nevertheless, HCG injections partly counteracted the plasma steroid deprivation, indicating that ovaries from fish reared under constant photothermal conditions suffer from a lack of gonadotropin stimulation, maybe caused by plasma LH suppression. Such finding was confirmed by the in vitro ovary incubation test. HCG and IGF-1 treatments induced broad testosterone and 17-beta-estradiol elevations and the exposure to constant photothermal conditions, in some cases, decreased that response to HCG. In conclusion, we show that the inhibition of reproductive cycle in Eurasian perch females by constant photothermal conditions of rearing may be related to lower sex-steroid levels and to an inhibition of ovarian regulation by gonadotropins (at least LH), probably stopping gonadogenesis before vitellogenesis stage. (C) 2009 Elsevier Inc. All rights reserved

Disorders of lambs thyroid by a glucosinolate metabolite: the 5-vinyl-l,3-oxazolidine-2-thione (5-VOT)

The impact of 5-VOT on thyroid was studied in two lambs. They received ad libitum water, hay and concentrates without rapeseed from ten days of age till weaning (65 days of age). At 85 days of age, one of them was fed with the same diet but mixed with 100g/d of a rapeseed containing high level of progoitrin: 71.4µmol/g DM (variety Jet Neuf). Blood samples were taken fortnightly for the determination of TSH (Thyroid Stimulating Hormone), T3 (Tri-iodothyronin) and T4 (thyroxin) plasma concentrations

Repeated water emersions and domestication have no marked influence on stress physiology but modulate the abundance of several immune proteins in Eurasian perch

First International Conference of Fish and Shellfish Immunology, 2013 June 25-28, Vigo, SpainInternational audienceno abstrac

CORRELATION BETWEEN BREAKDOWN PRODUCTS OF GLUCOSINOLATES AND THE AMOUNT OF RAPESEED MEAL INTRODUCED IN THE DIETS OF 80 LAMBS AND 32 BULLS. EVOLUTIONOF 5-VINYL-1,3-OXAZOLIDINE-2-THIONE (5-VOT) AND THIOCYANATE IONS IN BIOLOGICAL FLUIDS AND ORGANS

A large-scale experimentation has been conducted in Belgium since 4 years in order to study the influence of antinutritional rapeseed factors and their degradation products in ruminants. Animals have been fed with iso-energetic, isolipidic and isoproteic diets containing various proportions of industrial rapeseed meal (lambs: 0% to 40%; bulls: 0% to 34%). The trials and the study of zootechnical, physiological, histological aspects were co-ordinated by the University of Namur. The University of Gembloux was concerned by chemical aspects (analysis of glucosinolates, aromatic choline esters and their respective degradation products such as 5-vinyl-1,3-oxazolidine-2-thione, nitriles, isothiocyanates, thiocyanate ions and trimethylamine). In this presentation we would like to point out the results concerning the evolution of the SCN- ions concentration in plasma, the correlation between the proportions of rapeseed meal in the diets of growing-fattening ruminants and SCN- ions, and 5-VOT content in muscle, some organs (thyroid, kidney, liver and lung), plasma and urine. Correlations (for lambs and for bulls) have been established between thiocyanate ions concentration and the percentage of rapeseed meal in the diets. SCN- ions were specially accumulated in kidney and lung although the 5-VOT is observed in high concentration in thyroid

Influence of short-term exposure to low levels of 17 alpha-ethynylestradiol on expression of genes involved in immunity and on immune parameters in rainbow trout, Oncorhynchus mykiss

International audienceFish are exposed to endocrine-disrupting chemicals (EDC), which are well known to disturb not only the reproductive system but also the immune system in vertebrates. However, the mechanisms by which these compounds are able to modify fish immunity are not well understood. In order to test the EE2 effects on immunity in selected organs, we exposed rainbow trout male juveniles for 3 weeks to EE2 concentrations ranging from 0.01 to 1 mu g/L. The results of this study suggest that EE2 affects the immunity of rainbow trout in a tissue dependent manner. This molecule affects both cellular and humoral immune systems. Indeed, blood leukocyte populations, as well as hepatic and plasma lysozyme, plasma MPO and renal complement activities, are modulated by EE2. Moreover, EE2 alters the gene expression of some mucus compounds, hepatic expression of complement sub-unit and lysozyme, or genes involved in the hepatic phagocytosis and transport of immunoglobulin across the liver

The trenbolone acetate affects the immune system in rainbow trout, Oncorhynchus mykiss

International audienceIn aquatic systems, the presence of endocrine-disrupting chemicals (EDC) can disrupt the reproductive function but also the immune system of wildlife. Some studies have investigated the effects of androgens on the fish immune parameters but the mechanisms by which the xenoandrogens alter the immunity are not well characterized. In order to test the effects of trenbolone acetate (TbA) on fish immune system, we exposed rainbow trout male juveniles during three weeks to TbA levels at 0.1 and 1 mu g/L. The present results suggest that TbA impacts, in a tissue-dependent manner, the rainbow trout immunity by affecting primarily the humoral immunity. Indeed, TbA inhibited lysozyme activity in plasma and liver and enhanced the alternative complement pathway activity (ACHSO) in kidney. In plasma, the modulation of the complement system was time-dependent. The mRNA expression of genes encoding some cytokines such as renal TGF-beta 1, TNF-alpha in skin and hepatic IL-1 beta was also altered in fish exposed to TbA. Regarding the cellular immunity, no effect was observed on the leucocyte population. However, the expression of genes involved in the development and maturation of lymphoid cells (RAG-1 and RAG-2) was decreased in TbA-treated fish. Among those effects, we suggest that the modulation of RAG-1 and mucus apolipoprotein-A1 gene expression as well as plasma and hepatic lysozyme activities are mediated through the action of the androgen receptor. All combined, we conclude that trenbolone affects the rainbow trout immunity

Chemical changes and influences of rapeseed antinutritional factors on lamb physiology and performance. 3. Antinutritional factors in plasma and organs

The impact of a high level of rapeseed meal in the diet on the concentration of antinutritional factors in plasma and organs was studied in 66 Texel, Suffolk or crossbred lambs. From 1 month of age till slaughter (132+/-21 days), they were fed ad libitum with concentrates containing 0% or 25% of rapeseed meal obtained either Samourai or Honk rapeseed varieties. Lambs were weaned at 88+/-8 days of age and 24+/-5 kg live weight. Blood and organ samples were taken fortnightly for the determination of antinutritional factors. In plasma and organs, the thiocyanate concentrations were systematically higher in the Samourai and Honk lots than in the control. After weaning, the SCN- concentration in plasma increased up to 490 mu mol l(-1) in the Samourai lot. The goitrogen 5-vinyl-1,3-oxazolidine-2-thione (5-VOT) was determined in muscle, organs (thyroid, liver, kidney and lung) and biological fluid (plasma). The 5-VOT was present only after the ingestion of rapeseed meal but not to the same extent for the two varieties. The Honk rapeseed meal induced a 5-VOT level significantly (p<0.05) higher in the target organs such as lung and thyroid than Samourai. Very low levels were found in muscle, liver, kidney, plasma and lung. (C) 2000 Elsevier Science B.V. All rights reserved

OPTIMAL LEVEL OF RAPESEED MEAL IN DIETS OF LAMBS.

Two experiments were carried out in order to improve the strategy of rapeseed meal (RPM) incorporation in the diets of lambs. In a first experiment, the effects of RPM obtained from either a high-glucosinolate (HG) cultivar (Honk RPM) or a double-low strain (Samourai RPM) were studied. Two types of concentrates containing 25% of RPM were compared to a Control concentrate. In a second experiment, the effects of various proportions (0 – 40%) of an industrial low glucosinolate (LG)-RPM were studied in order to determine the disorder-threshold in diets for young ruminants. One hundred forty six Texel, Suffolk or crossbred lambs ranged in age from 1 to 2 months were used. Neither the Samourai nor the Honk RPM did affect negatively animal performance whatever the parameter considered (growth, food intake and conversion, slaughter performances). Low (P < 0.05) proportions of C10:0, C12:0 and C14:0 and high contents of C18:1trans, C22:2 were determined in the perirenal fat of lambs receiving the Honk RPM. The industrial LG-RPM had no negative effects on animalperformance, best results were obtained with 25 and 30% of RPM. The Samourai RPM had no effect on the thyroid weight, whereas, the Honk RPM modified (P < 0.05) the histology of this organ; the percentages of large thyroid follicles being higher (P < 0.05) in the Honk group than in the Control and Samourai groups. High levels of Canola industrial LG-RPM(from 20%) induced also an hyperthyroidism. The Samourai and Honk RPM decreased (P < 0.05) the secretions of thyroid hormones while the industrial LG-RPM did not affect these hormones in any way. RPM had no significative effects on other hormones. It was concluded that disturbance in thyroid histology and activity induced by the ingestion of RPM did not affect the physiology and performance of lambs and that the levels between 25 to 30% of a LG-RPM were optimal for growing and fattening lambs

Glucosinolates metabolites in plasma, milk and thyroid of gestating and lactating ewes

The effects of high level of rapeseed meal in the diet on the concentration of antinutritional factors (glucosinolates metabolites) in blood plasma, milk and thyroid were studied in 90 ewes. From the 100th day of gestation, ewes bearing two foetuses were divided into three groups and were fed with pasture hay ad libitum and 500 g/d of diet containing 0 or 40% rapeseed meal obtained from either Apex or Synergy variety. During the 47 first days of lactation, 1200 g/d of the same meal were given. Thereafter, during 3 weeks, the ewes were only fed with hay. Blood and milk samples were taken fortnightly for the determination of SCN- and 5-vinyl-1,3- oxazolidine-2-thione (5-VOT) concentrations. One ewe from each group was slaughtered at the end of rapeseed meal distribution and another one three weeks later for thyroid analyses. SCN- and 5-VOT concentrations in blood plasma increased significantly (P<0.05) and regularly until one month of rapeseed supplementation to the withdrawal of rapeseed in the diet. One to three weeks after the end of rapeseed meal distribution, the SCN- and 5-VOT plasma concentrations came back at the basal level. Some changes were also observed for SCN- and 5-VOT contents in milk. The results indicated a great capacity of the ewes to excrete SCN- and 5-VOT by the milk. A 5-VOT accumulation was observed in the thyroid according to the level of progoitrin in the diet, but no SCN- accumulation. The 5-VOT concentration in thyroid of the ewes fed during three weeks with hay came back to zero. The thyroid analysis showed the reversible aspect of the thyroid hypertrophy due to 5-VOT accumulation