The biological selenium status of livestock in Britain as indicated by sheep erythrocyte glutathione peroxidase activity.

The reliability of erythrocyte glutathione peroxidase activity as an indicator of selenium status in livestock is discussed. Based on this measurement, a survey is described of the biological selenium status of sheep on each of 329 farms in Britain. Results showed that 47 per cent of these farms were probably unable to provide grazing livestock with sufficient selenium to maintain blood levels greater than 0.075 microgram per ml. Increased selenium deficiency from the increasing use of home grown feeds as a major constituent of livestock rations may be causally related to the increase of white muscle disease and other selenium responsive diseases in Britain.     

富硒饲料及富硒畜禽产品开发

由于硒对于畜禽具有促进生长和构成组织、调节机体的生理过程等基本功能,在动物营养中起着非常重要的作用。富硒畜禽产品是人体补硒的重要途径之一,因此开发富硒饲料及富硒畜禽产品有重要的经济和社会意义。     

有机栖与畜禽营养

有机硒的主要优点,是硒的有效含量高.现普遍认为饲料中有机硒比无机硒能更好地存留在动物体内(Mutanen,1986;Pehrson,1993;Mahan,1995).Mnhan等(1996)报道,与亚硒酸钠相比,硒酵母使机体中硒的储存量显著提高,母乳中硒的浓度提高80%.研究人员指出,有机硒(起初发现是以含硒氨基酸的形式)是通过积极运输机制穿过肠壁被吸收的,而无机硒则是通过被动扩散过程被吸收的.虽然有机硒和无机硒被用来合成谷胱甘肽过氧化酶(GSH-Px)的能力大约相同,然而有机硒在动物体内的存留量明显要高(Perhson,1993;Mahan,1995;Edens,1996;Mahan和Kim,1996).随着饲料中硒含量的增加,在某些特定组织如脑和肌肉中,不同硒源的硒存留量差异更明显(Whanger和Butter,1988).当动物处于应激条件时,有机硒较高的存留量,能被用来合成更多的GSH-Px,以便消除由于应激而产生更多的自由基(主要是通过降低氧化磷酸化的偶联作用,导致电子渗透的增加和超氧化基的过量产生).     

Poisoning of livestock by Swainsona spp.: current status

SUMMARY Epidemiological, clinical and pathological features of poisoning of livestock by plants of the genus Swainsona are reviewed in the light of the recent identification of the active principle, swainsonine. This indolizidine alkaloid acts by inhibiting lysosomal α-mannosidase and the disease is identified as an induced mannosidosis. This knowledge allows recommendations to be made for the management of animals exposed to Swainsona.     

有机硒的合成及其在养殖中的应用

<正>硒是维护健康,防治克山病、大骨节病、糖尿病、肿瘤、心血管疾病等所必需的微量元素,是生物体内谷胱甘肽过氧化合物酶的重要成分,它的主要功能是清除生物体内产生的多余的自由基,提高生物体免疫水平。硒还可以参与辅酶A、辅酶Q的合成,刺激免疫球蛋白的生成,有抗氧化、抗癌作用,其抗氧化能力是VE的50～500倍。硒在体内具重要的生物学作用,参与GHS-Px的合成,保护细胞膜的结构和功能,拮抗及降低某些有毒元素及物质的毒性,影响视力传导和     

酵母硒在畜禽生产中的应用

酵母硒具有促进动物生长、增强免疫功能、提高胴体品质和改善繁殖性能等营养生理作用。本文主要介绍了酵母硒在畜禽生产中的营养作用。     

Comparison of 3 methods of selenium assessment in cattle.

Three tests are routinely done to assess blood status of selenium in cattle: serum selenium, whole blood selenium, and glutathione peroxidase. The objective of this study was to compare the various analytical methods for determining blood selenium status in groups of mature cows and beef calves. Twenty to 30 blood samples per herd were collected from 8 beef herds in central Alberta and 1 dairy in Alberta herd twice a year from the spring of 1992 through the fall of 1995, and once from 185 spring calves in 2 beef herds in Saskatchewan. Serum and whole blood samples were submitted to 1 laboratory and whole blood samples were submitted to a 2nd laboratory. Samples for glutathione peroxidase determinations were submitted to a 3rd laboratory. Pearson's correlation coefficients and Cohen's kappa were calculated for each possible comparison among the different measures. The best agreement was observed between serum and whole blood analysis within Laboratory A. The remaining comparisons reflected poor agreement. Comparison of herd-level assessment resulted in better agreement than comparison of individual sample results among laboratories and procedures for all combinations tested. Serum selenium analysis was the only laboratory procedure for which external reference material was utilized. Serum selenium, whole blood selenium, and glutathione peroxidase measure different compartments of the blood selenium pool. The time frame of interest, supplementation practices, and the stability of recent dietary intake determine the optimum assessment method for individual animals or herds. Determination of the serum status or of blood selenium is more consistently measured at the herd-level than for individual samples.     

The use of blood analyses to evaluate mineral status in livestock.

Animal responses are useful means of evaluating and assessing nutritional status. Blood mineral concentrations can be useful nutritional responses, although there are important limitations. The nutritional value in monitoring blood mineral concentrations varies with the specific mineral, being generally most valuable for those minerals in which homeostasis is regulated primarily by renal excretion, as opposed to regulation by variable absorptive efficiency. Examples of minerals for which blood concentrations are good measures of nutritional intake are selenium and magnesium. Blood mineral concentrations are affected by multiple variability factors. The strategy for use in mineral status assessment is to minimize non-nutritional variation by grouping animals for testing based on physiologic factors that affect, or are likely to affect, the concentration of the mineral or minerals being tested. Care should be taken to use the proper sampling protocol, so as not to cause artifactual variation. Removal of the serum from the clot within 2 hours of sample collection is an important step, among others. Sampling adequate numbers of animals and evaluating the herd mean and SD can minimize the effect of random variation on interpretation.     

Effect of selenium supplementation and source on the selenium status of horses

This study was conducted to determine the effect of Se supplementation and source on the Se status of horses. Eighteen 18-mo-old nonexercised horses were randomly assigned within sex to 1 of 3 treatments: 1) control (CTRL, no supplemental Se, 0.15 mg of Se/kg of total diet DM); 2) inorganic Se (INORG, CTRL + 0.45 mg of Se/kg of total diet DM from NaSeO3); or organic Se [ORG, CTRL + 0.45 mg of Se/kg of total diet DM from zinc-L-selenomethionine (Availa Se, Zinpro, Corp., Eden Prairie, MN)]. Horses were acclimated to the CTRL diet (7.1 kg of DM alfalfa hay and 1.2 kg of DM concentrate per horse daily) for 28 d. After the acclimation period, the appropriate treatment was top-dressed on the individually fed concentrate for 56 d. Jugular venous blood samples were collected on d 0, 28, and 56. Middle gluteal muscle biopsies were collected on d 0 and 56. Muscle and plasma were analyzed for Se concentrations. Glutathione peroxidase activity was measured in muscle (M GPx-1), plasma (P GPx-3), and red blood cells (RBC GPx-1). Data were analyzed as a repeated measures design. Mean plasma Se concentration on d 28 and 56 was greater (P < 0.05) for Se-supplemented horses compared with CTRL horses, and tended (P < 0.1) to be greater in ORG vs. INORG on d 28. Mean muscle Se concentration and P GPx-3 activities increased (P < 0.05) from d 0 to 56 but were not affected by treatment. Mean RBC GPx-1 activity tended to be greater (P < 0.1) in ORG than INORG or CTRL horses on d 28, and tended to be greater (P < 0.1) for INORG compared with ORG horses on d 56. Mean RBC GPx-1 activity of INORG and ORG horses was not different from that of CTRL on d 56. Mean M GPx-1 activity decreased (P < 0.01) from d 0 to 56. In conclusion, zinc-L-selenomethionine was more effective than NaSeO3 at increasing plasma Se concentration from d 0 to 28; however, both supplemental Se sources had a similar effect by d 56. No difference in Se status due to Se supplementation or source could be detected over a 56-d supplementation period by monitoring middle gluteal muscle Se, M GPx-1, or P GPx-3. Results for RBC GPx-1 also were inconclusive relative to the effect of Se supplementation and source.     

Effect of selenium source and dose on selenium status of mature horses

This study was conducted to determine the effects of either dietary Se source or dose on the Se status of horses. Twenty-five mature horses were blocked by BW and randomly allocated to 1 of 5 dietary treatments that comprised the same basal diet that differed only in Se source or dose. Treatments were as follows: negative control (0.085 mg of Se/kg of DM), 3 different dietary concentrations of supplemental organic Se (Se yeast; 0.2, 0.3, and 0.4 mg of total Se/kg of DM), and positive control (0.3 mg of total Se/kg of DM) supplemented with Na selenite. Horses initially received the control diet (6 kg of grass hay and 3 kg of concentrate per horse daily) for 56 d to allow diet adaptation. After the period of diet adaptation, horses were offered their respective treatments for a continuous period of 112 d. Jugular venous blood samples were collected before the morning feed on d 0, 28, 56, 84, and 112. Whole blood and plasma were analyzed for total Se, glutathione peroxidase activity in whole blood (GPX-1) and plasma, and thyroid hormones (thyroxine and triiodothyronine) in plasma. The proportion of total Se as selenomethionine (SeMet) or selenocysteine in pooled whole blood and plasma samples was determined on d 0, 56, and 112. Data were analyzed as repeated measures. Total Se in blood and plasma and GPX-1 activity were greater in all supplemented horses (P < 0.001, except P < 0.01 for GPX-1 in horses supplemented with the least dose of Se yeast) with a linear dose effect of Se yeast for whole blood and plasma Se (P < 0.001) and a quadratic dose effect (P < 0.05) for whole blood GPX-1 activity. A plateau for total Se in plasma was achieved within 75 to 90 d, although this was not observed in blood total Se or GPX-1 activity. On d 84 and 112, horses supplemented with Se yeast showed greater total Se in blood (P < 0.05) compared with horses supplemented with Na selenite, and a source effect (P < 0.05) was observed in the relationship between total blood Se and GPX-1 activity. Selenocysteine (the predominant form of Se in whole blood and plasma) increased in all horses supplemented with Se. The SeMet content of whole blood and plasma increased in horses supplemented with Se yeast, but it was not observed in those supplemented with selenite. The rate of increase in SeMet over time was greater in whole blood (P < 0.05) and plasma (P = 0.10) with the Se yeast product. In conclusion, Se yeast was more effective than Na selenite in increasing total Se in blood, mainly as consequence of a greater increase of the proportion of Se comprised as SeMet, but it did not modify GPX-1 activity.     

A survey of the selenium status of beef cows in Alberta.

An epidemiological survey was conducted in Alberta to measure the selenium status in blood of beef cows during the fall and to determine the risk of selenium deficiency among specific geographic regions of Alberta. Three census divisions of Alberta based on the Statistics Canada Census of Agriculture were chosen as the study areas for the project. Soils and plants in area A (Edmonton area) and area B (Calgary area) were known to be deficient in selenium, while soils and plants in area C (southeast corner of Alberta) were known to have adequate levels of selenium. Blood samples were collected from 335 cows on 29 farms from the 3 study areas. These samples were collected from cows that had recently been removed from pasture in October and November 1992. Answers to a short questionnaire pertaining to various herd characteristics and management practices were also obtained for each herd. The average value of selenium for all cows sampled was 2.20 mumol/L. The average value of selenium of cows in areas A and B was 1.93 mumol/L. The average value of selenium of cows in area C was significantly (P < 0.05) higher at 2.70 mumol/L. Nine percent of the cows in the study were considered marginal or deficient in selenium (< 1.27 mumol/L selenium). Herds located in area C, herds that were provided with supplemental feed on pasture, and herds that were pregnancy checked had higher average herd selenium values than did other herds. Cow-calf producers located in areas with selenium-deficient soils should pay particular attention to selenium supplementation for their cows. Some of the negative "geographic" effects on selenium values can be overcome by more progressive management practices.     

The influence of supplements of selenite, selenate and selenium yeast on the selenium status of dairy heifers.

The aim of the study was to define possible differences between selenite, selenate and selenium yeast on various aspects of selenium status in growing cattle. Twenty-four Swedish Red and White dairy heifers were fed no supplementary selenium for 6 months. The basic diet contained 0.026 mg selenium/kg feed dry matter (DM). After the depletion period the animals were divided into 4 groups; group I-III received 2 mg additional selenium daily as sodium selenite, sodium selenate, and a selenium yeast product, respectively. Group IV, the control group, received no additional selenium. The total dietary selenium content for groups I-III during the supplementation period was 0.25 mg/kg DM. After the depletion period the mean concentration of selenium in blood (640 nmol/l) and plasma (299 nmol/l) and the activity of GSH-Px in erythrocytes (610 mukat/l) were marginal, but after 3 months of supplementation they were adequate in all 3 groups. The concentration of selenium in blood and plasma was significantly higher in group III than in groups I and II, but there was no significant difference between groups I and II. The activity of GSH-Px in erythrocytes did not differ between any of the supplemented groups. The animals in the control group had significantly lower concentrations of selenium in blood and plasma and lower activities of GSH-Px in erythrocytes than those in the supplemented groups. The activity of GSH-Px in platelets was also increased by the increased selenium intake. There was no difference in the concentration of triiodothyronine (T3) between any of the groups, but the concentration of thyroxine (T4) was significantly higher in the unsupplemented control group.     

Seasonal variation of selenium status of Norwegian dairy cows and effects of selenium supplementation

Blood selenium levels were found to fluctuate throughout the year, being highest during the indoor season when the greatest amounts of compound concentrates were fed. From October to January the average blood selenium levels increased from 0.10 μg/ml to 0.18 μg/ml (15 cows). Subcutaneous injections of barium selenate (500 mg selenium) increased the blood selenium levels significantly. The treated group (15 cows) reached average levels of about 0.21 μg/ml blood during the indoor season.The effect of oral supplementation of sodium selenite (for 2 months) on the levels of plasma selenium, blood selenium and glutathione peroxidase activity was investigated. Plasma selenium was found to give an immediate reflection of the daily selenium intake. Maximum activity of glutathione peroxidase was reached 1 month after the end of the supplementation period.It is concluded that if selenium enriched concentrates are used in a normal feeding regimen, further supplementation with selenium does not seem to be necessary.     

奶牛硒营养状况评价

针对奶牛机体硒营养状况评价及影响因素作一综述。     

Effects of selenium source on measures of selenium status and immune function in horses

The effects of selenium (Se) supplementation and source on equine immune function have not been extensively studied. This study examined the effects of oral Se supplementation and Se source on aspects of innate and adaptive immunity in horses. Fifteen horses were assigned to 1 of 3 groups (5 horses/group): control, inorganic Se (sodium selenite), organic Se (Se yeast). Immune function tests performed included: lymphocyte proliferation in response to mitogen concanavalin A, neutrophil phagocytosis, antibody production after rabies vaccination, relative cytokine gene expression in stimulated lymphocytes [interferon gamma (IFNγ), interleukin (IL)-2, IL-5, IL-10, tumor necrosis factor alpha (TNFα)], and neutrophils (IL-1, IL-6, IL-8, IL-12, TNFα). Plasma, red blood cell Se, and blood glutathione peroxidase activity were measured. Plasma and red blood cell Se were highest in horses in the organic Se group, compared with that of inorganic Se or control groups. Organic Se supplementation increased the relative lymphocyte expression of IL-5, compared with inorganic Se or no Se. Selenium supplementation increased relative neutrophil expression of IL-1 and IL-8. Other measures of immune function were unaffected. Dietary Se content and source appear to influence immune function in horses, including alterations in lymphocyte expression of IL-5, and neutrophil expression of IL-1 and IL-8.     

Observations on the selenium status of cattle in the north-east of Scotland.

Cattle on 18 of 21 farms in north-east Scotland were found to have low whole blood activities of the selenium-containing enzyme, glutathione peroxidase (less than 5 units per ml whole blood), and a low blood concentration of selenium (less than 0.05 mg per litre). These cattle had all been fed on locally produced feedstuffs without any mineral supplementation. The low selenium status in cattle occurred on farms with soils derived from a range of parent material, no one particular type predominating.     

Current status and future perspectives for sequencing livestock genomes

Only in recent years, the draft sequences for several agricultural animals have been assembled. Assembling an individual animal’s entire genome sequence or specific region(s) of interest is increasingly important for agricultural researchers to perform genetic comparisons between animals with different performance. We review the current status for several sequenced agricultural species and suggest that next generation sequencing (NGS) technology with decreased sequencing cost and increased speed of sequencing can benefit agricultural researchers. By taking advantage of advanced NGS technologies, genes and chromosomal regions that are more labile to the influence of environmental factors could be pinpointed. A more long term goal would be addressing the question of how animals respond at the molecular and cellular levels to different environmental models (e.g. nutrition). Upon revealing important genes and gene-environment interactions, the rate of genetic improvement can also be accelerated. It is clear that NGS technologies will be able to assist animal scientists to efficiently raise animals and to better prevent infectious diseases so that overall costs of animal production can be decreased.     

Hair analysis as an indicator of mineral status of livestock

Despite several inherent characteristics that would appear to make hair a useful biopsy tissue, many problems make interpretation of data derived from hair analysis difficult. Endogenous minerals are incorporated into hair by several routes. Most attention on hair mineral incorporation has focused on element uptake within the hair follicle. Minerals incorporated within the follicle are presumably chemically or physically associated with cortical cells of the hair shaft and reflect mineral status at the time that the hair filament was synthesized. Because hair follicles in most species regularly go through cycles of intense metabolic activity and quiescence, mineral incorporation through the follicle is not a continual process. Mineral deposition onto hair does not cease when the follicle is not producing a hair fiber. The hair shaft is continuously exposed to several elements through contact with secretions from sebaceous, apocrine and eccrine glands. Significant quantities of major and trace elements of endogenous origin are adsorbed onto the hair surface via these secretions, especially when hair growth is not occurring or is very slow. For several elements significant correlations exist between mineral concentrations in hair and mineral intake. These correlations, however, are usually quite low. Non-dietary factors such as sex, age, hair color, sire, body location and contamination affect mineral levels in hair. Dietary intake of calcium, phosphorus and iron are also known to affect uptake of other elements in hair. Because many factors cause variation in mineral content in hair, hair analyses are not precise indicators of mineral status. Hair mineral analyses may be useful, however, when combined with other indicators of mineral status to provide a more precise assessment of mineral status in livestock.