Cadmium is a heavy metal present in soils from natural and anthropogenic sources. Plant uptake of Cd at levels present in the soil solution is dependent on a system that is largely metabolically mediated and competitive with the uptake system for Zn and possibly other metals. Much of the Cd taken up by plants is retained in the root, but a portion is translocated to the aerial portions of the plant and into the seed. The amount of Cd accumulated and translocated in plants varies with species and with cultivars within species. Soil, environmental and management factors impact on the amount of Cd accumulated in plants. Potential methods of reducing the accumulation of Cd in crops include reduction of Cd input to the soil system, site selection, management practices which decrease the concentration of Cd in the soil solution and its uptake and translocation by plants, and development and production of plant cultivars with the genetic tendency for low Cd uptake.

The importance of copper (Cu) for the proper functioning of many biological systems is well recognized. Copper deficiency significantly affects ruminant livestock production in large areas of Canada as well as many other parts of the world. Selected aspects of recent research into Cu deficiency in ruminants have been reviewed, including the biochemistry and physiology of Cu deficiency as well as the metabolism of Cu. Because of the wide occurrence of Cu deficiency in ruminants grazing in areas of high molybdenum (Mo) and/or sulfur (S), research on the mechanisms of interference in Cu metabolism has received wide attention. Similarities in the physiological effects of the combination of molybdate and sulfide (or sulfate) and of thiomolybdates in ruminants, strongly suggest that thiomolybdates are primarily involved in the induction of Cu deficiency. Thiomolybdates appear to induce Cu deficiency by (i) limiting Cu absorption, (ii) binding Cu in albumin, thus delaying Cu uptake by the liver, (iii) depleting liver Cu, (iv) altering liver Cu and Cu from other tissues to a less available form, (v) increasing biliary Cu excretion, (vi) limiting reabsorption of biliary Cu, (vii) increasing urinary Cu excretion, and (viii) increasing endogenous secretion of Cu. Copper, S and/or Mo have also been identified as factors in the etiology of polioencephalomalcia and abmosal ulcers but the mechanisms involved are not clear. Key words: Ruminants, copper, defiency, metabolism, sulfur

The effects of diet composition and chemical form of Se on intestinal flow, absorption, and retention of Se were determined in sheep by the balance technique and by disappearance of Se from sites along the gastrointestinal tract with reference to dual-phase digesta markers. Six sheep with ruminal and duodenal cannulas were used in a crossover design with a split-plot arrangement of the Se isotope treatments. Sheep were fed a forage (alfalfa hay)-based (.37 mg Se/kg) or concentrate (barley)-based (.27 mg Se/kg) diet at 90% of ad libitum intake. Selenium stable isotopes (enriched [77Se]yeast, enriched [82Se]selenite) and fluid (Co-EDTA) and particulate (Cr-mordanted fiber) markers were administered simultaneously into the rumen four times daily for 7 d, and total collections of feces and urine were made every 24 h for these and the following 7 d. A larger proportion (51 to 61%) of the Se tracers flowing to the duodenum was associated with the particulate fraction, mainly as bacteria-associated Se, than with the fluid fraction. The [82Se]selenite was more available (P < .05) for absorption and retention than [77Se]yeast, indicating that inorganic chemical forms of Se are as available to the ruminant as organic forms of Se commonly found in feedstuffs. Selenium absorption and retention were greater (P < .05) in sheep receiving the concentrate-based diet than in sheep receiving the forage-based diet. Thus, the availability of Se from inorganic and organic sources in sheep seems to be influenced by diet composition.

. 2002. Concentration of cadmium and other elements in the grain of near-isogenic durum lines. Can. J. Anim. Sci. 82: 27-33. Durum wheat (Triticum turgidum L. var durum) shows genetic variation for concentration of the heavy metal cadmium in the grain. This variation is being exploited to develop cultivars with low cadmium concentration, but there is no information on the effect of incorporation of the trait on uptake of other elements or on economic traits such as yield. Five pairs of near-isogenic high/low cadmium durum wheat lines and their parents were grown in a randomized complete block trial with three replications. Trials were grown at Swift Current, Saskatchewan in 1994, at Swift Current, Stewart Valley and Regina, Saskatchewan in 1995and 1996, at Langdon and Fargo, North Dakota in 1995 , and at Casselton and Langdon, North Dakota in 1996. Grain yield, test weight, kernel weight and protein concentration were determined. Grain cadmium, calcium, copper, iron, magnesium, manganese, nickel and zinc were measured by atomic absorption or inductively coupled plasma emission spectroscopy. The low cadmium trait had no significant effect on average yield, grain protein concentration, test weight, or kernel weight as indicated by comparison of the high and low cadmium isolines. Average grain cadmium concentration differed among years within locations, among locations within years, and among genotypes. The average grain cadmium concentration of the high cadmium isolines was approximately double that of the low cadmium isolines. There were significant genotypic differences in grain concentration of the other elements, but the differences were not associated with the high and low cadmium isogenic lines. The low cadmium allele seems to be specific for cadmium, lowering cadmium without altering concentrations of other elements or affecting economic traits. . On a mesuré le rendement grainier, le poids spécifique, le poids de l'amande et la concentration de protéines du blé cultivé. La concentration de cadmium, de calcium, de cuivre, de fer, de magnésium, de manganèse, de nickel et de zinc dans le grain a été déterminée par spectroscopie d'absorption atomique ou par spectroscopie d'émission avec plasma induit par haute fréquence. Le gène responsable de la réduction de la teneur en cadmium n'a pas d'incidence sensible sur le rendement moyen, la concentration de protéines dans le grain, le poids spécifique ni le poids de l'amande lorsqu'on compare les lignes isogéniques à teneur élevée et faible en cadmium. La concentration moyenne de cadmium dans le grain varie d'une année à l'autre au même endroit, d'un endroit à l'autre la même année et d'un génotype à l'autre. La concentration moyenne de cadmium dans le grain des lignées isogéniques à teneur élevée en cadmium est à peu près le double de celle observée chez les lignées à faible teneur. La concentration des autres éléments dans le grain présente de fortes variations génotypiques, mais celles-ci n'ont aucun lien avec les lignées isogéniques à forte ou à faible teneur ...

The most common way to test seed quality is to use a simple and reliable but time-and space-consuming germination test. In this paper we present a fast and simple method to analyse cabbage seed deterioration by measuring ethanol production from partially imbibed seeds. The method uses a modified breath analyser and is simple compared to gas chromatographic or enzymatic procedures. A modified method using elevated temperatures (408C instead of 208C) shortened the assay time and improved its sensitivity. The analysis showed an inverse correlation between ethanol production and seed quality (e.g. the final percentages or speed of germination and the number of normal seedlings). The increase in ethanol production was observed when cabbage seeds were deteriorated by storage under ambient conditions or hot water treatments, both of which reduced the number of normal seedlings. Premature seeds produced more ethanol upon imbibition than mature seeds. Ethanol production occurred simultaneously with oxygen consumption, indicating that lack of oxygen is not the major trigger for ethanol production.

No abstract

. 2003. Copper and health status of cattle grazing high-molybdenum forage from a reclaimed mine tailing site. Can. J. Anim. Sci. 83: 479-485. High concentrations (21-44 mg kg -1 dry matter) of Mo have been identified in forage in several reclaimed mining areas in British Columbia. Since Mo concentrations greater than 5 mg kg -1 in forage dry matter may result in molybdenosis because of a secondary Cu deficiency in ruminants, a study was undertaken to determine if cattle can safely graze the reclaimed land. For 12-wk grazing periods in 1994, 1995 and 1996, 32 cow/calf pairs grazed high-Mo forage at a reclaimed mine tailings site located at the Highland Valley Copper mine near Logan lake, BC. Half of the animals in the trial received a Cu supplement (All-Trace copper bolus) and the other half served as a control group. There were no significant differences (P < 0.05) in weight gain, liver Mo, serum Cu and Mo, and milk Cu and Mo between the two treatment groups of cows. Liver Cu was higher for the Cu bolus group at certain time periods in 1994 and 1995, indicating that the bolus was effective at supplying Cu. At all times, the liver Cu levels for the animals remained above the recommended critical level of 25 mg kg -1 dry matter. Animals appeared healthy and no signs of Cu deficiency were observed. . Une concentration de Mo supérieure à 5 mg par kg de matière sèche pouvant entraîner la molybdénose consécutive-ment à une carence secondaire en cuivre (Cu) chez les ruminants, les auteurs ont tenté d'établir si les bovins peuvent paître sans danger sur ces terres. Trente-deux couples vaches/veaux ont brouté dans des champs à forte concentration de Mo pendant 12 semaines en 1994, 1995 et 1996, sur d'anciens sites restaurés à la mine de cuivre Highland Valley, près de Logan Lake, en Colombie-Britannique. La moitié des animaux ont reçu un supplément de Cu (cuivre pour bol alimentaire All-Trace), l'autre moitié servant de témoins. Les auteurs n'ont relevé aucune variation significative (P < 0,05) entre les deux traitements pour le gain de poids et la concentration de Mo dans le foie, de Cu et de Mo dans le sang, et de Cu et de Mo dans le lait. Le groupe qui avait reçu le Cu alimentaire présentait plus de Cu dans le foie à certains moments, en 1994 et 1995, signe que cette technique donne de bons résultats pour compenser le manque de Cu. La concentration de Cu dans le foie des animaux reste toujours au-dessus du seuil critique recommandé de 25 mg par kg de matière sèche. Les animaux semblaient tous en bonne santé et aucun symptôme de carence en cuivre n'a été observé.

An inductively coupled plasma mass spectrometer with a newly designed continuous flow hydride generator was used for the determination of Se in biological materials. The design of the hydride generator was important in minimizing interference from HCl and in maximizing analytical sensitivity. Two sample preparation procedures incorporating either 3.8 or 7.2 M HCl in the final sample solutions were compared. Interference from Cu was eliminated by the addition of 0.2 M NaI to the sodium borohydride solution (3.8 M method) or by maintaining a high concentration of HCl in the sample solution (7.2 M method). The 3.8 M method had the advantage of minimizing exposure of expensive equipment to corrosive HCl fumes, whereas the 7.2 M method did not contaminate equipment with I and had no measurable sample-to-sample cross-contamination. In practice, cross-contamination from sample to sample in both methods was negligible during analysis. An important factor in minimizing cross-contamination from sample to sample was the elimination of the air bubble normally entrained between samples. Determination of isotopic tracer enrichment was linear from 0 to 320% enrichment, which provided a broad range for isotope dilution analysis. A detection limit of 6.4 pg of Se was observed under optimum conditions, whereas a detection limit of 1.3 ng of Se was found for routine analysis of 1-g samples of plant material. Selenium was accurately determined by isotope dilution analysis in a variety of biological reference materials.