Grain cadmium and zinc concentrations in wheat as affected by genotypic variation and potassium chloride fertilization

Thirteen bread wheat (Triticum aestivum L.) and two durum wheat (Triticum turgidum L. var. durum) cultivars were grown over six site-years to identify differences in grain Cd and Zn concentrations, as affected by genotypic variation and soil application of potassium chloride (KCl) fertilizer. Application of KCl fertilizer did not consistently affect grain Cd concentration of wheat cultivars, but increased average grain yield and decreased average grain Zn in 4 of 6 site-years. However, soil type and year had significant effects on grain Cd and Zn, indicating a strong environmental effect on grain quality. Grain concentrations of Cd and Zn were generally lower for the clay loam (CL) than the fine sandy loam (FSL) soils. The wheat cultivars showed significant genotypic differences in grain concentrations of Cd and Zn, suggesting the potential of breeding to reduce Cd and increase Zn concentrations in grain. The two durum cultivars contained high concentrations of Cd but not Zn compared to the bread wheat. The interaction between cultivars and site-years was significant for grain Zn, but not for grain Cd, suggesting that grain Cd is a more stable trait than grain Zn across environments. Grain Zn and Cd were not related to each other but they both correlated negatively with grain yield. The lack of relationship between Zn and Cd suggests that breeding for enhanced Zn concentration can be attained without necessarily affecting grain Cd concentration. The negative relationship between Cd and Zn concentration and dry matter yield was likely the result of biological dilution, suggesting that genetic improvement leading to increased yield may concurrently decrease mineral concentration. Results of this study are useful to improve the mineral composition of wheat used for human consumption through the development of cultivars and use of agronomic management practices that increase Zn and/or reduce Cd concentrations in wheat grain.     

Occurrence of 'attaching and effacing' lesions in the small intestine of calves experimentally infected with bovine isolates of verocytotoxic E coli

Nine calves (five colostrum-fed, four colostrum-deprived) were challenged with two field strains of Escherichia coli which produced either verocytotoxin 1 (VT1) or verocytotoxin 2 (VT2). Although three colostrum-fed calves had blood and mucus in their faeces, no diarrhoea was observed. Three of the four colostrum-deprived calves had diarrhoea and in two of them severe lesions were detected in the small intestine. Focal changes were detected in the colon of three calves. E coli were associated with the lesions in the small and large intestine and were shown by transmission electron microscopy to be intimately attached to the enterocyte surface with effacement of microvilli (attaching and effacing lesions). This is the first report of E coli which produce VT2 being associated with disease in calves.     

Effects of endophyte-infected fescue and cimetidine on respiration rates, rectal temperatures and hepatic mixed function oxidase activity as measured by hepatic antipyrine metabolism in sheep

The effects of endophyte-infected fescue (Kentucky 31) hay and cimetidine on respiration rates, rectal temperatures and hepatic antipyrine uptakes of three mature ewes were measured in 15 experiments. Hepatic antipyrine uptake was measured as an indirect indicator of hepatic mixed-function oxidase (MFO) activity. Five experiments on each ewe were conducted during consumption of endophyte-free (one exp/ewe, control), endophyte-infected (two exp/ewe, EIF) and endophyte-infected fescue hay plus cimetidine (800 mg/d i.v., two exp/ewe, EIFC). Respiration rates increased (P less than .05) 2.6-fold after 11 d on EIF from 26 to 68 and decreased (P less than .025) to 27 breaths/min after 4 d of cimetidine treatment. Rectal temperatures increased (P less than .05) 1.1 degrees C after 8 d on EIF. Cimetidine lowered temperatures to control levels by d 4. Endophyte-infected fescue hay increased (P less than .05) hepatic antipyrine uptake 70% after 11 d, but uptake was lowered to control levels by cimetidine by d 4. Increased respiration rates and rectal temperatures in animals consuming EIF seem to be related to increased MFO activity. Cimetidine reversed some of these effects.     

A survey of antimicrobial resistance in Salmonellae isolated from animals in England and Wales during 1984-1987

Resistance to 14 antimicrobial substances was tested in 18,647 salmonella strains isolated from animals, their environment and from animal feeds during the period 1984-1987. Of the 2284 Salmonella dublin strains the percentage sensitive to all the antimicrobial substances ranged from 18.1 to 26.8. Resistance to the higher concentration of streptomycin (S25) ranged from 1.9 to 6.4%, whereas the corresponding figures when the lower concentration (S10) was used were 32.3 and 63.8%. Resistance to the higher sulphonamide concentration (Su500) never exceeded 3.3%, although in 1987 70.3% of strains showed resistance to the lower concentration. In general, less than 1% of strains showed resistance to the other antibacterial substances. No strains resistant to amikacin (AK), apramycin (Apr), gentamicin (CN) and colistin (CT) were detected. Of the 8677 S. typhimurium strains the percentage sensitive to all the antimicrobial agents ranged from 6.6 in 1985 to 13.6 in 1987. Resistance to tetracycline (T), ampicillin (PN), trimethoprim (TM) and chloramphenicol (C) ranged from 36.5 to 58.8%, the highest percentages being detected with tetracyclines. Less than 1% of strains showed resistance to furazolidone and none was resistant to amikacin and colistin. Resistance to apramycin ranged from 3.1% in 1984 to 11.6% in 1985; the figures for gentamicin were approximately half that of apramycin. In 1984, 41.6% of strains showed resistance to neomycin but only 8.5% in 1987. The fall in neomycin resistance was associated with the epidemic spread of the commonest phage-type DT204C becoming sensitive to neomycin. Of the 7687 strains of serotypes other than S. typhimurium and S. dublin the percentage sensitive to all antimicrobial agents ranged from 23.7 in 1985 to 14.7 in 1987. Resistance to tetracyclines and sulphonamides (Su500) ranged from 5.2 to 12.1% and 5.8 to 13.3% respectively. Resistance to the other antimicrobial agents was usually less than 5%.     

Differentiation of Salmonella typhimurium DT204c by plasmid profile and biotyping

Seventy per cent of the United Kingdom isolates of Salmonella typhimurium from calves are phage type 204c and the study of the epidemiology of this organism requires additional methods of strain characterisation. This paper describes the applications of biotyping and plasmid-profile analysis for this purpose. One hundred and eleven isolates from 73 outbreaks of disease were examined. All belonged to the same primary biotype, although strains from 39 of the outbreaks differed in secondary tests in failing to ferment m-inositol at 25 degrees C. Four different antibiotic resistance patterns were detected among the isolates, which possessed seven distinct plasmid profiles. The spread of a distinct type through the calf marketing chain was investigated by using these techniques.     

Validation of the species composition index

This paper is a validation of the Species Composition Index (SCI). The SCI is a data-handling technique which expresses the botanical composition of a sward as a vector. Inclusion of these vectors allows the incorporation, in response models, of the dynamic changes in species composition of sods which occur over time. The SCI was developed originally with a data set which was obtained in a beef (Bos taurus L.) steer 3-year experiment where several dependent variables (forage growth, consumption and animal performance) were measured concurrently with several environmental, plant and animal characteristics. The SCI was then validated with a different data set, obtained over another 3-year period, with the same species combined in different ways and more complex treatments.

The SCI was related to the effects, if significant, of year, season, grazing pressure, forage quality, precipitation and air temperature on the dependent variables in the two data sets independently. The SCI was superior to the traditional classification variable ‘treatments’ in accounting for variation in the dependent variables in both data sets. When ‘treatments’ was entered into the model, coefficients of determination of 0·26, 0·43, 0·58 and 0·44 were obtained for forage growth and consumption, average daily gain and beef production with the first data set, and of 0·13, 0·40, 0·36 and 0·37 in the second data set, respectively; when SCI was used, coefficients increased to 0·40, 0·52, 0·68, 0·55, 0·42, 0·61, 0·58 and 0·58, respectively. Thus, the effectiveness of the SCI was similar in the two data sets and the SCI appears to be a useful tool for quantitatively describing dynamically changing sward compositions.     

Evaluation of a combined laser Doppler flowmetry and iontophoresis technique for the assessment of equine cutaneous microvascular function

A combined laser Doppler flowmetry and iontophoresis (LDFI) technique, used routinely to assess human microvascular function, was evaluated as a noninvasive technique for assessment of equine microvascular function, to facilitate the study of diseases such as laminitis. Baseline and vasoactive agonist-induced (acetylcholine and nitroprusside) microvascular flux was quantified at 2 sites (on the dorsal pastern adjacent to the coronary band and over the gluteals) in 6 clinically normal horses on 5 or 6 separate occasions under standardised conditions. Both agonists significantly increased microvascular flux. Skin pigmentation significantly attenuated the baseline flux, but not the magnitude of the agonist-mediated vasodilatory response. While LDFI was simple to perform, its value as a clinical and research tool for assessing the equine cutaneous microcirculation is limited by its poor reliability, as indicated by the marked intra- and intersubject variability in baseline and agonist-mediated microvascular flux.     

Cloning: pathways to a pluripotent future

In this month's essay, Anne McLaren traces the winding and pitted pathways that connect the early days of the cell theory of biology in the 1830s to the new and unfolding era of cloning science and technology that came to worldwide attention in 1997 with the announcement of the birth of Dolly, the Scottish cloned sheep. The possibilities, including the potential for new medical treatments and perhaps even human cloning, are fantastic ... and ethically charged.     

Characterization of lipid in loin and bacon from finishing pigs fed full-fat soybeans or tallow.

This experiment tested whether the lipid composition of pork could be altered by changes in dietary lipid, that what effects these changes would have on production and meat characteristics. Pigs were fed diets containing 10 or 20%+ extruded full-fat soybeans (FFS) or 4% tallow for a 3- or 6-wk finishing period, with a corn-soybean meal diet fed as a control. Seventy barrows and 70 gilts were allotted into seven treatment groups with four pens per group. Analysis was on 28 experimental units, which were composite samples from pens. The significance of treatment, sex, and treatment x sex interaction F-statistics was evaluated on chloroform-methanol extractable total lipid, triacylglycerol, phospholipids, cholesterol, individually fatty acids (FA), and the major classes of FA obtained from longissimus muscle and bacon. Treatment effects (P less than .05) were detected for cholesterol content of longissimus and for total lipid and phospholipid content of bacon. Treatment effects (P less than .01) were detected for monoenoic, dienoic, and polyenoic (P) FA in both tissues, and for saturated (S) FA in bacon (P less than .05). Treatment effects (P less than .001) were detected in both tissues for the P:S ratio. The P:S ratio increased 54% for longissimus and 100% for bacon in the pigs fed FFS for 6 wk compared with pigs consuming a corn-soybean meal diet.