Classification of cassava into ‘bitter’ and ‘cool’ in Malawi: From farmers' perception to characterisation by molecular markers     

Jonathan Mkumbira  Linley Chiwona-Karltun  Ulf Lagercrantz  Nzola Meso Mahungu  John Saka  Albert Mhone  Mpoko Bokanga  Leon Brimer  Urban Gullberg  Hans Rosling 《Euphytica》2003,132(1):7-22

Cassava roots, a major food in Africa, contain cyanogenic glucosides that may cause toxic effects. Malawian women farmers considered fields of seemingly similar cassava plants to be mixes of both ‘cool’ and ‘bitter’ cultivars. They regard roots from ‘cool’ cultivars as non-toxic. Roots of ‘bitter’ were considered to require extensive traditional processing done by women to be safe for consumption. But curiously, these women farmers preferred ‘bitter’ cultivars since toxicity confers protection against theft, which was a serious threat to the food security of their families. We studied how well these farmers comprehend the effects of genetic variations in cassava when dealing with cyanogenesis in this complex system. Using molecular markers we show that most plants farmers identified as belonging to a particular named cultivar had a genotype typical of that cultivar. Farmers' ethno-classification into ‘cool’ and ‘bitter’ cultivars corresponded to a genetic sub-division of the typical genotypes of the most common cultivars, with four-fold higher cyanogenic glucoside levels in the bitter cultivars. Examining morphology, farmers distinguished genotypes better than did the investigators when using a standard botanical key. Undoubtedly, these women farmers grasp sufficiently the genetic diversity of cassava with regard to cyanogenesis to simultaneously benefit from it and avoid its dangers. Consequently, acyanogenic cassava – the breeding of which is an announced good of some cassava genetic improvement programmes – is not a priority to these farmers. Advances in molecular genetics can help improve food supply in Africa by rapid micropropagation, marker assisted breeding and introduction of transgenic varieties, but can also help to elucidate tropical small-scale farmers' needs and skills. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Intermediate landscape disturbance maximizes metapopulation density     

Ádám Kun  Beáta Oborny  Ulf Dieckmann 《Landscape Ecology》2009,24(10):1341-1350

The viability of metapopulations in fragmented landscapes has become a central theme in conservation biology. Landscape fragmentation is increasingly recognized as a dynamical process: in many situations, the quality of local habitats must be expected to undergo continual changes. Here we assess the implications of such recurrent local disturbances for the equilibrium density of metapopulations. Using a spatially explicit lattice model in which the considered metapopulation as well as the underlying landscape pattern change dynamically, we show that equilibrium metapopulation density is maximized at intermediate frequencies of local landscape disturbance. On both sides around this maximum, the metapopulation may go extinct. We show how the position and shape of the intermediate viability maximum is responding to changes in the landscape’s overall habitat quality and the population’s propensity for local extinction. We interpret our findings in terms of a dual effect of intensified landscape disturbances, which on the one hand exterminate local populations and on the other hand enhance a metapopulation’s capacity for spreading between habitat clusters.  相似文献   

Bleeding of Farmed Atlantic Cod: Residual Blood,Color, and Quality Attributes of Pre- and Postrigor Fillets as Affected by Perimortem Stress and Different Bleeding Methods     

Hanne Digre  Ulf Erikson  Ekrem Misimi  Inger Beate Standal  Lorena Gallart-Jornet  Siriporn Riebroy 《Journal Of Aquatic Food Product Technology》2013,22(4):391-411

The main objectives of the study were to (a) assess the effect of perimortem stress on blood drainage, (b) compare the efficiency of gill cutting and direct gutting as bleeding methods, and (c) compare pre- and postrigor filleting strategies for presence of residual blood in Atlantic cod fillets. Anesthetized cod had significantly higher drainage of blood compared to stressed fish. Nevertheless, the visual assessments of residual blood were not affected by stress or bleeding method. Some minor, but significant, differences between pre- and postrigor fillets were found. Stressed fish were initially less light in color than those unstressed, but after ice storage there was no noticeable difference. However, initially, the largest difference in fillet color was due to different bleeding methods. Fillets cut from fish subjected to gill cutting were lighter and less red in color than those bled by direct gutting. After 7 and 21 days of storage, the color differences observed in fresh and salted fillets, respectively, were mainly due to the different rigor status when they were filleted, indicating that fillets cut postrigor were superior to fillets cut prerigor. Prerigor filleting resulted in lower water holding capacity after ice storage in anesthetized, direct gutted cod.  相似文献   

Farmer awareness of cow longevity and implications for decision-making at farm level     

Hanna Bergeå  Anki Roth  Ulf Emanuelson  Sigrid Agenäs 《Acta Agriculturae Scandinavica, Section A - Animal Sciences》2016,66(1):25-34

The aim of this study was to investigate if farmer awareness of longevity can explain why the longevity of dairy cows does not increase in Sweden, despite the fact that the genetic trend for longevity in Swedish dairy cattle is positive. In this study, farmers’ decisions were put in the forefront through a qualitative study with semi-structured interviews. The results showed that farmers seemed well aware of biological factors related to cow longevity, that they think the demands on dairy cows have increased over time and that they correlate the higher demands to shorter longevity. However, the farmers had not worked explicitly with longevity of their own herd. There are subjective management decisions behind a culling of a dairy cow, and the reporting of culling reasons does not mirror the farmer’s reasoning behind the decisions, which is a key factor determining longevity.  相似文献   

Fumonisin B2 production by Aspergillus niger   总被引：1，自引：0，他引：1  

Frisvad JC  Smedsgaard J  Samson RA  Larsen TO  Thrane U 《Journal of agricultural and food chemistry》2007,55(23):9727-9732

The carcinogenic mycotoxin fumonisin B2 was detected for the first time in the industrially important Aspergillus niger. Fumonisin B2, known from Fusarium verticillioides and other Fusaria, was detected in cultures of three full genome sequenced strains of A. niger, in the ex type culture and in a culture of F. verticillioides by electrospray LC-MS analysis of methanolic extracts from agar plugs of cultures grown on several substrates. Whereas F. verticillioides produced fumonisins B1, B2, and B3 on agar media based on plant extracts, such as barley malt, oat, rice, potatoes, and carrots, A. niger produced fumonisin B2 best on agar media with a low water activity, including Czapek yeast autolysate agar with 5% NaCl. Of the media tested, only rice corn steep agar supported fumonisin production by both F. verticillioides and A. niger. However, A. niger had a different regulation of fumonisin production and a different quantitative profile of fumonisins, producing only B2 as compared to F. verticillioides. Fumonisin production by A. niger, which is a widely occurring species and an extremely important industrial organism, will have very important implications for biotechnology and especially food safety. A. niger is used for the production of citric acid and as producer of extracellular enzymes, and also as a transformation host for the expression of heterologous proteins. Certain strains of A. niger produce both ochratoxin A and fumonisins, so some foods and feeds may potentially contain two types of carcinogenic mycotoxins from this species.  相似文献   

Variations of Neospora caninum antibody levels in milk during lactation in dairy cows     

Chanlun A  Emanuelson U  Aiumlamai S  Björkman C 《Veterinary parasitology》2006,141(3-4):349-355

A longitudinal study was performed to investigate the variations of Neospora caninum antibody levels in individual milk during lactation as well as the association between antibody levels in serum and milk. Serum and milk samples of 15 milking cows were collected between February 2003 and September 2004 in three smallholder dairy farms in Khon Kaen province in northeast Thailand. All samples were analyzed for presence of antibodies by an N. caninum iscom ELISA test kit and the results were given as percent positivity (PP). The effects of time between calving and sampling, lactation number, and season on milk and serum PP were studied using Generalized Estimation Equations methods. All cows were antibody positive in either milk or serum at the first two consecutive samplings. Although serum and milk PP varied considerably, milk PP was consistently positive throughout the study. Cows of all lactation groups had a higher adjusted mean of milk PP at calving compared to later months after calving although the only significant difference was in first lactation. Serum and milk PP were always lower in first lactation than in second and later lactations. An adjusted mean of milk PP for cows classified as having serum PP> or =55 was significantly (P<0.05) higher than that of cows classified as having lower serum PP. Our results indicate that individual milk can be an alternative material to demonstrate presence of N. caninum antibodies in lactating cows.  相似文献   

Association between costly veterinary-care events and 5-year survival of Swedish insured warmblooded riding horses     

Egenvall A  Bonnett BN  Olson P  Penell J  Emanuelson U 《Preventive veterinary medicine》2006,77(1-2):122-136

Our objective was to estimate the 5-year survival to death in insured warmblooded riding horses (as reflected by a life-insurance claim) in horses with or without at least one costly veterinary-care event (VCE) in 1997. We also determined the impacts of gender, age, previous diagnosis of veterinary claim, geographic variables, cost for veterinary claims and life-insurance value upon the survival. The design was a retrospective cohort study using a population of warmblooded riding horses insured in a Swedish animal-insurance company (Agria Insurance, P.O. 70306, SE-107 23 Stockholm, Sweden) in 1997. All horses in this population had insurance both for veterinary-care and life ("complete" insurance reimbursing the insurance holder for most medical problems). We followed two cohorts (2,495 horses with > or = 1 VCE and 15,576 horses with no VCE in year 1997). The median VCE cost in horses with > or =1 VCE was 3,800 SEK, with 10th and 90th percentiles of 1,400 and 11,400 SEK respectively. In total 944 of the 2,495 horses (38%) in the VCE-positive cohort and 2,962 of the 15,576 horses (19%) in the VCE-negative cohort had died (had a settled life-insurance claim) after the follow-up time. An exponential-regression model showed that geldings had a higher risk of claimed death compared to mares and mares had a higher risk compared to stallions. The risk of death increased linearly with age. The risk of death increased with increasing life-insurance value. Horses with previous lameness had the lowest survival, and for high-cost claims this increased risk was not associated with age.  相似文献   

Evaluation of perioperative analgesia by nociceptive flexor reflex in pigs under ketamine-azaperone-general anaesthesia     

Rintisch U  Baars J  Lahrmann KH 《Berliner und Münchener tier?rztliche Wochenschrift》2012,125(3-4):96-102

The objective of the investigation was to evaluate quantitatively the analgesic efficacy of the Ketamine-Azaperone-general anesthesia during surgical procedures on pigs by nociceptive flexor reflexes (NFR). The study was performed in 30 four to five month old male pigs which were castrated. The NFR was evoked every minute over the N. ulnaris by multiple electrical stimulation consisting of five single stimuli (2 Hz). The reflex response was derived electromyographically (EMG) by surface electrodes placed over the M. deltoideus. The root-mean-square amplitude within the time interval of 80-240 ms after the last stimulus was calculated as measure for the reflex size. The threshold was fixed at 40 microV. Beside electrical NFR recording the surgical tolerance was determined by the traditional interdigital reflex and the defense reaction to defined surgical test stimuli which were incisisions in the scrotal skin, in the tunica vaginalis and in the testis, pulling off the spermatic cord, clamping and cutting off the spermatic cord and final wound disinfection. All surgical pain stimuli were performed simultaneously with the electrical stimuli. After induction of anesthesia the NFR amplitude declined from 3500 microV below the threshold of 40 microV. At 98% of the surgical stimuli without defense reaction were below the reflex threshold. At 93% with defense reactions demonstrated reflex amplitudes above the threshold. When the interdigital reflex was suppressed, 89% of the NFR values fell below the threshold of 40 microV. These findings demonstrate a good correlation of NFR-amplitudes with reactions to traditional controls of analgesia.  相似文献   

Can farm animals help to study endocrine disruption?     

Magnusson U 《Domestic animal endocrinology》2005,29(2):430-435

The phenomenon of endocrine disruption can be regarded as part of the disciplines of toxicology and environmental toxicology. These two disciplines have generated guideline protocols on how various effects of chemicals should be tested as a basis for regulatory decisions. These protocols almost exclusively involve laboratory rodents and the data obtained are then used for human risk assessment. Would it be justifiable, then, to introduce or promote the use of other species in these test protocols? There are, at any rate rationales for studying effects in species other than laboratory rodents: (1) other species may better mimic the human system; (2) they may in some cases be more useful for studying a certain mechanism or phenomenon; (3) they may highlight the diversity of effects or sensitivity between species. However, there are at least two basic criteria that must be met for a species before it can be introduced in this context: (a) we must have a good understanding of the physiological system to be studied; and (b) we must have a number of tools to study effects on this system. When it comes to the reproductive system – regarding which most endocrine disruption has been reported – farm animals are second only, or in some respects superior, to laboratory rodents with respect to these criteria. This review gives examples of how farm animals can be of use in the study of endocrine disruption with a focus on the author's own data from studies in the pig.  相似文献   

A recent growth increase of European beech (Fagus sylvatica L.) at its Mediterranean distribution limit contradicts drought stress     

Willy Tegel  Andrea Seim  Dietrich Hakelberg  Stephan Hoffmann  Metodi Panev  Thorsten Westphal  Ulf Büntgen 《European Journal of Forest Research》2014,133(1):61-71

Future changes in tree growth, associated with a warmer and drier climate, are predicted for many species and locations across the European Mediterranean Basin. However, quantification of the intensity and severity of related consequences for forest ecosystem functioning and productivity remains challenging. Species-specific distribution limits that are particularly sensitive to small changes in the ambient climate may provide an ideal test bed to assess the nature of past growth trends and extremes and their responsible controls. Here, we seek to understand how twentieth century climate change affected the growth of European beech (Fagus sylvatica L.) nearby its south-eastern distribution limit in Albania and Macedonia on the Balkan Peninsula. We sampled 93 living trees from undisturbed mixed forest stands at ~1,450 m a.s.l. and 29 timbers from nearby historical buildings. Application of different tree-ring detrending techniques allowed robust composite chronologies with varying degrees of high- to low-frequency variability to be developed back to 1648 ad. Comparison with local meteorological station measurements and continental grid-box climate indices revealed spatiotemporal instability in growth–climate response patterns. Nevertheless, year-to-year and decadal-long fluctuations in radial beech growth were significantly (P < 0.001) negatively correlated at ?0.61 with June–September temperature over the 1951–1995 period. This (inverse) relationship between increased beech growth and decreased summer temperature is somewhat indicative for the importance of plant-available soil moisture, which likely controls ring width formation near the species-specific south-eastern distribution limit. Significant positive correlations between beech growth and drought (scPDSI; r = 0.57) confirm metabolistic drought constraints. However, an unexpected late twentieth century growth increase not only contradicts the previously observed growth dependency to summer soil moisture, but also denies any putative drought-induced forest ecosystem suppression in this part of the Mediterranean Basin.  相似文献