Particulate metmyoglobin reducing activity and its relationship with meat color

There is controversy about the effect of storage time on metmyoglobin (MetMb) reducing activity in the sarcoplasmic fraction of meat and the role of this reducing activity in maintaining the color of red meat. The presence of metmyoglobin reducing activity in the myofibrillar fraction of muscle extracts was investigated as a possible reason for this controversy. NADH-dependent MetMb reducing activity was found in the particulate fraction of meat following sedimentation of a meat homogenate at 35 000g. There was 5.8 times more MetMb reducing activity in the particulate fraction compared with that of the sarcoplasmic (supernatant) fraction. The presence of metmyoglobin reducing activity in the myofibrils (MMRA), defined as the activity in the sediment after centrifugation of a meat homogenate at 2 000g, was confirmed. The myofibrillar fraction contained 63% of the total MetMb reducing activity available in the meat. The relationship between muscle MetMb reducing activities and meat color parameters was investigated in a beef patties system. The particulate MetMb reducing activity (PMRA) in beef patties was found to be a good indicator of the total metmyoglobin reducing activity in meat and was positively correlated with the color parameters of the patties, suggesting that PMRA may be associated with red meat color of meat patties.     

Dynamic manganese-enhanced MRI signal intensity processing based on nonlinear mixed modeling to study changes in neuronal activity

We analyze data on the impact of testosterone on the dynamics of Mn²⁺ accumulation measured by magnetic resonance imaging in three songbird brain areas: the nucleus robustus arcopallii (RA), area X, and the high vocal center (HVC). Birds with and without testosterone were included in the experiment, and repeated measurements were available in both a preand post-drug administration period. We formulate a nonlinear modeling strategy, allowing for the incorporation of (1) within-bird correlation, (2) the nonlinearity of the profiles, and (3) the effect of treatment. For two of the outcomes (RA and area X), biological theory suggests a parametric form, but for HVC this is not the case. Because the HVC outcome bears some resemblance with the two-compartment model known from pharmacokinetics, this model was considered a sensible choice. We use a different model, based on fractional polynomials, as a sensitivity analysis for the latter. All methods used provide good fits to the data, confirm results from previous, simple analyses undertaken in the literature, but were able to detect additional effects of treatment that had so far gone undetected. The fractional polynomial and two-compartment models provide similar substantive conclusions; the two together can be seen as a form of sensitivity analysis.     

Resistance to Meloidogyne chitwoodi,M. fallax and M. hapla in wild tuber-bearing Solanum spp.

Summary Over 5000 plants from 64 tuber-bearing wild Solanum spp. have been individually screened for resistance to Meloidogyne chitwoodi, M. fallax and M. hapla. Seedlings were analyzed by means of counting number of egg masses and resistance was verified by retesting low-scoring plants using stem cuttings. Resistance to both M. chitwoodi and M. fallax was observed in S. bulbocastanum, S. cardiophyllum, S. brachistotrichum, S. fendleri and S. hougasii. Only in S. chacoense and to a lesser extent in S. stoloniferum and S. gourlayi differential results between M. chitwoodi and M. fallax were observed. Resistance to M. hapla was found in S. bulbocastanum, S. brachistotrichum, S. cardiophyllum, S. arnezii, S. chacoense, S. tarijense, S. boliviense, S. gourlayi, S. microdontum, S. sparsipilum, S. spegazzinii, S. sucrense, S. acaule and S. hougasii. The occurrence of resistance in wild Solanum species in relation to their taxonomic status and the implications for introgression of resistance into S. tuberosum are discussed.     

Digestibility of a complete ration in horses fed once or three times a day and correlation with key blood parameters

To determine the influence of feeding frequency on apparent digestibility and blood metabolites in horses, four geldings were fed a complete ration either once (at 08:00 h) or three times a day (at 08:00, 13:00 and 18:00 h). Horses were provided with a mixture of cereals and chopped alfalfa hay at maintenance level for energy supply, 344 kJ/kg BW(0.75) on a daily basis. After three weeks' adaptation, total amounts of faeces and urine were collected for five days, using collection harnesses. Serial blood samples were taken at -30, -15, 0, 5, 15, 30, 45, 60, 90, 120, 180, 240, 300, 360, 480 and 600 min after feeding and analysed for glucose, L-lactate, triglycerides (TG), non-esterified free fatty acids (NEFA) and triiodothyronine (T(3)). Apparent digestibility coefficients of dry matter (DM), crude protein (CP), ether extract (EE), crude fibre (CF), ash and nitrogen-free extract (NFE) were not significantly different (P>0.05) between the two feeding frequencies. Basal plasma glucose, plasma glucose curves and other plasma blood metabolites were not affected by meal frequency. The horses fed the whole ration in one morning feeding did not consume the entire meal at once, but spared feed for ingestion throughout the day, which may explain the lack of effect. Feeding frequency did not affect plasma glucose response (area under curve :AUC) (P=0.705), but AUC (glucose) was negatively correlated with CP (R(2)=0.76; P=0.005) and CF digestibility (R(2)=0.61; P=0.022). Further research is needed to clarify whether different endocrine responses or differences in passage rate can explain these correlations.     

Two latent variable risk assessment approaches for mixed continuous and discrete outcomes from developmental toxicity data

Measurements of both continuous and discrete outcomes are encountered in many statistical problems. Here we consider the particular context of teratology studies, where quantitative risk asessment is aimed at determining the effect of dose on the probability that an individual fetus is malformed or of low birth weight, both being important measures of teratogenicity. We will introduce two different joint marginal mean models for outcomes of a mixed nature. First, we propose the Plackett-Dale approach, where for each binary outcome it is assumed that there exists an underlying glatent variable. The latent malformation outcomes are then assumed to follow a Plackett distribution. The second approach we consider is a probit approach. Here it is assumed that there exists an underlying continuous variable for each binary outcome, so the joint distribution for weight and malformation can be assumed to follow a multivariate normal distribution. In both cases, specification of the full distribution will be avoided using pseudolikelihood and generalized estimating equations methodology, respectively. Quantitative risk assessment is illustrated using data from two developmental toxicology experiments.     

The assessment and the farmers’ perceived ranking of feed resources and coping strategies with feed scarcity in smallholder dairy farming in selected district towns of Jimma Zone,Ethiopia

Inadequate quantity and quality of feed resources are major constraints limiting milk production and reproductive performance of dairy cattle in Ethiopia. The aim of this study was to assess dairy cattle feed resources, feeding practices, the farmers’ perceived ranking of feed resources, causes of feed shortage, and coping strategies to feed scarcity in smallholder dairy system in selected district towns of Jimma Zone, Ethiopia. Data were obtained by interviewing 52 randomly selected smallholder dairy farmers using structured questionnaires and through direct observations. Results showed that 20 main feed types used by dairy farmers were identified and categorized into natural pastures, crop residues, green feeds, hay, agro-industrial by-products, concentrate mix, and non-conventional feeds. Overall, natural pasture (mean rank = 0.453), non-conventional feeds (0.307), cut green feeds (0.086), conserved hay (0.076), crop residues (0.049), and concentrate feeds (0.029) were ranked as the main feed resources in decreasing order of importance. Natural pasture grazing (92.2% of the respondents), hay (35.6%), and green feeds (29.4%) were the most important conventional basal feeds used. Wheat bran (11.7% of the respondents) followed by commercial concentrate mix (9.4%), Noug seedcake (8.3%), grain (7.8%), and molasses (6.1%) were the concentrate supplements used. Overall, bulule-flour mill leftovers (67.2% of the farmers), bean and pea hulls (57.2%) and atella-local brew by-product (37.2%), enset (Ensete ventricosum, 34.4%), and sugarcane top (32.2%) were the non-conventional feeds available and used during feed scarcity. Barley and teff (Eragrostis teff) straws and maize and sorghum stovers were the main crop residues used in the dry seasons. Overall, 73.9, 12.2, 12.2, and 1.7% of the respondents practiced free grazing, zero grazing, semi-zero, and a combination of zero- and free-grazing systems, respectively. Over 84% of the respondents in the dry season and 50% in the wet season reported experiencing a shortage of feeds. Poor feed availability (73.9% of the respondents) was reported as the main causes of feed shortage followed by shortage of pastureland (7.8%). Increased use of bulule (55.6% of the respondents), crop residues (16.1%), non-conventional feed resources (14.4%), conserved hay (11.1%), purchased green feeds and concentrates (1.1%), and reducing herd size (1.1%) were the farmers’ adopted coping strategies to mitigate feed shortage. It is suggested that technical intervention to improve the quality and efficient utilization of the existing feed resources is crucial to enable sustainable feed supply and boost milk production. Technologies that are easy to adopt, feasible, and low cost are also needed to be developed in participatory manner.     

Analysis of population structure and genetic diversity reveals gene flow and geographic patterns in cultivated rice (<Emphasis Type="Italic">O. sativa</Emphasis> and <Emphasis Type="Italic">O. glaberrima</Emphasis>) in West Africa

To fully exploit the diversity in African rice germplasm and to broaden the gene pool reliable information on the population genetic diversity and phenotypic characteristics is a prerequisite. In this paper, the population structure and genetic diversity of 42 cultivated African rice (Oryza spp.) accessions originating from West Africa (Benin, Mali and Nigeria, Liberia etc.) were investigated using 20 simple sequence repeats (SSR) and 77 amplified fragment length polymorphisms (AFLP). Additionally, field trials were set up to gain insight into phenotypic characteristics that differentiate the genetic populations among rice accessions. The analysis revealed considerably high polymorphisms for SSR markers (PIC mean?=?0.78) in the germplasm studied. A significant association was found between AFLP markers and geographic origin of rice accessions (R?=?0.72). Germplasm structure showed that Oryza sativa accessions were not totally isolated from Oryza glaberrima accessions. The results allowed identification of five O. glaberrima accessions which grouped together with O. sativa accessions, sharing common alleles of 18 loci out of the 20 SSR markers analyzed. Population structure analysis revealed existence of a gene flow between O. sativa and O. glaberrima rice accessions which can be used to combine several interesting traits in breeding programs. Further studies are needed to clarify the contributions of this gene flow to valuable traits such as abiotic and biotic stresses including disease resistance.     

Indirect effects of bottom fishing on the productivity of marine fish

One quarter of marine fish production is caught with bottom trawls and dredges on continental shelves around the world. Towed bottom‐fishing gears typically kill 20–50 per cent of the benthic invertebrates in their path, depending on gear type, substrate and vulnerability of particular taxa. Particularly vulnerable are epifaunal species, which stabilize the sediment and provide habitat for benthic invertebrates. To identify the habitats, fisheries or target species most likely to be affected, we review evidence of the indirect effects of bottom fishing on fish production. Recent studies have found differences in the diets of certain species in relation to bottom fishing intensity, thereby linking demersal fish to their benthic habitats at spatial scales of ~10 km. Bottom fishing affects diet composition and prey quality rather than the amount of prey consumed; scavenging of discarded by‐catch makes only a small contribution to yearly food intake. Flatfish may benefit from light trawling levels on sandy seabeds, while higher‐intensity trawling on more vulnerable habitats has a negative effect. Models suggest that reduction in the carrying capacity of habitats by bottom fishing could lead to lower equilibrium yield and a lower level of fishing mortality to obtain maximum yield. Trawling effort is patchily distributed – small fractions of fishing grounds are heavily fished, while large fractions are lightly fished or unfished. This patchiness, coupled with the foraging behaviour of demersal fish, may mitigate the indirect effects of bottom fishing on fish productivity. Current research attempts to scale up these localized effects to the population level.     

Potentials and Limitations of Existing Forecasting Models for <Emphasis Type="Italic">Alternaria</Emphasis> on Potatoes: Challenges for Model Improvement

Alternaria species, including A. solani and A. alternata, are a serious threat to potato cultivation and cause necrotic leaf spots, leading to premature defoliation and yield losses. To reduce the impact of the disease, a timely prediction of a disease outbreak is important. Worldwide, modelling attempts have been made to predict the occurrence of Alternaria in order to take adequate measures. In the present paper, we made an effort to classify the existing prediction models and subdivided them into three categories: plant-based, pathogen-based and plant-pathogen-based models. Plant-based models predict the susceptibility of the host crop and presume that Alternaria inoculum is abundantly present and not the restrictive factor, whereas pathogen-based models consider one or more stages of the Alternaria life cycle and suppose that the host crop is always susceptible. The plant-pathogen-based models try to take into account the complete plant-pathogen-environment relationship. In this paper, a critical review of the described models for Alternaria leaf spot is presented. To illustrate the discrepancy between the predicted and the observed dates of the first Alternaria symptoms or the discrepancy between the suggested first treatment and necessity to treat Alternaria, the existing models were subjected to the Belgian weather conditions. It turns out that these models are not applicable in Belgium or similar regions. This can be partially attributed to the fact that most of the currently available models are too simplistic (only plant- or pathogen-based) for regions where the disease pressure highly fluctuates between growing seasons and between locations within one season. Finally, perspectives for model improvement are given taking into account both plant, pathogen and environment.