The aim of the study was to compare the productivity and logging costs using the small class harvester Vimek 404 T5 in thinning of birch plantations and young coniferous stands. It was found in the study that due to a lower fuel consumption, maintenance costs and initial investment, the cost of a working hour of the harvester Vimek 404 T5 is significantly smaller than the cost of a working hour of the middle class harvester. The study confirmed that Vimek 404 T5 is a suitable harvester for thinning in a birch plantation; the study also confirmed the previous conclusions about the main advantages of Vimek harvester compared to a middle class harvester in the first thinning – low fuel consumption and costs of maintenance, high productivity and equipment compactness, which allow to reduce the strip road area. The average productivity for Vimek 404 T5 in birch plantation was 6.2 m**3 per productive hour, but in young conifer stand the productivity was 4.9 m**3 per productive hour. The average stem volume in the birch plantation was 0.06 m**3, but in conifer stand 0.05 m**3. Productivity for the same dimension trees in the birch plantation is not significantly different from the data obtained in the thinning of the coniferous stands.

The homogeneous and light wood of birch is suitable for different types of treatment processes and is highly valued for products where visual aspect is important, however, birch assortments are highly susceptible to damages caused by fungi during the storage. Such fungal damages cause discoloration of birch roundwood intended for further woodworking. Sapwood discoloration development and its influencing factors for birch roundwood were analyzed in the summer - autumn period of the year 2016 (August, September and October). Control cut for assessment of sapwood discoloration development was made in four birch roundwood stacks in the districts of Auce and Daugavpils. In order to evaluate the influence of harvesting type, side surface damages, placement in pile, storage duration, diameter, distance from the end plane, daily average temperatures, precipitation amount and relative humidity on development of sapwood discoloration, 616 discs from birch log end planes were prepared. After conducting multiple factor linear regression, it was concluded that a significant development of discoloration and its changes for birch roundwood are promoted by harvesting type, placement in pile, distance from the end plane, daily average temperatures and relative humidity (R2 = 0.450). For birch logs that are prepared by harvester with the daily average air temperature + 6 °C, the first signs of discoloration appear after 17 – 18 days, but on all logs stacked in pile they appear after 68 – 69 days. Whereas, with the daily average temperature of + 18 °C, the first signs of discoloration can occur after only six days, but on all logs stacked in pile they appear after 23 days.

A pilot-scale horizontal subsurface flow constructed wetland was installed at the farm Mezaciruli, Zalenieki County, Jelgava region, in the middle part of Latvia, in August 2014 to improve stormwater quality collected from the farmyard and demonstrate applicability of constructed wetland as a convenient treatment option for contaminated surface runoff. The examined water treatment system consists of a sedimentation pond as a pretreatment plant, a water pump, a water distribution well, and a horizontal subsurface flow constructed wetland with the surface area of 160 m2 . During the observation period of 27 months (2014 – 2016) water quality parameters such as total suspended solids (TSS), nitrate nitrogen (NO3 -N), ammonium nitrogen (NH4 -N), total nitrogen (TN), orthophosphate phosphorus (PO4 -P), and total phosphorus (TP) were monitored and nutrient removal efficiency of the system was examined. Water samples collected at the inlet and outlet were compared. Monitoring results obtained during this study show that on average concentrations of TN and TP were reduced by 22% and 80%, respectively. However, nitrate - nitrogen concentrations on average increased by 10%, as during the time period from June, 2015 to March, 2016 reduction in NO3 -N concentrations was not observed.

The plants emit different types of volatile organic compounds (Bio VOC’s) and can improve air quality: they effectively remove organic pollutions and reduce the number of microorganisms in the air by releasing phytoncides. The lack of negative ions in the air can cause deterioration of the health of humans breathing it. At the same time, an air saturated with negative ions can improve the state of health and provide a comfortable environment. In this article, the influence of the plants (Cupressus macrocarpa) on the number of ions is proved, based on a series of experiments performed with applying high-voltage pulses (air ionizer). This work is devoted to the elaboration of the mathematical relationship between the air ions concentration and the factors influencing it. For this purpose an experimental stand was made, consisting of two equal compartments: one contained the plants while another one was used as a control without plants. It was concluded that the plants, in general, are able to stabilize the ion concentration and to reduce its fluctuations. The plants help to increase the concentration of negative ions and to decrease the concentration of positive ones.

The growing economy with following industrialization and urbanization has led to environmental contamination with trace elements worldwide. In urban environment, the large inputs of anthropogenic contaminants in atmosphere are arising from mobile and stationary sources. The snow sample analysis is one of methods to monitor air contamination with heavy metals in urban areas. The aim of this research is to analyse heavy metal contamination and distribution in urban environment of Jelgava city. The samples were collected twice in January and February. Snow samples were collected in 20 urban area sampling plots and one natural area sampling plot with three repetitions taken from 1.0 to 1.5 kg of snow. The concentration of trace elements was estimated in 126 melted and filtrated snow water using inductively coupled plasma spectrometer (ICP-OES). The average heavy metals and nutrients concentrations were calculated for each sample. The concentrations data of trace elements were analysed using agglomerative hierarchical clustering method. The results show differences between results in January and February. The differences are related to anthropogenic impact intensity differences during the exposition periods of snow. The clustering results of snow samples taken in January show three clusters, but snow samples taken in February show four clusters.

As European Union member states – Latvia and Lithuania have changed their national height systems from Baltic Normal Height System 1977 to European Vertical Reference System realizations. Performing practical Global Navigation Satellite System (GNSS) measurements and obtained data mathematical processing, there is a possibility to calculate point height difference between GNSS data and data of 1st order levelling networks. The aim of the research is to gain insight for methodology development of geodetic point height testing using GNSS measurements. To achieve the goal following tasks are set: 1) perform GNSS measurements of first order levelling network in Latvia and Lithuania; 2) do data processing to get point ellipsoidal height and compare with the point normal height; 3) detect technically feasible accuracy of geoid model for precise height measurements with GNSS method within research area. Performing GNSS measurements at the same time in the territory of Latvia and Lithuania, the experience of mutual cross-border cooperation was accumulated. The results were adjusted with academic software package Bernese and were obtained point ellipsoidal and normal heights. The height measurement accuracy using GNSS method depends on geoid model accuracy and more precise results can be obtained increasing used geoid model accuracy to 1.5 to 2 cm.

β-galactosidase (EC 3.2.1.23) is one of the widely used enzymes for lactose-free milk production and whey permeate treatment. Enzymes can be obtained from microorganisms, plants and animals. Nowadays, microorganisms are becoming an important source for production of commercially available enzymes, which are of great interest and offer several advantages such as easy handling and high production yield. The aim of this review was to summarize findings of research articles on the application of commercially available β-galactosidase preparates in dairy industry, to analyse and compare the most suitable β-galactosidase commercial preparates for lactose hydrolysis. The results showed that the main factor to choose an appropriate β-galactosidase for lactose hydrolysis was reaction condition. Enzymes from microorganisms contain a wide range of optimal pH from 4.0 (Penicillium simplicissimum and Aspergillus niger) to 8.5 (Bacillus subtilis). The greatest commercial potential has enzymes obtained from fungi (Aspergillus oryzae and Aspergillus niger) and yeasts (Kluyveromyces lactis and Kluyveromyces fragilis). Fungal origin enzymes are more suitable for the hydrolysis of lactose in acid whey due to its acidic pH but yeasts origin enzymes for milk and sweet whey. In the study, commercial preparates from different suppliers with the purpose to analyse their lactose hydrolysis potential and give more detailed characteristics of each preparate advantages and drawbacks were also summarized.

Human milk provides infant with the required nutrients for growth and development. The aim of preliminary study was to determine macro- and micronutrients content in mature human milk among lactating women residing in Latvia and dietary habits affecting it. The study was carried out from November 2016 to February 2017. In total, 24 pooled diurnal milk samples were collected from mothers whose infants had reached the age of at least two months. Personal information of each participant was recorded, including mother’s age, weight and height parameters, sex and age of an infant, parity, breastfeeding pattern, milk expression method used for sampling. Eating habits were obtained using Monthly Food Frequency Questionnaire. Analysed elements were determined using inductively coupled plasma mass spectrometry (ICP‑MS Agilent 7700x, Japan). Concentrations ranged from 227.52 to 398.34 mg LE-1 for calcium, 58.56 – 256.38 mg LE-1 for sodium, 445.33 – 736.71 mg LE-1 for potassium, 25.73 – 49.52 mg LE-1 for magnesium, till 3.17 mg LE-1 for iron, 0.28 – 2.77 mg LE-1 for zinc, 0.06 – 0.43 mg LE-1 for copper, 2.00 – 44.00 µg LE-1 for manganese, 1.00 –10.00 µg LE-1 for chrome which is comparable to data obtained from other studies although chrome and manganese concentration was even higher than observed in literature. Cobalt and selenium content was below detection limit. Zinc content in human milk negatively correlated with baby’s age (p is less than 0.05). The content of majority of essential minerals in human milk was affected by mother’s dietary habits; however, more samples need to be analysed for representative conclusions.

Salty snacks are popular appetizers consumed between meals and are one of favourite components of menu at different social gatherings and private celebrations. Consumers base their choice of snacks not only on flavour and smell of product, but also on different kinds of parameters like colour, texture and nutritional value as well as other information labelled on packaging. Typically salty snacks are associated with potato (Solanum tuberosum) crisps, but in present paper there were viewed also vegetable crisps and snacks. The aim of this research was to evaluate nutritional value and physical quality of potato and vegetable crisps and wholegrain snacks in Latvian market. From January to March 2017, 22 potato and vegetable crisps and wholegrain snack samples from Latvian market were analysed. For all samples, information on the labels was analysed as well as salt content, thickness, crispness and colour using standard methods. For 31.8% of the investigated samples, presented information on label and determined salt content do not differ significantly (p is greater than 0.05). That means that 68.2% of the analysed potato, vegetable crisps and snacks on the packaging labels have represented incorrect salt content. Positive moderate correlation (r = 0.489) between potato and vegetable crisps thickness and crispness was found out. Raw materials and ingredients of samples directly impact colour values. If a sample contains beetroot, the colour results would indicate dark red. All potato crisps colour values point out light yellow colour.

The review looks at the current status of cavy production in Cameroon and situates cavy culture in the area of their contribution to meat production, income generation for cavy farmers in Cameroon. It also reviews research and development of cavy culture in Cameroon. It indicates that cavy culture is an affordable way out of malnutrition for rural women and their families as well as a sustainable way of income generation for these women. It highlights the work done by the various promotion agencies like Heifer international Cameroon and the programme for the support of non-conventional livestock production (PAPENOC) in capacity building for cavy farmers as well as providing material support (improved animals, forage resources and veterinary care). It stresses the need for capacity building for cavy farmers as a means of promoting cavy culture in Cameroon and summarises present and past student/staff research on cavies at the Faculty of Agronomy and Agricultural Sciences, University of Dschang in collaboration with the Institut de Recherches Zootechniques et Vétérinaires (presently Institute of Research for Agricultural Development-IRAD). Development needs are also summarised in the challenges for research on breeding and selection, nutrition, animal health and management practices. The paper indicates that cavy production in Cameroon will have a face lift as a new project on ‘Harnessing husbandry of domestic cavy for alternative and rapid access to food and income in Cameroon and the eastern Democratic Republic of the Congo’ has been implemented since early 2012. It concludes that this project offers a golden opportunity to move the agenda for domestic cavy production forward in Cameroon.