This study is important to contribute morphometry researches and give an example of how to accomplish studies about lakes. The aim of the study is to use the latest technology to determine the morphometric parameters and their variability compared to the previous research results. Research focuses not only on local water body morphometry and bathymetry, and their influencing factors, but also deals with methodological issues regarding measurements of morphometric characteristics and data interpretation as well as state of the art visualization of results. On many occasions, there is a lack of research on morphometry of water bodies or they have taken place in the last century, which has led to the use of obsolete research methods in modern morphometry studies that do not produce the results of a high level of detail. The aim of the study is to use the latest technology to determine the morphometric parameters and their variability compared to the previous research results. The study consists of analysis of the literature on morphometry, methodology used in bathymetry studies, history of research, research methods used in the previous studies. The research object is Lake Kisezers including its morphometry, bathymetry, and influencing factors. The results of the study show that morphometric parameters of Kisezers differ from the results of previous studies. The results of the study confirm that Lake Kisezers is exposed to various influencing factors, mainly anthropogenic. The main factor influencing morphometry and hydrological regime in Kisezers is the water level fluctuations influenced by Riga Hydroelectric Power Plant.

Global scale environmental problems and economic issues are the main aspects what point out exigency to do research in the construction of renewable building materials. Renewable building materials are those materials that can be regenerated quickly enough and in theory, their production could be carbon-neutral. In order to evaluate the thermal efficiency of renewable materials in the framework systems of building envelope structures, test samples were made with the filling of renewable materials. The aim of the work is to find out the thermal conductivity coefficient of these natural composites and to compare them. Different size test samples were created for determination of thermal conductivity coefficient: 1.type as reference value: (width x height x depth) 290 x 290 x 30 mm; 2.type as experimental construction value (imitation of real wall construction): (width x height x depth) 980 x 980 x (165; 250; 345) mm. In this research as renewable insulating materials were used: maple leaves, legume (Galega orientalis), the composition of hemp shives (Bialobrzeskie) and sapropel with lime. A renewable insulating materials (also known as eco-thermal insulating) as alternative building materials discussed in this research work meets the requirements of the normative documents of the Republic of Latvia on sustainable construction principles. The analysis of results indicates significant difference among investigated materials – 0.040 W mE−1KE−1 lowest obtained value of thermal conductivity coefficient.

This paper investigates the effect of fuel bias between the primary and secondary injectors of a staged fuel injection system on the performance of a high output single cylinder spark-ignited internal combustion engine. It is known that staged fuel injection systems are widely used in motorsports applications where high engine speeds are coupled with high power output, therefore, the aim of this study is to evaluate the effect of a secondary fuel injector installed on a Honda CRF450R single cylinder four-stroke gasoline engine. The said engine was equipped with a programmable Performance Electronics PE3-SP0 control unit and a secondary fuel injector identical to that of OE. Power measurements were carried out on a Dynojet-200ix chassis dynamometer in four different modes with altered fuel proportion between injectors, with each measurement being repeated three times. Ambient conditions were monitored with Performance Electronics Pe3Monitor software and the fuel map was adjusted to produce a stable air-fuel ratio. The results were averaged and compared numerically and by coefficient of correlation. It was observed that the data as obtained from the chassis dynamometer software SportDyno 4 contains a lot of noise, both mechanical and electrical in nature, and the changes in power output are highly dependent on engine and equipment temperature. The best results were obtained by using both injectors with fuel proportion biased to the front of the system.

Perfect packaging exists in nature – examples include banana peel (Musa sapientum fixa cortices L.) and eggshell (Ovi testa L.), together with the many smart materials and systems that control plant and biological functions. Smart packaging is a type of packaging, which in addition to performing the four basic functions of packaging such as protection, communication, convenience and containment, also offers several additional functionalities depending on the type of product. Changes in consumer preference for safe food have led to innovation in packaging technology. The market for smart packaging systems has a promising future by integrating them into packaging materials. For food retailers, smart packaging is a huge development in helping to reduce food waste. The aim of this study was to assess the awareness and attitudes of food manufacturers and retailers to the introduction of smart packaging systems into the Latvian market. A survey reflected knowledge about active and intelligent packaging and its possible introduction into the Latvian market. Ten manufacturers and ten food retailers from different regions in Latvia answered 16 questions, including how well they were informed about smart packaging and how much consumers would be willing to pay for it. In addition, the food manufacturer and food retailer confidence in the impact of smart packaging on a product storage quality was analysed. The results revealed that manufacturers and retailers in Latvia have a poor understanding of the new opportunities which could be offered by using technologies of smart packaging.

Bovine colostrum is a mammary gland secret which, due to its high immunoglobulin concentration, is necessary for the transfer of passive immunity to the calf, preventing diseases caused by microbial infections in the newborn ruminants. Colostrum, however, may contain pathogens and can be an infection transmitter, affecting morbidity and mortality rates of calves in the farms. Total plate count and immunoglobulin concentration are two main factors affecting colostrum quality, therefore the aim of the study was to analyse Latvian dairy herd colostrum quality. Colostrum was collected from Holstein Black cows within the first six hours after calving, lactation period of animals ranged from 1st to 4th lactation. Colostrum samples (n=51, 50 mL) were collected from December 2018 to February 2019. Immunoglobulin concentration (n=51) was defined by colostrometer (COLOSTROMETERtm Biogenics, USA), total solids content by optical refractometer (Model BX, UK). Staphylococcus spp. colony–forming unit (CFU) (LVS EN ISO 6888-1+A1:2007), the presence of Listeria spp. (LVS EN ISO 11290-1+A1:2007) and Salmonella spp. (LVS EN ISO 6579-1:2017) were examined in the colostrum samples (n=20). Despite the high immunoglobulin concentration in the analysed samples, our research findings demonstrate suboptimal colostrum quality received by calves. That indicates the necessity for regular colostrum quality control and better management practise providing on the farm.

In recent years, the effective immunostimulating properties of β-glucans have been widely proven not only in mammals, but also in aquatic animals. The aim of this study was to determine the effect of dietary β-glucan supplements on the percentage of individual types of leukocytes and the haematocrit of the sea trout (Salmo trutta L.). Investigations were performed at the state fish farm ‘Tome’, hatchery ‘Pelči’ of the Institute of Food Safety, Animal Health and Environment ‘BIOR’, during a six month period (September 2018 – February 2019). On the basis of feeding with immunostimulant diets, a total of 15 000 sea trout were assigned into five groups. For blood collection healthy fish were randomly selected once a month, five 5 individuals from each group. Blood smears were made to determine the leukocyte differential count. Sampling was done once a month (September 2018 – January 2019) (n=125). Haematocrit was determined by the standard microhaematocrit method. Sampling was done once a month (January 2019 – February 2019) (n=50). We concluded that the dietary β-glucan supplements can improve the haematocrit level and effect the percentage of individual types of leukocytes of the sea trout, stimulation of the preparation for parr-smolt transformation.

Parafasciolopsosis is a parasitological disease which is caused by the liver fluke Parafasciolopsis fasciolaemorpha. This parasite which belongs to herbivores often causes invasion in elks (Alces alces). The aim of our study was to diagnose the parasite and investigate what kind of histopathological changes it caused in the liver tissue. The study took place in Latvia University of Life Sciences and Technologies, Faculty of Veterinary Medicine, Laboratory of Comparative Pathology and Laboratory of Parasitology. During the study from 2017 to 2018 we collected liver samples and faeces from 46 felled elks of different age and gender, from all over Latvia. Ten grams of faeces were examined for trematode eggs by sedimentation method and a section of liver was examined for the presence of flukes and the histological structure of the liver. In this study Parafasciolopsis fasciolaemorpha were found in 11 samples of liver from 46 elks, with invasion extensity of 24%. The histopathological examination of the liver samples revealed fibrosis, proliferation of bile ducts, pericholangitis, calcerous deposits in bile ducts and other notable histological changes in the liver tissue that can cause hepatic trematodes.

New types of polymer fertilizer series ‘Vitanoll’ are used in adaptive-varietal agro technology in the cultivation of seed potatoes. The experiments were conducted on sod-podzolic soils, typical of the North-West region of the Russian Federation. The aim of the research was to study the effect of new polymer fertilizers on potato yield. Research tasks included assessing the effect of various polymer fertilizers (Polymer-N, Polymer-P, Polymer-K.), as well as the effect of Polymer-N on different potato varieties. Based on the studies conducted, the most responsive potato varieties to polymeric fertilizers with nitrogen were identified. They turned out to be Salin (increase of 7.1 t haE−1) and Mocart (increase of 4.1 t haE−1). Evaluation of the influence of different types of polymer fertilizers revealed that the most effective are polymer fertilizers with potassium.

The aim of the work was to study accessions of Dactylis glomerata L. of different origin for breeding in the Leningrad region. The work was carried out at the Leningrad Agricultural Research Institute. The study involved 15 accessions. The nursery was founded in 2016 and included two replications for green yield and two – for seed production. Cutting and sampling for biochemical studies were conducted in May-June 2018, seeds were collected in July. The amount of ascorbic acid, carotenoids and chlorophylls and crude protein were determined. Statistical analysis included the calculation of the parameters of variation, ANOVA and correlation analysis. Three groups were identified by the degree of ripeness: a small group of early maturing – 31 days, a group of late maturing (single accession from Karelia) – 51 days, a large group of middle maturing – 34–37 days. For the late maturing accession the mechanism of regulation of the beginning of heading is due to the sensitivity to photoperiod. The adaptive potential of widely zoned varieties is wider than for localized. Their productivity is higher. The content of pigments in the green mass is closely correlated. The system of pigments in the complex of characters is separate, but is positively associated with the seed productivity and negatively – with the content of ascorbic acid. The seed productivity of the accessions is related to the total pigment content and power of the generative shoots (length and mass).

The article deals with the issue of rural population decline in Poland in 1995−2017. The aim of the study was to present the phenomenon of depopulation involving a decrease in the number of people living in rural areas in Poland at the local level. Based on the literature, the potential effects of depopulation on local development were indicated. The data of the Central Statistical Office and the results of own research carried out in three rural communes in 2019 were used. The occurrence of regional differentiation of rural depopulation processes in Poland was found. Analysing the phenomenon at the local level, it was found that as much as 38.6% of rural communes were characterized by depopulation (a loss of over 5% of the population), including for 10.7% of communes, the population decline in the analysed period was more than 15%. These areas can be considered as problem areas. A particularly unfavourable situation occurs in eastern Poland and the Opolskie Voivodeship. There was a positive correlation between the loss of population and the development of own revenues of communes’ budgets. Studies show that the phenomenon of depopulation is mainly caused by a negative natural increase, which was preceded by a migration outflow associated with the lack of jobs in rural areas.