Forage Base Research Articles

Modern trends in the management of forage base organization in the conditions of digitalization of agriculture

The main approaches to the management of fodder resources are disclosed, taking into account the multidimensionality of fodder production and directions of growth of efficiency and sustainability of the fodder base. The analysis of feed resources use efficiency indicates the presence of reserves for optimization of rations in livestock breeding, which acts as one of the key factors in reducing excessive wear and tear of livestock and ensuring the necessary forage effect. The main directions of the use of digital solutions in the systems of fodder production are revealed, vectors for improving the management of fodder base organization on the basis of optimization and interaction of information flows of its functioning are determined.

Effect of Global Warming on the Fish Population Parameters in the Upper Volga Reservoirs

As a result of global warming, the average annual water temperature has significantly increased in the Upper Volga reservoirs. Warming and the subsequent deterioration of the oxygen regime had a significant effect on most of the fish populations inhabiting temperate waters. This led to changes in the population structure of many fish species. Such phenomena as the disappearance or a sharp decline in the abundance of cold-water species (European smelt, vendace, burbot and pike) in the Rybinsk reservoir coincided with the period of warming. The disappearance of European smelt in the Rybinsk Reservoir and the favorable temperature regime contributed to the appearance and rapid increase in the abundance of the Caspian invader, the Black Sea sprat, which occupied the empty niche of the European smelt and became instead the dominant species in the pelagic zone of the Upper Volga reservoirs. Warming resulted in a decrease in the abundance and the growth rate of burbot and pike. Climate warming had an indirect effect on many species through oxygen deficiency or transformation of the forage base (ruff, zander, perch, roach), which also led to a decrease in abundance and the growth rate.

О расчете приемной емкости северо-западной части Каспийского моря в интересах искусственного воспроизводства водных биоресурсов в Волжско-Каспийском рыбохозяйственном бассейне

After release into the natural habitat, juveniles of semi-passable and passable fish, raised in sturgeon hatcheries and spawning farms of the Astrakhan region, do not stay in the river and roll into the sea. The main food objects for it are organisms of the “soft” benthos – crustaceans, worms and insect larvae. According to the results of research in 2020-2023, data from the analysis of the feed base during the period of the most intense food competition showed that the biomass of benthic invertebrates in the western part of the Caspian Sea is 121.1 thousand tons, production is 484.5 thousand tons. Taking into account the diets, age composition and abundance of each species of fish living in the water area of the settlement of factory juveniles, the volume of withdrawal of forage organisms is determined. livestock. The main consumers of “soft” benthos are representatives of cyprinid, atherine and goby fish species, which makes them the main food competitors of the produced juveniles. The reserve of “soft” benthos products is distributed among the factory juveniles according to the weight and daily diet of each species during the feeding period at sea. When calculating the permissible volume of release of each of the artificially reproducible water bodies, the coefficients of the maximum possible use of the feed base by juvenile fish and an increase in its number, taking into account death during adaptation to the natural environment, are used. Based on the calculations carried out, it is shown that the potential of the forage base of the western part of the Northern Caspian Sea is not a limiting factor in the stocking of the marine area with objects of artificial reproduction. The above method of calculating the receiving capacity is used in the preparation of an annual plan of measures for the artificial reproduction of aquatic biological resources.

Identifying the Forage Base and Critical Forage Taxa for Chesapeake Waterbirds

Identifying the Forage Base and Critical Forage Taxa for Chesapeake Waterbirds

Ecologo-faunistic review of tetranychid (Acariformes: Tetranychoidea) and phytoseiid mites (Parasitiformes: Phytoseiidae) in the Transcarpathian Region, Ukraine</p >

The results of long-term research on tetranychid and phytoseiid mites in the Transcarpathian region of Ukraine are summarized. Transcarpathian Tetranychoidea are represented by 28 species from 10 genera, and the same list for Phytoseiidae included 49 species from 11 genera. For 77 species of mites from 21 genera, species composition, abundance, trophic specialization, and biotopic distribution in different altitudinal zones of Transcarpathia, Ukraine was analysed. Ten species of tetranychid mites (Bryobia rubrioculus, Tetranyhus horridus, Amphytetranyhus viennensis, Eotetranycuus carpini, E. quercicola, Neotetranychus rubi, Oligonychus ununguis, Panonychus ulmi, T. turkestani and T. urticae), and 11 species of phytoseiid mites (Neoseiulus umbraticus, Kampimodromus aberrans, Amblyseius andersoni, A. rademacheri, Euseius ucrainicus, Dubininellus echinus, D. juvenis, Typhloctonus aceri, T. tuberculatus, Anthoseius (A.) rhenana and A. (A.) clavata) were common to all three studied altitudinal zones. The species diversity of tetranychids was highest in the lowlands (23 species), slightly lower in the foothills (19 species), and the lowest in the mountain zone (11 species). For phytoseiid mites, it was the highest in the foothills (38 species), 25 in the lowlands and 21 in mountains. Among the tetranychids, the transzonal species A. viennensis retained its dominant status in all altitudinal zones. In the lowland, the highest rates of occurrence and dominance indices were observed for the species B. rubrioculus and T. turkestani, and in the foothills—for P. ulmi and T. horridus. The species composition of mites in the lowlands and mountains varied the most for both predators and phytophagous mites. Among the tetranychids, the most striking marker species in the mountains were P. ulmi and N. rubi. Only in the mountains were found such phytoseiid species as N. alidis, N. montanus, T. runiacus, T. mutatus, and A. salviae, which could thus be considered strictly mountainous. All of them have fragmented habitats and are tied to mountainous regions. In that altitudinal zone, an exceptionally high occurrence rate and dominance index were established for N. montanus among the phytoseiids. This is most probably due to significantly greater differences in the temperature and humidity regimes and range of host plants and, for predatory mites, prey species. The results of this study provide additional information about the structure of the communities of phytophagous and predatory mites in the natural zones of the mountain landscape and changes in the composition of the communities under the influence of environmental factors and the forage base, which is a consequence of the altitudinal distribution of the investigated biocenoses.

ОСОБЕННОСТИ СЕЗОННОГО РАЗВИТИЯ ПАСТБИЩНОЙ РАСТИТЕЛЬНОСТИ В ПУСТЫННОЙ ЗОНЕ РЕСПУБЛИКИ КАЛМЫКИЯ

The Republic of Kalmykia is one of the largest areas of sheep and beef cattle breeding. The basis of the forage base is made up of natural lands. For the rational use, conservation and increase of productivity of pastures and hayfields, it is necessary to know the composition of vegetation, the phases of its development and other features. Climatic and weather conditions, which are characterized by the greatest variability, which causes significant fluctuations in yields, affects the composition of cenoses, affects the timing and forms of use of forage lands, are crucial in the formation of the harvest of natural herbages, along with nutrients and biological characteristics of plants. Therefore, the study of the conditions for the formation of yields on pastures is of great practical importance. The article presents data on climatic indicators for two weather stations of the Republic of Kalmykia – Yashkul and Lagan for the long-term period 1993-2022 and describes in detail the year 2023 (long-term, annual, monthly, maximum, minimum air temperature, amplitude of fluctuations, precipitation), productivity of pasture grass. The average annual temperature for 2023 was 12.9 °C at the Yashkul weather station and 12.7 °C at Lagan. The intra-annual precipitation distribution in 2023 is also heterogeneous. The annual course of precipitation has shown that most of it falls in the spring period (53...79 mm). The months in which precipitation exceeds the norm alternate with their reduction. A significant increase in precipitation was noted in February, May, June, and July by 20...57 mm above the average annual norm.

Feeding conditions of the interspecific bumblebee association (Hymenoptera, Apidae, <i>Bombus</i>) in the central forest-steppe of the Omsk Region

This article reports that the main food plants of bumblebees of the interspecific association of the central forest-steppe of the Omsk Region during the period of flight activity (I decade of May – III decade of September) are 120 plant species from 30 families. Common and fairly common species predominate, which, under the condition of medium, high and superfroductivity, form the forage base. All rare, quite rare, very rare, as well as unproductive common and unproductive fairly common plant species perform a supporting function in the nutrition of bumblebees. At the beginning of the flight activity of bumblebees, low and medium-productive species predominate, then after the beginning of flowering of new species, highly and super-productive ones are included in the feed spectrum – there is a change in food conditions from unfavorable to favorable. During the main flight period, bumblebees feed or forage on 99 plant species, among which fairly ordinary medium-productive species predominate. Before the second decade of August, three peaks in the expansion of the food spectrum were revealed: in the third decade of May (by 15 species), in the second decade of June (by 31 species) and in the second decade of July (by 20 species). The exclusion of plants from the bumblebee diet occurs every decade. The greatest peaks were recorded in the II decade of July and in the III decade of August – by 21 species. Starting from the first decade of September, there is a change in food conditions from favorable to unfavorable. In general, the feed base of bumblebees of the interspecific association of the central forest-steppe of the Omsk Region has a stable character and allows to provide bumblebees with a sufficient volume of full-fledged feed.

Whole-lake food web model indicates alewife invasion fueled lake trout restoration and altered patterns of trophic flow Lake Champlain

Food web responses to invasion can be context-dependent and therefore difficult to predict based only on invasion histories. Alewives (Alosa pseudoharengus) had generally negative impacts on the native fish communities of the Laurentian Great Lakes after they invaded in the 19th century and were thus expected to negatively impact the Lake Champlain food web after entering the lake in 2003. We evaluated the impact of alewives on the Lake Champlain food web by compiling 25 years of biomass, abundance, and diet data and constructing an Ecopath with Ecosim model of the coldwater food web. Model projections indicated that, contrary to the Great Lakes experience, biomass of native predators increased, mortality rates decreased, and overall trophic level of the pelagic fish community decreased after alewife entered the system. Consequently, the amount of primary production supporting predator biomass increased in response to the addition of prey fish production. The model suggests that alewife invasion in Lake Champlain could have altered food web structure by transferring more energy to tertiary consumers via pelagic pathways at the expense of other energy pathways and “jump started” wild lake trout recruitment by expanding the forage base. In contrast to the Great Lakes response to alewife invasion, Lake Champlain may represent an alternate trajectory for alewife invasion and demonstrates that alewife impacts are context-dependent.

91 Grazing management–Tools for Improving the Efficiency of Grazing Beef Production

Abstract The beef sector is facing mounting challenges related to its perceived impact on climate change and other negative ecological externalities that can occur from the rearing of beef cattle. This would include greenhouse gas emissions (GHG), soil degradation, eutrophication of water ways and a decrease in biodiversity, to name a few. Within the industry, the largest contributor of GHG comes from the grazing sector, predominantly in the form of enteric methane (CH4) produced during the reticulo-rumen fermentation process. This presents a unique challenge, as the grazing sector is one where animal scientists have low precision with respect to experimental design and data collection, and where producers assert a lower level of dietary control relative to confined operations. While enteric CH4 inhibitors are getting closer to regulatory approval, their ability to reduce emissions in grazing systems is still relatively unknown due to the “pulse” supplementation strategy being unstudied to date. Therefore, management decisions that improve the quality of the forage base are the most practical strategies to reduce enteric CH4 production. This would include strategies such as adaptive grazing management, inclusion of high-quality forages, and improved forage diversity as potential tools to reduce emissions, dependent on geographic location. Furthermore, how the human dimension influences soil-plant-animal interrelationships may lead to beneficial ecological outcomes such as carbon sequestration and soil health. Therefore, potential “win-win” outcomes may be achieved. However, climatic gradients, and more specifically moisture, can influence or limit outcomes and thus interpreting research should be done on a geographical and climatic specific basis. The objective of this presentation is to outline and examine how management decisions can influence the efficiency and environmental impact of U.S. beef production, and to identify potential limitations and knowledge gaps in need of future research.

362 The Influence of Supplemental Protein Level on the Intake, Digestion, and Metabolism of Beef Cattle Consuming Low-Quality, High-Fiber Roughages

Abstract Two studies were conducted to evaluate the influence of graded levels of supplemental protein on the intake, digestion, ruminal fermentation, and metabolism of beef cows consuming low-quality forage base diets (6% CP and 74% NDF). For both studies, 15 ruminally cannulated cows (4/5 yrs age, 803 and 757 kg = avg BW for study 1 and 2, respectively) were stratified by BW and, within stratum, randomly assigned to three supplemental treatment groups (n = 5). In study 1, cows were assigned to the following treatments: 1) control, no supplement; 2) 0.25 % BW of a 20% CP supplement; and 3) 0.25 % BW of a 40% supplement. Both supplements were composed of soybean meal and ground corn with the composition adjusted to hit the target CP level. In study 2, cows were assigned to the following alfalfa pellet supplement treatments: 1) control, no supplement; 2) 0.20 % BW of alfalfa pellets, and 3) 0.40 % BW of alfalfa pellets. In study 1, forage intake, DM fill, liquid fill and total tract digestibility were not influenced by supplemental treatment (P ≥ 0.49). However, total DM intake increased linearly (P = 0.02) with increasing supplemental protein, with the 40% CP supplemented cows consuming 39% more DM than control cows. No treatment differences (P ≥ 0.97) were observed for heart rate or surface temperature just before feeding (hour 0) nor 5 hours post-feeding averaging 46.0 bpm, 15.3°C, and 35.2°C, respectively. In study 2, both forage intake and total intake increased linearly (P ≤ 0.02) with increasing amounts of supplemental alfalfa. Cattle supplemented alfalfa pellets at 0.4% of BW had 33 and 71% greater forage and total DM intake compared with non-supplemented control cows, respectively. In contrast, there were no treatment effects (P ≥ 0.11) on DM fill and total tract digestibility averaging 15.73 kg and 44.99%, respectively. In contrast, liquid fill tended to increase (P = 0.08) linearly with increasing levels of supplemental alfalfa. Heart rate nor surface temperature prior to feeding and 5-hours post feeding were influenced (P ≥ 0.83) by the addition of supplemental alfalfa averaging 51.91 bpm, 15.05°C and 31.75°C, respectively. In summary, overall total DM intake was enhanced with the addition of supplemental protein, however, only modest effects were observed in ruminal fill and total tract digestion. Additionally, heart rate and surface body temperatures were not influenced by supplemental treatments under the conditions of these studies.

Comparative analysis of the results of backcrossing during selection of carp

A study of the fish-breeding and biological characteristics of two- and three-year-old hybrids of third-generation carp and reverse-crossing carp was carried out. As a result, a higher Fulton fatness coefficient was revealed in returncrossing carp, as well as their more effective plastic exchange, characterized by feed payment. The exterior indicators for the progonicity index of both two-yearolds and three-year-olds in return-crossing carp had lower values than in hybrids. Consequently, in this group of fish, as a result of the return crossing of carp hybrids with an improver breed (Moscow scaly), a more pronounced high-spin was observed. The additional calculation carried out for the variation of the studied index revealed slightly lower coefficient of variation in two- and three-year-old carp hybrids than in return-crossing carp, which can be explained by the effect of stabilizing selection during three generations of breeding. The use of such an important indicator as the mass accumulation coefficient made it possible to establish its higher values in two-year-old carp of return crossing. The consequence of such a high weight gain in this repair group of carp may be a significantly lower average weight in yearlings of return crossing when stocking outgrowth ponds (15.8 g versus 88.3 g in third-generation carp hybrids). The highest indicators for the accumulation mass coefficient were noted for both two-year-olds and three-year-olds of two groups of carp in the period from May to June, which corresponded to a more intensive development of the natural forage base in the growing ponds during this period of time.

Influence of invasive bigheaded carps on abundance of Gizzard Shad in the Tennessee River

AbstractObjectiveThe Tennessee River basin and its cascade of reservoirs are home to some of the most diverse freshwater fish assemblages in the world. This unique system is threatened by the ongoing invasion of Silver Carp Hypophthalmichthys molitrix and Bighead Carp H. nobilis, hereafter referred to together as “bigheaded carps.” Bigheaded carps may directly compete for food resources with native clupeid species such as Gizzard Shad Dorosoma cepedianum, and this potential interaction could have damaging ecological and economic consequences. High relative abundances of Gizzard Shad are crucial to the Tennessee River food web and associated fisheries because of their role as a forage base for piscivorous species.MethodsWe analyzed a collection of annual gillnetting and electrofishing data spanning from 1990 to 2017 to test whether Gizzard Shad relative abundances have changed in Tennessee River reservoirs since the arrival of bigheaded carps.ResultOur analyses indicated that Gizzard Shad abundances have been declining but were already declining prior to the arrival of bigheaded carps in the Tennessee River.ConclusionAt this stage in the invasion, we could not attribute a cause‐and‐effect relationship to the inverse correlation between Gizzard Shad and bigheaded carps, but we advise continued monitoring of indicators of harmful interactions.

Fish in Burial Practice of the Sargat Culture Population of the Early Iron Age of the Baraba Forest-Steppe (According to the Materials of the Mound No. 51 of the Ust-Tartas Burial Ground)

Purpose. The Sargat culture fish remains are still given very little attention. The purpose of this work is to present materials that testify to the use of fish in the burial practice of the Sargat population of Baraba.Finds (artefacts). In the field season of 2022, the Toguchin team of the IAET SB RAS explored the mound no. 51 of the Ust-Tartas burial ground of the Sargat culture. Among the various artifacts found on the mound territory there were objects containing animal bones, and objects containing fish remains, as well as objects containing both animal bones and fish remains.Methods. Preparation of the osteological collection of fish remains was carried out in 2022–2023 using a cameral processing method. The collection contains mainly scales, bones of the visceral part of the skeleton of the head, bones of the skull. Fragments of the axial skeleton (vertebrae, Weberian apparatus, urostyle) and pharyngeal teeth appear in a smaller number. In the pocess of the collection formation, it was found that the best preservation of samples is ensured by materials that have not been preliminary washed and cleaned: the bone structures are less brittle. Therefore, fragments of the fish skeleton were separated from the soil in the laboratory.Results. For the most part, accumulations of fish remains are represented by large specimens of older age groups (from 7+ years, mostly 10+ and more). The identified species composition of fish in samples of the Early Iron Age includes representatives of the family Cyprinidae (ide Leuciscus idus, goldfish Carassius gibelio) and family Percidae (perch Perca fluviatilis). In addition to the listed species, remains of the family Acipenseridae (sterlet Acipenser ruthenus) and the family Cyprinidae (golden crucian carp C. Carassius) were noted in the earlier objects. Object 10 stands out: it is a butt containing not only tools and animal bones, but also fish remains. For the first time, the fact of fish use in the funeral rite of the Sargatians was revealed. The fish remains in the mound testify that the population of the Sargat culture who created this site practiced fishing along with their main occupation – cattle breeding.Conclusion. Materials of the mound no. 51 of the Ust-Tartas burial ground, containing fish remains, are an example of the local population adaptation to the natural environment. The Tai tract was a natural oasis, which not only provided a forage base for livestock but also ensured an easy catch of fish. Human adaptation to the natural conditions in the Baraba region was quite successful, as evidenced by the fact that fish was a part of the funeral rite along with products of animal origin. It was often included in butts in some objects, which correlates with sacred actions.

FEATURES OF THE FORMATION OF THE FOOD SUPPLY OF THE REPUBLIC OF SAKHA (YAKUTIA)

The conducted studies of the functioning of agriculture in the Republic of Sakha (Yakutia) as the basis of food supply made it possible to identify its regional features. Having rich natural resources, the republic cannot fully provide the local population with the necessary food. The region’s provision level with meat is still below 30%, with milk and vegetables - below 60%. This is due to several factors affecting agriculture in the region and insufficient funding from the state. Scientific studies show a reduction in the number of cattle over the past 20 years from 289.7 to 180.9 thousand heads, or by 37.56%, due to a decrease in the forage base in the context of a reduction in pasture and hayfield areas. The territorial location of the Republic in the northern regions of Russia, the sharply continental climate, the peculiar way of life, the high level of urbanisation and the outflow of residents to the other areas of the country dictate the need for priority state support. Currently, the region is managed based on targeted programs. However, state support funds are inconsistent and unstable, which causes the need to develop organisational and economic measures for the sustainable development of the region’s industry and improve the current state support mechanism with an emphasis on the conservation and reproduction of local animal breeds (Yakut breed of cattle), the development of gene pool farms in the region, the preservation of traditional industries and the rural way of life.

The effect of weather factors on the efficiency of macro- and microfertilizers for the red clover cultivation in the conditions of the Kostroma region

Strengthening the forage base is an important task for the successful development of animal husbandry in the Kostroma region, and the main role in this belongs to red clover. The purpose the current study was to identify the dependence of the productivity of clover green mass on the type and dose of top dressing, when using sparing doses of fertilizers and environmentally friendly types of processing. The study was carried out on the basis of the Kostroma Research Institute of Agriculture in 2020–2022. The two-factor trial consisted of 15 options (three backgrounds – Control, Ozone and “Aquamix”, and 5 options for different doses of top dressing) in three sequences, the area of one plot was 6 m2. There was taken the clover variety ‘Soligalichesky mestny’ as the most adapted to the soil and climatic conditions of the region. During the study, there was found a dependence of the efficiency of the applied fertilizers on weather factors during the vegetation period. Thus, under favorable climatic conditions, the complex “Aquamix” was effective both in pre-sowing treatment and in the form of foliar top dressing. In the variants with its use, there was obtained a significant improvement of green mass productivity and general productivity indicators. The P30K30 dose was the most effective among all mineral top dressings. When increasing the dose and introducing nitrogen (N30P45K90) in the top dressing, productivity and quality of the green mass decreased mainly due to grass lodging. During the unfavorable vegetation period (summer drought), microelements did not affect forage mass productivity and quality. Only top dressing with mineral fertilizers was effective, and the best result was obtained with a higher dose and the full composition of top dressing (N30P45K90). Seed ozonation was effective under all weather conditions. The best result in a favorable year was obtained in the variant Ozone + P30K30 (+43.8 t/ha of green mass, or 153 %), in an unfavorable year it was Ozone + N30P45K90 (+16.1 t/ha, or 111 %). The dose of mineral top dressing ought to be adjusted depending on the weather conditions of a particular vegetation period.

Experimental Field Tests of the Suitability of a New Seeder for the Soils of Northern Kazakhstan

Kazakhstan is historically a livestock country, and the production of feed requires no less attention than the production of grain. To improve the forage base, one solution is the sowing of high-yielding fodder seeds. An experimental seeder was developed with new design solutions for the sowing machine, with three blades installed at an angle of 120° relative to the lower part of the blower shaft, deviated vertically by 8–10°, along with components with a radius vector of 10–15° and the blower shaft attached to the top of the sowing cylinder. The closing part of the disc coulter contained the press rollers with a disc diameter measuring 350 mm. The field tests were conducted with the parameters between the discs set to α = 10°, a disc vanishing point of β = 40°, a coulter angle of 32°, and an individual 320-mm press roller with a cylindrical 60-mm rim, a leash, and a section for setting the seed placement depth. The wheatgrass varieties “Burabay” and awnless brome “Akmola emerald” were sown. The research showed the higher efficiency of the experimental seeder with seeding units and sowing parts compared to a serial seeder in terms of agricultural performance. The increase in seed germination was 3.56%. The experimental seeder surpassed the regular seeder by 4.95% in terms of the depth uniformity of the seed placement, in terms of yield increase by 5.361 cwt/ha, with reductions in traction resistance of 12.3%, and in fuel consumption by 10%. The economic efficiency from the fuel reduction and yield increase was estimated at around 7700 USD/ha per year.

Predicting sport fish mercury contamination in heavily managed reservoirs: Implications for human and ecological health.

Mercury (Hg) is a concerning contaminant due to its widespread distribution and tendency to accumulate to harmful concentrations in biota. We used a machine learning approach called random forest (RF) to test for different predictors of Hg concentrations in three species of Colorado reservoir sport fish. The RF approach indicated that the best predictors of 864 mm northern pike (Esox lucius) Hg concentrations were covariates related to salmonid stocking in each study system, while system-specific metrics related to productivity and forage base were the best predictors of Hg concentrations of 381 mm smallmouth bass (Micropterus dolomieu), and walleye (Sander vitreus). Protecting human and ecological health from Hg contamination requires an understanding of fish Hg concentrations and variability across the landscape and through time. The RF approach could be applied to identify potential areas/systems of concern, and predict whether sport fish Hg concentrations may change as a result of a variety of factors to help prioritize, focus, and streamline monitoring efforts to effectively and efficiently inform human and ecological health.

Density- and size-dependent mechanisms modulate the outcome of stocking in a naturally recruiting freshwater piscivore (northern pike, Esox lucius): A replicated whole-lake experiment

Despite the widespread use of stock enhancements to improve fisheries across the world, there is a lack of robust knowledge under which conditions fish stocking provides additive effects rather than merely replacing a fraction of natural recruitment. Fully controlled and replicated studies at the level of entire ecosystems are needed to provide answers. Properly monitored experimental releases also allow testing mechanisms of density- and size-dependent population regulation. In this study, the population-level outcome of stocking juvenile pike (Esox lucius L.) in naturally reproducing lentic stocks was investigated. We used a replicated before-after-control-impact design in 15 experimental lakes involving two stocking densities and unstocked controls. Releasing age-0 pike failed to generate additive effects at the age-2 cohort. As expected from theory, we observed density-dependent mortality and differential survival of wild and stocked pike. Stocked and wild fishes showed contrasting responses in terms of growth to variation in predator density, competitor density and the forage base, suggesting both subpopulations differed in their response to stocking-induced changes in population traits (e.g., density). Despite the lack of additive effects caused by stocking, a fraction of the stocked individuals established in the stock-enhanced cohort, indicating that replacement of wild recruits by stocked conspecifics had occurred. Depending on the origin of the stocking material, pike stocking thus has the potential for genetic hybridization, while not necessarily benefiting fisheries catch. We conclude that whenever a natural pike population exists, stocking juvenile pike will not produce additive effects in lakes and that enhanced pike populations will be strongly regulated by size- and density-dependent juvenile mortality and less by density-dependent growth.

DESEMPEÑO PRODUCTIVO DE VACAS LECHERAS ALIMENTADAS CON PRADERAS DE KIKUYO SOBRESEMBRADAS CON CENTENO EN SISTEMAS DE PRODUCCIÓN DE LECHE EN PEQUEÑA ESCALA EN LOS VALLES ALTOS DE MÉXICO

<p><strong>Background: </strong>Small-scale dairy systems contribute to mitigate rural poverty as they provide a stable source of incomes to farming families, and also contribute with over 30% of national milk production. However, the dependency on external inputs affects their profitability and sustainability, which added to difficult agroclimatic conditions and limiting management factors as high stocking rate in pastures. It is therefore necessary to evaluate feeding strategies better adapted to conditions in these systems to improve cattle diets based on quality forages reducing external dependency and thus, costs. A means to increase herbage yields in pastures is overseeding with annual fast-growing cereals. <strong>Objective: </strong>The objective was to evaluate the productive performance of dairy cows on two feeding strategies based on grazing, and the analysis of costs in small-scale dairy systems in the highlands of central Mexico. <strong>Methodology: </strong>Eight Holstein cows were used on continuous day grazing (8 h/day) under on-farm research with a double cross-over design. Treatments ere: continuous intensive grazing of Kikuyu grass pastures (KY) or Kikuyu grass overseeded with rye (KYCEN) from 6:00 to 16:00 h, plus 4.5 kg DM/day of commercial concentrate. Two groups of four cows balanced for days in milk and daily milk yield were formed, and each group randomly assigned to one of the treatment sequences: KY-KYCEN-KY y KYCEN-KY-KYCEN, with three experimental periods of 14-day each, with 10 days for adaptation to diets and four days for sampling. Pastures were assessed with a split-plot design. Records were for milk yield and composition, live weight and body condition. A partial budget analysis was performed to compare income and feeding costs. <strong>Results: </strong>There were no statistical differences (P>0.05) in productive performance, with mean 3.5% fat corrected milk yield of 17 kg/cow/day, with 36.6 g/kg, 28.5 g/kg and 43.4 g/kg for milk fat, protein and lactose respectively. There were no significant differences (P>0.05) between treatments for sward height or herbage mass, but there were significant differences (P<0.05) for DM and OM content between treatments, and for CP, NDF, ADF, IVDMD, and EM (P<0.05) between periods. <strong>Implications:</strong> In the face of complex agroecological scenarios for small-scale dairy systems, it is necessary to assess forages better adapted for these conditions as the inclusion of a fast growing cereal as rye to increase pasture production and increase the forage base in the diets with farm resources as Kikuyo grass, in order to increase the profitability of farms. <strong>Conclusions: </strong>Since there were no statistical differences in the productive performance of dairy cows, or in economic performance, the conclusion is that treatment KY is the recommended option for this season. Treatment KYCEN requires expenditures in seed and labour, so that it is not a viable option for small-scale dairy systems in this season.</p>

Impacts of the High-Pressure Bratskoye Hydroelectric Power Station on the Zooplankton of the Bratskoye Reservoir

During the growing season of 2022, the studies were carried out in the water area of the Bratsk Reservoir (the Angara River) and in the near-dam site of the Bratsk high-level hydroelectric power station. The ecological effects of the hydroelectric dam on the zooplankton in the regulated section of the river were studied and the impact of the zooplankton downstream drift on the feeding conditions of the fish in the Bratsk Reservoir was assessed. It is established that the water column stratification is a significant factor in the ecological differentiation of plankton communities in the upper reaches of the hydroelectric power station. Unlike the warmed-up layer of the epilimnion, a specific, poor in species, low-abundant and low-productive plankton develops in the cold-water hypolimnion, which enters the dam intakes. A rigorous analysis does not reveal a transformation of the community composition, a statistically significant decrease in abundance and productivity, increased mortality of invertebrates during their passage through the dam, deterioration of the water ecological quality in the lower reaches of the hydroelectric power station. Both live and dead zooplankton drifting downstream from the reservoir makes up a significant proportion of the diet of fish, which during the feeding period come as close as possible to the hydroelectric power station and form aggregations exceeding those in the water area of the Bratsk Reservoir in density. The data obtained testify to the effective adaptation of lake-river planktocenosis to the specific natural and technogenic mode of operation of a large hydraulic structure. The local impact of the Bratsk hydroelectric power station has no ecologically significant negative effect on the plankton of the Bratsk Reservoir and the Angara River ecosystems and has a positive effect on the fish population in the lower reaches through the enrichment of its forage base.