Fish production and some traits of meat quality in rainbow trout (Oncorhynchus mykiss) farmed in different production systems

St. Stoyanova*, Y.Staykov, G. Zelqzkov, I. Sirakov, G.Nikolov

Department of Biology and Aquaculture, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria (Manuscript received 26 October 2016; accepted for publication 22 November 2016)

Abstract. The rainbow trout (Oncorhynchus mykiss), an important species in Bulgarian aquaculture, is farmed in different production systems as raceways, net cages etc. The aim of the present study was to evaluate the effect of two different rearing systems on fish production, survival rate, meat chemical, mineral composition and farming economic efficiency of culticated rainbow trout (Oncorhynchus mykiss). The information from a survey on fish production and economic efficiency traits was collected from two national rainbow trout farms using the two commonest fish farming systems: in raceways, Happy Fish Ltd fish farmandinnetcages,ForestGroupLtdfishfarm.Theaverageindividualweightgain(g),totalweightgain(kg), feedconversionratio,productioncostsof1kg fish and the economic efficiency coefficients were determined for the two studied fish farms. The final live weight of rainbow trout in net cages was 0.30 kg vs 0.35 kg in raceways. The average individual weight gain was higher in raceways farming system (0.30 kg) than in net cages farm (0.26 kg). The mortality rate of fish in raceways was considerably lower: only 1% as compared to that in net cages (4%). The feed conversion ratio at the end of the experiment showed identical values for trout in both farms 1.01. The meat water content of fish reared in raceways and net cages was 77.46±0.65% and 74.52±0.52% respectively (P≤0.01).The protein content of fish meat was higher in fish farmed in net cages 18.84±0.29% as compared to fish cultivated in raceways 17.60±0.49% (P≤ 0.05). Meat fat content of rainbow trout, reared in the net cage system was also considerably higher (5.26±0.30%) than the respective parameter in fish farmed in ponds(3.60±0.15%)(P≤0.001).The content of Ca and P washig her in rainbow trout sreared in race ways(138.96±1.12mg.kg-1and2844.32±39.31mg.kg- 1) compared with the values of these parameters of fish in net cages (134.46±1.96 mg.kg-1 and 2690.31±42.81 mg.kg-1) (P≤ 0.05). The K and Na content exhibited the opposite tendency with substantially higher values in trouts farmed in net cages (2658.26±48.75 mg.kg-1 and 671.31±16.16 mg.kg-1) than in fish in raceways (2552.90±39.93 mg.kg-1 and 569.32±13.75 mg.kg-1)(P≤0.05, P≤0.001). The production costs of 1 kg rainbow trout were by 17.27% lower in the Forest Group farm than in the Happy Fish farm. The coefficient of economic efficiency in the net cage farm was by 23.44%higher than that of the race ways production system.

 

Reclamation of lands disturbed by mining activities in Bulgaria

I. Kirilov, M. Banov*

Institute of Soil Science, Agrotechnologies and Plant Protection, 7 Shousse Bankya, 1080 Sofia, Bulgaria (Manuscript received 5 August 2016; accepted for publication 7 November 2016)

Abstract. Disturbed by the mining industry area in Bulgaria is about 24.113 ha of which only 8.253 ha are reclaimed. Reclamation of disturbed areas covers a complex of engineering, technical, ameliorative, agricultural, forestry and other activities, which aim at restoration of the disturbed terrains and their re-entry into economic turnover in accordance with environmental conditions and area landscape. All disturbed lands as well as their adjacent areas that have completely or partially lost productivity as a result of the negative impact of mining activities and land damage are subject to reclamation. Land reclamation is a two-step process which includes: technical reclamation and biological reclamation. Technical reclamation is performed by the land owner and covers cleaning and preparation of the terrain, leveling, final formation and laying a humus soil layer on site by adding appropriate “improvers” (e.g. fertilizers, texture enhancers, etc.). Biological reclamation covers restoration of the productivity of the disturbed areas. Reclamation technologies applied in Bulgaria as a whole have led to a state of these territories that requires both maintenance and search for new ways of integration of the reclaimed landscapes with modern economic activities. The aim of the study is analysis and applying reliable modern practices that ensure good results in visual qualities of landscape and more options for future use of the reclaimed land.

 

Effect of green manure cover crops on tomato greenhouse production

I. Tringovska, V. Yankova, D. Markova

Maritsa Vegetable Crops Research Institute, 32 Brezovsko shosse, 4003 Plovdiv, Bulgaria (Manuscript received 22 August 2016; accepted for publication 27 September 2016)

Abstract. Cover crops are an important component in sustainable vegetable production with main purpose to reduce the use of synthetic inputs, especially nitrogen fertilizers. The aim of the current study was to evaluate the effect of cover crops as hairy vetch (Vicia villosa Roth), winter pea (Pisum sativum L.) and white mustard (Sinapis alba L.) on (i) greenhouse tomato yield and fruit quality and (ii) root-knot nematodes infestation. The experiment was carried out during two consecutive years (2014 – 2015) in an unheated greenhouse at Maritsa Vegetable Crops Research Institute. Cover crops were grown before the main crop and plowed under and incorporated into the soil a week before transplanting the tomato plants. Control plots did not receive green manures. Two variants of fertigation were applied – optimal and 50% reduced amount of nitrogen fertilizer. Green manures did not change significantly the yield of tomato plants as well as did not influence on fruit quality parameters as brix, total sugars and titrable acidity. A slight negative effect was observed on Vitamin C content in tomato fruits. By green manuring with hairy vetch a reduction of the amount of nitrogen fertilizer used for fertigation could be achieved. Hairy vetch and white mustard as green manures suppressed to some extent the development of Meloidogyne spp.

Selectivity and stability of herbicides and their tank mixtures for the seed yield of sunflower (Helianthus Annuus L.)

G. Delchev1*, T. Barakova2

1Department of Plant Production, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria 2Field Crops Institute, 6200 Chirpan, Bulgaria

(Manuscript received 16 May 2016; accepted for publication 11 August 2016)

Abstract. The research was conducted during 2012 – 2014 on pellic vertisol soil type. Under investigation were 4 sunflower hybrids (Helianthus annuus L.): hybrid Bacardy (an imitolerant hybrid by ClearField plus technology), hybrid Estiva (an imitolerant hybrid by ClearField technology), hybrid Sumico (a tribenuron-methyl tolerant hybrid by ExpessSun technology) and hybrid Arizona (a hybrid by conventional technology). Factor A included the years of investigation. Factor B, herbicides and tank mixtures, included 20 rates. It includes 3 variants by ClearField plus technology, 5 variants by ClearField technology, 5 variants by ExpessSun technology and 7 variants by conventional technology. All variants are on herbicide Gardoprim plus gold 500 SC (S- metolachlor + terbuthylazine) – 3.5 l/ha, which treated after sowing before emergence of the sunflower. It is found that the highest seed yield is obtained at herbicide tank mixture Pulsar plus + Stomp aqua by ClearField plus technology. Tank mixture Listego + Dash + Sharpen by ClearField technology and Express + Trend + Select super by ExpressSun technology also lead to obtaining high seed yields. The most unstable are secondary weed infested checks by the fourth technologies for sunflower growing which are treated with soil-applied herbicide Gardoprim plus gold only. Technologically the most valuable are herbicide combination Pulsar plus + Stomp aqua and herbicide Pulsar by ClearField plus technology, tank mixtures Listego + Dash + Sharpen and Listego + Dash by ClearField technology and Express + Trend + Select super and Express + Lactofol B + Select super by ExpressSun technology. Tank mixtures of herbicides Smerch, Pendigan, Wing, Raft, Pledge and Modown with Amalgerol premium by conventional technology have low estimates due to insufficient control of some weeds in sunflower crops.

Panthaleus major /Duges/ of cereals in Bulgaria

V. Maneva*, D. Atanasova

Institute of Agriculture, 1 Industrialna Str., 8400 Karnobat, Bulgaria
(Manuscript received 30 June 2016; accepted for publication 19 September 2016)

Abstract. Until recently, Penthaleus major (Dugès) has not been recognized as an economically significant pest for the cereal crops. After climatic changes, its population began to grow and inflict damages around the world. The aim of this study was to investigate its distribution in Bulgaria and establish whether it presents a danger to the cereal crops. In the autumn of 2015 and the spring of 2016, a monitoring survey was conducted to establish Penthaleus major (Dugès) with the cereal crops in Bulgaria. Over 60 sowed fields were investigated from all around the country. Samples were taken to identify the pest. It was established that Penthaleus major (Dugès) inflicted harm to the wheat in north-eastern (12-14 mites per stem) and south-eastern Bulgaria (6-8 mites per stem). Its density was under the threshold of economic harm. There was not found infestation of barley, rye, oat and triticale. On the field boundaries bordering the areas attacked by the mite were reported the following weeds: Capsella bursa pastoris (L.) Medic, Descurania sophia (L.) Welb. et Berth, Senecio spp., Sisymbrium orientale Torn., Taraxsacum officinale Weber, Anthemis spp., Bromus arvensis L., Eragrostis pilosa (L.) P.B. Lolium temulentum L., which can be habitat for Penthaleus major (Dugès).

Comparative analysis of plane geometric parameters of various types of cow milking parlors

D. Georgiev*

Department of Agricultural Engineering, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria (Manuscript received 5 May 2016; accepted for publication 11 September 2016)

Abstract. Geometric planning parameters of milking parlors of similar capacity and different arrangement of animals on cow platform were analyzed. Indicator (K) was calculated to reflect the ratio of length (L) to width (W) of the cow platform. It can be used by designers and farmers for practical purposes to select the type or capacity of a cow milking parlor when reconstruction an existing facility (at particular planning parameters available). This study discusses alternative solutions for milking parlors of various configurations (tandem, herringbone, and parallel type parlors) of capacity from 2×5 to 2×10 cows. The following planning parameters were investigated: absolute and relative (per milking stall) floorage area of milking parlors with various configuration (without entrance/exittrafficlanes)atrespectivecapacity;ratioindicator(К)ofthemaindimensions(lengthandwidth)ofthemilkingzoneasguidance forselectionofa milking parlor at specified conditions (reconstruction of existing facility). For each alternative the dimensions (length and width) at respective capacity and configuration were taken, and only the milking zone without animal entrance and exist lanes was considered. Conclusions drawn from the results are aimed at minimizing the relative area of milking stalls in the design of milking parlors at specified technological conditions.

Effect of fluorescence on the technological characteristics of cocoons at different cooking temperatures

M. Panayotov*

Department of Animal science-Non-ruminant and other animals, Faculty of Agriculture, Trakia Univercity, 6000, Stara Zagora, Bulgaria (Manuscript received 5 May 2016; accepted for publication 11 August 2016)

Abstract. The subject of research are Bombyx mori L. cocoons, differentiated by the nature of their fluorescent radiation. In each fluorescent group 2 subgroups were formed prepared for unreeling through cooking at 80 and 90°C for 5 min. To account for the effect of fluorescence at various cooking temperature levels the basic technological traits signs of the silk filament and cocoons have been defined and analysed: total length of the silk filament (m), nonbroken filament length (m, %), raw silk pesentage (%) and reelability (%). It was found that fluorescence of cocoons has statistically significant (p≤0.01- 0.001) effect on the phenotypic manifestation of the technological traits. Within the two cooking temperature levels, the yellow fluorescent cocoons demonstrate higher values at 80 °C, and violet ones at 90°C. The better technological qualities and the lower cooking temperature in the yellow fluorescent cocoons give reason to believe that their use is economically more profitable for the silk reeling industry compared with violet fluorescent cocoons.

Biochemical and chemical investigations of pikeperch fingerlings (Sander Lucioperca L.) after wintering

A. Ivanova*, R. Atanasova

Institute of Fisheries and Aquaculture, 248 Vasil Levski, 4003 Plovdiv, Bulgaria (Manuscript received 14 September 2016; accepted for publication 13 October 2016)

Abstract. The purpose of the present study was to investigate some basic biochemical and chemical parameters of pikeperch (Sander lucioperca L.) yearlings reared in ponds after wintering. The investigation has been carried out in the Institute of Fisheries and Aquaculture, Plovdiv. The fish included in the study were randomly selected from one pond, with area of 0.40 ha. Blood samples were collected from 10 pikeperches with average weight from 80 to 100 g. Blood biochemical parameters were individually analysed. For hemoglobin determination, blood was anticoagulated with sodium citrate. Samples for body tissue analysis (without the head and viscera) were collected from 4 fish, autoclaved and used for analysis of water content, % (drying at 105 оС, 24 h; Bulgarian State Standard – SR ISO 5984), protein content, % (Kjeldahl method, Bulgarian State Standard – SR ISO 5983 semi-automated DK 6 digester unit and UDK 132 distillation system, Velp Scientifica), fats (%) by the method of Smidt-Boudzynski Ratzlaff and ash (%) by burning in a muffle furnace at 550 oС, BSS – SR ISO 6496. The average blood serum total protein was 66.1±0.12 g.l-1, blood glucose concentration was 92.8±3.42 mg.100 ml-1 (5.15 mmol.l-1) and average hemoglobin content was 44.7±0.33 g.l-1. The average protein content in analysed fish samples was 16.65±0.23 %. Protein content was the highest among studied dry matter components, followed by the ash (1.97±0.06 %) and fat content (0.84±0.03 %). The levels of blood serum total protein, blood glucose and hemoglobin content as well as body composition parameters – water, protein, fat and ash of pikeperch fingerlings (Sander lucioperca L.) after wintering reflect the specific equilibrium of plastic and energy substances after the winter period, with no deviations from the reference ranges.

Efficacy and timing of some new products against pear psylla (Cacopsylla pyri L.) (Hemiptera: Psyllidae): II. Spirodiclofen

V. Arnaudov*

Institute of Fruit Growing, 12 Ostromila, 4004 Plovdiv, Bulgaria
(Manuscript received 30 June 2016; accepted for publication 7 September 2016)

Abstract. The effectiveness of spirodiclofen (Envidor® 240 SC) in the control of pear psylla (Cacopsylla pyri L.) on pear trees was evaluated in field experiments,carriedoutincommercialpearorchardinthevillageDinknearPlovdiv (Bulgaria)during2014–2015.Theefficacyofspirodiclofen(Envidor240 SC ® at a dose of 600 and 800 ml/hl) in controlling this pest was compared to that of abamectin (Vertimec 018 EC at a dose 150 ml/hl). Each one of the insecticides was applied only once in the presence of predominantly “yellow” eggs and the first hatched larvae from the second generation of C. pyri. Аpplied only once at a dose of 800 ml/hl, spirodiclofen (Envidor® 240 SC) effectively reduces populations of the pest, achieving from 92.6 to 96.4% efficacy 21 days after treatment (DAT). Envidor 240 SC applied at a lower dose of 600 ml/hl had a slightly worse effect, achieving from 90.0 to 93.1% efficacy 21 DAT. The effectiveness of spirotetramat at both doses after only one application was very high and insignificantly different. In comparison with the reference insecticide (abamectin) the efficacy of spirodiclofen was slightly weaker in the first two weeks after treatment and insignificantly different at the end of the third week after the treatment (the total reduction of larvae ranged between 82.4 – 87.4% 3 DAT and 90.0 – 96.4% 21 DAT in the spirodiclofen treated plots, while in the abamectin treated plot it ranged between 92.9 – 96.5% 3 DAT and 94.0 – 98.7% 21 DAT. Spirodiclofen (Envidor® 240 SC), both tested doses gave similar results, which are significantly weaker in the first days after treatment, but significant enough and improved in time. This active substance, in contrast to abamectin, demonstrated a slow initial activity and a longer persistence. Spirodiclofen can be considered as a reliable tool to control of C. pyri and possible alternative to abamectin to prevent the risk of resistance in pest populations.

Clinical toxicological investigations on acute carbofuran intoxication in quails (Coturnix coturnix)

R. Binev1*, I. Valchev1, R. Mihaylov2, Y. Nikolov1

1Department of Internal Non-Infectious Diseases, Faculty of Veterinary Medicine, Trakia University, 6000 Stara Zagora, Bulgaria 2Department of Animal Morphology, Physiology and Nutrition, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria

(Manuscript received 7 September 2016; accepted for publication 19 October 2016)

Abstract. The present studiy was conducted to evaluate the toxic effects of the carbamate insecticide carbofuran (Carbosan 35 ST) after experimental acute intoxication in quails (Coturnix coturnix). Experiments for monitoring of changes in clinical indices and some haematological parameters. Quails were divided into 5 groups: one control and 4 experimental. They were treated by increasing single doses of the tested pesticide: 1.05 mg/kg (experimental group I), 2.1 mg/kg (experimental group II), 5.25 mg/kg (experimental group III) and 10.5 mg/kg (experimental group IV), corresponding to 1/10 LD50, 1/5 LD50, 1/2 LD50 and LD50 oral doses for albino rats, respectively. In three consecutive days prior to the treatment (hours –48, –24 and 0) and 1, 3, 5, 7, 24 and 48 hours thereafter, the clinical status was registered to evaluate rectal body temperature, faeces excretion, locomotion, perception etn. and were obtained blood samples from v. subcutanea ulnaris or v. metatarsea ulnaris for analysis of haemoglobin content (HGB). It was found out that the tested carbamate insecticide had some toxic effects manifested clinically with hyperaemia, arexia, difficulty in focusing the eyes, salivation with thick saliva discharge, diarrhoea, generalised tremor, clonic tonic spasms (especially of cervical muscles), depression and hypochromaemia. The described changes were the most obvious between post treatment hours 1 and 3, and then the studied parameters regained their control values. The tolerated dose of carbofuran was 1.05 mg/kg (1/10 LD50 for albino rats), the minimum toxic dose was 2.1 mg/kg (1/5 LD50 for albino rats), and minimum lethal dose – 10.5 mg/kg, equal to LD50 for albino rats.