نشریه حفاظت و بهره برداری از منابع طبیعی
سال سوم شماره 1 (بهار 1389)

Local scouring around bridge piers has been considered as an undesirable and against the bridge safety event. In this process the bed materials in the vicinity of circular bridge pier are moved and a scour hole appears around the bridge pier. Bridges are one of the most important parts of the transportation system, but the safety and stability of the bridge structure will be in danger during a flood in the river because of local scouring. Thus, the foundation of the bridge piers must be embedded in a depth deeper than the maximum local scour depth according to the design flood. If the suitable solutions not applied, the bridge failures will probable. Bridge failure imposes many direct and indirect costs. Previous studies approve that the geometric parameters are one of the most effective parameters in the estimation of maximum local scour depth. In this study, the effect of pier diameter variation in the maximum local scour depth has been evaluated by SSIIM program. In the next step, the effect of slot in the reduction of local scouring around circular bridge pier was numerically simulated. In order to verifying the numerical results, the available experimental data by previous studies was used. The results show that increasing the bridge diameter with twice, the maximum depth of scour around piers increase less than 60 percent. Also SSIIM program can be used for simulating the effect of slot in the reduction of local scouring around circular bridge pier.

Evening primrose scientifically known as Oenothera biennis belongs to Onagraceae family is an ornamental and medicinal plants with seed containing oil in which in some temperate regions is accepted as an alternative for oilseed plants by farmers. The seeds of plant contain 20-30% oil with unsaturated fatty acids like linoleic acid (more than 70%) and gamma linolenic acid (7-12%). Recently, root and crown rot together yellowing and necrosis and finely decline are appeared in evening primrose cultivated in green space of faculty of agriculture. To study the causal agents of observed disorders, 24 samples were transferred to laboratory and sterilized using hypochlorite 50% for 30 min. then samples were cultured in potato dextrose agar (PDA) medium. After one week a fungus with white grayish colony with black sclorut (55-115 µm) and oval colorless conidia (100-160 µm) was observed. The characters of isolated fungus were similar to Macrophomina phaseolina. The single hyphe of isolated fungus was propagated and inoculated to non-contaminated plants. One month later a black colony of fungus with a high number of sclorut was observed. Re-inoculation of pathogen showed the similar symptoms. The present manuscript is the first report of evening primrose root decline in Iran.

The purpose of this study was to determine desirable size and minimum economic of farm size in farming systems including peasant, production cooperative, commercial (small, medium and large) in Golestan province. The methodological approach was a descriptive and survey type. The target population in the study consisted total farming systems units in Golestan province, including peasant, production cooperative and commercial exploiters. In all farming systems, using multistage cluster and stratified sampling techniques and Cochran,s formula 358 exploiters (farmers) were chosen including 164 peasant, 80 production cooperative and 50 commercial (small, medium and large) exploiters. Data were collected through a questionnaire and its content and face validity were obtained by experts of farming systems. The reliability analysis was conducted with completing 30 questionnaires out of the target population and Cronbach,s alpha value was 0.88. Data were analyzed using SPSS, V.11.5. The results showed that average farm size in total farming systems were less from their desirable size. Minimum economic of farm size in peasant exploiters was more than their average farm size but minimum economic of farm size in production cooperative was less than their average farm size. In commercial exploiters, farm size enables to provide income which it can provide flowing expenses of production and yearly expenses of exploiters and provide additional income for them. In farming systems that farm size is not desirable, this study suggested using scale profit and in farming systems that their minimum economic of farm size is less than their average farm size, this study suggested to adopt supportive politics and farm integration.

An experiment was conducted to study the effect of different levels of prebiotic on performance, carcass composition and blood parameters of broilers for 42 days. A completely randomized design with 320 Ross 308 chickens was used. Four treatments including: 1) control (without prebiotic) 2) recommended level, 3) 50% higher and 4) 50% lower than recommended level of prebiotic were considered. Each treatment consisted of five replicates of 16 chickens. For performance traits (gain, feed intake and feed conversion ratio), there were no significant differences among treatments in different production periods. The result of carcass percent indicated that there were no significant effects among treatments but thigh percent in second treatment was significantly higher compared to fourth treatment (P<0.05). No significant differences for blood parameters (glucose, cholesterol, triglyceride, HDL and hematocrite) were found among treatments. In current experimental condtion, no significant differences were found among different levels of prebiotic on performance and blood parameters.

In recent decades, irradiation has been applied in different areas of animal science researches. Ionizing rays such as gamma, electron, X-ray, ultraviolet, infrared and microwave are the main rays used in feedstuffs processing. In different studies, irradiation has been used for increasing protein quality, improving nutrient digestibility, microbial decontamination of poultry ration.

This experiment was conducted to determine the effect of different levels of prebiotic and probiotic on broiler's performance at different weeks of rearing period, PER, MEI and MEI conversion ratio of Ross 308 male broiler chicks in a completely randomized design with 2×3 factorial arrangements with two level of Perimalac (without Perimalac and 900 gr ton-1 primalac) and three levels of Fermacto (without Fermacto, 1 and 2 kg ton-1 fermacto). For this purpose, a control basal diet was formulated according to NRC (1994) recommendations for starter (0-21d) and grower (22-42d) periods. Therefore, there was 6 dietry treatments which was fed ad-libitum to five replicates of 16 birds. The result of experiment showed that using 2 kg/t Fermacto increased body weight gain (BWG) at 35 and 42 d. Perimalac also increase BWG at all different weeks of experimental period. There was no significant effect of using different levels of Fermacto on feed intake. Perimalac improved feed efficiency in the 2end, 3th and 6th weeks of experiment, while adding different levels of Fermacto had no significant effect on feed efficiency. Increasing of MEI was observed when primalac was used in the diet but different levels of fermacto had no effect on the MEI. The result showed that using 2 kg/t Fermacto increased PER and MEI conversion ratio at the whole of rearing period. The protein efficiency ratio was increased in starter and grower period when Perimalac was used as a supplement in the diet.

The present study was conducted to investigate the effect of feed restriction severity and meal feeding regimes on live body weight and protein and energy efficiency ratio of Ross broiler chicks. 300, Ross 308 male broiler chicks were reared on the floor pens for 42 days. Birds fed ad libitum for the first week post hatch. Feed restriction schedule was applied from 7 to 14 or 7 to 21 days of age. Chickens in treatment 1 fed ad libitum (AL) throughout the experiment. Birds in treatment 2 and 3 were subjected to quantitative feed restriction based on maintenance (QFRM) or 50% of growth (QFRG) energy requirements. Birds in treatment 4 and 5 were subjected to quantitative feed restriction based on a meal feed schedule from 7 to 14 (MF14) or 7 to 21 (MF21) days of age. Five replicate groups of 12 broilers were allocated to each treatment. Results indicated birds were affected by feed restriction regimes had lower live body weight rather than control group (P<0.05). However, live body weight of MF groups was similar to control group due to compensatory growth but quantitative feed restriction reduced live body weight compared to AL or MF regimes due to incomplete compensatory growth (P<0.05) at the end of experiment. Control group have a numerically superior energy and protein intake (12483.4 kcal and 801.1 g, respectively). Energy efficiency ratio and protein efficiency ratio were superior for birds in MF1 compared to other treatments (17.1 and 2.67, respectively).

This experiment was conducted to determine the effect of delay in harvesting of Kenaf on chemical components and disappearance characteristics. Harvesting began 85 d after planting (DAP) with additional harvests at 25-d intervals (85, 110 and 135 DAP). Three mature rams of Zel breed were rumen cannulated to calculate ruminal disappearance percent of DM, CP, NDF and OM. Ration was formulated with 60 percent forage and 40 percent concentrate that were offered to the rams in 2 meals daily. To investigate the effects of harvesting intervals on quality of kenaf leaves DM, Ash, OM, CP, EE, NDF and ADF in each harvesting were determined. Incubation time of nylon bags were 0, 4, 8, 16, 24, 48 and 72 hours. Results of current study showed that delay in harvesting time caused a significant decline in CP component of leaves. Harvesting intervals had significant effects on NDF content of leaves (P<0.05). There were no significant differences between effective degradability for different passage rates (P>0.05). In additions, (a) fraction of protein was significantly affected by harvesting intervals, (38.82, 36.17 and 33.43 respectively). In different harvesting, there were no significant differences between sum of (a) and (b) fraction of CP. Results of current study showed that delay in harvesting time decreased effective degradability of protein, significantly (P<0.05). Maximum of NDF effective degradability in different passage rate were seen in second harvesting and had significant difference with the other harvesting times (P<0.05). The results of this experiment showed that plant maturity leads to an obvious decrease of rumen degradability of Kenaf leaves by the reduction of the cell contents to cell walls ratio, but it only has a little effect on rumen degradation of CP and thus kenef leaves could be used as a protein source in ruminant rations.

Quantitative analysis of production through evaluating level of factors usage is as the major agricultural policies, which follows increasing in production by optimum usage of resources. This study has conducted to analyze the role of extensional educations and expert services on some production factors at broiler farms in Gorgan district. The cross-section survey data were gathered from 71 farms, which selected via random sampling, interviews and researcher-made questionnaires in spring 2009. Thereafter, the mechanization level of each broiler farms was determined attentive expert's viewpoints, and classified into mechanized and semi-mechanized groups, and they were compared with technical efficiency, conversion coefficient, capacity, dead percent and race indices between groups. On the basis of results, in order to improve in production indices of mechanized and semi-mechanized broiler farms, the existence gap can reduce through improving in technological knowledge. Finally, regarding the findings of research, some suggestions have been recommended to policymakers and planners for this field.