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51.
Mehdi Zolfaghari Mohammad Reza Imanpour Esfandyar Najafi 《Aquaculture Research》2011,42(11):1594-1599
The effects of photoperiod (12L:12D and 18L:6D) and feeding frequency (three, four and five evenly spaced daily feedings) of 10% biomass per day during light hours on growth and stress response of Persian sturgeon (Acipenser persicus) fingerlings were evaluated. The interaction between photoperiod and feeding frequency was not significant (P>0.05). Faster growth was observed in fish exposed to an 18L:6D photoperiod (P<0.01). The feed conversion efficiency (FCE) was also better with an 18L:6D photoperiod (P<0.05). Fish fed four and five meals per day grew similarly (P>0.05) and faster than when fed only three meals (P<0.01). The FCE with four or five meals per day was better than with three meals (P<0.05). At harvest, the proximate composition was similar in all treatments (P>0.05). Stress indicators (cortisol, glucose and haematocrit) did not differ between photoperiods (P<0.05). The results showed that 0.9–8.0 g Persian sturgeon fingerlings should be reared with an 18L:6D photoperiod and fed four times per day to obtain good growth and FCE. 相似文献
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P Langendijk H van den Brand R Gerritsen H Quesnel NM Soede B Kemp 《Reproduction in domestic animals》2008,43(2):131-136
Contents This study presents relationships between peripheral progesterone and Insulin-like Growth Factor-1 (IGF-1) concentrations during the early luteal phase in sows. Data were derived from three experiments, one with primiparous weaned sows (n = 21) and two with multiparous sows that either ovulated during lactation (n = 23) or after weaning (n = 12). The sows that ovulated during lactation did so due to an intermittent suckling regime (inhibition of suckling for 12 h each day from day 14 of lactation) or due to treatment with PG600. IGF-1 concentrations varied considerably among experiments, and were the lowest in the multiparous sows, regardless of whether they were weaned or lactating: 68 ± 5 and 85 ± 8 ng/ml in the two experiments with multiparous sows vs 188 ± 15 ng/ml in the primiparous sows. Progesterone concentrations were lowest for the lactating sows. Overall, the increase in progesterone during the early luteal phase was strongly correlated with IGF-1 concentrations (r = 0.7). However, the correlation was low in multiparous lactating sows (r = 0.28; p < 0.10) and nonsignificant in multiparous weaned sows (r = 0). The weaned multiparous sows had IGF-1 levels comparable to lactating multiparous sows, but higher progesterone levels. In conclusion, these data show a positive relationship between peripheral IGF-1 and progesterone concentrations in vivo during the early luteal phase. In lactating sows, IGF-1 concentrations are probably a limiting factor for progesterone secretion, although other factors may be involved. 相似文献
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The concentrations of cadmium (Cd), lead (Pb), chromium (Cr), copper (Cu), zinc (Zn), and iron (Fe) in water and selected fish species (Oreochromis nilzinc (oticus and Clarias gariepinus) from Benue-Niger River Confluence, Nigeria were investigated. The water and fish sample digests were quantified using an atomic absorption spectrophotometer. The study aimed to assess any possible human health risk associated with water and fish consumption from the selected geographical area. The concentration of the metals in the surface water ranged from 0.007 to 0.039, 0.106 to 0.240, 0.092 to 0.0164, 0.682 to 0.878, 0.058 to 0.309, and 0.136 to 1.645 mg/L for Cd, Cr, Cu, Fe, Pb, and Zn, respectively, while the concentrations of the metals, Cd, Pb, Cr, Cu, Zn, and Fe in these fish species ranged from 0.034 to 0.679, 0.500 to 1.75, 0.152 to 0.351, 0.36 to 1.01, 5.32 to 7.41, and 4.25 to 9.17 mg/kg, respectively. Cd, Cr, and Pb levels in fish were higher than the provisional tolerable weekly intake of 7, 1.5, and 25 μg/kg bw, respectively, according to the World Health Organization. Dry season values of the metals in water samples were higher, and sharptooth catfish had higher amounts of the metals. The hazard quotient (HQ) for Cd indicated a possible potential health concern with fish consumption from this area. 相似文献
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A. Halajnia S. Oustan N. Najafi A. R. Khataee A. Lakzian 《Communications in Soil Science and Plant Analysis》2016,47(9):1162-1175
The potential use of a layered double hydroxide (magnesium aluminum nitrate (Mg-Al)-LDH) to suppress the leaching of nitrate from a calcareous sandy loam soil and to enhance the nitrogen utilization efficiency of maize was assessed. The results of column studies showed that nitrate leaching efficiently decreased by 24, 46, and 76% compared to control when 2.5, 5, and 10 g LDH kg–1 soil were applied, respectively. Nitrate leaching was also reduced by use of LDH in pot experiments. The hindrance effect of LDH in using ammonium nitrate was higher than urea. Application of 2.5, 5, and 10 g LDH kg–1 soil increased mean nitrogen uptake of maize by 14, 20, and 44% over the control. The studied LDH has a potential to be used as a nitrate-selective exchanger to reduce risks of nitrate leaching. However, the use of Mg-Al-LDH (4:1) can be limited because of its relatively high solubility in soil. 相似文献
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Hygroscopic thickness swelling rate of composites from sawdust and recycled plastics 总被引:1,自引:1,他引:0
Saeed Kazemi Najafi Azadeh Kiaeifar Mehdi Tajvidi Elham Hamidinia 《Wood Science and Technology》2008,42(2):161-168
The thickness swelling rates of compression molded wood plastic composites (WPCs) prepared from 50% by weight sawdust and
50% by weight virgin and/or recycled plastics (HDPE and PP) were studied. Thickness swelling rates of the manufactured WPCs
were evaluated by immersing them in water at room temperature and monitoring thickness changes for several weeks. A swelling
model developed by Shi and Gardner (Composites Part A, 37:1276–1285, 2006) was used to study the thickness swelling process
of WPCs. The parameter K
SR of the model can be used to quantify the swelling rate. The results indicated that composites containing PP had lower equilibrium
thickness swelling and also shorter equilibrium time (time to reach equilibrium thickness swelling). The swelling model developed
was a good predictor of the hygroscopic swelling process of wood plastic composites. Composites containing PP (virgin and
recycled) had higher K
SR than those containing HDPE. The minimum and maximum K
SR values were observed in composites made of virgin HDPE and a mixture of recycled plastics, respectively. With increasing
recycled plastic content K
SR linearly decreased. 相似文献
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Eurasian Soil Science - A litho-toposequence of soils in a semi-arid region in southwestern Iran was investigated for their pedological properties. Nine representative pedons on different... 相似文献