Browsing by Author "Lawrence, Addison L."

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    Availability of Dietary Zinc Sources and Effects on Performance of Pacific White Shrimp Litopenaeus vannamei(Boone)
    Bharadwaj, Anant S.; Patnaik, Susmita; Browdy, Craig L.; Lawrence, Addison L. (Commercial Fish and Shellfish Technologies Program, Virginia Tech, 2012-06-01)
    A study was conducted to evaluate the response of Pacific white shrimp Litopenaeus vannamei to inorganic or chelated sources of dietary zinc. Two sets of diets, one supplemented with zinc from zinc sulfate (55, 80, 116, 168, 243 and 363 ppm zinc) and the other with zinc from a chelated source (methionine hydroxy analog chelate; 39, 52, 65, 78 and 104 ppm zinc) were fed to replicate groups of juvenile shrimp (N = 8; 0.4 g initial weight) for 6 wk. All experimental diets contained 1.38% phytic acid reflecting levels in typical commercial feeds. Final weight, growth rate and biomass of shrimp fed zinc sulfate supplemented diets (243 and 363 ppm total zinc) were significantly higher (p < 0.05) than that in shrimp fed the base diet. In contrast, performance of shrimp fed the chelated source of zinc was significantly higher than shrimp in the control group at much lower levels of supplementation (65 and 78 ppm total zinc). Results indicate that shrimp required 3-4 times more dietary zinc from zinc sulfate than zinc from a chelated source to promote comparable growth when fed diets containing phytic acid. The chelate tested proved to be a safe, effective and available source of zinc for the Pacific white shrimp.
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    Effects of dietary protein and water exchange on water quality, survival and growth of postlarvae and juvenile Litopenaeus vannamei
    Wang, Lan-mei; Lawrence, Addison L.; Castille, Frank; Zhao, Yun-long (Commercial Fish and Shellfish Technologies Program, Virginia Tech, 2012-06-01)
    Two growth trials were conducted with Litopenaeus vannamei to evaluate effects of dietary protein and water exchange on survival, growth and water quality. In both trials, protein levels were 12, 15, 20, 26 and 35%. In the first trial, 6.21 g juvenile shrimp were stocked for 23 days at either zero or high (2750% daily) water exchange. At high exchange, survival was greater than 93% for all protein levels. Final body weight (FBW) and weight gain (WG) increased with protein level from 12% to 20% (P < 0.05). FBW and WG at 20 and 26% protein were lower than that at 35% protein. At zero exchange, survival decreased with protein above 20%. At zero exchange, water quality decreased (high ammonia, nitrite, nitrate and low pH, alkalinity) with protein greater than 15%. WG with 12% protein was greater at zero exchange than at high exchange. In the second trial, 0.22 g postlarvae were stocked for 26 days at either zero or high (5440% daily) water exchange. At high exchange, survival was 90% or greater for all protein levels. FBW and WG increased with protein level from 12% to 20% (P < 0.05). At zero exchange, FBW and WG were maximum with 20% protein. Survival was lowest at 35% protein. For 35% protein, survival was lower at zero than at high exchange. For all protein levels except 35%, WG was higher at zero than at high exchange. The results suggest that lower protein diets can replace high protein (35%) commercial diets and obtain high growth rate for both juvenile and postlarvae L. vannamei at zero exchange. Further, a 20% protein diet, which contained 25.3% marine animal meals, was adequate for shrimp growth, survival and water quality at zero exchange.
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    Effects of water exchange and reducing dietary vitamin and mineral supplementation on survival and growth of Litopenaeus vannamei
    Wang, Lan-mei; Lawrence, Addison L.; Castille, Frank; Zhao, Yun-long (Commercial Fish and Shellfish Technologies Program, Virginia Tech, 2012-06-01)
    A growth trial was conducted with Litopenaeus vannamei to evaluate effects of dietary vitamin and mineral supplementation (VMS) and water exchange on survival, growth and water quality. Four levels (0, 25, 50 and 100%) of VMS were evaluated using a 20% protein base diet. Postlarvae weighing 0.22 g were stocked for 26 days with either zero or high (5440% daily) water exchange. Growth was greater at zero than high exchange. However, growth was not affected by the level of VMS at both high and zero exchange. Survival for 0% VMS was lower than survivals for 25 to 100% VMS at high exchange. For 0% VMS, survival at high exchange was lower than survival at zero exchange. Results suggested that at zero water exchange, diets without VMS can replace diets with VMS without reducing survival.